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“What Test is Best” Choosing Radiology Exams in Emergency Settings. Dr. C. Freeman PGY-4 Dr. A. Olivier. Objectives. To provide a guide to selecting the appropriate imaging studies in common emergency settings.
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“What Test is Best”Choosing Radiology Exams in Emergency Settings Dr. C. Freeman PGY-4 Dr. A. Olivier
Objectives • To provide a guide to selecting the appropriate imaging studies in common emergency settings Please note: the goal of this talk is NOT to review how to read radiological exams.
Modalities • Plain Films • Based on differential attenuation of X-rays by different tissues • Ultrasound • Uses sound waves • Real time • Very accessible • No radiation
CT • Computer reconstruction of 2 dimensional X-ray data • reconstructions in any plane • Accessible, fast
WHAT IS A “SPIRAL CT”?????? • Helical movement (patient and gantry move at the same time) • Almost all modern CT’s are helical • Exceptions: Head CT, High Resolution CT of the chest
MRI • Soft tissue differentiation (e.g. Soft tissue tumors) • many other specialized indications (e.g. acute stroke) • limited accessibility, expensive • Expanding role in many clinical situations
CHEST“the patient who is short of breath” • Common Causes… • CHF, atelectasis, pneumonia, pneumothorax, pulmonary embolus • start with a Chest X Ray
Left diaphragm now seen Left diaphragm silhouetted Atelectasis
Pneumothorax Inspiration-expiration may increase sensitivity
Tension pneumothorax • ***EMERGENCY • place needle in 2nd intercostal space (mid clavicular line)
Pneumonia Air bronchograms Silhouette sign
Pulmonary Emboli • CXR • non specific, non sensitive • V/Q Scan • useful if high probability or low probability • CT Pulmonary Angiogram
CXR: HAMPTON’S HUMP • Chest X-ray not useful to rule in or rule out PE • BUT may help to find other cause of SOB (e.g. CHF)
V/Q Scan VENTILATION POSTERIOR PERFUSION LATERAL • High probability: Treat (anticoagulate) • Low probability: unlikely to have PE • Intermediate Probability: ??? CT Angiogram
Aortic Dissection • CT • Trans-esophageal echo
GI/GU • Again, begin with a plain film • Remember utility of upright and decubitus films for identifying free air and air fluid levels • Often move on to another exam depending on plain film findings
^^^ ^ ^ Free Air • Upright Chest X-Ray is the most sensitive test for free air
FREE AIR • we see both sides of the bowel wall • “Riegler’s sign”
Renal Colic Plain Films CT IVP (ultrasound sometimes useful…e.g. if pregnant)
Ureteric calculus • note how well a calcified stone is seen on plain films.
“Left flank pain” • IVP • Shows function and obstruction • HOWEVER…largely replaced by CT
Renal Colic: CT Now Preferred Modality
RLQ Pain, Fever, WBC……? Appendicitis • Plain film of limited utility • may see appendicolith • Ultrasound • No radiation • In females, can also see adnexa • Especially good in thin patients • CT • If overweight
..? Appendicitis • RLQ PAIN • appendicolith
Bowel Obstruction “distended abdomen with obstipation and peritoneal signs” • start with a plain film • supine and upright views • lateral decubitus if upright not possible
Small Bowel Obstruction • Multiple air-fluid levels • distended bowel loops • note the value of upright (or decubitus) view
Large Bowel Obstruction: Contrast Enema • Confirms the site of abrupt narrowing at the splenic flexure (large arrow)
Bowel Obstruction…after the plain film • Depends on the clinical scenario • May monitor patient • May go directly to the Operating Room • May proceed to CT • helps to define location and cause of obstruction
Pancreatitis • Clinical/Biochemical Diagnosis • Ultrasound to identify cause (i.e. biliary stones) • CT is used to identify and follow complications • ***NOT TO DIAGNOSE • Will MISS diagnosis in 30% of cases
Scrotal Pain History and Physical first May proceed directly to the OR Ultrasound is the modality of choice Can identify status of blood supply
RUQ Pain • Ultrasound is the modality of choice • CT can miss acute cholecystitis or cholelithiasis
Neuroradiological Emergencies Start with a CT **Except cord compression May ultimately need an MRI
Clinical Settings • Seizures • Trauma • Headache • Stroke
CT: Stroke • Some advanced CT techniques …”CT Perfusion” helpful • In the USA, many centers MRI is the initial exam • Some specialized MRI Techniques can identify brain at risk (“penumbra”) vs. dead brain
Intra - Cranial Bleeds • Subarachnoid Hemorrhage • Subdural Hemorrhage • Epidural Hemorrhage CT