Radiology

Which have ionizing radiation?

Xray CT Nuclear Medicine Mammo-very low

What are 2 most useful for fractures?

Xray MRI

MRI T2

Better contrast, especially with water and better for pathology such as tumors Fat appears dark and blood, edema, and CSF appears white

MRI T1

Better resolution and better for anatomy Fat appears white and water appears dark

CT image - darkest to lightest

Air Fat Water Soft tissue Non-flowing blood Bone Metal

standard radiograph - darkest to lightest

Air Fat Water/soft tissue Bone Metal

nuclear medicine

Brain, thyroid, lungs, gallbladder, bones, kidneys, PET. Large variety of studies throughout Uses radioactive substance injected into patient Radiation detected by sensors (detectors) placed around body part of interest. Ionizing radiation but short half lives Patient must hold still for imaging up to an hour Common scans are PET, bone scan, ventilation-perfusion (V/Q) lung scan, thyroid scan May help distinguish benign from malignant nodules seen on CT or MRI. Lowest spatial resolution (1-3 lp/CM)

Imaging back musculature

CT scan and MRI both are effective in soft tissue-MRI better at showing edema however. US for superficial muscles-deeper structures difficult to discern. Muscle diagnosis often clinical and palpable, not much imaging utilization.

Imaging spinal cord / nerves

CT scan for nerves when surrounded by fat, and large enough to discern MRI for cord detail, spinal and cranial nerves US for infants, soft tissue nervous pathology

Which can generate 3D images

CT, MRI, ultrasound

X-ray

Chest, skull, bones, abdomen; Upper GI, lower GI, IVP, arthrogram (joints) High Spatial Resolution (5-10 lp/mm) Good for bone and lung detail Fair for soft tissue discrimination; not great contrast resolution Uses ionizing radiation STANDARD XRAY TUBE (cathode ray tube)

MRI

Head, neck, chest, abd, pelvis, extremities; angiograms, functional imaging (brain activation) Used throughout body-supplement X-ray, US or CT scan Main benefit; highest contrast resolution (like CT) Spatial resolution limited (1-3 lp/mm) Use powerful magnetic fields and radio waves to chemically flip hydrogen atom spins to generate signal. Multiple imaging sequences used; complex physics Very useful for motionless extremities, head and neck. Faster sequences used for chest and abdomen. Can image blood flow, thromboembolic disease. 2D and 3D acquisitions Main utility is lack of bone artifact in head and neck, and improved ligament and cartilage visualization in musculoskeletal. No ionizing radiation/SAFE for non-instrumented patients. Distinguish at least 7 tissue types (dark to bright) air, metal, flowing blood, fluid, calcifications, soft tissue, hemorrhage, stationary blood, fat. Functional MRI

CT

Head, temporal bones, neck, chest, Abdomen, pelvis, extremities; arthrogram, angiograms Used throughout body Lower Spatial resolution (1-2 lp/mm) Higher Contrast resolution Ionizing radiation Often use iodine contrast Newest scanners have multiple detectors IV CONTRAST RAPID SCAN SEVERE PAIN LIFE SAVING can be converted to 3D

Best contrast

MRI

Best for nerve roots?

MRI

Best spatial

Mammogram

Ultrasound

Ob, Pediatric head, skin and subq, abdomen, pelvis, joints. GALLBLADDER and STONES. Piezoelectric crystal to produce sound waves Variable frequency and focused to see at depth Decent spatial and contrast resolution (lp/mm 2-6) No Ionizing radiation/SAFE Small machines At least 7 tissue types; decent spatial and good contrast resolution Doppler to view flow Great for gallstones, OB, Blood flow

Radiograph VS. Digital image

Original method was to expose film (silver halide emulsion) with x-rays, develop film into radiograph Current method is to use a detector or phosphor plate which converts x-rays into light or is excited by x-rays, then have computer read the light produced or the excitation and generate a digital image

Resolution: distinguishing separate items

Spatial resolution: seeing difference between two objects of similar density. Seeing edges. Line Pairs per MM: spatial resolution; count the distinct white lines in one MM Contrast resolution: distinguishing between different densities of objects. Appreciating the gray scale.

which modality for bone, discs, nerves, etc

Spine x-rays; cervical, thoracic, lumbar CT scan for foraminal and disc detail; best for fracture depiction MRI for thecal sac, spinal cord, nerve root detail; best for cord injury US helpful in fetuses and infants, imaging developing bones, thecal sac; can localize bony landmarks in adults

spondy-

Spondy--losis; degenerative changes at posterior discs and facets; can lead to nerve dysfunction (pinched nerves) Spondy--litis; inflammation of vertebra, infectious or autoimmune; painful Spondy--lolysis; pars fracture; can be very painful, typically no nerve dysfunction Spondy--lolithesis; slippage of one vert body on another, often pinching nerves at foramen; can be due to spondylolysis

MRI imaging types

T1 vs. T2 imaging; relaxation times of protons excited by magnet and radiowaves -process gives off energy measured for image. Higher the energy the brighter the image. T1 is best for detail, but cord and CSF are both grey. T2 is best for CSF distinction from cord and cord edema. Fluid is white, cord is grey. T2=H20

MRI image is best for cord edema?

T2

Xray vs CT

XR better for spatial resolution CT better for contrast resolution

2 for infant cord pathology?

US MRI

Spine imaging

Vertebral bodies; rectangular, smooth cortex Pedicles; oval, well defined Facets; best seen lateral or oblique-superior and inferior articulations Transverse process; symmetric, thoracic partly obscured Lamina; posterior edge of canal Spinous Process; on lateral view of C-spine, tips gently curve

PET

a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task

Dark to light on an Xray

air, fat, muscle, bone, metal

Scottie dog

appears on a 45° oblique neck - one pars interarticularis (part of the lamina that makes up the shoulder region of the dog) Ear - one superior articular process Eye - pedicle Head - one transverse process front legs - formed by one inferior articular process

Which have greater frequencies, Xrays or Gamma?

gamma

winking owl sign

pedicle erosion -due to metastasis -no pedicle, cancer - the pedicle b/l will not be more white -5 cancers that spread to the bone: breast, lung, prostate, arenal carcinoma, thyroid

mammogram

x-ray examination of the breast to detect breast cancer Detecting early breast cancer Partially responsible for decreasing breast cancer mortality (2% per year since 1990) Low dose Ionizing radiation limited to breasts Highest spatial resolution >12 lp/mm.