Department of Radio-Diagnosis


Dept. data last updated on :22/05/2023



Computed Tomography (CT or CAT) Scan of the Brain

What is a CT scan of the brain?

(Head CT Scan, Intracranial CT Scan)

A CT of the brain is a noninvasive diagnostic imaging procedure that uses special X-rays measurements to produce horizontal, or axial, images (often called slices) of the brain. Brain CT scans can provide more detailed information about brain tissue and brain structures than standard X-rays of the head, thus providing more data related to injuries and/or diseases of the brain.

During a brain CT, the X-ray beam moves in a circle around the body, allowing many different views of the brain. The X-ray information is sent to a computer that interprets the X-ray data and displays it in a two-dimensional (2D) form on a monitor.

Brain CT scans may be done with or without "contrast." Contrast refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your physician will notify you of this prior to the procedure.

Other related procedures that may be used to diagnose brain disorders include X-rays magnetic resonance imaging (MRI) of the brain positron emission tomography (PET) scan of the brain , and cerebral arteriogram .

What is the function of the brain?

As part of the central nervous system (CNS), the brain is an important organ that controls thought, memory, emotion, touch, motor skills, vision, respirations, temperature, hunger and every process that regulates our body.

Illustration of the anatomy of the adult brain

What are the different parts of the brain?

The brain can be divided into the cerebrum, brainstem, and cerebellum:

  • Cerebrum. The cerebrum (supratentorial or front of brain) is composed of the right and left hemispheres. Functions of the cerebrum include: initiation of movement, coordination of movement, temperature, touch, vision, hearing, judgment, reasoning, problem solving, emotions, and learning.
  • Brainstem. The brainstem (midline or middle of brain) includes the midbrain, the pons, and the medulla. Functions of this area include: movement of the eyes and mouth, relaying sensory messages (hot, pain, loud, etc.), hunger, respirations, consciousness, cardiac function, body temperature, involuntary muscle movements, sneezing, coughing, vomiting, and swallowing.
  • Cerebellum. The cerebellum (infratentorial or back of brain) is located at the back of the head. Its function is to coordinate voluntary muscle movements and to maintain posture, balance, and equilibrium.

More specifically, other parts of the brain include the following:

  • Pons. A deep part of the brain, located in the brainstem, the pons contains many of the control areas for eye and face movements, facial sensation, hearing, and equilibrium.
  • Medulla. The lowest part of the brainstem, the medulla is the most vital part of the entire brain and contains important control centers for the heart and lungs.
  • Spinal cord. A large bundle of nerve fibers located in the back that extends from the base of the brain to the lower back, the spinal cord carries messages to and from the brain and the rest of the body.
  • Frontal lobe. The largest section of the brain located in the front of the head, the frontal lobe is involved in personality characteristics and movement.
  • Parietal lobe. The middle part of the brain, the parietal lobe helps a person to identify objects and understand spatial relationships (where one's body is compared to objects around the person). The parietal lobe is also involved in interpreting pain and touch in the body.
  • Occipital lobe. The occipital lobe is the back part of the brain that is involved with vision.
  • Temporal lobe. The sides of the brain, these temporal lobes are involved in memory, speech, and sense of smell.

What are the reasons for a CT scan of the brain?

A CT of the brain may be performed to assess the brain for tumors and other lesions, injuries, intracranial bleeding, structural anomalies (e.g., hydrocephalus , infections, brain function or other conditions), particularly when another type of examination (e.g., X-rays or a physical exam) are inconclusive.

A brain CT may also be used to evaluate the effects of treatment on brain tumors and to detect clots in the brain that may be responsible for strokes . Another use of brain CT is to provide guidance for brain surgery or biopsies of brain tissue.

There may be other reasons for your doctor to recommend a CT of the brain.

What are the risks of a CT scan of the brain?

You may want to ask your doctor about the amount of radiation used during the brain CT procedure and the risks related to your particular situation. You should keep a record of your past history of radiation exposure, such as previous CT scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time.

To safeguard your health, consider the following precautions before scheduling a brain CT:

  • Pregnancy : If you are pregnant or suspect that you may be pregnant, you should notify your doctor. Radiation exposure during pregnancy may lead to birth defects. If it is necessary for you to have a CT of the brain, special precautions will be made to minimize the radiation exposure to the fetus. Contrast media: If contrast media is used during a brain CT, the patient may develop an an allergic reaction to the media. Some patients should not have an iodine-based contrast media. Patients who are allergic to or sensitive to medications should notify their doctor. When you schedule your brain CT scan, you should inform the access center representative if you have had an allergic reaction to any contrast media or if you have kidney failure or other kidney problems. IV contrast will not be administered if you have had a severe or anaphylactic reaction to any contrast media in the past. You may be able to have the scan performed without contrast media or have an alternative imaging exam. . A reported seafood allergy is not considered to be a contraindication for iodinated contrast. Nursing mothers may want to wait 24 hours after contrast material is injected before resuming breastfeeding.
  • Diabetes: Patients taking the diabetes medication metformin (Glucophage) should alert their doctors before having an IV contrast injection as it may cause a rare condition called metabolic acidosis. If you take metformin, you will be asked to stop taking it at the time of the procedure and wait 48 hours after your procedure before restarting this medication. A blood test to check kidney function may be required before you can resume taking metformin.

There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

How do I prepare for a CT scan of the brain?

