Thoracic Radiology
Erin Porter, DVM, DACVR * Special thanks to Drs. Matt Winter, Dan VanderHart and Kip Berry for many shared slides and images Interpretation Principles and Extrathoracic Structures Interpretation Principles Objectives Review how to appropriately perform thoracic radiographs X-ray technique Understand factors for obtaining high quality radiographs Perform proper patient positioning Know standard projections and differences between Be able to quality control thoracic radiographs Develop a systematic approach to thoracic interpretation Indications Respiratory signs Coughing or dyspnea Cardiovascular signs Trauma Regurgitation Weight loss Health screen Cancer screening/metastatic check Pitfalls Proper Quality Control is the veterinarian’s responsibility Never take a single projection Numer of views are not the client’s choice • Collimate! Avoid “dog-o-grams” X-ray technique High kVp Naturally high contrast region of body Maximize latitude (shades of gray) Radiographic Technique kV 95 mA 800 Highest mA mSec 3.2 Shortest time Minimizes the effect of respiratory motion < 1/60th of a second mAs 2.5 Low mAs Expose during inspiration Collimate to reduce scatter Projections Minimum of TWO orthogonal radiographs 1 - Ventrodorsal (VD) or Dorsoventral (DV) Names based on entrance to exit of beam 2 - Right or left lateral Right or left refers to recumbency THREE views preferred Right and left lateral VD or DV DV or VD? DV DV Critical animals Better visualization of caudal pulmonary vasculature VD Easier to get straight Better visualization accessory lung lobe and great vessels VD Patient Positioning – Lateral Pull thoracic limbs forward Reduce superimposition by musculature Center on heart (Caudal edge of scapula) Collimate beam Thoracic inlet to caudal lung tips (last rib) Thoracic spine to sternum Positioning – VD or DV V- trough is helpful Sternum straight Lined up with spine Collimate Thoracic inlet to last rib Effect of Recumbency Conspicuity of lung lesions Nodule, pulmonary pattern, or mass Nondependent lobe → up → aerated (gas opaque) Soft tissue lesions surrounded by air Dependent lobe → down→ deflated (soft tissue opaque) Soft tissue lesions less visible due to silhouetting Effect of Recumbency Right Lateral Left Lateral Diaphragm crura parallel Right crus cranial to left CVC inserts into right Heart is more oval Diaphragm crura diverge dorsally Left crus cranial to right CVC inserts into right Heart is more round Effect of Recumbency VD Diaphragm crura have 3 humps Cardiac silhouette is more oval DV Diaphragm is one smooth curve Cardiac silhouette is more round Effect of Recumbency Pleural Effusion Positional Radiography Humanoid Sternal Recumbency – Horizontal Beam Positional Radiography Evaluation for pneumothorax Dorsal Recumbency – Horizontal Beam Lateral recumbency – Horizontal Beam Positional Radiography Cranial Mediastinal Evaluation VD Patient Erect – Horizontal Beam Quality Control Better films require less interpretation skills Poor films require better interpretation skills Frustrating to interpret Difficult to standardize normal Improper positioning and technique lead to interpretation errors Quality Control – Exposure Appropriate mA Peripheral areas of analog film should be black Rule - Should be able to just outline one’s finger when placed between film and view boxes Digital radiographs should not be grainy (Quantum mottle) Indicator of underexposure Underexposed Quantum mottle Quality Control – Exposure Appropriate kVp • Check x-ray penetration of organs? • • Dark enough to see dorsal spinous processes through scapula (Lateral) or vertebrae over heart (VD/DV) Not so dark that cannot see pulmonary vessels in periphery Quality Control - Positioning Is all anatomy included? Is the heart centered? Inspiratory? Quality Control - Positioning Is the patient lateral? Superimposition of rib heads, costal junctions Oblique Lateral Positioning Is the patient straight? VD or DV Symmetric Ribs similar length Spine and sternum superimposed Dorsal spinous processes centered on vertebral bodies “Tear drop” shape Examples of improper positioning Quality Control- Respiration Inspiration Expiration T12 Caudal lung tips extend to T12 Diaphragm further from cardiac silhouette Larger triangle between cardiac silhouette, diaphragm and caudal vena cava Lungs have appropriate opacity T10 Caudal lung tips cranial to T12 Diaphragm closer to cardiac silhouette Smaller triangle between cardiac silhouette, diaphragm, and caudal vena cava Lungs have increased soft tissue opacity Principles of Radiographic Interpretation Interpretation Paradigm Must have a systematic approach to image interpretation! 27 Organ by Organ Left-to-right Concentric circles (outside in or inside out) Compartmental Approach 27 Interpretation Paradigm Compartmental Approach Separate Thorax into 4 Compartments (all views) Evaluate Each Compartment Separately Tie It All Together Create a check list and stick with it! Compartmental Approach ① Extra-thoracic ② Pleural Space ③ Mediastinum ④ Lungs Compartmental Approach ① Extra-thoracic ② Pleural Space ③ Mediastinum ④ Lungs Compartmental Approach ① Extra-thoracic ② Pleural Space ③ Mediastinum ④ Lungs Compartmental Approach ① Extra-thoracic ② Pleural Space ③ Mediastinum ④ Lungs Extrathoracic Structures Extrathoracic Structures Objectives Recognize normal extrathoracic structures Review common extrathoracic abnormalities Extra-thoracic Structures Thoracic skeleton Vertebrae Ribs Sternum Proximal thoracic limbs Muscle, fat, skin Intercostal spaces Caudal cervical region Diaphragm Cranial abdominal organs Liver Stomach Extrathoracic Structures Ribs Trace entire rib margin Opacity Course/contour Alignment Rt vs Lt – symmetry Evaluate intercostal spaces Change your perspective… Normal Appearances Ribs Smoothly margined widening Stippled mineralization of the costal cartilages 1 yr Bassett Hound 1 yr Dalmatian Extrathoracic Structures Common Abnormalities Aggressive, traumatic, degenerative skeletal lesions Cutaneous/body wall nodules, masses or fake-outs Cranial peritoneal abnormalities (fluid, air, masses) Cranial abdominal organ abnormalities (liver and stomach) Diaphragmatic hernias Extrathoracic Structures Acute Rib Fractures Chronic Rib Fractures Extrathoracic Structures Sternum Aggressive lesion Diskospondylitis Extrathoracic Structures Aggressive lesion on scapula Extrathoracic Structures Musculoskeletal Abnormalities Extrathoracic Structures Nipple fake-out Nipple-o-gram Diaphragm Anatomy Tendinous center Three thin peripheral muscles Par costalis Oblique attachment to 8th13th ribs Par sternalis Attachment to xiphoid cartilage Par lumbalis Right and left crura Attach at L3-L4 Diaphragm Insertion L3 L4 L5 Extrathoracic structures Diaphragmatic Hernia Extrathoracic structures PPDH Cranial Abdomen Pneumoperitoneum Decreased Detail Cranial Abdomen Biliary tract calculi Cranial Abdomen GDV Questions?
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