CAMRT MRI Exam cheat sheet

MRI screening is a two-stage process: a written questionnaire completed and signed by the patient, followed by a verbal interview by a technologist; ambiguity is resolved by the radiologist before entry to the controlled area.

The four static magnetic field zones: Zone I (public, unrestricted), Zone II (transition, supervised screening), Zone III (restricted, access controlled by staff with MR safety training), Zone IV (the magnet room itself, highest risk, physically restricted).

Absolute contraindications to MR include intraocular or intracranial ferromagnetic foreign bodies, ferromagnetic aneurysm clips, and any implanted device documented as MR-unsafe; a pacemaker is conditional or unsafe depending on the specific system and must be verified against manufacturer labeling.

MR-Conditional labeling means the device is safe under specified conditions (field strength, maximum spatial gradient, SAR limits, coil type); it does not mean safe under all scanning conditions.

Pregnancy: no confirmed adverse effect of MRI fields on the fetus, but the technologist follows institutional policy; gadolinium-based contrast is generally avoided in pregnancy unless clearly indicated, and breastfeeding interruption guidance follows the specific agent's labeling.

Metallic projectile risk scales with the mass, shape, and ferromagnetic content of the object and with proximity to the bore; the field extends well beyond the bore opening, so the 5-gauss line is the practical boundary for ferromagnetic hazards.

Quenching: an intentional or accidental loss of superconductivity causes rapid helium boil-off and oxygen displacement; response is to evacuate the magnet room, keep the door open, avoid entering, and follow the facility's emergency procedure.

Patient heating is monitored through SAR (specific absorption rate, W/kg); whole-body average is limited to 4 W/kg over 6 minutes in first-level controlled mode, and higher levels require active physiological monitoring.

TR controls the amount of longitudinal magnetization recovery and therefore T1 weighting; TE controls the amount of transverse decay and therefore T2 weighting. Short TR + short TE = T1-weighted; long TR + long TE = T2-weighted; long TR + short TE = proton density.

Spin echo refocuses static field inhomogeneity with a 180-degree pulse, so SE sequences are less susceptible to susceptibility artifact than gradient echo; gradient echo uses a flip angle and short TE, giving fast acquisition and T2* sensitivity.

FLAIR suppresses CSF signal by applying an inversion pulse with TI chosen so CSF longitudinal magnetization is near zero at the excitation; STIR suppresses fat by the same inversion mechanism with a shorter TI.

For fat suppression, chemical (spectral) saturation is fast and works well on high-field systems with good homogeneity; STIR is more robust to field inhomogeneity and is preferred when homogeneity is poor or at low field.

FOV, matrix, and slice thickness determine voxel volume; reducing FOV or increasing matrix reduces voxel size and signal-to-noise ratio, so SNR must be traded against spatial resolution.

Parallel imaging reduces acquisition time and echo train length by undersampling phase-encode lines, at the cost of SNR and possible aliasing; the acceleration factor and reference lines must be set consistently.

Diffusion-weighted imaging uses strong bipolar gradients; the b-value determines diffusion weighting, and the ADC map removes T2 shine-through so restricted diffusion can be distinguished from T2 prolongation.

Slice order, gap, and number of slices must be planned so that the prescribed volume covers the anatomy without gap artifact; interleaved acquisition reduces cross-talk between adjacent slices.

Larmor frequency: f = gamma x B0, where gamma for hydrogen is 42.58 MHz/T; at 1.5 T the proton resonance is about 63.9 MHz and at 3 T about 127.7 MHz.

Superconducting magnets use niobium-titanium coils cooled by liquid helium to about 4 K; the fringe field is described by gauss lines (5 gauss, 1 gauss) that define the safety perimeter and siting constraints.

The gradient system produces spatially varying fields for slice selection, phase encoding, and frequency encoding; gradient slew rate (T/m/s) and maximum amplitude determine the achievable echo spacing and acoustic noise.

RF coils: transmit coils create the B1 field; receive coils detect signal. Surface coils give high SNR near the coil, and phased-array coils combine multiple elements with parallel acquisition capability.

