Psoas muscle abscess causing fever of unknown origin: the value of Tc-99m (V) DMS imaging

Evaluation of Tc-99m (V) DMSA binding to human plasma proteins

As a critical step toward elucidating the mechanism of localization of Tc-99m (V) dimercaptosuccinic acid (DMSA), we investigated its binding and transport in blood in comparison with Ga-67 citrate. The studies were performed in vitro by incubating Tc-99m (V) DMSA with blood (one sample at 4 degrees Celcius and another at 37 degrees Celcius) to assess its binding to plasma proteins using ultrafiltration, dialysis, electrophoresis, gel filtration chromatography and affinity chromatography. A parallel experiment for determining the blood binding of Ga-67 citrate was performed using the same procedures. Using ultrafiltration, dialysis, electrophoresis and gel filtration chromatography, labeled plasma samples showed that protein binding for Tc-99m (V) DMSA was 45-54% at 37 degrees Celcius and 73-80% at 4 degrees Celcius. The figures for Ga-67 citrate were 43-53% at 37 degrees Celcius and 75-81% at 4 degrees Celcius. Electrophoresis showed that Tc-99m (V) DMSA was mostly bound to plasma albumin (36.05 +/- 2.48% at 37 degrees Celcius and 60.04 +/- 1.87% at 4 degrees Celcius), and that the proportion of Ga-67 radioactivity associated with beta-globulin was 34.23 +/- 1.37% at 37 degrees Celcius and 55.71 +/- 3.69% at 4 degrees Celcius. In affinity chromatography experiments, Tc-99m (V) DMSA did not bind to transferrin, unlike Ga-67 citrate. This study demonstrates that, at the radiopharmaceutical tracer level, most Tc-99m (V) DMSA in blood is protein-bound, primarily to albumin, but not to transferrin. In contrast, Ga-67 citrate was bound primarily to transferrin. The knowledge that albumin is the main transport protein of Tc-99m (V) DMSA may contribute to a better understanding of its biodistribution and pharmacokinetics.

99mTc(V)-DMSA SPECT for the assessment of disease activity in Graves' ophthalmopathy

OBJECTIVE

The aim of this study was to evaluate the use of 99mTc(V)-dimercaptosuccinic acid (99mTc(V)-DMSA) scintigraphy for the assessment of disease activity in patients with Graves' ophthalmopathy (GO) and compare their clinical parameters.

METHODS

The study involved 20 patients who were clinically inactive and eight patients who were clinically active, a total 28 GO patients (18 female, 10 male; mean age: 39.2+/-13.4 years) and 12 control subjects (six female, six male; mean age: 57.12+/-12 years). Planar and SPECT orbital images were obtained 4 h after the intravenous injection of 555-740 MBq 99mTc(V)-DMSA, using low-energy, high-resolution, parallel-hole collimators with dual-head detectors. All SPECT data were reconstructed on conventional axial, sagittal and coronal projections using an iterative reconstruction. Semi-quantitative evaluation was performed comparing the orbital activity with nasal activity based on four grades. GO was classified according to the NOSPECS classification of the American Thyroid Association. Disease was considered clinically active if symptoms and signs deteriorated over 3 months.

RESULTS

No significant correlation was detected between clinical activity and classification (P=0.192). However, clinical activity and 99mTc(V)-DMSA uptake were significantly correlated (P=0.0001). There was no correlation between the clinical classification and scintigraphic grading. Bilateral orbital index of the active group was significantly higher than that of the inactive group (P=0.0001).

CONCLUSION

99mTc(V)-DMSA imaging discriminates the active from inactive GO as well as showing an ongoing subclinical inflammation in the orbits of the patients with GO, regardless of the disease activity clinically. Our results revealed that 99mTc(V)-DMSA is a promising agent for the diagnosis of active Graves' ophthalmopathy.

The value of Tc-99m (V) dimercaptosuccinic acid in detecting intra-abdominal infection: compared with gallium scan

OBJECTIVE

Gallium-67 (Ga-67) and labeled leukocytes are useful in the detection of an unknown infectious source. However, the delay in the diagnosis of a Ga-67 citrate scan (gallium scan) and the complicated labeling technique of a leukocyte scan are major drawbacks to their clinical use. Recently, Tc-99m (V) dimercaptosuccinic acid (DMSA) has been found to be very useful in the detection of infection. Tc-99m (V) DMSA is inexpensive, easy to prepare, and provides a result within hours. In this study, we evaluated the potential of Tc-99m (V) DMSA scan (DMSA scan) in the detection of intra-abdominal infection.

