1. GRADIENT ECHO
1.1. CHARACTERISTICS
1.1.1. USE ALPHA < 90 RF PULSE
1.1.2. OMIT ANY 180 REFOCUSING RF PULSE
1.1.3. REFOCUSING WITH FREQUECY ENCODING GRADIENT MAGNETS, Br, READ GRADIENT
1.1.3.1. REFOCUS WITH Br AT NEGATIVE POLARITY AT HALF THE DURATION
1.1.3.2. APPLY Gss, G(phi) & RF THEN GRADIENT Br
1.1.3.2.1. FLIPPING POLARITY CAUSES RAPID DE-PHASING OF AND FLIP OF SPINS
1.1.3.2.2. PRODUCES A GRADIENT ECHO
1.1.3.2.3. RATE AT WHICH SPINS COME BACK TOGETHER GIVES INFO ABOUT TISSUE
1.1.4. NO SPIN ECHOES, GRADIENT ECHOES INSTEAD
1.2. SHORT Tr
1.2.1. FASTER IMAGING
1.2.2. LOWER IMAGE CONTRAST
1.2.3. EMPLOY ERNST ANGLES
1.2.3.1. FLIP ANGLE THAT CREATES STRONGEST MR SIGNAL
1.3. DENOTATION
1.4. EXAMPLES
1.4.1. FAST
1.4.1.1. FAST ANGLE SHOT
1.4.2. FLASH
1.4.2.1. FAST LOW ANGLE SHOT
1.4.3. FISP
1.4.3.1. FAST INVERSION STEADY STATE PROCESSION
1.5. DOMINATED BY T2*
1.5.1. (ADDITIONAL) MAGNETIC GRADIENT AND QUICK SPEED CAUSE VARIATIONS IN Bo TO MAKE UP MOST OF A GRADIENT ECHO
1.6. T2* IMAGING USES
1.6.1. CARTILAGE & JOINT LIGAMENTS
1.6.1.1. CARTILAGE BRIGHT
1.6.1.2. BONE DARK
1.6.2. DYNAMIC CONTRAST ENHANCED IMAGING (DCE)
1.6.3. BRAIN
1.6.3.1. CEREBRAL HEMORRHAGE
1.6.3.2. AVM- ARTEREOVENOUS MALFORMATIONS
1.6.4. CALCIFICATIONS
1.6.5. SUSCEPTIBILITY WEIGHTED IMAGING, SWI
1.6.5.1. USED TO MAGNIFY FACTORS OF TISSUES WITH HEMOGLOBIN IN CONTENT
1.6.5.2. FLOW IN MICROVASCULATURE
1.6.5.3. VARIOUS NEURODEGENERATIVE DISORDERS ASSOCIATED WITH IRON DEPOSITS
1.6.5.3.1. PARKINSONS
1.6.5.3.2. HUNTINGTONS
1.6.5.3.3. ALZHEIMERS
1.6.6. PERFUSSION IMAGING
1.6.6.1. STROKE/ STROKE EVOLUTION
1.6.6.2. FLOW IN MICROVASCULATURE/ MICROCAPILLARIES
1.6.6.3. FLOWS OF VOLUME OF BLOOD
1.6.6.4. TRAUMA
2. ECHO PLANAR
3. MRA- ANGIOGRAPHY
3.1. FLOW
3.1.1. TYPES
3.1.1.1. PLUG
3.1.1.2. LAMINAR
3.1.1.3. TURBULENT
3.1.2. FLOW VOID
3.1.2.1. SE PULSE SEQUENCE
3.1.2.2. ALL SPINS KNOCKED DOWN BY 90 HAVE BEEN REPLACED BY FRESH BLOOD
3.1.2.3. ARTERIAL CIRCULATION
3.1.2.3.1. APPEARS DARK
3.1.2.4. IN FAST FLOWS
3.1.3. FLOW RELATED ENHANCEMENT (FRE)
3.1.3.1. SE PULSE SEQUENCE
3.1.3.2. TISSUE LONG T1 AND USE A SHORT Tr