Shielding: passive shielding uses steel in the walls; active shielding uses a secondary superconducting coil to contain the fringe field. The RF shield (copper) prevents external RF interference from entering the room.

Image contrast depends on proton density, T1, and T2; tissues with short T1 (fat) are bright on T1-weighted images, and tissues with long T2 (fluid) are bright on T2-weighted images.

Gradient echo sequences use a flip angle less than 90 degrees; the Ernst angle gives maximum signal for a given TR and T1, and steady-state sequences depend on the balance of spoiling and refocusing.

Signal-to-noise ratio increases with voxel volume, number of excitations (NEX/NSA), and coil proximity; SNR improves by the square root of the number of acquisitions, so quadrupling NEX doubles SNR.

Chemical shift artifact arises from the frequency difference between fat and water protons (about 3.5 ppm, roughly 220 Hz at 1.5 T); it appears as a bright/dark rim at fat-water interfaces along the frequency-encode direction.

Aliasing (wrap-around) occurs when the object extends beyond the FOV in the phase-encode direction; remedies include increasing FOV, phase oversampling, or saturation bands.

Motion artifact appears as ghosting along the phase-encode direction; remedies include respiratory gating, swapping phase and frequency directions, averaging, and faster sequences.

Susceptibility artifact is caused by local field distortion near metal or air-tissue interfaces; it is worse with gradient echo, longer TE, and higher field strength, and can be reduced with spin echo, shorter TE, and smaller voxels.

Zipper artifact is a bright line across the image caused by RF interference entering the room; it indicates a breach in the RF shield or an external RF source.

Quality control includes daily (or per-use) checks of the RF system, weekly or monthly phantom SNR and uniformity measurements, and annual preventive maintenance; acceptance testing establishes baseline values for comparison.

Geometric distortion is assessed with a phantom of known dimensions; distortion increases with gradient nonlinearity away from isocenter and with susceptibility effects.

Gadolinium-based contrast agents are paramagnetic and shorten T1 and T2; they are used at typical doses of 0.1 mmol/kg for extracellular agents, and the effect is greatest on T1-weighted images at low concentration.

Gadolinium agents are classified as linear or macrocyclic and by ionicity; macrocyclic agents are more stable and release less free gadolinium, which matters for patients with renal impairment.

Nephrogenic systemic fibrosis risk is associated with impaired renal function (eGFR thresholds vary by agent and policy) and with linear agents; screening for renal function and prior reactions precedes administration.

Adverse reactions range from mild (nausea, flushing, hives) to severe anaphylactoid reactions; emergency equipment and protocols must be available wherever contrast is administered.

Extravasation of gadolinium is managed by stopping the injection, elevating the limb, and applying cold compresses; large-volume extravasation may require surgical consultation.

Iodinated contrast is not used in MRI, but patients may confuse prior contrast studies; the technologist verifies the agent, concentration, and dose against the order.

Sedation and analgesia for claustrophobic or pediatric patients require monitoring of vital signs and airway; the technologist's scope is defined by institutional policy and provincial regulation.

Standard brain planes: axial slices are prescribed parallel to the anterior commissure-posterior commissure line or the orbital-meatal line; sagittal and coronal planes are prescribed perpendicular to the axial plane.

Spine: sagittal T1 and T2 and axial T2 are standard; the conus medullaris typically terminates at L1-L2 in adults, and the cauda equina lies below that level.

Knee: sagittal and coronal planes are prescribed perpendicular and parallel to the posterior condylar line; the menisci appear as low-signal triangles on all sequences.

Liver: the right lobe is separated from the left by the main lobar fissure and the middle hepatic vein; segmental anatomy follows the Couinaud system based on portal and hepatic veins.

Fluid-sensitive sequences (T2, STIR, PDFS) show edema and joint effusion as high signal; T1-weighted images show fat as high signal and fluid as low signal.

Common pathology appearances: infarction shows restricted diffusion in acute stroke; demyelination shows T2 hyperintensity; tumors often show enhancement after gadolinium; hemorrhage signal varies with the age of the blood products.

