13. Medical Imaging Basics_Baruah_NOTES1.pdf

Medical Imaging Basics INSTRUCTOR: Dhiraj Baruah, MD, FSCMR, FNASCI Professor, Radiology Thoracic and Cardiovascular Divisions Director, Thoracic Imaging Vice Chair, Quality and Safety Medical University of South Carolina 96 Jonathan Lucas Street, CSB 211G, MSC 323 Charleston, SC, USA, 29425 Email:...

Medical Imaging Basics INSTRUCTOR: Dhiraj Baruah, MD, FSCMR, FNASCI Professor, Radiology Thoracic and Cardiovascular Divisions Director, Thoracic Imaging Vice Chair, Quality and Safety Medical University of South Carolina 96 Jonathan Lucas Street, CSB 211G, MSC 323 Charleston, SC, USA, 29425 Email: [email protected] Phone # (Office): 843 792 4363 Fax #: 843 792 1889 OUTLINE: 1. Medical Imaging - Basics OBJECTIVES: After studying this unit you should be able to: 1. Understand different imaging techniques. 2. Understand terminology used in radiology. 3. Understand recent advances. READING REFERENCE: 1. Brant and Helms' Fundamentals of Diagnostic Radiology – section 1. Medical Imaging - Basics Dhiraj Baruah, MD, FSCMR, FNASCI Professor, Radiology Course Director, Medical Student Rotation Director, Thoracic Imaging Vice Chair, Quality and Safety Let`s Step Back in Time Current Imaging Departments X-ray - Plain radiograph Fluoroscopy Ultrasound Angiography Nuclear medicine CT MRI CTA MRA What is a radiographic image? • Representation of waves interacting with matter • Radiowaves, X-rays, other electromagnetic waves or sound waves Copyright 1996, University of California Regents Images are in pixels – • Pixels – 2D • Representing a 3D body part (Voxel) Image Quality – Signal to noise Contrast to noise RESOLUTION  Spatial  Temporal  Contrast Ultrasound - grayscale  Grayscale - Echogenicity  Echotexture – heterogenous, homogenous  Bright: Hyperechoic ( Echodense )  Dark: Hypoechoic ( Echolucent )  Anechoic – No echos (black)  Posterior Shadowing  Posterior Acoustic enhancement M-mode • Fetal heart rate • Superior temporal resolution (~3ms) Grayscale US (2D) • Hyperechoic stone with shadowing in right kidney lower pole Grayscale • Anechoic round cyst with acoustic enhancement US-contrast Agitated saline infusion echo – microbubbles crossing from RA to LA too early Color doppler • Shows direction and velocity of blood Pulsed wave doppler • Cirrhosis and reversal of portal venous flow • Patent is not the same as normal! Ultrasound on your Smartphone Nuclear IMAGING • General Nuclear Medicine • Increased radiotracer uptake • Photopenic defect • • • • • • PET Hypermetabolic activity Cardiac SPECT and PET Myocardial perfusion or viability Limited spatial resolution Attenuation artifacts V/Q scan – ventilation and flow (perfusion) • Chronic PEs • The only thing we can say is: high probability … PET-CT • Hypermetabolic – usually bad but nonspecific (neoplasm, infection, inflammation) SPECT – stress/rest PERFUSION w or w/o attenuation correction • Large LAD territory myocardial infarct X-ray / Plain Film / Radiography • Density/Opacity vs. Lucency • Increased opacification • Increased lucency • • - X-ray attenuation 5 major levels Gas Fat Water Calcium Metal X-ray / Plain FILM / Radiography - Devices OVERLIE structures - PROJECTION IMAGING The obvious…. The obvious…. The obvious…. X-ray / Angiography • Angiography with contrast (Iodinated) • DSA – Digital Subtraction Angiography • Arteriogram • Venogram • Lymphangiogram • Renal imaging • CO2 contrast Angiography - DSA • CO2 (portal system) • Iodinated contrast (hepatic vein) Angiography – terms to know • Opacification of vessels • Early vs. late filling • Filling defect • Active extravasation • Aneurysm • Stenosis • Occlusion • Dissection • Stent / stent-graft X-ray / Fluoroscopy • Collimation • Water soluble contrast (usually iodinated) • Barium sulphate suspension • Air-contrast • Look for stricture, mass, filling defect, extravasation (leak) Fluoroscopy Enema • …and vaginogram = Rectovaginal fistula CT - CTA  CT-attenuation (CT is based on X-rays)  Hounsfield Units (HU)  DENSITY / Lucency 5 major levels of CT attenuation Gas Fat Water Calcium Metal Hypodense, hypoattenuating hyperdense, hyperattenuating Enhancement?  Need IV contrast (pre- AND Postcontrast images to be sure) Hyperenhancing Vs Hypoenhancing Postprocessing : MIP (maximum intensity projection) • Accentates high-density structures – e.g. vessels , berry aneurysm MINIP = minimum intensity projection • Accentuates low-density structures • Pneumomediastinum CTA = CT angiogram • Need contrast • Timing is important • For heart – need ECG synchronization Multiplanar reformatting vs. Volume rendering – 3D VR • Large coronary artery bypass graft (CABG) aneurysm compressing the main pulmonary artery 3D movie Tetralogy of Fallot (TOF) • With absent main pulmonary artery, patent ductus arteriosus (PDA dependent) 4D cine “movie” • Mitral valve prolapse and atrial septal defect • TOF - Absent Pulmonic valve, large Pulmonary arteries compressing airways MRI - MRA • SIGNAL INTENSITY!!! • Hyperintense • Hypointense • More versatile • No ionizing radiation • Far better soft tissue contrast MRI - MRA • SIGNAL INTENSITY depends on tissue and sequence used 100s of SEQUENCES…E.g.: • T1, T2 or Proton Density - weighted • Diffusion weighted • Flow mapping • ENHANCEMENT – Need contrast! (Gd –based) • Hyperenhancement • Hypoenhancement MRI – static T2w T2w T1w • Infiltrative HCC with portal vein invasion MR Enterography (MRE) – cine and enhancement Active Crohn disease MRI - cine 4-chamber view of heart MRI - flow Bidirectional flow in main pulmonary artery in TOF (pulmonic regurgitation) MRA = MR angiogrpahy Pulm Arteries Right Coronary Artery SVC Left Coronary Artery RV • Arteriography or venography – depends on timing • Without or with contrast • MRAs can also be volume rendered Time resolved MRA – 4D imaging • Repeat 3D MRAs as the contrast is flowing through the system • St.p. Senning procedure for transposition of great arteries (dTGA) Advanced: Parametric imaging – pixelwise calculated data from images PARAMETRIC maps • T2* map • T1 map • Perfusion map • Tractography • Iodine map Advances – quick look MR Elastography (MRE) SOFT STIFF Artificial Intelligence 3D Printing Customized Medical Implants Virtual Reality in Imaging Echopixal – x x Thanks Any questions?