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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

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HT Radiology Studies 12/7/06-2/6/07 CXR28 KUB11 CT chest1 CT head1 CT abdo-pelvis19 Fluoro1 minute

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What is his increased risk of dying of a malignancy due to his radiation exposure during this hospital stay?

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How much radiation did HT receive? Scan#Exposure/scan mSv Total CXR280.02 KUB111 CT chest18 CT head12 CT A/P1910 Fluoro1 minute0.1 /min TOTAL

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So our patient received an estimated dose of ? mSv

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Cancer induction rates 8% fatal cancers per Sv (1000 mSv) = % fatal cancers risk for HT Fractionation reduces risk by 50% = % fatal cancers risk for HT Younger patient (