Anatomical coverage must include the region of interest plus margins for localization; off-axis prescriptions follow the structure being imaged, not a fixed body plane.

Informed consent for contrast or sedation is obtained by the responsible physician or delegate per institutional policy; the technologist confirms that consent is documented before administration.

Patient identification uses two identifiers (name and date of birth or health number) checked against the requisition before every study.

Claustrophobia management includes prone or feet-first positioning, a mirror or prism, earplugs or music, a companion in the room when policy allows, and a panic button; sedation is a last resort requiring monitoring.

Communication with pediatric patients uses age-appropriate explanation, a parent present when permitted, and distraction techniques; immobilization must never compromise the airway.

Handoff and documentation include the screening form, contrast dose, adverse events, and any deviation from protocol; these are recorded in the patient record and reported to the radiologist.

Interprofessional collaboration: the technologist consults the radiologist for protocol changes when the clinical question is unclear, and communicates with nursing and anesthesia for monitored patients.

MRI uses no ionizing radiation; the safety concerns are the static field, time-varying gradient fields, and RF fields, each with distinct biological effects.

Time-varying gradient fields can induce peripheral nerve stimulation; the threshold is described by dB/dt and is monitored by the system's stimulation limits.

RF fields deposit energy as heat; SAR limits depend on the operating mode (normal, first-level controlled, second-level controlled) and on patient factors such as body habitus and thermoregulation.

Standard precautions apply to all patients: hand hygiene, gloves for contact with blood or body fluids, and disinfection of coils and surfaces between patients.

Emergency response: the code team must be summoned, the patient removed from the magnet room before resuscitation when the team requires ferromagnetic equipment, and the magnet's field must be considered in any emergency equipment brought near the door.

Fire in the magnet room: use only MR-safe extinguishers and evacuate; never bring ferromagnetic firefighting equipment into Zone IV.

Cryogen safety: if helium is venting, evacuate and ventilate the area; asphyxiation risk is real because helium displaces oxygen, and entry requires self-contained breathing apparatus.

Scope of practice is defined by provincial regulation and institutional policy; the technologist performs only procedures for which they are trained and authorized.

Privacy and confidentiality: patient information is shared only on a need-to-know basis, and images and reports are handled per privacy legislation.

Informed consent, refusal, and capacity: a competent patient may refuse a study; the technologist documents the refusal and informs the radiologist rather than proceeding.

Incident reporting: adverse events, near misses, and equipment failures are reported through the facility's safety system so that root causes can be addressed.

Quality improvement uses measurable indicators such as repeat rate, protocol adherence, and turnaround time; PDSA cycles test changes on a small scale before wider adoption.

Continuing education and certification maintenance are professional obligations; the technologist tracks credits and renews credentials before expiry.

K-space: the center of k-space carries contrast information and the periphery carries spatial detail; phase-encode lines fill k-space, and the order of filling affects contrast and motion sensitivity.

Fourier transform reconstruction converts k-space data into the image; zero-filling interpolation increases matrix size without adding true resolution.

Fast spin echo (turbo spin echo) uses multiple 180-degree refocusing pulses per TR to fill multiple k-space lines; echo train length trades scan time against blurring and SAR.

Echo-planar imaging acquires all lines after a single excitation; it is fast and is used for diffusion and functional imaging but is sensitive to susceptibility and geometric distortion.

Fat suppression options: spectral saturation, STIR, Dixon (water-fat separation), and inversion recovery; Dixon provides both water and fat images from one acquisition.

Post-processing includes MPR (multiplanar reconstruction), MIP (maximum intensity projection), subtraction, and 3D volume rendering; these are performed on the scanner or a workstation and must preserve diagnostic quality.

Image archiving follows DICOM standards; the technologist verifies that images are sent to PACS and that the study is complete before the patient leaves.

Vital signs monitoring during sedation or contrast administration includes blood pressure, heart rate, respiratory rate, and oxygen saturation; baseline values are recorded before the study.

Renal function assessment before gadolinium includes eGFR or creatinine; the threshold and required action depend on the agent and institutional policy.

