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Emergency Department Imaging - Indications, capabilities and pitfalls Dr David Maritz.

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Presentation on theme: "Emergency Department Imaging - Indications, capabilities and pitfalls Dr David Maritz."— Presentation transcript:

1 Emergency Department Imaging - Indications, capabilities and pitfalls Dr David Maritz

2 The Problem Rising costs and cost efficient care Waiting times Ionising radiation Must become fully aware of indications, capabilities and limitations, pitfalls of imaging modalities Maximise diagnostic efficiency / improve patient care

3 Definitions Sensitivity –If a patient has the disease, we need to know how often the test will be positive, i.e.. ‘’positive in disease’’. –This is the rate of pick-up of the disease in a test. Specificity –If the patient is in fact healthy, we want to know how often the test will be negative, i.e.. ‘’negative in health’’ –This is the rate at which a test can exclude the possibility of the disease. Positive predictive value –If the test result is positive, what is the likelihood that the patient will have the condition? Negative predictive value –If the test result is negative, what is the likelihood that the patient will be healthy?

4 Overview Emergency and critical care imaging –Bedside ultrasound –CT –Radiography Decision rules –Canadian CT Head –CT Spine –Knee –Ankle –Elbow –Other ??

5 1. Bedside Ultrasound Improve diagnostic capabilities and guide invasive procedures Unexplained hypotension Unexplained dyspnoea Resuscitative procedures Real time imaging No ionizing radiation

6 Cardiac Ultrasound - introduction FAST Severe hypotension / PEA LY dysfunction Volume depletion Cardiac tamponade RV outflow obstruction Chest pain, tachycardia, dyspnoea Pericardial effusion / tamponade Risk stratification in PE Acute coronary syndrome Left ventricular function Sepsis Assess preload and LV dysfunction

7 Capabilities High negative predictive value Pericardial effusion / tamponade Acute valvular emergencies Low sensitivity ACS PE Thoracic aortic aneurysm / dissection Significant expertise Novice limited to identifying: Cardiac standstill Extent effusion LV function RV strain

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10 Limitations and pitfalls Subxiphoid views Obesity Abdo trauma / distension Parasternal Lung hyper expansion Physiological pericardial fluid / epicardial fat pad

11 Abdominal aortic ultrasound - capabilities Imaging test of choice for initial detection and measurement Accuracy similar to CT Rapid 95 – 98% sensitivity Even by novices

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13 Limitations and pitfalls Sensitive for identification of AAA Signs of rupture may be absent Stable patients – CT follow up Unstable patients – surgery Hindered by bowel gas / obesity

14 Trauma ultrasound - introduction Extended FAST – blunt and penetrating thoracoabdominal trauma Haemoperitoneum Haemopericardium Cardiac tamponade Pneumothorax / Haemothorax

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16 Capabilities Accuracies for Haemoperitoneum Sensitivities 86 – 94% Specificities 98% Detection solid organ injury IV contrast improves detection (stabilised micro bubbles) Free fluid in penetrating injury Specific 94% Positive predictive value 90% Sensitivity 46% Haemopericardium – 100% Haemothorax – 97% and 99% Pneumothorax – 98% and 99%

17 Capabilities Sonographic measurement of optic nerve sheath diameter Detection papilloedema Setting of raised ICP Greater 5 mm 100% sensitive 95% specific Usefulness ???

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19 Limitations and pitfalls Small amounts fluid missed Trendelenburg Full bladder Adiposity Bowel gas Subcutaneous emphysema Pneumoperitoneum Rib shadows Emphysematous lungs Distended painful abdomens

20 Pelvic ultrasound - capabilities Unstable female patients of childbearing age Intra-uterine vs. ectopic Viability Female trauma patient Abruption Uterine rupture Foetal distress / death Non-pregnant patient Ovarian torsion / tubo-ovarian abscess

21 Limitations and pitfalls Novice limited to Diagnosis pregnancy Ectopic Foetal demise Free fluid Obesity / bowel gas Transvaginal vs. transabdominal

