ACM: imaging modalities

MRI disadvantages

- $$, less availability - danger with metals, artificial valves, pacemakers - less capability to see bone, calcifications, ossification or periosteal reaction - claustrophobic pt - longer scan; pt motion

when to use x-rays

- CHF - pneumoniae - atelectasis - pleural effusion - constipation

non-contrast x-ray studies

- CXR (AP/lateral) - KUB (kidneys, ureters, bladder) - kidney stones bc made of Ca2+; can be used rather than CT

CT advantages

- MSK injuries, organs and brain - can change imaging plane - used for appendicitis when x-ray isnt - rapid scanning; preferred in ED - preferred for anything in the abdomen

common MRI scans

- abdomen, chest - head: brain; demyelinating dz like MS (not seen on CT) - MSL: bone, joint, soft tissue - spine

relevance for US

- abdomen: GB, pancreas, aorta, kidneys, abscess, ascites - pelvic: pregnancy & gyn - thyroid - transrectal: prostate

IR is used for

- arteriograms/venograms - angioplasty - embolization - central line placement - catheter/drainage tube placements - filter/stent placements - pain management

MRI advantages

- best resolution for soft tissue problems - no radiation - multiplanar, 3D - study of choice for stroke

oblique x-ray

- body part is rotated 45 degrees so its not AP or lateral

what does nuclear medicine evaluate?

- bones for fractures, arthritis, infection or tumor - kidney function - structure/function of GB (HIDA) - bleeding into bowel - lungs for respiratory and BF problems; structures & function of heart (stress test) - brain for malignancy - thyroid for nodules

common CT scan studies

- chest (can differentiate bw hilar & vascular structures) - head (test of choice for head trauma bc shows bleed) - abdomen (typically w/ IV contrast unless for kidney stones) - pelvis (staging of bladder, prostate, rectal and gyn carcinomas)

x-ray film densities

- dense objects = white (done, dental enamel, metal, stones) - air = black - soft tissue, fluid, organs = gray

US disadvantages

- field of view is limited especially in fatties - can only see outer surface of bony structures - waves are reflected by air or gas so not ideal for GI tract

ultrasound

- high frequency sound waves to evaluate organs, masses, fetus and vessels - bone and muscle = white - soft/hollow areas = dark

lateral xray

- named by the side of the pt that is closest to the film - ex. right lateral: pt lays/stands on right side closest to the film

US advantages

- noninvasive, no ionizing radiation - inexpensive machines - real time images - can be used as a doppler to see blood movement - clear imaging for soft tissues

CT exams

- pathology, fractures, masses, soft tissue, fluid, muscles, organs - vascular structures - IV contrast - intestinal tract - oral/rectal contrast - bx and catheter placement under CT guidance

disadvantages to x-ray

- radiation - acute fracture may not be seen (in early stages when bone repair may have not begun yet) - 2D, not 3D

x-ray

- used for bone pathology, fractures, alignment - evaluates lungs, air fluid levels, soft tissue structures - inexpensive, readily available

CT scan

- uses thin x-ray beam of radiation that rotates around a patient - 3D image - cross sectional planes: sagittal (lateral), median, coronal (frontal), and axial (transverse) planes

mammography

- x-ray that evaluates breast tissue for identification & location of masses - often performed with US of the breast - compresses brast for optimum evaluation

mnemonic for CT

4 Cs - cuts/cross sections - cranial trauma (initial test) - creatinine (check prior to contrast) - contrast frequently used >75% of time

mnemonic for MRI

6Ms - magnets (no radiation) - memory (brain pathology) - messenger (spinal pathology) - muscular injuries - metal (watch for this in pts) - masses (adrenal/renal)

axial x-ray

Any projection in which there is longitudinal angulation of the central ray with respect to the long axis of the body part. Looking "up"—doing a splice of the body. Example of going upward into the jaw @ the palate

MRI vs CT in detecting hemorrhage

CT better within first 24-48hrs

advantages of nuclear medicine

CT can be applied to display images in slices ability to obtain an image of physiologic function

CT vs MRI

MRI superior when imaging... - brain, spinal cord - MSK soft tissues (joints) - adrenal/renal mass - areas of high CT bony artifact

when to use CT

SOB, abdominal pain, head trauma stroke (MRI is still test of choice tho??) respectability of tumors ER for fast imaging

nuclear medicine

Uses radioactive materials (radioisotopes) to image structures within the body - inject IV or ingested orally then collects in the target specific organ - pt returns hours after injection for the imaging

how many views should be used when ordering an x-ray?

at least 2

contrast x-ray

barium enema or swallow; hardly used since we have colonoscopy/endoscopy now

posteroanterior x-ray

beam enters back and exits front

anteroposterior x-ray

beam enters from of pt and exits back; film is located behind the pt

densities of CT films

bone = white air = black muscle, soft tissue and fluid = gray high dense materials (barium or metal) produces artifacts - bright stars with sharp geometric radiating lines

disadvantages of nuclear medicine

displays 3D data in 2D time of consumption for use in acute setting

CT disadvantages

more radiation $$ not during pregnancy can't use IV contrast if bad renal function

when to use MRI

neuromuscular d/o brain, spinal cord muscles, tissues, bone

when to use US

pregnancy vasculature abdominal pin GB appendix pancreas spleen kidney masses, stones arterial and venous circulation

interventional radiology (IR)

subspecialty of radiology utilizing minimally invasive image-guided procedures to diagnose and treat diseases in nearly every organ system - uses real time fluoroscopy to perform invasive procedures often with the administration of contrast

tangential x-ray

very rare Any projection in which the central ray passes between or passes by (skims) body parts to project an anatomic structure in profile and free of superimposition You are looking at a very specific bone and trying to focus on it and everything else is blurry