If you are having computed tomography angiography (CTA) , you will be given specific instructions when you make your appointment. The following instructions will help you prepare for your brain CT:

  • Clothing : You may be asked to change into a patient gown. If so, a gown will be provided for you. Please remove all piercings and leave all jewelry and valuables at home.
  • Contrast media: You will be asked to sign a consent form that will detail the risks and side-effects associated with contrast media injected through a small tube places in a vein called an intravenous (IV) line. The most common type of brain CT scan with contrast is the double-contrast study that will require you to drink a contrast media before your exam begins in addition to the IV contrast. If you had mild to moderate reactions in the past, you will likely need to take medication prior to the brain CT scan.
  • Food and drink : If your doctor ordered a brain CT scan without contrast, you can eat, drink and take your prescribed medications prior to your exam. If your doctor ordered a CT of the brain with contrast, do not eat anything three hours prior to your brain CT. You are encouraged to drink clear liquids.
  • Diabetics : Diabetics should eat a light breakfast or lunch three hours prior to the scheduled scan. Depending on your oral medication for diabetes, you may be asked to discontinue the use of your medication for 48 hours afterthe brain CT scan. If you have a CT scan with Johns Hopkins radiology, detailed instructions will be given following your examination.
  • Medication : All patients can take their prescribed medications as usual, unless otherwise directed.

Based on your medical condition, your doctor may request other specific steps for brain CT preparation.

Photo of person in CT scanner

What happens during a CT scan of the brain?

Brain CT scans may be performed on an outpatient basis or as part of your hospital stay. Procedures may vary depending on your condition and your physician's practices.

Generally, a brain CT scan involves the following steps:

  • If you having a procedure done with contrast, an IV line will be started in the hand or arm for the injection of the contrast media. For oral contrast, you will be given a liquid contrast preparation to swallow.
  • You will lie on a scan table that slides into a large, circular opening of the scanning machine. Pillows and straps may be used to prevent movement during the procedure.
  • The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner will enable two-way communication between the technologist and the patient. You may have a call button so that you can let the technologist know if you have any problems during the procedure. The technologist will be watching you at all times and will be in constant communication.
  • As the scanner begins to rotate around you, X-rays will pass through the body for short amounts of time. You will hear clicking sounds, which are normal.
  • The X-rays absorbed by the body's tissues will be detected by the scanner and transmitted to the computer. The computer will transform the information into an image to be interpreted by the radiologist.
  • You must remain very still during the procedure. You may be asked to hold your breath at various times during the procedure.
  • If contrast media is used for your procedure, you may feel some effects when the media is injected into the IV line. These effects include a flushing sensation, a salty or metallic taste in your mouth, a brief headache or nausea and/or vomiting. These effects usually last for a few moments.
  • You should notify the technologist if you experience any breathing difficulties, sweating, numbness or heart palpitations.
  • When the procedure has been completed, you will be removed from the scanner.
  • If an IV line was inserted for contrast administration, the line will be removed.

While the brain CT itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure (e.g. surgery). The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.

What happens after a CT of the brain?

If contrast media was used during your brain CT scan, you may be monitored for a period of time to check for any side effects or reactions to the contrast media. Notify your radiologist or if you experience itching, swelling, rash or difficulty breathing. If you notice any pain, redness and/or swelling at the IV site after you return home following your procedure, you should notify your doctor as this could indicate an infection or other type of reaction.

Otherwise, there is no special type of care required after a CT of the brain. Most patients are permitted to resume their usual diet and activities. Your doctor may provide additional or alternate instructions after the procedure, depending on your particular situation.




Standard Operating Procedure for

Magnetic Resonance Imaging Equipment –

1.5 Tesla (Siemens Avanto)


Department Of Radiodiagnosis













This document is intended to provide safety guidelines for users of magnetic resonance imaging (MRI) equipment in clinical use.


This guidance is intended to:

·        Bring to the attention of those involved with the clinical use of such equipment important matters requiring careful consideration after installation of equipment

·        Be an introduction for those who are not familiar with this type of equipment .

·        Act as a reminder of the legislation and published guidance relating to this equipment

·        Reflect current risks and hazards of MRI for safe usage.













2.     Defined terms

MR ENVIRONMENT -‘the three dimensional volume of space surrounding the MR magnet that contains both the Faraday shielded volume and the 0.50 mT field contour (5 gauss (G) line). This volume is the region in which an item might pose a hazard from exposure to the electromagnetic fields produced by the MR equipment and accessories.’ The updated definition now specifically prohibits items containing conductive, metallic and magnetic materials.



A locally defined volume containing the full extent of the 3 mT magnetic field contour, or other appropriate measure, around the MRI scanner. For the majority of MRI units, restrictions on the introduction of grossly ferromagnetic objects associated with the risk of projectiles are applied to the entire magnet room and consequently only 2 defined areas, MR CONTROLLED ACCESS AREA and MR ENVIRONMENT are sufficient.


MR SAFE-‘an item that poses no known hazards resulting from exposure to any MR environment. MR Safe items are composed of materials that are electrically nonconductive, nonmetallic, and nonmagnetic’ *

MR CONDITIONAL- ‘an item with demonstrated safety in the MR environment within defined conditions. At a minimum, address the conditions of the static magnetic field, the switched gradient magnetic field and the radiofrequency fields. Additional conditions, including specific configurations of the item, may be required.’

MR UNSAFE -an item which poses unacceptable risks to the patient, medical staff or other persons within the MR environment.’









Free access to the MR CONTROLLED ACCESS AREA but not the MR ENVIRONMENT.

They may supervise other persons only in this area.

Eg- management, clerical staff, radiologists without any formal safety training



Free access to the MR ENVIRONMENT but not to supervise others.

People who additionally are given free access to the MR ENVIRONMENT and take responsibility for their own safety within the MR ENVIRONMENT

Eg- supporting clinical staff, basic researchers.



