Case Author(s): John R. Leahy, M.D. and Keith Fischer, M.D. , 6/20/99 . Rating: #D3, #Q4

Diagnosis: Osteoporosis

Brief history:

61 rear old man evaluated for osteoporosis.

Images:

Bone densitometry report. Does this patient have osteoporosis?

View main image(mm) in a separate image viewer

View second image(ct). CT through the abdomen obtained several months prior to density measurement.

Full history/Diagnosis is available below

Diagnosis: Osteoporosis

Full history:

61 year old man with hemochromatosis has bone density measurement as part of a pre liver transplant evaluation.

Radiopharmaceutical:

none.

Findings:

Densitometry report shows average bone mineral density for L1-L4 is 1.28 standard deviations below the mean peak bone mineral density in young adults. This is at the low end of the normal range, and does not meet WHO criteria for osteoporosis.

Scan image from the densitometry report shows increased density in the right upper quadrant which overlies most of the L1 and L2 vertebral bodies.

Discussion:

The measurement of bone mineral density using dual photon absorptiometry is usually straight forward. There are occasions, however, when simple review of the numbers generated in the report can lead to misinterpretation of the patient's true bone density. Several conditions or confounding variables have been identified which can artifactually alter the measured bone density. These include the following: recent nuclear medicine scan, recent intravenous or oral contrast, orthopedic devices, spinal deformities, degenerative changes, post operative changes, aortic calcifications, metastatic soft tissue calcifications, and calcium containing tablets in the GI tract. These can all lead to a false elevation of the measured density. In women over the age of 65, almost one third have significant degenerative spine changes which can affect measured spine density.

In this case, the source of the artifactual density is the patient's dense iron laden liver, which has resulted from longstanding hemochromatosis. When a potential factor is recognised, steps can be taken to minimize the effect of the artifact. Scans can be delayed, the vertebral bodies affected by the artifact can be eliminated from the calculation, or the hip can be used as an alternate measurement site.

Reference: Sandler MP, et al: Diagnostic Nuclear Medicine, 3rd ed. Baltimore, Williams and WIlkins 1996; p 1014-1018.

Followup:

In this case, the vertebral bodies affected by the artifact were removed from the calculations. Repeat quantification, this time using only the third and fourth vertebral bodies show that density is 2.82 standard deviations below the peak density in young adults. This measurement does meet WHO criteria for osteoporosis.

View followup image(mc). Density recalculated using the lower two vertebrae for the measurement.

Differential Diagnosis List

As above in the discussion.

ACR Codes and Keywords:

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

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Case number: mm042

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