203 new comparative imaging lecture.pptx

Introduction to Clinical Radiology Mod 203 Tutorial Prof Malcolm Johnston Chair of Radiology, BSMS Learning objectives After this session you should be able to: • Identify common imaging modalities • Understand how different modalities are used to evaluate a range of clinical scenarios • Be able...

Introduction to Clinical Radiology Mod 203 Tutorial Prof Malcolm Johnston Chair of Radiology, BSMS Learning objectives After this session you should be able to: • Identify common imaging modalities • Understand how different modalities are used to evaluate a range of clinical scenarios • Be able to outline the advantages and disadvantages of common imaging modalities including: XRay, CT, MRI and Ultrasound RADIOGRAPHY Strengths • Great spatial resolution- especially bone • Cheap & available • Easy interpretation Weaknesses • Projectional • Ionising radiation • Very limited soft tissue visualisation Absorption Computed Tomography CT scanning • Uses x-ray beam rotating around the patient. COMPUTED TOMOGRAPHY Strengths • Cross-sectional • Spatial resolution • Widely available Weaknesses • Ionising radiation • Limited soft tissue contrast Non Ionising • Ultrasound • MRI Ultrasound Ultrasound Ultrasound Strengths • Non-ionising radiation • Multiplanar • Dynamic • Doppler Weaknesses • Operator-dependent • Can’t see through bone or gas MRI Magnetic Resonance Imaging (MRI) Magnetic Field Strength 1.5 Tesla (Earths magnetic field: 5x10-5 T) Magnet: Niobium-Titanium superconductor in liquid helium (-269 ºC) Radio-frequency coil: fire short wave RF pulse into patient MAGNETIC RESONANCE IMAGING Examples: Pacemaker Intracranial aneurysm clips Magnetic Resonance Imaging Strengths • Non-ionising & Multiplanar • Exquisite soft tissue contrast • Reproducible & non-operator dependent Weaknesses • Limited availability • Magnetic field • Some patients/equipment not suitable • Expensive shielding • Can be difficult to appreciate calcification or gas Comparing CT and MRI • CT – FAT : dark grey – BONE: white – Fluid: Intermediate grey – Soft tissues: varied intermediate grey • MRI – FAT: Bright grey/white – BONE: Black (but bone marrow = fat) – Fluid: white (on T2 sequence) – Soft tissues: much clearer soft tissue contrast CT and MRI pelvis both axial (transverse) CT and MRI of the brain both axial (transverse) CT abdomen axial MRI knee saggital 2 ANTENATAL ASSESSMENT DISCUSSION 3 ASSESSMENT OF THE PAEDIATRIC BRAIN DISCUSSION 4 ASSESSMENT OF SUSPECTED RENAL CALCULI DISCUSSION 5 ASSESSMENT FOR SUSPECTED GALLSTONES DISCUSSION Whole Group task Overall advantages and disadvantages: • XR • CT • MR • USS Conclusion After this session a learner should be able to: • identify common imaging modalities from patient studies • Understand how different modalities are used to evaluate a range of clinical scenarios • Be able to outline the advantages and disadvantages of common imaging modalities including: XRay, CT, MRI and Ultrasound ANY QUESTIONS?