Imaging Sciences Interesting Cases
Case 207
Daniel Ginat, MD, MS
Clinical Presentation: The patient is a 46-year-old female, with a history of sarcoma, presented for a follow-up CT scan.
Imaging Findings: Multiple concentric ring artifacts are noted.
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| Figure 1: Axial CT section obtained through the level of the pelvis demonstrates ring artifacts (arrow). Quantum mottle is also apparent, secondary to a low-mAs technique in combination with a large body habitus. |
Diagnosis: Ring artifact
Discussion: Third generation CT scanners are known as "rotate/rotate" because the X-ray tube and detector array are linked and rotate together as a unit. Thus, if a detector malfunctions, a circular tracing will appear on the reconstructed image and is called ring artifact. This artifact will usually be seen on at least several contiguous slices, which can help distinguish it from a real finding. Nevertheless, these artifactual rings or bands may sometimes mimic aortic dissection. Fortunately, advances in instrumentation have made ring artifacts quite rare in current practice.
References:
- Bushberg JT, Seibert JA, Leidholdt EM Jr, Boone JM. The Essential Physics of Medical Imaging. 2nd ed., Lippincott Williams & Wilkins, 2002:335.
- Curry TS, Dowdey JE, Murry RC. Christensen's Physics of Diagnostic Radiology. 4th ed., Lippincott Williams & Wilkins, 1990:320.