Developed and Designed by Kelly Emrick, DHSc, PhD, MBA

MRI Protocols Study Guide
🎓 Student Study Guide · 1.5T / 3T Systems

MRI Protocols Study Guide

Brain · Spine · MSK · Abdomen · Liver · Angiography · Pelvis

Common MRI Protocols at a Glance
Click any exam card below to jump to its detailed study section
🧠
Brain MRI
T1 · T2 · FLAIR · DWI · SWI
🦴
Spine MRI
T1 · T2 · STIR
🦵
Knee MRI (MSK)
PD · PD Fat Sat · T2
🫀
Abdominal MRI
T1 · T2 · Fat Sat · DWI
🫁
Liver MRI
T1 In/Out Phase · DWI
🩸
MR Angiography
TOF · Phase Contrast
⚕️
Pelvis MRI
T1 · T2 · STIR
📊 Quick Reference Table
MRI Study Key Sequences Imaging Plane(s) Clinical Purpose Key Note
Brain MRI T1, T2, FLAIR, DWI, SWI Axial, Sagittal, Coronal Stroke, tumors, MS, seizure DWI for acute stroke; FLAIR for periventricular lesions
Spine MRI T1, T2, STIR Sagittal + Axial Disc herniation, cord compression, fractures STIR lights up edema and infection
Knee MRI (MSK) PD, PD Fat Sat, T2 Sagittal + Axial + Coronal Ligament/meniscus tears, cartilage PD Fat Sat = gold standard for cartilage
Abdominal MRI T1, T2, Fat Sat, DWI Axial, Coronal Organ characterization, masses, MRCP Breath-hold every sequence — critical!
Liver MRI T1 In/Out Phase, DWI Axial HCC, metastases, fatty liver, hemangioma Dynamic contrast timing is everything
MR Angiography TOF, Phase Contrast Axial / 3D Vessel stenosis, aneurysm, vascular malformation TOF = no contrast; CE-MRA = contrast needed
Pelvis MRI T1, T2, STIR Multiplanar (all 3) Prostate/cervical/rectal cancer staging, uterine pathology High-resolution T2 is the workhorse sequence
🧠 Quick Memory Tips
  • T1 = Anatomy — Fat is bright (white). Great for anatomy, post-contrast enhancement, blood products.
  • T2 = Pathology — Fluid is bright (white). Most pathology = fluid → shows bright. “Water = bright, bad = bright.”
  • FLAIR = T2 with CSF suppressed — Turns off the bright CSF so periventricular lesions pop. “FLAIR = Fluid Lesion Amplification + Removal.”
  • DWI = Motion of water molecules — Restricted diffusion (acute stroke, abscess, dense tumor) appears bright. “DWI = Detects Where It’s stuck.”
  • STIR = Fat suppressed T2 — Turns off fat, fluid remains bright. Perfect for edema and bone marrow lesions.
  • SWI = Blood & calcium detector — Microbleeds, iron, venous blood appear dark. “SWI = Sees What Is invisible.”
🧠

