Case Author(s): Scott St. Amour, J. Walllis , 5/12/95 . Rating: #D2, #Q4

Diagnosis: Collimator contamination

Brief history:

Evaluate for metastatic disease

Images:

Anterior and posterior whole body images

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Full history/Diagnosis is available below

Diagnosis: Collimator contamination

Full history:

The patient has lung cancer with a known pelvic metastasis. Previous computed tomography studies have shown a large expansile destrictive lesion in the left ilium, which has been treated with radiation therapy.

Findings:

Markedly increased uptake is seen in the pelvis at the site of the patients known tumor.

A linear area of increased uptake is seen extending from the calvarium to the right leg, most intense at the two ends of the line, and apparent on the anterior view only.

Discussion:

The degree of increased uptake in the pelvis would be compatible with either Paget's disease or tumor. Previous CT examination suggests the latter.

The linear increased uptake is due to contamination of the anterior detector, likely on the collimator. The contamination is likely a Tc-99m tracer, since it was apparent on the 140 kev bone imaging window without excessive scatter or collimator penetration. A line was generated due to the scanning motion whole body camera. The greater intensity at both ends is due to the fact that the camera spends several minutes in stationary mode at both ends of the body, in order to equalize time over the body during the scan.

Major teaching point(s):

Contamination appears differently on whole body images compared with spot views. In either case, it should be recognized and not confused with bone lesions.

ACR Codes and Keywords:

References and General Discussion of Bone Scintigraphy (Anatomic field:Skeletal System, Category:Other(Artifact))

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Case number: bs022

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