The pathology problem – chapter 17

Attenuation varies depending on
the thickness and the composition of the patient’s tissues.

Pathological conditions add
another dilemma because the radiographer must also realize that conditions can affect the overall thickness and composition of the patient’s tissues.

the medical science that is concerned w/all aspects of disease, including the structural and functional changes caused by a disease process.

Certain diseases can
increase or decrease tissue thickness or alter tissue composition (change the effective atomic number or density)

Fluid absorbs
more radiation than air

A greater amount of air
results in less attenuation of radiation

radiographers must
read the x-ray requisition
take an adequate pt history
closely observe the pt

For a pt with pneumonia or emphysema
it may be necessary to adjust the technical factors

by taking a good history
the radiographer can determine how long the pt has had the condition and what signs and symptoms the pt has exhibited

If a disease causes the body tissue to increase in thickness, effective atomic number and/or density
there will be a greater attenuation of the x-ray beam – more photons will be absorbed by the body tissues.

Additive conditions
These diseases are harder to penetrate and are called additive conditions because they require increasing technical factors to achieve the proper IR exposure. Inverse relationship b/w additive condition and IR exposure. With an increase in body tissue, the beam is attenuated more resulting in less exposure to the IR and less density.

As additive conditions are present
IR exposure will decrease as the extent of the disease increases (inverse relationship)

If a disease causes the body tissue to decrease in thickness, effective atomic number and/or density
there will be less attenuation of the x-ray beam – more photons will pass thru the tissue to reach the IR. Destructive conditions cause an increase in IR exposure

Destructive conditions
These conditions require decreasing the exposure to achieve the proper IR exposure. Direct relationship b/w destructive conditions and the IR exposure. IR exposure will increase as the extent of the disease increases.

Technical factors must be increased
to compensate for an increase in the thickness of the part

Proper measurement of the body part and the use of technique charts
will ensure that the correct technical factors are selected

If a kidney stone causes severe hydronephrosis
adjustments in the technical factors may be required

To produce a visible difference
requires a minimal change of 25-50% in the overall exposure to the IR for film/screen radiography.

Conditions that do not require factor changes
ulcers, diverticula, simple fractures. – do not affect the thickness or alter the composition of the body tissues and cause no structure or functional changes. Not all pathologies will or can be demonstrated on a radiograph.

Certain conditions are diagnosed through laboratory testing
diabetes mellitus, anemia, and meningitis

Additive conditions
increased attenuation – many diseases result in increased thickness, effective atomic #, and/or density of the body tissue. These diseases absorb more radiation and require increased technical factors. As the extent of the additive condition increases, the IR exposure decreases.

Bone has a higher
effective atomic # and greater tissue density than muscle

Increased technical factors depends on
the extent of the disease – the degree to which the body tissues are affected. Each pt will be different

As a general rule, additive conditions
will require an increase in kVp to adequately penetrate the thicker, more opaque body parts. A 15% increase will double the exposure.

5-15% increase in kVp will
compensate for most additive pathologic conditions.

AEC systems will compensate
for most pathological changes by adjusting the exposure automatically. However, the compensation will be the result of increased mAs rather than increased kVp.

Increased attenuation conditions
All over the body: Abscess, Edema, Tumors
Chest: atelectasis, bronchiectasis, cardiomegaly, congestive heart failure, empyema, pleural effusions, pneumoconiosis, pneumonia, pneumonectomy, pulmonary edema, TB.
Abdomen: Aortic aneurysm, ascites, cirrhosis, calcified stones
Extremeties/Skull: Acromegaly, chronic osteomyelitis, hydrocephalus, osteoblastic metastases, osteochondroma, Paget’s disease, Sclerosis

Decreased attenuation conditions
All over: anorexia nervosa, atrophy, emaciation
Chest: emphysema, pneumothorax
Abdomen: Aerophagia, bowel obstruction
Extremeties/Skull: Active osteomyelitis, aseptic necrosis, carcinoma, degenerative arthritis, fibrosarcoma, gout, hyperparathyroidism, multiple myeloma, osteolytic metastases, osteomalacia, osteoporosis

encapsulated infection increases tissue thickness – particularly in the lungs

swelling – causes increased tissue thickness

abnormal new growth – increased tissue thickness

collapse of lung – airlessness – causes lung tissue density to increase

chronic dilatation of the bronchi – peribronchial thickening

enlargement of the heart – increased thickness of the part

congestive heart failure
cardiac output is diminished. Increases venous congestion in the lungs; lung tissue density is increased and the heart is enlarged as well.

pus in thoracic cavity – increase in tissue density

pleural effusions (hemothorax, hydrothorax)
pleural cavity fills with fluid – displaces normal lung tissue – increased tissue density

inhallation of dust particles that cause fibrotic (scarring) changes – density increases

removal of a lung – increase in density since tissue is removed

inflammation of lung tissues causes fluid to fill in alveolar spaces – fluid has greater tissue density

pulmonary edema
fluid fills interstitial lung tissues and alveoli – tissue density increases – typical with congestive heart failure

infection by a mycobacteria – fluid builds up in lungs – increased tissue density

If abdomen is distended
it may be necessary to increase technical factors

aortic aneurysm
large dilatation of aorta resulting in increased thickness of the part

fluid accumulation within the peritoneal cavity causing increased tissue thickness. The free fluid has a “ground glass” appearance.

