Fundamentals of X-Ray, CT, MRI and USG (Physics, Basics) MCQs

Radiology · 34 free questions with answers & explanations.

1. On MRI, a tissue with a short T1 relaxation time will appear bright on T1-weighted sequences. Which of the following tissues is characteristically hyperintense on T1-weighted MRI?
2. A patient undergoes a CT scan of the abdomen. The Hounsfield unit (HU) value of a hepatic lesion is reported as -60 HU. What does this attenuation value most likely represent?
3. In diagnostic ultrasound, the transducer operates on which physical principle to generate images?
4. In CT imaging, which interaction of X-rays with tissue is MOST responsible for image contrast at the energies used in diagnostic CT (80–140 kVp)?
5. On MRI, the T2* (T2-star) effect differs from T2 relaxation in that T2* decay also includes signal loss due to:
6. In ultrasound, which artifact is responsible for the bright reflections seen behind gallstones, producing posterior acoustic shadowing?
7. In CT, increasing the tube current (mAs) while keeping kVp constant will primarily:
8. In MRI, the 'time of repetition' (TR) and 'time of echo' (TE) determine image contrast. A sequence with SHORT TR and SHORT TE produces:
9. On CT, the Hounsfield Unit (HU) value of simple hepatic cyst should be:
10. In ultrasound physics, which property of a transducer determines axial resolution (ability to distinguish two structures along the beam axis)?
11. Gadolinium-based contrast agents (GBCAs) are contraindicated in patients with GFR <30 mL/min/1.73m² primarily due to risk of:
12. In MRI physics, the term 'flip angle' refers to the angle through which the net magnetisation vector is rotated by the RF pulse. A flip angle of 90° is used in conventional spin-echo sequences. In gradient echo (GRE) sequences, a smaller flip angle (e.g., 10–30°) is used. What is the PRIMARY advantage of using a smaller flip angle in GRE sequences?
13. In CT physics, the 'partial volume effect' leads to a voxel displaying an averaged attenuation of two different tissues when both are included within the same voxel. Which CT parameter change MOST effectively reduces the partial volume effect?
14. During ultrasound examination, a structure that is filled with fluid (e.g., a cyst) shows posterior acoustic enhancement — the tissue deep to the cyst appears brighter than the adjacent tissue at the same depth. This artefact occurs because:
15. In CT, the Hounsfield unit (HU) scale is defined with water as 0 HU and air as −1000 HU. A lesion in the liver measures +60 HU on non-contrast CT and shows minimal enhancement (+65 HU) on contrast-enhanced CT. An adjacent lesion measures −50 HU. The −50 HU lesion most likely contains:
16. In MRI, a susceptibility-weighted imaging (SWI) sequence is performed on a patient with suspected microhaemorrhages. SWI uses a fully-flow-compensated long TE gradient echo sequence combined with filtered phase information. Microhaemorrhages appear as dark foci (blooming artefact) on SWI because:
17. The inversion time (TI) in an inversion recovery MRI sequence is chosen to null the signal from a specific tissue. To null CSF signal (producing FLAIR), the TI for CSF (T1 ~4000 ms) at 1.5T is approximately:
18. The Nyquist theorem in MRI states that to avoid aliasing (wrap-around artifact), the sampling frequency must be:
19. In CT imaging, the Hounsfield unit (HU) value of fresh blood (acute hematoma) on unenhanced CT is approximately:
20. In Doppler ultrasound, the Doppler frequency shift equation is: Δf = (2 × f0 × v × cosθ) / c. To maximize the frequency shift and thereby improve sensitivity for low-velocity flow detection, the angle θ between the ultrasound beam and the vessel should be:
21. In MRI physics, the term 'T2* (T2-star) relaxation' refers to which phenomenon?
22. In CT physics, the Hounsfield Unit (HU) of water is defined as 0. Which of the following CT density values is CORRECT for cortical bone?
23. Which ultrasound artefact is responsible for the appearance of bright posterior echoes deep to an anechoic structure such as a cyst or fluid-filled viscus?
24. In digital radiography, which of the following best describes the 'quantum mottle' (noise) on a radiograph?
25. In MRI physics, the STIR (Short Tau Inversion Recovery) sequence is used to suppress which tissue?
26. Increasing kVp in an X-ray unit while keeping mAs constant will PRIMARILY result in:
27. In colour Doppler ultrasound, the colour coding convention for direction of blood flow is:
28. On MRI, fat appears bright on T1-weighted images. When a fat-suppression technique (chemical shift fat sat) is applied, the signal from fat drops significantly. Which MRI property of fat is responsible for its T1 hyperintensity?
29. In CT imaging, which of the following tissues has the highest Hounsfield Unit (HU) value?
30. In colour Doppler ultrasound, the colour coding convention is that blood flowing TOWARDS the transducer is displayed in RED and AWAY from transducer in BLUE. This is remembered by the acronym:
31. Which CT artefact is caused by the finite width of the X-ray beam and occurs when a high-density object (eg metallic prosthesis) partially occupies a voxel along with adjacent soft tissue?
32. In MRI, the phenomenon of 'chemical shift artefact' (Type 1) occurs at fat-water interfaces because:
33. In MRI, the concept of T1 recovery (longitudinal relaxation) refers to:
34. A patient undergoes CT pulmonary angiography (CTPA) for suspected pulmonary embolism. Which of the following represents the optimal scanning window for CTPA?