Radiology Physics:

Welcome! This site is designed for radiologists to gain a better understanding of radiology physics through interactive simulations and animations. Right now, we have topics on MRI physics, CT physics, X-ray physics, and Ultrasound physics. We try to focus on practical physics, concepts that actually impact radiation exposure and image quality. Most of these topics find their way into Board exams and similar tests, although some of the MR topics are above that level.

Computed Tomography (CT) Physics

• Filtered Backprojection and Helical CT – Fan-beam geometry, filtered versus raw backprojection, and pitch.
• Dose Measurement in CT – Measures of dose, effects of patient size, and dose reduction techniques.
• Cardiac CT – Prospective and Retrospective gating, temporal resolution, and radiation dose.
• Beam Hardening and Dual-Energy CT – Tissue contrast in CT, beam hardening effects, and dual-energy CT (e.g. virtual non-contrast).
• CT Physics Review Questions

MRI Physics – Basics

• Tissue Contrast in MRI – T1, T2, Gadolinium, and Inversion Recovery
• Spatial Localization in MRI – Gradients, Fourier transform, Frequency and Phase Encoding, and K space
• MRI Pulse Sequences – Spin Echo and Gradient Echo, as well as FSE, SSFP, and EPI
• Image Formation Parameters and Artifacts – Bandwidth, Reduced K-space acquisition, and scanner artifacts
• Chemical Shift Phenomena and the Dixon method of fat suppression
• Diffusion-Weighted Imaging – Diffusion, DWI sequence, ADC maps, and more advanced topics including DTI and IVIM.
• Basic MRI Physics Review Questions

MRI Physics – Advanced

• MR Flow-Related Phenomena – Flow voids, flow-related dephasing, flow-related enhancement, and flow compensation.
• K-Space Trajectories – Cartesian versus Radial, K-Space Ordering for MR Angiography.
• Phase-Contrast MR Angiography
• Cardiovascular MR Pulse Sequences – Black blood, bright blood, and delayed enhancement (including PSIR).
• Parallel Imaging
• Advanced MRI Physics Review Questions

Radiography and Fluoroscopy (X-Ray) Physics

• Magnification and Collimation – Detector geometry, focal spots, resolution, and patient dose.
• X-Ray Interaction with Matter – X-ray generation, attenuation, dose, and image contrast.
• Signal-to-Noise in Fluoroscopy – Image quality, SNR, quantum mottle, and grids.
• X-Ray Physics Review Questions

Ultrasound Physics

• Pulsed-Wave Doppler – Pulse repetition frequency, aliasing, and spectral doppler.

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Naveed Ahmad

Dr. Naveed Ahmad completed his residency training in Diagnostic Radiology at Columbia University affiliated hospitals , New York, NY and went on to complete his Cross-Sectional Imaging fellowship at Medical College of Wisconsin affiliated hospitals in Milwaukee . Dr Ahmad is the co-author Radiology Review: Radiology Physics and creator of the online Radiology source, RadQuiz.com. He is board certified Radiologist with a concentration in body and MSK imaging evaluations.

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