Free access and to supervise others in the MR ENVIRONMENT. 

People who need to perform safety screening of other people and take responsibility for the safety of others within the MR ENVIRONMENT.

Eg-radiographers, clinical scientists.







An MR OPERATOR is an MR AUTHORISED PERSON who is also entitled to operate the MRI equipment. 

MR OPERATORS are normally radiographers or radiologists but may include assistant practitioners, physicists, maintenance and research staff.

Sites may designate two types of MR Operators – clinical and technical/non clinical.




It is recommended that the chief executive or the general manager delegate the day-to-day responsibility for MR safety to a specified MR RESPONSIBLE PERSON who might most effectively be the clinical director, head of the department, clinical scientist, medical physicist or MR superintendent radiographer of the institution where the equipment is located.


Each MR RESPONSIBLE PERSON should retain close contact with other relevant groups or committees responsible for safety and welfare of personnel on site, such as a research ethics committee, local safety committee and local radiation safety committee. Links should be established with any appropriate district, regional and/or professional bodies.





The MR SAFETY EXPERT will have an advanced knowledge of MRI techniques and an appropriate understanding of the clinical applications of MRI. Ideally they will be a physicist with expertise in MRI. The MR SAFETY EXPERT should be in a position to adequately advise on the necessary engineering, scientific and administrative aspects of the safe clinical use of the MR devices





During MRI diagnostic imaging and spectroscopy, individuals being scanned and those in the immediate vicinity of the equipment can be exposed to three variants of magnetic fields simultaneously:

The hazards of each of these are discussed separately in the following sections-

Biological effects-- The World Health Organisation published a comprehensive review of the possible health effects of exposure to static electric fields and exposure to static magnetic fields in 2006 [18] and they noted that: ‘Physical movement within a static field gradient is reported to induce sensations of vertigo and nausea, and sometimes phosphenes and a metallic taste in the mouth, for static fields in excess of about 2 – 4 T. Although only transient, such effects may adversely affect people. Together with possible effects on eye-hand coordination, the optimal performance of workers executing delicate procedures (eg surgeons) could be reduced, along with a concomitant reduction in safety. Effects on other physiological responses have been reported, but it is difficult to reach any firm conclusion without independent replication.’

Projectile hazards-The force experienced in MRI scanners is at a maximum just inside the opening of the magnet. Normally all equipment brought into the scan room, from wheelchairs, stretchers and emergency trolleys to cleaning equipment, should not contain significant amounts of ferromagnetic material in order to avoid the projectile effect from the static magnetic field. 

Torque--ferromagnetic objects will also experience a torque that will try to align that object along magnetic field lines. Torque is largely shape dependent and is proportional to the field strength, B0, and to the angle the object is away from alignment with the field

Interaction with implantable medical devices

Any ferromagnetic component within an implantable medical device may experience both an attractive force (ie the device will try to move to the iso-centre) and/or a torque force (ie the device will try to turn to line up with field lines). Both of these effects can cause tissue damage and/or damage to the implantable medical device.

Examples of implantable medical devices are stents, clips, prostheses, pacemakers and neurostimulators.

Implantable medical devices fall into two main categories:

Active implantable medical devices.




Cochlear implants and drug pumps, where functionality is dependent upon an energy source such as electrical, mechanical or pneumatic power.

Some active implants contain an integral power source whereas others derive their necessary power through close coupling between an implanted coil and an external coil which forms part of the completed system. Active implants contain metal components, which may suffer damage during exposure to MR and the implant as a whole may be attracted by the magnetic field.

Cochlear implants usually have ferromagnetic components, and are activated by electronic and/or magnetic mechanisms. However, some devices are MRCONDITIONAL and the patient can be scanned in line with the implant manufacturer’s guidance.

• Non-active implantable medical devices. These are passive in that they require no power source for their function. For example:

Hip/knee joint replacements, heart valves, aneurysm clips, coronary stents and breast implants. Both active and non-active implantable medical devices can contain metallic components, which may render the device incompatible with MR and therefore contraindicated by the implant manufacturer or may cause artefacts that can affect image quality. However, there are a large number of implantable medical devices that are either MR_SAFE or MR_CONDITIONAL. Surgeons should be encouraged to provide patients with accurate documentation and information about medical devices implanted into them.

Peripheral nerve and muscle stimulation

At low frequencies, induced currents are able to produce the effect of stimulation of nerve and muscle cells .This stimulation can be sufficient to cause discomfort and in extreme cases might result in limb movement or ventricular fibrillation. The body is most sensitive to fibrillation at frequencies of between about 10 Hz and 100 Hz and to peripheral nerve stimulation at up to about 5 kHz. Above these frequencies, nerve and muscle cells become progressively less responsive to electrical stimulation.

Heat stress

Heat stress is of particular concern for some patients, such as those suffering from

·         hypertension, or

·         pregnant women, or

·         those on drugs such as diuretics or vasodilators

MR scanners limit temperature rise by limiting SAR.

Contact Burns-

The radiofrequency field will induce currents in conductors and can raise their temperature significantly. Burns to volunteers and patients from contact with such metallic objects can be avoided by

careful positioning and set up within the bore of the magnet. [contact with metal in clothing, coils, coil leads, ECG connectors and oxygen monitor probes]

Acoustic noise

The use of earplugs, ear defenders, or other means of hearing protection is highly recommended .

Staff training in the use and selection of ear protection is also necessary.



