Petra Lewis MD Professor of Radiology and OBGYN Geisel School
of Medicine at Dartmouth
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Learning objectives Understand the meaning of the silhouette
and sign signs Understand how these concepts can be applied in the
diagnosis and localization of pneumonias See how viral pneumonias
differ in appearance Describe how pleural effusions appear on chest
radiographs on different views Understand how the appearance of
effusions varies in empyema and hydropneumothorax Understand the
factors affecting the risks of medical radiation and how they can
be reduced. Calculate the risks to a real patient from his medical
radiation exposure during a single clinical episode
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What questions/difficulties did you have arising from the
case
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Pneumonias
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Silhouette sign
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RLL pneumonia
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Pleural effusions
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Pleural Effusions How much fluid do you need to see on A PA
CXR? A lat CXR? A supine CXR? A CT scan? How else can you visualize
pleural fluid? Characteristics of fluid vs consolidation?
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Small effusions
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Decubitus views
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Supine pleural effusions
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Radiation Risk
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Radiation risk What factors affect how much risk patients are
at from medical radiation?
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Relative risks of exams AXR Barium enema Bone scan CT
abdomen/pelvis CT head CT pulmonary angio CXR (PA ) CXR (PA and
lat) Low dose CT chest Lumbar spine Mammogram Myocardial perf PET
FDG scan UGI Wrist radiograph
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Radiation Equivalents Average background = 3mSv StudyPeriod
natural radiation Wrist radiograph 0.1 d CXR (PA ) 2 d CXR (PA and
lat) 12 d Mammogram 2 m AXR 3 m Lumbar spine 6 m Low dose CT chest
7 m CT head 8 m UGI 1.7 y Bone scan 2.0 y Barium enema 2.7 y
Myocardial perfusion 3.1 y CT abdomen/pelvis 4.7 y PET FDG scan 4.7
y CT pulmonary angio 5.0 y Metter et al. 2008, 248, 254-263.
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Case study HT abdominal CT 27 year old with complicated
pancreatitis