3.1.3.3. SPINS IN TISSUE ARE ONLY PARTIALLY SATURATED OR UNSATURATED IN SLOW MOVING FLOW
3.1.3.4. VENOUS CIRCULATION
3.1.3.4.1. APPEARS BRIGHT
3.1.3.5. IN SLOW FLOWS
3.1.4. EFFECT ON RFs DEPENDS OF VELOCITY OF FLOW
3.1.4.1. MAGNITUDE EFFECT (INTENSITY)
3.1.4.1.1. FLOW VOID
3.1.4.1.2. FLOW RELATED ENHANCEMENT FRE)
3.1.4.2. PHASE SHIFT EFFECT
3.1.4.2.1. APPLY GRADIENT ECHO
3.2. USES
3.2.1. SUSPECTED VASCULAR DISEASE
3.2.1.1. CAROTID AND VERTEBRAL ARTERIES, ARTERIES OF NECK
3.2.1.2. CIRCLE OF WILLIS
3.2.1.3. ARTEREOVENOUS MALFORMATIONS (AVM) IN BRAIN
3.2.1.4. ANEURYSMS
3.2.1.5. PERIPHERAL CIRCULATION
3.3. TYPES OF MRA
3.3.1. WHICH MECHANISM IS SENSITIVE TO FLOW?
3.3.1.1. INTENSITY
3.3.1.2. PHASE
3.3.1.3. CONTRAST ENHANCED
3.3.2. INTENSITY BASED MRA
3.3.2.1. TIME OF FLIGHT (ToF)
3.3.2.2. OPTIMUM WHEN
3.3.2.2.1. FLOW PERPENDICULAR TO IMAGING PLANE
3.3.2.2.2. USING THIN SLICES
3.3.2.2.3. ON FASTER FLOWS
3.3.2.3. PROBLEMATIC WHEN
3.3.2.3.1. MEANDERING BLOOD VESSELS
3.3.2.3.2. REGIONS OF TURBULENT FLOW CAUSEING DIFFERENCES IN CONTRAST
3.3.3. PHASE BASED MRA
3.3.3.1. ADVANTAGES
3.3.3.1.1. SENSITIVE TO SLOW FLOW RATES
3.3.3.1.2. OBTAIN ACCURATE FLOW DIRECTION
3.3.3.1.3. OBTAIN FLOW VELOCITY
3.3.3.2. DRAWBACKS
3.3.3.2.1. TAKES MORE TIME THAN ToF BASED MRA
3.3.4. CONTRAST ENHANCED MRA
3.3.4.1. USED FOR BODY MRA, NOT BRAIN MRA
3.3.4.2. INJECT A BOLUS OF CONTRAST INTO PT
3.3.4.3. IMAGE FIRST PASS OF CONTRAST THROUGH VASCULATURE
3.3.4.4. 3 TESLA PREFERRED TO 1.5T IN CONTRAST ENHANCED MRA
3.3.4.4.1. REQUIRES LESS CONTRAST INJECTION
3.3.5. DOES IT HAVE A TIME COMPONENT?
3.3.5.1. 2-D
3.3.5.1.1. QUICKER IMAGING
3.3.5.1.2. AT COST OF IMAGE QUALITY
3.3.5.2. 3-D
3.3.5.2.1. DETAILED IMAGE QUALITY
3.3.5.2.2. TIME CONSUMING
3.3.6. CT VS MRA
3.3.6.1. CONVENTIONAL MRA
3.3.6.1.1. AS GOOD AS CT , CONVENTIONAL ANGIOGRAPHY
3.3.6.1.2. CT USES HIGH DOSES, BUT MRA DOES NOT
3.3.6.1.3. ALWAYS USE MRA NOT CT ON PEDIATRIC PT'S
3.3.6.2. CT MRA
3.3.6.2.1. FOR IMAGING CORONARY ARTERIES
3.3.6.3. MAA
4. CONTRAST AGENTS IN MR
4.1. MR USES CONTRAST AGENTS FOR