The 2004 ICNIRP report recommendation regarding exposure to pregnant patients is:

‘There is at present insufficient knowledge to establish unequivocal guidance for the use of MRI procedures on pregnant patients. In these circumstances, it is advised that MR procedures may be used for pregnant patients only after critical risk/benefit analysis, in particular in the first trimester, to investigate important clinical problems or to manage potential complications for the patient or fetus.’’

Pregnant staff conclusion

The fetus and noise exposure Since the early 1990s concerns have been expressed regarding the possible effects of excessive noise on fetal health. Reviews of the evidence and American Academy of Paediatrics 1997 remain inconclusive regarding effects on prematurity or fetal hearing following exposure to noise.



There should be no hazards from cryogens provided adequate attention has been paid to the provision of venting directly to the outside of the building of all potential sources of helium and nitrogen following normal boil-off or in the event of a pressure release valve bursting. The hazards in the use of low temperature liquefied gases for MR systems are:

1.     asphyxiation in oxygen-deficient atmospheres

2.     Cold burns, frostbite and hypothermia from the intense cold

3.     Explosion following over-pressurisation from the large volume expansion of the liquid following evaporation.








Exposure limits and guidance

Exposed groups- A number of organizations have proposed limits to protect exposed persons from effects of EMF and noise.

Exposed persons can be grouped into three categories

·         Patients for diagnosis, volunteers engaged in clinical trials and careers.

·         Staff (employed / self-employed workers).

·         Generalpublic (visitors/educational visitors).

Modes of operation

·         NORMAL MODE of operation when risk of ill effect to the patient is minimized.

·         CONTROLLEDMODE of operation when the exposure is higher than the normal mode and although the risks are minimized, some people may experience some effects at this level, such as sensory disturbance or transient discomfort due to PNS. The patient will benefit by the enhanced imaging performance. Scanning requires patient monitoring .

·         RESEARCH/ EXPERIMENTALMODE when exposure is only restricted to prevent harmful effects. Scanning in this mode will require approval of a research ethics committee and patient monitoring .

Occupational exposure to noise is now specifically regulated by the Control of Noise at Work Regulations 2005 .



Scanning patients with implants where MRI may be contraindicated

The following should be considered:

·         Consideration of alternative imaging modalities

·         Consideration of scanning on a MRI scanner with a lower static and/or gradient fields, which may require referral to other centers if not available locally.

·         Advice from the implant manufacturer.

·         Available Professional Body recommendations

·         Published evidence of scanning the device

·         Available data about the device

·         Assessment of possible artefacts

·         MRI device parameters.

·         Identification and implementation of appropriate precautions to minimize the risk.

·         Appropriate programming of the device

·         Suitable monitoring (e.g. SAR levels, physiological signals) during the scan. Physiological monitoring may require additional suitably trained personnel to operate and/or interpret the results.

·         SAR exposure including consideration of methods to reduce it, e.g. reduced flip angles, longer TRs, use of transmit/receive coils.

·         Provision of procedures to ensure that a suitable clinician is available and in the department at the time of the scan, e.g. for cardiac devices, a cardiologist or cardiac physiologist.

·         Procedures for post scan evaluation of the patient.

Patient consent should be obtained for this procedure. An MR unit should not feel pressured into adopting the above procedure if they do not feel confident in the skills and experience available to them (e.g. mobile or stand alone units).

Screening prior to examination

·         Screening should take place on several occasions prior to actually starting the examination.

·         The first patient interview will cover major safety questions such as pacemakers, aneurysm clips, electronic implants and pregnancy. This should take place at the time that the request is generated in order to prevent an inappropriate examination being booked.

·         On arrival in the unit the patient should be asked to complete a screening form.

·         An appropriately trained and experienced MR AUTHORISED PERSON should then review the screening form with the patient.

·         The person performing this review should understand all the issues and potential hazards within the MR environment and should be familiar with the screening form.

·         The patient and the member of staff should sign the form.

·         Immediately prior to entering the scan room it is recommended that the MR OPERATOR performing the examination should visually and verbally screen the patient.

·         Procedures should be in place for patients who are unable to complete a checklist or have an identified medical history, for example an unconscious and unidentified patient with head injury.

·         It should set out how safety checks can be instituted in this case (eg check X-ray, physical examination for pacemaker by referring consultant).

·         While the use of conventional metal detectors is not recommended, ferromagnetic detection systems may additionally be used .

·         Screening must take place every time the patient attends the MR unit, even if the patient has already had a previous MR examination.

·         Screening consent/checklist forms should conform to standards for patient information - plain English, 14-point size font minimum and available in alternative languages appropriate to local population (Hindi, Urdu, etc.) and will include the following:

        Recent surgery, pregnancy, breastfeeding, medication, conditions relating to thermoregulatory function, breathing disorders, allergies to drugs and/or contrast medium etc.

        Implantable medical devices including: cardiac pacemakers, cardioverter defibrillators, heart valves, electronically activated implantable drug infusion pumps, cochlear implants, neurostimulators, programmable hydrocephalus shunts, aneurysm clips, ocular implants, penile implants, joint replacements, etc.

        Metallic objects: bullets, pellets, shrapnel, or other types of metallic fragments - body piercing ,hairpins, jewelry, brassieres, hearing aids, spectacles, dentures with metal components, make-up, tattoos, transdermal patches ,clothing with metallic / conductive content ,magnetized bank, credit and library cards.


Patient clothing



The space available in the magnet interior with or without the radiofrequency coils can be restrictive. Patients who are not normally claustrophobic may find it unpleasant. Exceptionally, an accompanying relative or attendant appropriately screened, checked and authorised, may be allowed to remain in the scan room in verbal and, if necessary, physical contact with the patient.