Calcified stones
Calcium may be deposited, increases effective atomic # of the tissues

fibrotic changes in the liver cause liver to enlarge and ascites can result. Increases thickness of liver and abdomen

conditions that result in new bone growth

overgrowth of hands, feet, face and jaw due to oversecretion of growth hormones in an adult – increases bone mass

Chronic osteomyelitis
chronic bone infection resulting in new bone growth at the infected site

dilatation of fluid-filled cerebral ventricles causing enlargement of head – increased thickness

osteoblastic metastases
spread of cancer to bone – can result in uncontrolled new bone growth

tumor arising in the bone and cartilage – increases thickness of the bone

Paget’s disease (osteitis deformans)
occurs in bone cell activity which leads to new bone growth – result – increased bone thickness in pelvis, spine, and skull

increase in hardening (bone in this case) – increases density of bone tissue

Decreasing mAs 50%
will reduce the exposure to the IR in half.

A decrease of 25-50% in mAs will
compensate for most of destructive pathologic conditions.

Anorexia nervosa
psychological eating disorder – extreme weight loss – body thickness is reduced

wasting away of body tissue with diminished cell proliferation – reduces thickness of part or entire body

general wasting away – reduced thickness

overdistention of the lung tissues by air – decreases lung tissue density

free air in the pleural cavity – displaces normal lung tissue and results in decreased density

The presence of air in the abdomen
may require a decrease to technical factors

psychological disorder resulting in abnormal swallowing of air – stomach becomes dilated and overall tissue density decreases

Bowel obstruction
An obstruction results in abnormal accumulation of air and fluid. If large amt of air is trapped, overall density of tissues is decreased

active osteomyelitis
With a bone infection, there is initially a loss of bone tissue resulting in a decrease in the thickness of the part

aseptic necrosis
death of bone tissue – decrease in thickness of the part

malignancies in bone can cause an osteolytic process, resulting in decreased thickness of the part

degenerative arthritis
inflammation of the joints resulting in destruction in the adjoining bone tissue – decreases composition of the part

malignant tumor of the metaphysis of bone causes moth-eaten appearance – reduced bone

areas of bone destruction result in punched-out lesions that reduce the bone composition

overscretion of the parathyroid hormone causes calcium to leave bone and enter bloodstream. Bone becomes de-mineralized and composition is decreased

multiple myeloma
malignant tumor arises from plasma cells of bone marrow and causes punched-out osteolytic areas on the bone. Reduces bone tissue

osteolytic metastases
when malignancies spread to bone, they produce destruction of the bone – reduces composition

defect in bone mineralization – results in decreased composition of the bone

defect in bone production due to the failure of osteoblasts to lay down bone matrix results in decreased composition of the bone

term for conditions that result in the destruction of bone tissues

the rad tech first needs to know
how the normal body attenuates the beam before knowing how to compensate for pathologies

Attenuation varies depending on
thickness and composition of the patient’s tissues

destructive conditions means
more photons are able to make it to the IR – overexposed

Repeats are reduced when
requisitions are read
adequate histories are taken
with close observation

An additive condition will
increase patient thickness or density
attenuate the beam more
result in less IR exposure
Requires an increase in technique to maintain IR exposure
Requires a 5-15% increase in kVp

A destructive condition will
decrease the patient thickness or density
attenuate the beam less
result in more IR exposure
Requires a decrease in technique to maintain IR exposure
Requires a 25-50% decrease in mAs

As an additive condition increases,
the IR exposure will decrease (more white) – inverse relationship

As a destructive condition increases
the IR exposure will increase (more darks) – direct relationship

Whether or not a technical factor change is needed depends on the
extent of the condition

Small and localized pathologies often
do not require technical adjustments

Large and widespread pathologies often
DO require technical adjustments

How much is the minimal change needed to produce a visible difference if a technical change is needed
25-50% – to either increasing kVp or decreasing mAs. SID, too.

AEC will compensate automatically for
body habitus and pathologies – if the tissue is correctly positioned over the AEC chambers. It controls the TIME that an exposure is made. Shuts off when certain # of photons hit the IR. Adjusts time depending on subject density, therefore, it controls mAs. We can control mA, but the AEC controls the seconds. So it it adjusted with mAs.

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