The Pathology Problem

1
Chapter 17

• The Pathology Problem

2
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 patients
  tissues.

3
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.

4
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 technologists responsibility to keep
  the patient dose for a given exam as low as
  possible without compromising image quality.

5
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.

6
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

7
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.

8
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.

9
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.

10
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.

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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.

12
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.

13
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.

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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.
• Pagets 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.

15
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

16
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.

17
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.

18
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.

19
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.

20
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.

21
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.

22
Conditions of the Extremities of the Skull

• Gout during the chronic stages of the metabolic
  disease, areas of bone destruction result in
  punched-out 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.

23
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.