Positioning the patient-Two issues are important here: patient comfort and patient safety.

·         The prevention of burns is the major concern.

·         Poor positioning of the patient and associated cables, leads and sensors, have been the cause of many burns

·         Electrical burns may not be painful immediately as they can start to cause tissue damage at temperatures as low as 43°C .

·         To avoid burns caused by RF heating -

        Ensure that sufficient insulation is placed between the cable and the patient if contact cannot be avoided

        Do not loop conductive cables or allow cables to cross one another

        Do not pass cables diagonally across the patient

        Ensure that cables run parallel to the bore of the magnet and as close to the center of the bore as possible

        Ensure that cables do not touch the bore of the magnet

        Ensure that cables exit the bore of the magnet as close to the center as possible

        Ensure that the patient’s skin does not touch the bore of the magnet, or come within 1 cm of touching, transmitting rf coil elements. Use insulation such as the foam pads provided by the mr manufacturer if necessary

        Ensure that no conductive loops form with any parts of the patient’s body -- avoid skin-to-skin contact. Foam pads can be placed between the thighs, between the arm or hand and the trunk and between the ankles to avoid the formation of any conductive loops

        Ensure that sensors are placed outside the scanning area whenever possible, as well as away from rf coil

        ensure that regular checks for damage are made on all coils, cables and leads for damage and do not use if damage is seen

        Use only high impedance leads; fibre optic leads are preferred

        Ensure that the patient is instructed to inform staff immediately if they feel any focal warming

        Ensure that the sites of all sensors are regularly checked for any evidence of heating if the patient is unconscious or for any reason unresponsive

        Ensure that you are familiar with and follow the manufacturer’s instructions at all times. This includes using only the monitoring equipment, ECG wires, leads, electrodes and accessories recommended by the MR system manufacturer.

Panic alarm -An alarm / panic button must be provided at all times. The device should be given to all patients with an explanation of its intended use.

Patient monitoring

Patients should be monitored routinely if the potential exists for a change to their physiological status during the MR procedure.

For patients who are unstable, anaesthetised, sedated or at risk, monitoring is required.

All monitoring should be undertaken using dedicated MRCONDITIONAL equipment.

Use only high impedance leads (fibre optic leads wherever possible).

Care must be taken to place all leads, electrodes and sensors correctly.

Patients who are being monitored must be advised to inform staff immediately if warming or discomfort is felt at the sensor site.

Responsibility for the correct placing of all leads, cables and sensors must be clearly defined and included in local procedures.

The MR OPERATOR must always maintain visual and audio contact with the patient.

The MR OPERATOR must not leave the control room whilst the patient is on the table unless it is to enter the scan room.


A nominated consultant anaesthetist should be responsible for anaesthesia services in MR units. Adequate space should be made available for the provision of anaesthesia services. Immediate access from the scan room to the anaesthetic preparation/recovery area is essential as, in the event of an emergency, resuscitation should not take place within the magnet room.

Patients should be prepared in a side room outside the MR ENVIRONMENT

Plastic intravenous cannulas should be carefully taped to the patient and plastic connectors used at all times.

Drip set-up, patient intubation and induction of anaesthesia with or without ventilation should be carried out in the side room.

Visual inspection and full monitoring (as above) are essential.

All equipment entering the MR PROJECTILE ZONE must be suitable [62]. The hazards associated with using the wrong equipment include the projectile effect, burns and equipment malfunction.

Record Keeping

The data should be recorded chronologically in a log of scans, the current volume of which should be available at all times at the operator’s console. All volumes of the scan log, all the patients’ and volunteers’ records should be held in safe keeping for a period that ensures compliance with the current guidance from the Department of Health. It should be in a form from which full details can be retrieved within this period if required.


Contrast media and anti-spasmodics

The administration of contrast media to patients must be under the supervision of a registered medical practitioner. The medically qualified professional will take the ultimate responsibility for the health of the patient during the scan and any subsequent deleterious effects that arise from the administration of the contrast medium.

Contraindications to administration of contrast agents Prior to administration, care should be taken to ensure that there are no contraindications relating to administration of the agent to the patient

The unit must have readily available drugs and equipment to deal with all possible reactions including anaphylactic shock

Records of administration Full details of the contrast medium administered must be recorded including the

        name of the administrator

        name of the contrast agent


        batch number


        quantity administered

        method of administration

Adverse events-

Suspected adverse drug events are to be reported to appropriate authority.

MR suite recommendations

Number of entrances

The number of entrances should be kept to a strict minimum.

A single door large enough for staff, patient access on a trolley or bed, equipment replacement and dewars in the case of superconducting magnets.

All doors to the MR suite should be self-closing and locking with security locks that can be operated by MR AUTHORISED PERSONNEL only from the outside, but freely opening from the inside in case of emergency.

Naturally, any device used for unlocking doors must not be ferromagnetic.

Entrance doors to the MR ENVIRONMENT should not open directly onto public areas and should be visible from the operator’s console


Adequate security lockers should be provided to accommodate personal belongings that will be either attracted by the static magnetic field or suffer damage.

Any devices used for locking/unlocking doors to these lockers must not be ferromagnetic.

Venting cryogens

In the case of superconducting magnets it will be necessary to duct the cold vapours produced by boil-off out of the MR ENVIRONMENT to the outside of the building. Access will be necessary to bring dewars to the point of filling and adequate ventilation must be provided during the filling process. Dewars and ducting must be made from non-ferromagnetic material

It is essential that temperature and humidity are measured in the scan room. The protection of the patient from heat stress and burns due to RF exposure is only limited by the room being maintained at moderate levels


Ferromagnetic material detectors

ACR recommends that: ‘the use of ferromagnetic detection systems is recommended as an adjunct to thorough and conscientious screening of persons and devices approaching Zone IV.