Brain MRI

Most commonly ordered MRI — broad diagnostic utility
T1 T2 FLAIR DWI SWI Axial Sagittal Coronal
🩺 Why It’s Ordered (Clinical Indications)
  • Stroke: DWI detects ischemic stroke within minutes — CT misses early strokes
  • Brain tumors: Primary (glioma, meningioma) and metastatic disease
  • Multiple Sclerosis: White matter plaques on FLAIR
  • Seizure workup: Identify structural causes (mesial temporal sclerosis)
  • Dementia / memory loss: Atrophy patterns, white matter disease
  • Headache evaluation: Rule out tumor, hemorrhage, venous thrombosis
  • Infection: Abscess, encephalitis, meningitis complications
  • Trauma: Diffuse axonal injury, contusions, subdural/epidural hematoma
🔬 Sequence-by-Sequence Breakdown
  • T1: Anatomy baseline. Shows gray/white matter, fat, subacute blood. Post-contrast: enhancement = BBB breakdown (tumor, abscess).
  • T2: Fluid = bright. Edema, CSF, most pathology lights up. Combined with T1 for full picture.
  • FLAIR: T2 with CSF suppressed. Periventricular MS plaques, subarachnoid hemorrhage, leptomeningeal disease.
  • DWI: Detects restricted diffusion. Acute ischemic stroke (bright DWI + dark ADC). Also: abscess, lymphoma, CJD.
  • SWI (Susceptibility Weighted): Detects blood, iron, calcium. Microbleeds, cavernous malformations, venous mapping.
🛠️ How to Perform It — Step by Step
Screen & Position: Screen for all metal/implants. Supine, head-first. Use dedicated head coil. Align laser to nasion. Foam earplugs for noise.
Immobilization: Use foam padding beside the head to minimize motion. Motion is the #1 enemy of brain MRI quality.
Scout/Localizer: 3-plane scout to identify anatomy. Use AC-PC line (anterior/posterior commissure) to align axial images consistently.
Run Sequences in Order: Typical order: Axial DWI → Axial FLAIR → Axial T2 → Axial T1 → Sagittal T1 → Coronal T2. DWI first = diagnose stroke immediately.
Contrast (if ordered): Gadolinium 0.1 mmol/kg IV. Run post-contrast T1 in all three planes. Confirms BBB breakdown (enhancement = pathology).
SWI (if ordered): Add as a separate axial series. Critical for trauma, hemorrhage, or cavernoma workup.
Quality Check: Review images before releasing patient. Check for motion artifacts, correct slice coverage (vertex to foramen magnum), adequate SNR.
📌 Mnemonic — Brain Sequences
“DWI First, FLAIR Finds, T2 Tells, T1 Takes contrast”
Run DWI first → always. FLAIR finds white matter disease. T2 shows all fluid. T1 post-contrast reveals enhancement.
⚠️ Technologist Tips Even subtle patient motion ruins DWI — coach the patient to stay still and breathe normally. For pediatric or claustrophobic patients, coordinate sedation with the ordering team in advance.
💡 Clinical Pearl If DWI shows a bright lesion and ADC is dark (restricted) = acute ischemic stroke. If ADC is bright (facilitated diffusion) = chronic or not a stroke. Always correlate both maps!
🦴

Spine MRI

Cervical · Thoracic · Lumbar — each region has its own workflow
T1 T2 STIR Sagittal Axial
🩺 Why It’s Ordered
  • Disc herniation / bulge: Most common indication. T2 sagittal shows disc anatomy and cord compression clearly.
  • Spinal stenosis: Narrowing of canal or neural foramina
  • Cord compression / myelopathy: T2 signal change in cord = urgency
  • Fractures: STIR differentiates acute from chronic (edema bright in acute)
  • Infection: Discitis/osteomyelitis — STIR + gadolinium essential
  • Tumors: Intradural, extradural, and intramedullary masses
  • MS plaques in the cord: T2 sagittal + STIR
  • Post-surgical evaluation: Recurrent disc vs. scar — needs gadolinium
🔬 Sequence Details
  • Sagittal T1: Anatomy, bone marrow signal, fat vs. fluid/tumor distinction. Fracture with dark marrow = acute/edematous.
  • Sagittal T2: Workhorse sequence. CSF bright, discs bright if healthy, cord signal abnormality visible, neural foramina assessment.
  • Sagittal STIR: Suppresses fat, fluid/edema remains bright. Critical for: bone marrow edema, infection, occult fractures, acute vs. chronic compression fractures.
  • Axial T2 (or T2*): Through levels of interest. Disc/nerve root relationships, foraminal stenosis, facet joint arthropathy.
  • Post-contrast T1 (if ordered): Infection workup, tumor, post-surgical recurrent disc vs scar (scar enhances, disc does NOT).
🛠️ How to Perform — By Region
CERVICAL
  • Supine, neck in neutral. Neck/spine coil.
  • Align to C2-C7.
  • Sagittal slices thin (3mm).
  • Axial through each disc level.
  • Saturation band over throat — reduces swallowing artifact.
THORACIC
  • Supine, body or spine coil.
  • Align T1-T12. Rib count to confirm level.
  • Breathing artifact: use respiratory gating or fast sequences.
  • CSF pulsation artifact on sagittal: use cardiac gating if needed.
LUMBAR
  • Supine, knees propped (reduces lordosis for better disc visualization).
  • Spine or body coil.
  • Align L1-S1. Axial through L3-L4, L4-L5, L5-S1 at minimum.
  • Most straightforward spine exam — best to learn first.
📌 STIR Mnemonic
“STIR = Sensitive To Injury + Reaction”
STIR suppresses fat and highlights fluid/edema — think acute trauma, infection, bone marrow changes. Any “hot” process in the spine will glow on STIR.
⚠️ Key Technologist Tips Always verify the exact level of interest with the ordering clinician. A patient with leg pain from L4-L5 needs axial slices THROUGH that disc, not just sagittals. Slice angulation: axial slices must be parallel to each disc — angle each individually using the sagittal scout.
🦵