Allergy history is obtained before contrast; prior reactions, asthma, and atopy increase risk and may require premedication per the radiologist's order.

Implanted device verification includes the device model, manufacturer, and MR safety status; the technologist documents the source of the information.

Patient comfort and positioning: padding at pressure points, ear protection, and a call device within reach reduce motion and improve image quality.

Post-procedure assessment after contrast includes checking the injection site for extravasation and observing the patient for delayed reactions before discharge.

Daily QA includes checking the magnet's cryogen level, the RF room door and shield integrity, and the function of the emergency stop and quench buttons.

Phantom QA measures SNR, uniformity, geometric accuracy, slice thickness, and ghosting; results are compared with baseline values established at acceptance testing.

Coil QA includes visual inspection for cracks, cable damage, and connector wear; a damaged coil can cause signal dropout or noise.

Gradient and RF calibration are performed by service engineers; the technologist reports abnormal acoustic noise, image artifacts, or system errors.

Preventive maintenance schedules follow the manufacturer's recommendations and may include helium refill, cold head service, and filter replacement.

Documentation of QA results supports accreditation and helps detect drift before it affects clinical images.

Anaphylactoid reaction: stop the injection, call for help, maintain the airway, give oxygen, and administer epinephrine per protocol; monitor vital signs until stable.

Extravasation: stop injection, remove the cannula per policy, elevate the limb, apply cold compress, and document the volume and site; follow up with the patient.

Vasovagal reaction: lay the patient flat, elevate the legs, monitor vital signs, and observe until recovery; distinguish from anaphylaxis by the absence of urticaria and bronchospasm.

Quench emergency: evacuate, do not re-enter, ventilate, and call the service engineer; the magnet may remain at field for a period after a quench.

Fire or code in Zone IV: remove the patient from the magnet room before bringing ferromagnetic equipment, and follow the facility's emergency plan.

Documentation of any adverse event includes the time, agent, dose, symptoms, treatment, and outcome, and is reported through the facility's incident system.

The requisition must match the patient and the ordered study; discrepancies are resolved with the ordering provider before scanning.

DICOM metadata includes patient identifiers, study description, sequence parameters, and contrast information; accurate entry supports interpretation and billing.

PACS workflow: images are sent to PACS, verified for completeness, and linked to the correct accession number; incorrect linking requires a merge by the PACS administrator.

Voice recognition and report dictation are performed by the radiologist; the technologist ensures that images and prior studies are available for comparison.

Data security: workstations are locked when unattended, and patient information is not stored on personal devices.

Downtime procedures include paper requisitions, local storage of images, and a plan for reconciliation when systems are restored.

Closed-loop communication: the sender states the message, the receiver repeats it back, and the sender confirms; this reduces errors in high-stress situations.

SBAR (Situation, Background, Assessment, Recommendation) structures handoff and escalation to the radiologist or nurse.

Conflict resolution uses respectful, direct communication and escalation through the chain of command when patient safety is at risk.

Teaching and mentoring: experienced technologists supervise students within their scope and document competency achievement.

Interprofessional rounds and huddles share information about complex cases, equipment issues, and scheduling changes.

Cultural safety and humility: communication adapts to the patient's language, beliefs, and preferences, and interpreters are used when needed.

Levels of evidence: systematic reviews and randomized trials rank above cohort studies, case reports, and expert opinion; the technologist appraises evidence when adopting a new protocol.

Critical appraisal includes checking the study design, sample size, bias, and whether the results apply to the local patient population.

Continuing education credits are required to maintain certification; the technologist selects activities relevant to current practice.

Protocol updates should be based on published evidence and validated locally before broad implementation.

Participation in quality improvement and research projects builds skills in data collection, analysis, and reporting.

Reflective practice: reviewing incidents and near misses informs changes in individual and team practice.

A just culture distinguishes human error from at-risk behavior and reckless behavior; reporting is encouraged without fear of blame for honest mistakes.

Risk assessment before scanning includes the patient's implants, foreign bodies, pregnancy status, and ability to cooperate.