It should be reiterated that their use is in no way meant to replace a thorough screening practice, which rather should be supplemented by their usage.’

Ferromagnetic detection systems come in different formats-

·         Passthrough systems

·         Pass-by systems

·         Handheld ferromagnetic detectors


Potential equipment failure

Superconducting magnet quench-

Superconducting magnets may occasionally lose field abruptly due to a process known as ‘quenching'. If the magnet is properly installed and the cryogen levels are adequately maintained, this will be an extremely rare event. Inductance of superconducting magnets is such that, in the event of a collapse of the field, dB/dt is small compared with the recommended safety levels (see section 3). In normal operation, the highest risk of a quench is when the current probe is inserted in order to change the field, or when liquid helium is being fed to the cryostat. Only suitably trained staff may carry out these operations.

It is a misconception that there can only be total quenches. For certain magnets one must allow for an emergency quench which produces only a partial quench, a second operation is required before the field is completely eliminated. Thus, even when a quench has occurred, care must still be taken in handling ferromagnetic objects near the magnet.

If there is inadequate venting, cold gas may spread through the patient area. It will form a white fog that eventually clings to the ceiling. The patient should be removed at once, since there may be oxygen depletion and the presence of very cold gases may cause a cold burn, frostbite or hypothermia.

Emergency quench buttonsto switch off the field should be provided, not only near the magnet but also near the entrance of the MR unit. Such buttons should be easily depressed in the case of an emergency and provided with a protective cover or box fitted over them. Each button should be accompanied by a notice indicating its purpose and noting the time required for the field to fall to a safe level following activation of the switch. This time is generally about 30 seconds.

Emergency procedures




Superconducting magnet quench

If the quench is initiated on purpose, the door to the scan room should be fixed open before initiating the quench.

A build-up of pressure in the scan room could make an inward opening door difficult to open.




















ALARA: As Low As Reasonably Achievable: Radiation must be kept As Low As Reasonably Achievable (ALARA). The principle that radiation exposures must be reduced to the lowest level that can reasonably be achieved.

CT: Computerised Tomography. Creation of transverse tomographic sectional imaging of the body using a rotating fan beam, detector array and computed reconstruction.

CTDI vol: Computerised Tomography Dose Index Volume.

CTDI vol is a measure of the radiation exposure per slice. CTDI vol is independent of scan length.

DLP: Dose Length Product: DLP is measure of total radiation exposure for the whole series of images DLP = CTDIvol x irradiated length.

Operator: Radiology technicians, technologists, and sonographers fall within the broad scope of a radiography profession. Radiographers are typically involved in initial patient evaluation and testing, providing diagnostic and evidentiary data for Physicians.

LMP: Last Menstrual Period. By convention, pregnancies are dated in weeks starting from the first day of a woman's last menstrual period (LMP). If her menstrual periods are regular and ovulation occurs on day 14 of her cycle, conception takes place about 2 weeks after her LMP.

Radiation (Ionising): Radiation that produces ionisation in matter. Examples are alpha, beta, gamma and x-radiation and neutrons. When these radiations pass through the tissues of the body, they have sufficient energy to damage DNA.

Radiation Medical Practitioner: A radiologist is a physician who reads and interprets digital images, or x-rays, of patients obtained through a variety of cameras, machines, and imaging equipment. The radiologist uses this information to help diagnose the patient and consult with the treating Physician to develop a course of treatment.

RSO: Radiation Safety Officer The appointed person to advise Management and Executive on all matters relating to radiation safety with the Organisation

Referral or Request Form: A request for a diagnostic imaging examination or procedure usually requires the completion of a written request or referral form, via which key information is communicated to the imaging facility from the referring Practitioner.


  • Only authorised department staff trained to operate the CT scanner are permitted to do so.

  • Do not enter the CT Scanning room if the x-ray warning light is illuminated.

  • External door should be locked whilst CT Scanning is in progress.

  • All doors must be closed during scanning.

  • All exposure parameters are to be checked prior to scanning.

  • During tube ‘warm up’ the Console desk must be attended to ensure that the room is not entered.

  • Remote injector must be used wherever possible.

  • CT Operator must not leave the scan console during scanning.


INTRODUCTION:Standard Operating Procedures (SOPs) are succinct formal documents designed to achieve consistency in specified trial functions by specifying standard practice in performing those functions.

AIM: Standard Operating Procedures (SOPs) are succinct formal documents designed to achieve consistency in specified trial functions by specifying standard practice in performing those functions.

PURPOSE AND SCOPE: The purpose of this SOP is to describe the process of radiation for any patient undergoing a CT scan.

The SOP will cover: ·

  • Procedure for identification of individuals undergoing a CT medical exposure.

  • Procedure for making enquires of females of childbearing age.

  • Procedure for justification / authorisation of a CT medical exposure.

  • Procedure for Review of Justification Protocols.

  • Procedure for the assessing of the patient radiation dose.

  • Procedure for accidental or unintended radiation exposure.

  • Procedure for Ensuring that all Operators understand the Principles of Dose Reduction.

  • Procedure for the Provision of CT Imaging Protocol and Standard Exposure Factors.

ROLES AND RESPONSIBILITIES: Key roles and responsibilities are defined :

The Responsible Person (Licence Holder): the person who has the overall management responsibility of the radiation source or practice.

The Medical Radiation Practitioner: the person responsible for the justification and optimisation of the medical procedure involving the exposure of the patient to ionizing radiation.

