Presentation on theme: "Emergency Department Imaging - Indications, capabilities and pitfalls Dr David Maritz."— Presentation transcript:
Emergency Department Imaging - Indications, capabilities and pitfalls Dr David Maritz
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
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?
Overview Emergency and critical care imaging –Bedside ultrasound –CT –Radiography Decision rules –Canadian CT Head –CT Spine –Knee –Ankle –Elbow –Other ??
1. Bedside Ultrasound Improve diagnostic capabilities and guide invasive procedures Unexplained hypotension Unexplained dyspnoea Resuscitative procedures Real time imaging No ionizing radiation
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
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
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
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
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
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%
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