RAD positioning chap 1 sec C

Collimation

The process of restricting and shaping the primary X-ray beam to match the specific area of the body being imaged. It minimizes the radiation dose to the patient, reduces scatter, leads to a shorter scale of contrast, and provides clearer structural delineation with increased contrast.

Long scale of contrast

A scale with more shades of gray produced using high kilovolt peak (kVp) settings, best for imaging soft tissues and chest X-rays where subtle density variations must be seen.

Short scale of contrast

A scale characterized mostly by black and white produced using low kilovolt peak (kVp) settings, best for imaging dense structures like bone fractures or dental work.

Kilovoltage (kVp)

Refers to the penetrating power of X-rays; high kVp gives high energy X-rays that can penetrate thick body parts, while low kVp results in weak X-rays that primarily show bones and backgrounds.

Milliamperes (mAs)

The total exposure that controls the number of X-ray beams used. High mAs ensures a bright image, while low mAs can lead to grainy or overly dark images.

Central ray

Center most portion of the x-ray beam emitted                     from the x-ray tube with                      the least divergence

Optimal exposure factor

Refers to achieving optimum brightness and contrast while visualizing sharp cortical margins and clear markings in the image.

Factors requiring decreased exposure

Factors such as age, emphysema, arthritis, atrophy, myeloma, osteomyelitis, sarcoma, and osteoporosis, which lower the density of the body part.

Atelectasis

The partial or complete collapse of a lung or lobe of a lung, requiring an increase in penetration factors due to the denser, collapsed tissue.

Advanced carcinoma

Late-stage cancer that creates dense cellular masses requiring higher X-ray penetration.

Edema

Swelling due to excess fluid, making tissue denser and requiring increased penetration.

Pleural effusion

Fluid buildup in the pleural cavity, creating a stark white shadow on X-rays that demands increased technical factors to penetrate.

Pneumoconiosis

Chronic lung disease caused by inhalation of mineral dusts leading to dense, fibrotic nodules that require increased X-ray power for penetration.

Osteopetrosis

A rare genetic disorder resulting in abnormally dense bones, necessitating increased exposure factors to penetrate.

Bleb wall

A fluid reservoir or pouch on the outer surface of the lung, just beneath the protective visceral pleura.

Involuntary muscle control exposure time

Reduced exposure times for involuntary muscle contractions such as peristalsis, systole, diastole, tremors, chills, or pain.

Diastole

The relaxation phase of the cardiac cycle, allowing for sharper images of coronary arteries during this relatively still phase.

Systole

The contraction phase of the cardiac cycle, during which motion artifacts can occur, requiring specialized gating for X-ray timing.

Long bone studies projections

Require at least two projections taken at 90° angles to un-superimpose structures, localize objects, and show true alignment.

Joints projections

Require a minimum of three projections (AP, Oblique, Lateral) to evaluate complex anatomy, cartilage, and uncover hidden fractures.

Clinical exceptions to multi-view positioning

Situations such as post-reduction limbs, cast checkups, routine pelvis studies, portable chest imaging for bedside patients, and standard abdomen studies that can be done with reduced views.

Right Hypochondriac Region

Contains the liver, gallbladder, and right kidney.

Epigastric Region

Contains the stomach, liver, pancreas, and right and left kidneys.

Left Hypochondriac Region

Contains the stomach, liver (tip), left kidney, and spleen.

Right Lumbar Region

Contains the liver (tip), small intestines, ascending colon, and right kidney.

Right Iliac Region

Contains the small intestines, appendix, cecum, and ascending colon.

Hypogastric Region

Contains the small intestines, sigmoid colon, and bladder.

Left Iliac Region

Contains the small intestines, descending colon, and sigmoid colon.

Left Lumbar Region

Contains the small intestines, descending colon, and left kidney.

Umbilical Region

Contains the stomach, pancreas, small intestines, and transverse colon.