Poma Radiology
Table of Contents

Radiology

 X-rays: four tissues recognized – calcium (bones), soft tissue (muscle, liver, heart, kidney etc), fat and air (in lung and gut). The calcium, which is the densest, causes the greatest blockage of X-rays and therefore appears whitest. Air the least dense allows x-rays to pass through making lungs and bowel to appear dark. Fat and general body tissue produce middle level shadows but difference between them is small and hence acquisition of information is less successful with X-rays.
- Views: front and lateral views
- Uses: fractures, and joint disease such as arthritis
- Soft tissues detail can be improved by using x-rays produced at much lower kV (normal 25-32kV), e.g. mammography
- Contrasting material: barium sulphate by mouth (for enema and GI studies) and iodine compounds by injection (excreted by kidneys) for angiography and IVUs. These help increase contrast between different soft tissues
 Fluoroscopy: using contrasting material and low levels of x-ray to produce a live image on a fluorescent screen.
- Uses: gastro-intestinal studies include barium meals for examination of stomach and duodenum and colon. Blood vessels demonstrated by iodine.
 Computed Tomography: using X-rays and computation to produce transverse slides of the body.
- pros: discriminate between fat and soft tissues (contrast resolution) – enhance with contrasting agents also
- cons: spatial resolution of CT is slightly less than X-ray image so bones not well shown, costly, subject to artifact due to movement and areas of high density such as base of skull
 Magnetic Resonance Imaging: Patient placed in a strong magnetic field and the hydrogen nuclei within the body align along the lines of the field. Subjection to RF radiation impart energy to nuclei and when released, a signal is emitted which is detected. Location of individual groups of nuclei is determined and slice images produced. Gadolinium for contrast.
- pros: contrast resolution is significantly greater than CT, produce pictures that are very close to naked eye appearance of living tissue, no x-rays
- cons: difficulties with lungs
 Ultrasound: using deep sea sonar and radar technology. Short pluses of sounds are produced at around 1000Hz and echoes from within the body tissues are recorded. Pictures show slices of the body from the sound transmission/reflection properties of the tissues rather than x-ray density.
- pros: movies images that is safe and flexible and cheap, targets specific problem
- cons: inability to penetrate bone or air containing structures, not as good as CT in providing an overview
- uses: pregnancy, examination of upper abdomen, gallbladder disease, cardiac and general vascular problems
 Interventional radiology: using X-ray, CT, ultrasound or MRI to perform surgical operations. US produce a movie image of needle/catheter insertion, CT for where lesion is obscured by gas or bone. MRI not frequently used as make surgery inaccessible.
- uses: sampling tumour, draining cysts, stretch blood vessels and heart valves back to normal, removing gallstones and renal calculi
 Nuclear medicine: diagnostic rays released within the patient’s body by decay of radioactive isotopes are detected by gamma camera for location of problems. Agents are usually ingested or injected into a vein and are taken up by a specific organ, e.g. iodine into thyroid gland. X-rays or CT can be used later for imaging.
- uses: demonstrating early disease and function, e.g. head, lung, bone (fracture), thyroid, renal (function), liver (lesions) and bile duct scan
- pros: relatively cheap, safe
- cons: limited in its ability precisely define the outline of organs
 Radiation oncology: radiation produced can be delivered in precise quantities to carefully defined location to kill the tumour cells. Ct and MRI are especially useful for combining information from many slices and 3D impression of the extent of tumour can be obtained.

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