Knee MRI (MSK)

Musculoskeletal MRI — ligaments, menisci, cartilage, bone marrow
PD PD Fat Sat T2 Sagittal Coronal Axial
🩺 Why It’s Ordered
  • ACL / PCL tears: Most common sports MRI. Sagittal plane is key for ACL.
  • Meniscal tears: Medial/lateral. Sagittal + coronal for complete assessment.
  • Cartilage damage: Chondromalacia, osteoarthritis, osteochondral lesions.
  • MCL / LCL injuries: Coronal T2 or PD Fat Sat.
  • Bone marrow edema / contusion: After trauma — PD Fat Sat or STIR.
  • Baker’s cyst / joint effusion: T2 fluid bright behind the knee.
  • Tendon injuries: Patellar tendon, quadriceps tendon.
🔬 Sequence Details
  • PD (Proton Density): High SNR with good contrast between fibrocartilage and fluid. Internal meniscal structure is best seen here.
  • PD Fat Sat: PD with fat suppression. Gold standard for cartilage evaluation. Bone marrow edema shows as bright. “The everything sequence.”
  • T2: Fluid very bright. Joint effusions, cysts, soft tissue edema all pop. Good for ligament tears.
  • T1 (sometimes added): Anatomy, bone marrow fat signal, confirm bony anatomy before/after contrast in staging.
🛠️ How to Perform
Positioning: Supine, knee slightly flexed (10–15°) with external rotation (~15°). This optimally displays the ACL by aligning it in the sagittal plane.
Coil selection: Dedicated knee coil. Wrap snugly for best SNR. Immobilize to prevent motion during scan.
Scout: 3-plane localizer. Align sagittal slices along the course of the ACL (follow the femoral intercondylar notch on the coronal scout).
Sagittal PD/PD Fat Sat: Primary plane for ACL, PCL, menisci, cartilage. Thin slices (3mm, no gap). Covers entire medial-to-lateral joint.
Coronal PD Fat Sat or T2: Medial/lateral meniscal horns, collateral ligaments, tibial plateau, joint space cartilage.
Axial PD Fat Sat or T2: Patellofemoral joint, trochlear groove, patellar cartilage, retinaculum, Baker’s cyst.
Quality Check: Confirm full meniscal coverage (anterior to posterior horns), entire ACL visualized, and patellar apex to femoral condyles on axial.
📌 Knee Anatomy Tip
“ACL = Sagittal, MCL = Coronal, Patella = Axial”
Each ligament is best seen in one primary plane. Know which plane shows which structure before you scan.
💡 Clinical Pearl — Meniscal Grading Grade 1 = PD signal within meniscus, doesn’t reach surface (normal variant / early degeneration). Grade 2 = Signal reaches one surface (partial tear). Grade 3 = Signal reaches two surfaces = true tear. Radiologists use this grading system — understanding it helps you know why image quality matters.
🫀