Near-miss reporting identifies hazards before harm occurs; trends are reviewed by the safety committee.

Checklists and time-outs before contrast administration or sedation reduce omissions and improve team communication.

Environmental safety includes checking for loose ferromagnetic objects, securing oxygen cylinders, and controlling access to Zone IV.

Emergency drills test the response to quench, fire, and medical emergencies and identify gaps in equipment or training.

Explanation before scanning includes the duration, noise, need to remain still, and the communication system; this reduces anxiety and motion.

Preparation instructions include removing metal objects, changing into a gown, and emptying pockets; lockers are provided for personal items.

Hearing protection is required for all patients because acoustic noise can exceed safe levels; earplugs and headphones are offered.

Positioning and comfort: the patient is centered in the coil, supported with padding, and given a call device.

Breath-hold instructions are practiced before the sequence so the patient can comply during acquisition.

Post-scan instructions include when results will be available and what to do if a delayed reaction occurs.

Hand hygiene is performed before and after patient contact and after removing gloves.

Personal protective equipment is selected based on the anticipated exposure; gloves are not a substitute for hand hygiene.

Coils, tables, and surfaces are disinfected between patients with facility-approved agents compatible with the equipment.

Patients with transmissible infections are scheduled and managed per institutional policy to reduce exposure.

Needlestick and sharps injuries are reported immediately and followed by post-exposure prophylaxis evaluation.

Waste is segregated according to facility policy, and contrast vials are handled to prevent contamination.

Confidentiality applies to images, reports, and conversations; discussion of cases occurs only in appropriate settings.

Informed consent requires capacity, disclosure of risks and benefits, and voluntariness; the technologist confirms that consent is documented.

Conflicts of interest are disclosed, and gifts or favors from vendors are governed by policy.

Professional boundaries: relationships with patients remain professional, and social media use must not disclose patient information.

Advocacy: the technologist speaks up when a patient's safety or dignity is at risk and escalates through the chain of command.

Documentation is accurate, timely, and objective; alterations are made per policy with an audit trail.

Practice is governed by provincial regulatory bodies, facility policy, and applicable privacy and health legislation.

Scope of practice defines the acts the technologist may perform; delegated medical acts require appropriate authorization and supervision.

Consent law: the patient or substitute decision-maker provides consent, and emergency exceptions apply when the patient cannot consent and treatment is necessary.

Mandatory reporting obligations may include child or elder abuse, communicable diseases, and unsafe practice; the technologist follows the applicable statute.

Documentation is a legal record; errors are corrected according to policy rather than erased.

Privacy legislation governs collection, use, and disclosure of personal health information and requires safeguards against unauthorized access.

Patient safety indicators include falls, contrast reactions, extravasation, wrong-site imaging, and retained foreign bodies; each is tracked and reviewed.

Root cause analysis examines system factors rather than individual blame after a serious event.

PDSA (Plan-Do-Study-Act) cycles test small changes and measure their effect before scaling.

Benchmarking compares local performance with published standards or peer institutions to identify gaps.

Patient feedback and complaints are reviewed and used to improve service delivery.

Accreditation standards require documented policies, competency assessment, and equipment maintenance records.

Static field effects include vertigo, nausea, and metallic taste at high field; these are transient and are managed by slow patient movement into the bore.

The static field exerts force and torque on ferromagnetic objects; the attractive force increases steeply as the object approaches the magnet.

Time-varying gradient fields can induce peripheral nerve stimulation and cardiac stimulation at high dB/dt; the system enforces limits.

RF energy deposition is measured as SAR; whole-body SAR limits are 4 W/kg (normal mode, 6 min) and higher in controlled modes with monitoring.

Implanted devices may heat or malfunction in the RF field; the device's MR safety labeling defines the conditions for safe scanning.

Pregnancy and pediatric patients require additional consideration of SAR and thermoregulation because of their smaller body size and higher water content.

Gadolinium dose is calculated by weight (typically 0.1 mmol/kg); the dose and agent are documented before injection.