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24 2. CT

25 CT Head - capabilities Emergent CT Minor head injury, headache, suspected intracranial infection Third generation scanners – fast and sensitive Bony injury Most acute haemorrhages

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28 Limitations and pitfalls Not all SOL – but mass effect and shift seen Ischemic stroke – lacks sensitivity early Minute amounts blood not seen Insensitive for early signs of axonal and cellular injury – mass effect and oedema seen Beam hardening artefact from skull base

29 CT head neck angiography / perfusion - introduction Rapid imaging vascular anatomy Identify site of lesion Replacing digital subtraction angiography Acute stroke and thrombolytics Intracranial aneurysm rupture / SAH Penetrating neck injuries Vertebrobasilar disease

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32 Capabilities Carotid artery / circle of Willis Rapid 3D data – advantage over catheter angiography Visualisation of vessel wall Venous rather than arterial access More readily available Rapid work up needed Contraindication to MRI Performed immediately after conventional CT

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34 Limitations and pitfalls Limited by technical factors Radiation dose safe in adults?? Iodinated contrast ?? Children ??

35 CT Chest - introduction Conventional CT / CTA Detailed evaluation coronary, pulmonary arteries and aorta CAD PE Aortic dissection Chest pain?? Triple rule out Single high resolution CTA chest

36 Capabilities Coronary heart disease Exceeding 95% Pulmonary embolism CTA test of choice MDCT in 10sec Exceeds 90% Aortic dissection Approaches 100%

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40 Limitations and pitfalls CT coronary angiography Technical expertise Patient factors CT pulmonary angiography Timing of contrast administration Sub segmental emboli may be missed CT Aorta False positives – motion artefacts

41 CT Abdomen - introduction Abdominal / pelvic pain Stable trauma patient Sensitivities 69 to 95% / specificities 95 to 100% for bowel mesenteric injuries Bowel obstruction Highly sensitive

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43 Capabilities Right upper quadrant pathology Right lower quadrant pathology Left upper quadrant pathology Left lower quadrant pathology MDCT Rapid Decreased motion artefact +- contrast

44 Limitations Children Fat planes less developed Radiation exposure Obesity

45 CT Angiography abdomen - Capabilities Arterial / venous structures Trauma 3D reconstructions

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48 Limitations Iodinated IV contrast Large radiation dose Stable patient Supine / motionless

49 3. Radiography

50 Radiography Chest - capabilities Rapid / portable Chest pain / dyspnoea / hypotension / thoracic trauma Unstable for CT Fever unknown source / altered mental status Diagnose life threatening conditions

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52 Limitations Lacks sensitivity Eg PE Lacks specificity Affected by patient position Initial screening examination Not be used to exclude dangerous conditions definitively

53 Radiography Abdomen - capabilities Lacks sensitivity of CT No contrast Portable Initial study – Abdo pain / vomiting / constipation Readily demonstrates High grade bowel obstruction Perforated hollow viscus injury Volvulus Pneumatosis intestinalis Additional findings Renal / biliary /appendiceal lithiasis Vascular calcification etc

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59 Limitations Poor sensitivity Not a definitive study Initial exam Follow on with CT if non-diagnostic

60 4. CT head rule

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63 Summary Both have sensitivities approaching 100% CCHR more specific for identifying need for neurosurgical intervention 76% versus 12% CCHR more specific for identifying clinically important brain injury 50% versus 12% CCHR results in lower CT rates 52% versus 88%

64 5. CT spine

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67 Summary NEXUS Sensitivity 99.6% Specificity 12.9% Negative predictive value 99.8% Low specificity: ?? Actually increase use of x ray. Therefore Canadian C-spine rule CCR validation - ? Selection bias in study Sensitivity 99.4% Specificity 45% Negative predictive value 100% Which rule?? Further outside validation needed

68 Groote Schuur Trauma CT neck

69 6. Knee

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73 Summary Pittsburgh Sensitivity 99% Specificity 60% Reduce x rays by 52% Ottawa Sensitivity 97% Specificity 27% Reduce x rays by 23%

74 7. Ankle

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76 Summary Sensitivity 99% Specificity 26 to 47% Reduce x rays by 30 to 40%


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