Abdominal MRI

Challenging but powerful — breath-holding discipline is everything
T1 T2 Fat Sat DWI Axial Coronal
🩺 Why It’s Ordered
  • Liver lesion characterization: CT found a mass — MRI differentiates benign from malignant (hemangioma vs. HCC vs. met)
  • Pancreatic pathology: Ductal anatomy, masses, IPMN (MRCP sequence added)
  • Adrenal masses: In/out-phase T1 to detect fat in adenoma
  • Renal masses: Better soft tissue characterization than CT
  • MRCP: Bile duct anatomy without contrast — heavy T2 for biliary tree
  • Inflammatory bowel disease: MR Enterography (special protocol)
  • Abdominal adenopathy: DWI helps identify malignant nodes
🔬 Sequence Details
  • T1 In-Phase / Out-of-Phase: The critical sequence. Fat-containing lesions drop signal on out-of-phase images — detects adrenal adenomas, steatosis.
  • T2 ± Fat Sat: Fluid bright. Cysts, bile ducts, hemangiomas, ascites. MRCP = heavily T2 weighted (very long TE).
  • DWI: Malignant tissue restricts diffusion → bright on DWI. Very useful for detecting liver mets, lymph nodes.
  • Dynamic Gadolinium (if ordered): Arterial, portal venous, delayed phases. Essential for HCC and lesion vascularity characterization.
  • Fat Sat sequences: Eliminates competing fat signal to reveal pathology.
🛠️ How to Perform
Patient Prep: NPO 4–6 hours before (reduces bowel peristalsis artifact). Explain breath-holding thoroughly BEFORE the scan. Practice breath-holds with the patient in the room before starting.
Coil & Position: Supine, feet-first or head-first. Body phased array coil over the abdomen. Arms above the head if patient tolerates (reduces wrap/fold artifact).
Coach Breath-Holds: Use the intercom every sequence. “Take a deep breath in… breathe out halfway… hold.” Each breath-hold is ~15–20 seconds. Consistent breath-hold position is critical (always exhale to same position).
Scout → Plan All Sequences: Use coronal scout to plan axial slices from diaphragm to iliac crests. Cover the whole abdomen.
Run T1 In/Out Phase First: Most diagnostic value early. Then T2, then DWI (free-breathing OK for DWI), then dynamic contrast if ordered.
Dynamic Contrast Timing: Use automated bolus tracking or fixed timing: Arterial ~20–25 sec, Portal venous ~60–70 sec, Delayed ~3–5 min post-injection.
Quality Review: Motion artifact? Aliasing? Did you cover the kidneys and adrenals? Check all phases of contrast if dynamic protocol was run.
⚠️ The #1 Challenge — Motion Artifact Abdominal MRI has the highest artifact burden of any region. Respiratory motion blurs images. Bowel peristalsis creates ghosting. Cardiac pulsation affects left lobe of liver. Solution: Good patient coaching, consistent breath-hold position, and using fat saturation consistently across sequences.
📌 In/Out Phase Mnemonic
“India Oscar” — India (In-phase) sees fat bright. Oscar (Out-of-phase) makes fat drop.”
If a lesion loses signal going from in-phase to out-of-phase, it contains intracellular fat = adrenal adenoma or hepatic steatosis.
🫁

Liver MRI

The most technically demanding abdominal MRI — dynamic contrast timing is critical
T1 In Phase T1 Out Phase DWI Dynamic Gd Axial
🩺 Why It’s Ordered
  • HCC (Hepatocellular Carcinoma): Arterial enhancement + portal venous washout = diagnostic criteria for HCC (LI-RADS system)
  • Liver metastases: DWI + portal venous phase most sensitive
  • Hemangioma: Classic: peripheral nodular enhancement in arterial, fill-in on delayed
  • Focal Nodular Hyperplasia (FNH): Central scar on delayed, homogeneous enhancement
  • Hepatic adenoma: Fat on in/out phase, varies by subtype
  • Fatty liver (steatosis): In/out phase signal drop quantifies fat
  • Cirrhosis staging: Nodular surface, parenchymal changes, portal hypertension
  • Pre-surgical planning: Anatomic mapping before hepatic resection
🔬 The Four Contrast Phases
  • Pre-contrast T1: Baseline. Hemorrhage, fat, iron all identified here. Must acquire before injecting contrast.
  • Arterial Phase (~20–25 sec): Liver supplied 75% by portal vein, but HCC is exclusively arterial fed → hypervascular lesions enhance here (HCC, FNH, adenoma).
  • Portal Venous Phase (~60–70 sec): Normal liver parenchyma peaks. Metastases and HCC washout → appear darker than normal liver. Most diagnostic phase for mets.
  • Delayed / Equilibrium Phase (~3–5 min): Fibrosis retains contrast. FNH central scar enhances. Hemangioma fills in (iso/hyperintense). Cholangiocarcinoma enhances (desmoplastic stroma).
🛠️ How to Perform
IV Access: 18-20g IV, antecubital preferred. Test flush before scanning. Power injector essential for consistent contrast timing.
Pre-Contrast Sequences: T1 in/out phase (breath-hold), T2 with/without fat sat (breath-hold), DWI (free-breathing, multiple b-values).
Contrast Injection: 0.1 mmol/kg gadolinium at 2 mL/sec followed by 20 mL saline flush. Use automated bolus tracking (SmartPrep/CARE Bolus) or fixed timing of ~20 sec for arterial phase.
Arterial Phase (critical): Must catch this window — missed arterial phase cannot be repeated (contrast moves to portal phase). Scanner operator must be at the console ready. Breath-hold command given when bolus tracking triggers.
Portal Venous Phase: ~60–70 sec post-injection. Breath-hold. Normal liver parenchyma is maximally enhanced.
Delayed Phase: ~3–5 min post-injection. Patient can rest between phases. Captures fibrotic/desmoplastic enhancement.
Hepatobiliary Phase (if using Primovist/Eovist): Special liver-specific contrast agent. 20-min delayed phase shows hepatocyte function. HCC = no uptake (dark). FNH = uptake (bright).
📌 HCC vs. Hemangioma — Quick Tell
“HCC Washes Out. Hemangioma Fills In.”
HCC: Bright arterial → Dark portal venous (washout). Hemangioma: Peripheral nodules arterial → Progressive fill-in → Iso/hyperintense on delayed. This distinction is essential for your board exams AND for clinical practice.
🩸