Injection technique: confirm patency, use an appropriate cannula, and check for blood return before injecting; power injectors require pressure-rated tubing.

Contraindications include prior severe reaction and severe renal impairment for some agents; the radiologist determines whether to proceed.

Pregnancy and lactation: gadolinium crosses the placenta, and breastfeeding guidance follows the agent's labeling.

Adverse reaction management is the same as for any anaphylactoid reaction: stop, call for help, airway, oxygen, epinephrine per protocol.

Post-injection observation includes checking the site and asking about symptoms before the patient leaves.

The region of interest is centered in the coil and at isocenter to maximize signal and minimize distortion.

Coil selection matches the anatomy: head coil for brain, phased-array body coil for abdomen, surface coils for small parts.

Patient orientation (supine, prone, decubitus) is chosen to answer the clinical question and to accommodate the patient's condition.

Padding and straps reduce motion and pressure injury; the patient is never left unattended in the magnet room.

Landmarking is set at the isocenter of the coil so that the prescribed slices cover the anatomy.

Off-center positioning increases gradient nonlinearity and can distort images; correction requires re-centering the patient.

TR and TE are the primary contrast parameters; flip angle controls contrast in gradient echo sequences.

NEX/NSA increases SNR by the square root of the number of acquisitions and increases scan time proportionally.

Matrix size and FOV determine voxel size; increasing matrix at fixed FOV reduces voxel size and SNR.

Bandwidth affects SNR and chemical shift; lower bandwidth increases SNR but worsens chemical shift artifact.

Echo train length in fast spin echo reduces scan time but increases blurring and SAR.

Parallel imaging acceleration reduces scan time and echo train length at the cost of SNR and possible artifact.

Phase-encode direction artifacts (ghosting, aliasing) are corrected by swapping phase and frequency directions, oversampling, or saturation bands.

Chemical shift is corrected by increasing bandwidth, using fat suppression, or choosing a sequence with less shift.

Susceptibility artifact is reduced with spin echo, shorter TE, smaller voxels, and lower field strength.

Zipper artifact indicates RF interference; check the door seal, filters, and external sources.

Motion artifact is reduced with gating, breath-hold, averaging, and faster sequences.

Geometric distortion from gradient nonlinearity is reduced by centering the patient and using distortion correction.

Fourier transform reconstruction converts k-space data to image space; partial Fourier and zero-filling affect resolution and SNR.

Parallel imaging reconstruction uses coil sensitivity information to unfold aliased data.

Multiplanar reconstruction reformats 3D data into any plane; resolution depends on the acquired slice thickness.

Maximum intensity projection highlights bright structures such as vessels in MR angiography.

Subtraction imaging highlights enhancement by subtracting pre-contrast from post-contrast images.

Post-processed images must be labeled and archived with the source data.

Explain the procedure in plain language, including noise, duration, and the need to stay still.

Use a call device and confirm the patient knows how to use it before starting.

Provide ear protection and explain its purpose.

Practice breath-holds before the sequence so the patient can comply.

Address anxiety with positioning options, music, and a companion when policy permits.

Give post-scan instructions and explain when results will be available.

SBAR structures communication with the radiologist, nurse, or anesthesia team.

Closed-loop communication confirms that critical messages are received and understood.

Escalate to the radiologist when the clinical question or protocol is unclear.

Coordinate with nursing for monitored or sedated patients.

Share equipment issues and scheduling changes in team huddles.

Respect role boundaries and consult the appropriate professional when a task is outside scope.

Record the screening form, contrast agent and dose, adverse events, and protocol deviations.

Document the time of contrast administration and the patient's response.

Record QA results and equipment issues in the appropriate log.

Correct errors per policy with an audit trail; do not erase entries.

Verify that images are archived to PACS and linked to the correct accession.

Maintain confidentiality when storing or transmitting records.

Maintain certification through continuing education credits and renewal before expiry.

Track credits and keep records of completed activities.

Select education relevant to current practice and emerging technology.

Participate in quality improvement and research to build skills.

Reflect on incidents and near misses to improve practice.

Mentor students and colleagues within your scope of practice.