Chapter 17
The Pathology Problem
Pathology and Radiation
Absorption
• As radiation passes through the patient it
undergoes attenuation or absorption of the
x-ray photons.
• Pathological conditions can affect the
overall thickness and composition of the
patient’s tissues.
Pathology
• The medical science that is concerned with 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).
– The disease will affect the degree of radiation
absorption for that specific body tissue.
– Example: fluid will absorb more radiation than air.
Technical Factor Adjustments
• To produce a visible difference requires a
minimal change of 25-50 percent in the
overall exposure to the image receptor for
film/screen radiography.
• It is the technologist’s responsibility to
keep the patient dose for a given exam as
low as possible without compromising
image quality.
Automatic Exposure Control
• AEC systems will compensate for most
pathological changes by adjusting the exposure
automatically.
• The compensation will be the result of increased
mAs rather than increased kVp.
Additive Conditions
• A disease that causes the affected 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 are absorbed, fewer will be available to
reach the image receptor.
• Requires increasing technical factors to achieve
the proper image receptor exposure.
– Image receptor exposure will decrease as the extent
of the disease increases- inverse relationship
Additive Conditions
• Additive conditions will require an increase in
kilovoltage to adequately penetrate the thicker, more
opaque body parts.
• An increase of 15 percent will approximately double
the exposure to the image receptor.
• An increase of 5-15 percent in kilovoltage will
compensate for most additive pathologic conditions.
Conditions affecting
Multiple Systems
• Abscess: an encapsulated infection increases
tissue thickness and may alter composition,
particularly in the lungs.
• Edema: swelling causes an increase in tissue
thickness and may alter composition if it occurs
in the lungs.
• Tumor: an abnormal new growth in tissue
results in an increase in tissue thickness and
may alter composition, particularly in the lungs
or bones or when calcification results.
Conditions of the Chest
• Atelectasis: a collapse of the lung results in
airlessness of all or part of the lung tissue. This
causes lung tissue density to increase.
• Bronchiectasis: the chronic dilation of the bronchi
can result in peribronchial thickening and small
areas of atelectasis. This causes an increase in
lung tissue density.
• Cardiomegaly: an enlargement of the heart causes
an increase in thickness of the part.
• Congestive Heart Failure: when the heart is in
failure, the cardiac output is diminished. This results
in backward failure, or increases venous congestion
in the lungs. Lung tissue density is increased and
the heart is enlarged as well.
Conditions of the Chest
• Empyema: pus in the thoracic cavity causes an increase
in tissue density.
• Pleural Effusions (Hemothorax, Hydrothorax): when
the pleural cavity fills with either blood or serous fluid, it
displaces normal lung tissue, this results in an increased
tissue density within the thoracic cavity.
• Pneumoconiosis: the inhalation of dust particles can
cause fibrotic changes. When healthy lung tissue
becomes fibrotic, density of the tissue increases.
• Pneumonectomy: the removal of a lung will cause the
affected side to demonstrate an increase in density since
normal air-filled lung tissue is removed.
Conditions of the Chest
• Pneumonia (pneumonitis): inflammation of the lung
tissues causes fluid to fill in the alveolar spaces. Fluid
has much greater tissue density than the air normally
present.
• Pulmonary Edema: when fluid fills the interstitial lung
tissues and the alveoli, tissue density increases. This is
a typical complication of congestive heart failure.
• Tuberculosis (advanced and miliary): an infection by a
mycobacteria causes the inflammatory response, which
results in an increase in fluid in the lungs. If the
mycobacteria were inhaled, it generally begins as a
localized lesion, which can spread to a more advanced
stage. If the infection reached the lungs by the
bloodstream, it has a more diffuse spread (miliary TB).
Increased tissue density results in both TBs.
Conditions of the Abdomen
• Aortic Aneurysm: a large dilation of the aorta will result
in increased thickness of the affected part.
• Ascites: fluid accumulation within the peritoneal cavity
causes an increase in tissue thickness. The free fluid
has a unique “ground glass” appearance
radiographically.
• Calcified Stones: stones are most commonly found
throughout the abdomen in such organs as the
gallbladder and the kidney. Calcium may be deposited,
which causes an increase in the effective atomic number
of the tissue.
• Cirrhosis: fibrotic changes in the liver cause the liver to
enlarge and ascites can result. The result is an increase
in the thickness of the liver and the entire abdomen.
Conditions of the Extremities
of the Skull
• Conditions that result in new bone growth are
termed osteoblastic.