MR Angiography (MRA)

Non-invasive vascular imaging — no radiation, no iodinated contrast
TOF Phase Contrast CE-MRA Axial 3D
🩺 Why It’s Ordered
  • Intracranial aneurysm: Circle of Willis TOF-MRA is screening standard
  • Carotid stenosis: Evaluate before stroke or TIA workup
  • Aortic pathology: Aneurysm, dissection (CE-MRA of aorta)
  • Peripheral vascular disease: Run-off MRA of legs for claudication workup
  • Renal artery stenosis: CE-MRA for renovascular hypertension
  • AVM / vascular malformation: TOF or CE-MRA for characterization
  • Portal vein thrombosis: Phase contrast or CE portal venography
  • Pre-surgical vascular mapping: Feeding vessels to tumors
🔬 TOF vs. Phase Contrast vs. CE-MRA
  • TOF (Time of Flight): NO contrast needed. Moving blood enters a pre-saturated tissue slab and appears bright. Best for intracranial vessels (Circle of Willis). Limitation: overestimates stenosis, misses slow flow.
  • Phase Contrast: Measures velocity of flowing blood. Quantifies flow (ml/sec). Great for CSF flow studies and cardiac-gated aortic flow. Can create both morphologic and velocity maps.
  • CE-MRA (Contrast Enhanced): Gadolinium injected, T1-weighted 3D spoiled GRE. Best for large vessels (aorta, renal, peripheral). Requires precise timing — short acquisition window after injection.
🛠️ How to Perform — TOF Brain MRA
Position & Coil: Head coil. Supine. Same as brain MRI setup.
2D vs. 3D TOF: 3D TOF is standard for intracranial vessels. Better SNR, thinner slices. Acquired as 3D axial slabs covering Circle of Willis.
Saturation Bands: Apply superior saturation band to suppress venous signal — only arteries visualized on standard MRA. Want venous? Use inferior saturation band instead.
MIP Post-Processing: Maximum Intensity Projection (MIP) reconstructions done at workstation. Display in multiple rotations. This is what the radiologist reads — submit quality source images AND MIPs.
CE-MRA Timing: For body CE-MRA — use test bolus or automated triggering. Acquisition must start at peak arterial enhancement. Too early = venous contamination. Too late = venous overlap.
📌 TOF Concept Mnemonic
“Fresh Blood Flows In Bright”
TOF works because unsaturated (fresh) blood flowing into a saturated imaging slab appears bright relative to the suppressed background tissue. No flow = no signal = dark vessel = stenosis/occlusion.
💡 NSF Warning — Gadolinium in Renal Failure Before gadolinium contrast in MRA, always check renal function (eGFR). eGFR <30 = high risk for Nephrogenic Systemic Fibrosis (NSF). This is a rare but serious fibrosing condition. Always verify renal function and use the lowest effective dose of macrocyclic (stable) gadolinium agents when renal impairment is present.
⚕️