4.1.1. PERFUSION STUDIES
4.1.2. STRUCTURAL INTEGRITY OF BLOOD-BRAIN BARRIER (BBB)
4.1.2.1. BBB LEAK
4.1.2.1.1. INDICATIVE OF PATHOLOGY
4.1.2.1.2. Gd DOES NOT CROSS BBB UNLESS THERE IS PATHOLOGY
4.1.2.1.3. PERMEABILITY OF BBB
4.1.2.2. TUMOR VASCULATURE
4.1.2.2.1. Gd CAN LEAK IN BRAIN TUMORS' VASCULATURE
4.2. CONTRAST AGENTS ACT ON THESE PARAMETERS OF IMAGE CONTRAST
4.2.1. PD (SD)
4.2.2. T1 RELAXATION
4.2.3. T2 RELAXATION
4.2.4. FLOW
4.3. CATEGORIES OF CONTRAST AGENTS (CA)
4.3.1. POSITIVE CA
4.3.1.1. RESULT IN BRIGHTER TISSUES
4.3.1.2. MOST CA'S WE USE
4.3.1.3. Gd
4.3.1.4. EASIER TO SEE BRIGHT CONTRAST THAN NEGATIVE SPACE
4.3.2. NEGATIVE CA
4.3.2.1. RESULT IN TISSUE DARKENING
4.4. HOW TO CREATE CONTRAST ON IMAGE W CA'S
4.4.1. ALTERING HYDROGEN CONCENTRATION
4.4.1.1. ALTERING SD
4.4.1.2. INCREASE H
4.4.1.2.1. PT DRINKS WATER
4.4.1.3. DECREASE H
4.4.1.3.1. ADMINISTER DIURETIC
4.4.1.3.2. ADMINISTER FAT BASED AGENTS
4.4.2. ALTER MAGNETIC ENVIRONMENT
4.4.2.1. ADMINISTER PARAMAGNETIC AGENT
4.4.2.1.1. Gd
4.4.2.1.2. DYPROSIUM
4.4.2.1.3. Mn
4.4.2.2. ADMINISTER SUPRAMAGNETIC AGENTY
4.4.2.2.1. IRON OXIDE
4.4.2.3. AGENTS HAVE 1+ UNPAIRED e-, SO ACT LIKE SMALL MAGNET
4.4.2.4. CONCENTRATION OF AGENT CHANGES Bo
4.4.2.4.1. CHANGE T1 AND T2 RELAXATION TIMES (QUICKER RELAXATION)
4.4.2.5. TIW IMAGE
4.4.2.5.1. T1 GETS BRIGHTER
4.4.2.5.2. USE PARAMAGNETIC CA (GD)
4.4.2.5.3. SE
4.4.2.5.4. IR
4.4.2.5.5. PRE AND POST CONTRAST
4.4.2.6. T2W IMAGE
4.4.2.6.1. T2 GETS DARKER
4.4.2.6.2. USE SUPRAMAGNETIC CA
4.4.2.6.3. SPECIALIZED IMAGING- FOR LESIONS ON LIVER
4.4.2.6.4. T2 PULSE SEQUENCES, SUCH AS SE
4.4.2.6.5. PRECONTRAST
4.5. GADOLINIUM
4.5.1. GADOLINIUM BASED CLINICAL CONTRAST AGENTS
4.5.1.1. MAGNEVIST (1988, IST CA)
4.5.1.2. DOATAREM
4.5.1.3. PROHANCE
4.5.1.4. OMNISCAN
4.5.1.5. OPTIMARK
4.5.2. Gd IS NEUROTOXIN
4.5.3. SPECIAL PRECAUTIONS AND GUIDELINES
4.5.3.1. Gd-DTPA REDUCES TOXICITY BY QUICKENING Gd'S REMOVAL FROM SYSTEM
4.5.3.2. SYSTEMIC INJECTION = NON-SPECIFIC PLACES IN BODY
4.5.3.3. ELIMINATION HALF-LIFE 1-2 HOURS
4.5.3.4. IMAGE IMMEDIATELY AFTER BOLUS INJECTION