• Acromegaly: an overgrowth of the hands, feet,
face, and jaw as a result of hypersecretion of
growth hormones in the adult will result in an
increase in bone mass.
• Chronic osteomyelitis: a chronic bone infection
results in new bone growth at the affected site.
• Hydrocephalus: a dilation of the fluid-filled
cerebral ventricles causes an enlargement of the
head, resulting in an increased thickness.
Conditions of the Extremities
of the Skull
• Osteoblastic Metastases: the spread of cancer to
bone can result in uncontrolled new bone growth.
• Osteochondroma: a tumor arising in the bone and
cartilage will result in an increased thickness of the
bone.
• Paget’s Disease (osteitis deformans): an increase
occurs in bone cell activity which leads to new bone
growth. The result is increased bone thickness with
the pelvis, spine, and skull most often affected.
• Sclerosis: an increase in hardening as a result of a
chronic inflammation in bone. This increases the
density of bone tissue.
Destructive Conditions
• A disease that causes the affected body tissue to
decrease in thickness, effective atomic number,
and/or density. There will be less attenuation of the
x-ray beam.
– More photons are absorbed, more will be available to
reach the image receptor.
• Requires decreasing exposure to achieve the proper
image receptor exposure.
– Image receptor exposure will increase as the extent of the
disease increases- direct relationship
Destructive Conditions
• These conditions cause the absorption of less
radiation and require a decrease in technical factors
to compensate for the changes in body tissue.
• Compensations can be made by decreasing the
mAs.
• A decrease of 50 percent in mAs will reduce the
exposure to the image receptor by half.
• A decrease of 25-50 percent in mAs will compensate
for most of these conditions.
Conditions affecting
Multiple Systems
• Anorexia Nervosa: a psychological eating disorder
which results in an extreme weight loss. Overall
body thickness is reduced.
• Atrophy: a wasting away of body tissue with
diminished cell proliferation, resulting in reduced
thickness of a specific part or the entire body.
• Emaciation: a generalized wasting away of body
tissue, resulting in reduced thickness of the body.
Conditions of the Chest
• Emphysema: the overdistention of
the lung tissue by air will result in a
decrease in lung tissue density.
• Pneumothorax: free air in the pleural
cavity displaces normal lung tissue
and results in decreased density
within the thoracic cavity.
Conditions of the Abdomen
• Aerophagia: a psychological disorder
resulting in abnormal swallowing of air.
The stomach becomes dilated from the air
and overall tissue density decreases.
• Bowel Obstruction: an obstruction in the
bowel results in the abnormal
accumulation of air and fluid, if a large
amount of air is trapped in the bowel, the
overall density of the tissues is decreased.
Conditions of the Extremities
of the Skull
• Conditions that result in the destruction of
bone tissue are termed osteolytic.
• 50 percent of the bone substance must be
lost before changes can be seen
radiographically.
• Active Osteomyelitis: with a bone infection,
there is initially a loss of bone tissue
(containing calcium), resulting in a decrease
in the thickness and composition of the part.
• Aseptic Necrosis: death of bone tissue
results in a decrease in composition and
thickness of the part.
Conditions of the Extremities
of the Skull
• Carcinoma: malignancies in bone can cause
an osteolytic process, resulting in decreased
thickness and composition of the part
• Degenerative Arthritis: inflammation of the
joints results in a destruction of adjoining bone
tissue, which decreases the composition of the
part.
• Fibrosarcoma: this malignant tumor of the
metaphysis of bone causes an osteolytic lesion
with a “moth eaten” appearance, the result is
reduced bone composition.
Conditions of the Extremities
of the Skull
• Gout: during the chronic stages of the metabolic
disease, areas of bone destruction result in punchedout lesions that reduce the bone composition.
• Hyperparathyroidism: oversecretion of the
parathyroid hormone causes calcium to leave bone
and enter the bloodstream. The bone becomes
demineralized and composition is decreased.
• Multiple Myeloma: this malignant tumor arises from
plasma cells of bone marrow and causes punched-out
osteolytic areas on the bone. Often many sites are
affected and reduced bone tissue composition results.
Conditions of the Extremities
of the Skull
• Osteolytic Metastases: when some malignancies
spread to bone they produce destruction of the
bone, resulting in reduced composition.
• Osteomalacia: a defect in bone mineralization
results in decreased composition of the affected
bone.
• Osteoporosis: a defect in bone production due to
the failure of osteoblasts to lay down bone matrix
results in decreased composition of the affected
bone.