Pelvis MRI

Gold standard for pelvic organ tumor staging — T2 is the workhorse
T1 T2 STIR DWI Axial Sagittal Coronal
🩺 Why It’s Ordered
  • Prostate cancer: PI-RADS scoring on multiparametric MRI (mpMRI). Used before biopsy and for staging.
  • Cervical cancer staging: T2 multiplanar shows parametrial invasion, vaginal extension
  • Rectal cancer staging: High-resolution T2 shows CRM (circumferential resection margin) — critical for surgical planning
  • Endometrial cancer: Depth of myometrial invasion determines surgery type
  • Uterine fibroids: Characterize fibroids, map for myomectomy or embolization planning
  • Ovarian masses: Benign vs. malignant characterization
  • Bladder cancer: Tumor depth, extravesical invasion
  • Fistula / perianal disease: Crohn’s-related, obstetric fistulas
🔬 Sequence Details
  • T2 Multiplanar (THE key sequence): Exquisite soft tissue contrast. Zonal anatomy of prostate (peripheral vs. transition zone). Tumor typically T2 hypointense (dark) against bright peripheral zone.
  • T1: Lymph node mapping, hemorrhage identification, bone marrow signal. Post-contrast for enhancement assessment.
  • STIR: Bone marrow edema, nodal edema, soft tissue infiltration. Lymph node signal.
  • DWI (mpMRI for prostate): Restricted diffusion in malignant tissue = bright DWI, dark ADC. ADC value helps grade aggressiveness.
  • DCE (Dynamic Contrast Enhanced): Part of prostate mpMRI. Early enhancement = increased vascularity = suspicious for cancer.
🛠️ How to Perform
Patient Prep (Prostate): Empty rectum recommended (gas causes susceptibility artifact). Moderate bladder filling preferred. Some protocols request 1mg glucagon IM to reduce bowel motion artifact.
Coil: Phased-array pelvic coil. Endorectal coil optional — adds SNR but is uncomfortable. 3T eliminates need for endorectal coil in most practices.
Position: Supine, feet-first or head-first. FOV centered on pelvis. Bladder should be in the FOV — check scout.
High-Resolution T2: This is the critical sequence. Use thin slices (3mm, no gap). Acquire in all three planes — especially axial oblique perpendicular to rectal/uterine axis (organ-specific angulation).
Organ-Specific Angulation: For prostate: axial slices perpendicular to prostate long axis on sagittal scout. For rectal cancer: oblique axial perpendicular to tumor. This is what separates a good pelvis MRI from a great one.
DWI: Run multiple b-values (b=0, 500, 1000, ≥1400 for prostate). ADC map automatically calculated. Free-breathing acceptable.
Gadolinium DCE (if ordered): Pre/dynamic/post-contrast T1 in axial plane. Power injector, 2 mL/sec. Timing similar to abdominal dynamic protocol.
📌 Pelvis T2 Tip
“T2 = The Pelvic Workhorse — Everything Starts Here”
In pelvis MRI, T2 multiplanar is so informative that many diagnoses can be made on T2 alone. DWI and DCE add confidence, especially for prostate. Always start protocol review with T2.
Key Parameters & Safety
Master these fundamentals — they apply to every exam you perform
⚙️ Key MRI Parameters Explained
  • TR (Repetition Time): Time between successive RF pulses. Long TR → more T2 weighting. Short TR → more T1 weighting. TR controls the T1 contrast.
  • TE (Echo Time): Time between RF pulse and signal collection. Long TE → more T2 weighting (fluids bright). Short TE → less T2 decay, good for T1.
  • Flip Angle (FA): Used in gradient echo sequences. Low FA → T2*/PD weighting. High FA → T1 weighting. Key for GRE sequences (VIBE, FLASH, SPGR).
  • FOV (Field of View): Anatomical coverage area. Larger FOV = less resolution but more coverage. Match FOV to organ size to maximize resolution. Never make FOV smaller than the anatomy!
  • Slice Thickness: Routine = 3–5 mm. Thinner slices (1–3 mm) for brain, spine, MSK for better detail. Trade-off: thinner = less SNR = noisier images.
  • Matrix: Number of pixels in frequency × phase direction. Higher matrix = better spatial resolution. Trade-off: longer scan time or lower SNR.
  • NEX / NSA (Averages): Number of excitations. Doubling NEX = √2 increase in SNR but doubles scan time. Use to boost SNR in noisy studies.