METHODS

A total of 33 patients who suffered from an unknown cause of fever after colorectal surgery were enrolled in this study. All patients received both a gallium scan and a DMSA scan. DMSA scintigraphy was performed 3-4 h after an injection of 740 MBq (20 mCi) of Tc-99m DMSA. After completion of the DMSA image, 111 MBq (3 mCi) of Ga-67 citrate was injected intravenously. Gallium scintigraphy was performed after 24 h and later as needed.

RESULTS

Of the 33 patients, 17 (51.5%) were diagnosed with intra-abdominal abscesses. For DMSA scans, the sensitivity, specificity, and overall accuracy were 88.2%, 93.7%, and 90.9%, respectively. For gallium scans, the diagnostic sensitivity, specificity, and accuracy were 100%, 87.5%, and 93.9%, respectively. No statistical difference was found in the diagnostic accuracy between these two diagnostic modalities using Fisher's exact test.

CONCLUSIONS

DMSA scan is a useful alternative to gallium scan in the detection of intra-abdominal infection in patients with colorectal surgery because Tc-99m DMSA is inexpensive, easy to prepare, and most importantly the result can be obtained within hours.

Active inflammatory bowel disease: evaluation with 99mTc (V) DMSA scintigraphy

PURPOSE

To evaluate the use of pentavalent (V) technetium 99m (99mTc) dimercaptosuccinic acid (DMSA) scintigraphy for the assessment of disease activity in patients with inflammatory bowel disease (IBD).

MATERIALS AND METHODS

99mTc (V) DMSA scintigraphy was performed in 76 patients. There were 36 patients with active IBD (11 with ulcerative colitis, 25 with Crohn disease), 28 patients with inactive disease (eight with ulcerative colitis, 20 with Crohn disease), and 12 patients with miscellaneous bowel disease. Sensitivity and specificity of 99mTc (V) DMSA scintigraphy in the diagnosis of IBD were calculated. In the group with active IBD, the disease activity and laboratory indices, as well as the endoscopic and histologic activity, were compared with the scanning activity index. Correlation coefficients between them were calculated with the Spearman rank test.

RESULTS

99mTc (V) DMSA scintigraphy had a 92% (33 of 36) sensitivity and an 86% (24 of 28) specificity in the detection of active IBD. A significant correlation between disease activity indices and scintigraphy score was demonstrated. Endoscopic and histologic activity was significantly correlated (P =.005 and.02, respectively, overall disease activity) with the scanning activity score. Of the group of patients with miscellaneous bowel disease, three with ischemic colitis had negative findings at scintigraphy.

CONCLUSION

99mTc (V) DMSA scintigraphy provides a noninvasive, practical, and accurate assessment of IBD activity.

Use of 99mTc (V) DMSA scintigraphy in the detection and localization of intestinal inflammation: comparison of findings and colonoscopy and biopsy

PURPOSE

To evaluate the potential use of technetium 99m (99mTc) (V) dimercaptosuccinic acid (DMSA) scintigraphy in the detection and localization of intestinal inflammation.

MATERIALS AND METHODS

In a prospective study, 62 patients who were suspected of having intestinal inflammation and 30 control subjects were enrolled. All patients underwent 99mTc (V) DMSA scintigraphy and colonoscopy with biopsy within 1 week. 99mTc (V) DMSA scintigrams were interpreted blindly with respect to clinical information, and radiotracer uptake in the bowel segments was graded. The findings were then compared with the results of the colonoscopy and colonoscopic biopsy.

RESULTS

In the detection of intestinal inflammation, findings at 99mTc (V) DMSA scintigraphy were as follows: true-positive in 55, false-positive in two, true-negative in 32, and false-negative in three. Overall sensitivity was 95%; overall specificity, 94%; and overall accuracy, 95%.

CONCLUSION

Our results show that 99mTc (V) DMSA scintigraphy is a useful noninvasive diagnostic test for the detection and localization of intestinal inflammation.