4.5.3.5. WARNING LABELS ON ALL CONTRAST AGENT BOTTLES
4.5.3.5.1. MAY CAUSE NEPHRAGENIC SYSTEMIC FIBROSIS
4.5.3.6. KIDNEYS HAVE SPECIAL DIRECTIVES
4.5.3.6.1. KIDNEY IMAGING IS DONE BEFORE ANY CA IS USED
4.5.3.6.2. KIDNEY FUNCTION BLOOD WORK- BUN, CREATINE
4.5.3.6.3. NORMAL KIDNEY CLEARANCE LEVELS
4.5.3.7. AMOUNT OF MAGNEVIST
4.5.3.7.1. 1 cc/10 LB
4.5.3.7.2. MULTISLICE 0.5 cc/10 LB
4.5.3.7.3. BRAIN METS = DOUBLE THE DOSE TO ID ALL (TINY) METS
4.5.3.8. IS PT ASTHMATIC? WHAT IS PT'S WEIGHT?
4.6. IODINE
4.6.1. 1ST AS CT CONTRAST
4.6.1.1. IF CA IS USED IN CT, YOU'LL SEE IT IN MR
4.6.2. Gd + Io FOR BRAIN IMAGING
4.6.3. 9-25 MILLION PT'S HAVE ADVERSE AFFECTS TO Io
4.6.4. Gd IS LESS TOXIC, WITH ONLY 1 DEATH AS OF 1996
4.7. CLINICAL APPLICATIONS
4.7.1. BRAIN METS
4.7.2. PRIMARY BRAIN TUMORS
4.7.2.1. GRADE I, II (LOWER)- WEAK OR NO ENHANCEMENT
4.7.2.2. GRADE III, IV (HIGHER)- STRONG ENHANCEMENT
4.7.2.3. GLIOMAS
4.7.3. TUMOR FOLLOW UP
4.7.3.1. DISTINGUISHING REOCCURANCE FROM RADIATION NECROSIS SCARRING
4.7.3.2. USE FUNCTIONAL MR (PET, SPEC)
4.7.4. INFLAMMATION
4.7.4.1. MS
4.7.5. INFECTION DETECTION
4.7.6. ISCHEMIC/ INFARCTED TISSUE
4.7.6.1. STROKE Dx BY PERFUSION MR/ DIFFUSION MR
4.7.7. BREAST MR
4.8. PULSE SEQUENCES
4.8.1. FIESTA
4.8.1.1. FAST IMAGING EMPLOYING STEADY STATE ACQUISITION
4.8.1.2. SHORT Tr & SHORT Te= T1W
4.8.1.3. FAST IMAGING OF FLUID FILLED STRUCTURES (CYSTS)
4.8.1.4. BREAST, KIDNEYS, LIVER
4.8.2. RODEO
4.8.2.1. SUPRESS FAT &Si
4.8.2.2. ROTATING DELIVERY OF EXCITATION OF RESONANCE
4.8.2.3. SPECIFICLLY FOR BREAST MR
4.9. MRM- MAMMOGRAPHY
4.9.1. FOR HISK RISK PT
4.9.1.1. FAMILY HX
4.9.1.2. POSITIVE BX
4.9.1.3. LUMPECTOMY WITH POSITIVE MARGINS
4.9.1.4. YOUNGER PT'S WITH DENSE BREASTS
4.9.1.5. WOMEN WITH DCIS- DUCTAL CARNCINOMA IN SITU (MILK DUCTS)
4.9.2. 3-5 MM LESIONS DETECTABLE
4.9.3. USED TO MONITOR TUMOR RESPONSE DURING NEOADJURANT CHEMOTHERAPY
4.9.3.1. Dx LUMP, CHEMO, SHRINK TUMOR, LUMPECTOMY AFTER IT SHRINKS
4.9.4. LIMITATIONS
4.9.4.1. MR CAN'T DETECT MICROCALCIFICATIONS (X-RAY CAN)
4.9.4.2. HIGH # OF FALSE POSITIVES- UNNECESSARY SURGERY, COSTLY