  • Bandwidth: Higher bandwidth = less chemical shift artifact (good near fat/water interfaces). Trade-off: lower SNR. Lower bandwidth = more SNR but more chemical shift.
📊 T1 vs. T2 vs. STIR — Signal Cheat Sheet
Tissue / FindingT1T2STIRDWI
FatBright ☀️IntermediateDark (suppressed)Intermediate
Water / CSF / FluidDarkBright ☀️Bright ☀️Variable
Acute Ischemia (stroke)Dark (early)IntermediateIntermediateBright ☀️ + Dark ADC
EdemaDarkBrightBright ☀️Intermediate
Subacute Blood (methemoglobin)Bright ☀️BrightVariableVariable
Chronic Blood (hemosiderin)DarkVery DarkDarkDark
Cortical BoneDarkDarkDarkDark
Tumor (solid)VariableOften BrightOften BrightOften Bright (restricted)
Post-Contrast EnhancementBright ☀️———
💉 Gadolinium Contrast — What You Need to Know
  • Standard dose: 0.1 mmol/kg IV (double dose 0.2 mmol/kg for some CNS/spine studies)
  • Mechanism: T1 shortening agent — enhances signal on T1 sequences. Areas with disrupted blood-brain barrier or high vascularity enhance.
  • Indications: Tumors, infection/abscess, MS plaques, post-surgical scar, vascular mapping
  • Macrocyclic vs. Linear: Macrocyclic agents (Dotarem, ProHance) are more stable. Use macrocyclic in any renal impairment case.
  • NSF Risk: eGFR <30 is high risk. Always verify renal function before administering contrast.
  • GBCA Retention: Gadolinium deposits in brain (dentate nucleus, globus pallidus) with repeated doses — inform patients per current ACR guidance.
🔢 Parameter Rules of Thumb
  • T1 imaging: Short TR (<700ms), Short TE (<30ms)
  • T2 imaging: Long TR (>2000ms), Long TE (>80ms)
  • PD imaging: Long TR (>2000ms), Short TE (<30ms)
  • STIR: TI (inversion time) = 150ms at 1.5T / 220ms at 3T
  • FLAIR: TI = 2200ms at 1.5T / 2500ms at 3T (suppresses CSF)
  • Slice thickness brain: 5mm routine axial; 3mm for posterior fossa / pituitary
  • Slice thickness spine: 3–4mm sagittal; 4–5mm axial
  • Slice thickness MSK: 3mm with no gap (or 10% gap max)
MRI Safety Essentials
Safety is non-negotiable — know these cold before you touch the scanner
🚫
No Metal Objects in the Magnet Room
The magnetic field is ALWAYS on — even when not scanning. Ferromagnetic objects (oxygen tanks, gurneys, IV poles, scissors, hairpins) become projectiles. The “missile effect” is fatal. Zone IV is the magnet room — only screened personnel and patients allowed.
🫀
Implant Screening — Pacemakers & Medical Devices
Cardiac pacemakers, ICDs, cochlear implants, aneurysm clips, and neuro-stimulators may be MRI-unsafe. Always verify with manufacturer documentation. MRI-conditional means it CAN be scanned under specific conditions (field strength, SAR limits). NEVER assume — always verify.
😰
Claustrophobia Management
~10% of patients experience significant anxiety. Strategies: verbal coaching, music/headphones, mirror glasses to see outside bore, feet-first entry when possible, short-bore magnets, anxiolytic pre-medication (coordinate with ordering provider), and always — never leave a claustrophobic patient alone in the scanner room.
🫘
Renal Function Before Contrast
Screen eGFR before gadolinium contrast. Risk of Nephrogenic Systemic Fibrosis (NSF) in severe renal failure (eGFR <30). Follow your facility’s contrast policy. Document renal function in the patient record.
🤰
Pregnancy Screening
MRI (without contrast) is generally considered safe in pregnancy when clinically indicated. Gadolinium contrast should be avoided unless the benefit clearly outweighs risk (Category C). First trimester: extra caution — discuss with radiologist. Always screen all female patients of childbearing age.
🌡️
RF Heating & SAR (Specific Absorption Rate)
RF pulses deposit energy as heat. SAR limits must be monitored — scanner does this automatically. Higher at 3T than 1.5T. Patients with implanted conductors (leads, wires) are at increased heating risk. Monitor for patient discomfort, tingling, or burning sensations during scan.
📌 The MRI Technologist Credo
“MRI is Physics + Anatomy + Clinical Reasoning — Master all three.”
The best technologists don’t just push the button. They understand WHY each sequence is run, WHAT it shows, and HOW to troubleshoot when something doesn’t look right. That’s what makes you irreplaceable.