The Operator: the person who exposes the patient to ionizing radiation.


PURPOSE: To ensure the correct identification of patients prior to exposure.

SCOPE: All CT examinations.

RESPONSIBILITIES: The operator initiating the exposure is responsible for ensuring the final check of patient identity has been made before proceeding. The operator checking patient identity will adhere to this procedure.

PROCEDURE: · The operator must undertake a positive patient identification (PPI) check and therefore they must ask the patient to state their name, address and date of birth. These details must be checked against the request form and if there are any discrepancies these must be investigated before undertaking the examination·

A history of any previous relevant X-ray investigations should, whenever possible, be taken from the patient prior to carrying out the new procedure to correlate the clinical detail provided on the radiology request form to that patient


PURPOSE: To prevent unnecessary irradiation of a foetus from a medical exposure by ensuring enquiries with regard to pregnancy are made in an appropriate and consistent manner.

SCOPE: All women of childbearing age who are to undergo CT examinations.

RESPONSIBILITY: The operator initiating the exposure is responsible for ensuring the final check of pregnancy has been made before proceeding. The operator checking pregnancy will adhere to this procedure

PROCEDURE: · The operator will require the outpatients to complete and sign the Pregnancy Questionnaire that will include questions on pregnancy and LMP .

For inpatients, the requesting doctor will complete a pregnancy information section as part of the CT Contrast Consent Form .

If the patient states that she is NOT pregnant following choosing one of the reasons in the table below then proceed with the exposure.

The patient should sign the Pregnancy Questionnaire

If the patient states that she IS pregnant: - Consult with the Radiation Medical Practitioner to check if the procedure may be safely deferred. The Radiation Medical Practitioner may contact the referrer directly or delegate the task to the operator.

  • If the procedure cannot be deferred justification can only be approved by the Radiation Medical Practitioner.

  • If the outcome of the decision is that the procedure is justified and must proceed due to its nature, then Radiation in Pregnancy Consent Formshould be administered by the Radiation Medical Practitioner.

  • Risks vs benefits should be concisely explained to the pregnant patient.

If the patient states that she CANNOT EXCLUDE PREGNANCY: Review her given date of LMP.

  • If the LMP date is within 10 days of the proposed examination date, proceed with the examination.

  • If the LMP date is over 10 days consult with the Radiation Medical Practitioner to check if the procedure may be safely deferred.

  • If the procedure cannot be deferred a pregnancy test must be arranged.

  • If the pregnancy test is negative proceed with the exposure.

If pregnancy test is positive the examination must not proceed until justification is provided by the Radiation Medical Practitioner.

For patients unable to communicate through illness, physical or mental disability or language barrier, all questions relating to pregnancy will be addressed to an escorting relative, carer or interpreter.


PURPOSE: Every medical exposure to be justified and authorised in advance. This procedure states how that justification takes place and how the operators conducting a medical exposure are made aware of the fact that justification has occurred.

SCOPE: All CT examinations.

RESPONSIBILITY: It is the responsibility of the Radiation Medical Practitioner to authorise each exposure (generically or individually) only if it is justified. It is the responsibility of the operator to effect a medical exposure only once authorisation has been obtained.


Radiation Medical Practitioners are entitled provide generic justification protocols or individual justification for CT examinations.

When justifying a medical exposure, consideration should be given to the following points: -

  • The objectives of the exposure.

  • The direct health benefit to the individual.

  • The individual detriment the exposure may cause.

  • The benefits and risks of alternative techniques which may meet the objectives with less or no detriment.

The following matters will demand special attention: -

  • Exposures on medico-legal grounds.

  • Exposures with no direct health benefit to the individual being exposed.

  • Exposure of females who are, or may be pregnant.

  • Urgent / out of hour’s exposures.

  • Children.

If sufficient clinical information is not made available by the referrer the Radiology Request Form will be returned in the cases of non-urgent referrals.

In the case of urgent referrals the Radiation Medical Practitioner will arrange for the referrer to be contacted to obtain the relevant information.

The examination must not proceed until the operator has either determined that the examination is generically justified as per the specific protocol OR - Had the examination justified individually and set a specific protocol by the Radiation Medical Practitioner with documented

All CT scans on either paediatric or pregnant patients MUST be justified on an individual basis.Generic justifications DO NOT apply.

All CT scans that DO NOT have generic justifications must be justified on an individual basis. These examinations include: CT Angiograms (CT Pulmonary Angiogram and CT Coronary Angiogram excluded) OR scan with multiple phases.


PURPOSE: Every medical exposure to be justified and authorised in advance. This procedure states the process for review of generic justification protocols.

SCOPE: All generic justification protocols for CT.

RESPONSIBILITY: It is the responsibility of the Radiation Medical Practitioner in conjunction with the CT Team Leader to ensure that all generic justification protocols are reviewed regularly.

PROCEDURE: · The generic justification protocols should be reviewed by the Radiation Medical Practitioner every 12 months.


PURPOSE: To detail how patient dose indicators are recorded for each medical exposure.

SCOPE: Covers all CT examinations.

RESPONSIBILITY: It is the responsibility of the operator who initiates the exposure to ensure that the appropriate patient dose indicator is recorded. This information is automatically attached to the patient’s scan as an image.

PROCEDURE: · The CT scanner will automatically record the CTDIvol and Dose Length Product (DLP) for the examination in the patient’s examination record which is stored· The scan can either be adjusted to reduce the dose .


PURPOSE: To ensure that all accidental and unintended exposures to patients or participants are properly investigated and recorded. To ensure that reportable incidents are reported to the appropriate authority.

SCOPE: Covers all CT examinations.

PROCEDURE: · Any member of staff who suspects that an accidental, unnecessary or unintended exposure has occurred will, as soon as possible, record relevant information and report full details of the incident to the RSO .

The RSO will arrange for an investigation to be carried out immediately as per the Radiation Management Plan.

Patients who undergo a procedure that was not intended, as a result of mistaken identification or other procedural failure, and consequently have been exposed to an ionising radiation dose, must be considered as having received an unintended dose of radiation.

If the person reporting the incident has reason to believe it was caused by a radiation equipment fault, that person will advise other staff not to use the suspect equipment until it has been checked.

The RSO will arrange for an assessment of the equipment to be made and will not allow it to be used for medical exposures until it is demonstrated that its performance is reliable and within recommended QA standards


PURPOSE: This is to ensure Radiation Dose should be managed and minimized following As Low As Reasonably Achievable (ALARA) principle.

SCOPE: All staff using the CT scanner should follow to procedure to reduced radiation exposure.


  • Departmental staff meetings, during which radiation protection information is disseminated, are held regularly and recorded.

  • The identity of the patient is checked prior to any radiation exposure.

  • All equipment is subject to regular preventative maintenance and independent radiation safety and performance assessment.

  • CT equipment faults are logged and reported to the CT Team Leader and the RSO.

  • All staff receive appropriate in-house training on the operation of equipment.

  • All untoward incidents are reported to the RSO

  • All radiation incidents are reported and investigated.

  • The cause of radiation incidents are reviewed and appropriate action taken to minimise the risk of recurrence.

  • Care is taken at all times whilst examining patients to select the most appropriate examination settings and operate it in accordance with manufacturer’s instructions .


PURPOSE: To identify the procedure for the provision of imaging protocols (standard image sequences) and the setting of standard exposure factors.

SCOPE: All CT examinations.

PROCEDURE: · Standard imaging protocols are agreed by the Radiation Medical Practitioner and documented by the CT Team Leader.

No alterations can be made to these protocols without consent of the Radiation Medical Practitioner.

Standard exposure factors for each type of CT examination are stored within the scanner’s anatomical programme lists on the CT scanner.

Any adjustment to the programmed exposure factors must be authorised by the CT Team Leader.

Ultrasound Study of Abdomen -standard operating procedure for scanning

Investigation slip/Referral form

·         An adequately filled referral form should include the following –

·         Patient name, age, sex

·         Referring clinician’s name

·         Brief clinical history/ provisional clinical diagnosis/indication for examination requested

·         Result of any relevant clinical exam finding/ lab report

Informed Consent & patient confidentiality

Ensure informed signed consent to be taken prior to the procedure.

In case of antenatal scan for any purpose ensure adequate filled PC-PNDT registration form (Form B) and follow the PC-PNDT protocol at all times.

Patient confidentiality as well as privacy is a must and needs to be respected at all times.

Patient preparation

  • The patient should preferably be fasting for 4-6 hours for hepatobiliary/ upper GIT ultrasound.
  • The patient should preferably have full urinary bladder for examination of KUB -Pelvic scans(in dwelling urinary bladder catheter to be blocked in advance to ensure adequately fill bladder at scan time).
  • Preferably adequate medical management for acute painful conditions prior to ultrasound to be done and patient should have stable vitals.
  • Ensure privacy of the patient.
  • Exposed part- lower chest- pubic symphysis(preferably all bandages/ stoma bags to be removed prior to exam).
  • In case of a female patient , ensure presence of another female attendant/ nursing staff /sonographer during examination .


Machine and probe preparation

  • Ensure scanner is capable of measurement in millimetres (mm).
  • Set to the scanner to the abdominal/gynaecological preset as per need.
  • Use a curvilinear probe (3-5 MHz) for general assessment & linear high freq. transducer (7-12MHz) for focussed / bowel assessment.
    • Prepare the probe:
      • Clean& disinfect probe surface
      • Put gel into probe cover, excluding air
      • Put gel onto tip of probe.
    • Do not use transvaginal probe (intra-cavitary) without clinical indication/request and prior informed written consent of the patient .

Ultrasonography assessment

  • The patient should be in the supine position and lateral decubitus can be done when required during the exam by sonographer .
  • Identify the structure of interest and follow systematic approach from one abdominal region to otherscanning in axial and longitudinal scans .
  • Ensure image sizing is appropriate for screen, between 5 cm and 7 cm depth.
  • Focal zone positioned at region of interest; multiple focal zones if possible to give good definition at various levels.

Pre void &Post-void residual estimation

  • Sometimes estimation of pre and post void urine is warranted , for which ensure immediate post void volume to be taken (do not prolong the duration post void for estimation)
  • Identify entire bladder in sagittal plane, measure longest anteroposterior dimension and then cranio–caudal dimension perpendicular to this .
  • Rotate probe through 90° and measure axial dimension .
  • use the following to standardise calculations: cranio–caudal (H) × anterior–posterior (D) × transverse diameter (W) × 0.5233 (prolate ellipsoid) = PVR volume.

Eligibility: proceeding to bladder wall thickness (BWT) measurement

  • If PVR ≤ 30 ml, proceed with BWT measurement.
  • If PVR > 30 ml, ask patient to revoid.
  • If, after re-void, PVR is > 30 ml but < 100 ml measure the BWT.
  • If PVR is > 100 ml, exclude patient from bladder ultrasonography.

Providing electronic images

Relevant electronic images for each patient, labelled and measured clearly with print outs provided for patient storage and clinician reference.

Provide printed / written ultrasound report to the patient as soon as possible after completion of the procedure.