Dobutamine thallium-201 myocardial SPECT in patients with left bundle branch block and normal coronary arteries.

UNLABELLED: Dobutamine is a positive inotropic and chronotropic agent and is being widely used as a pharmacologic stress agent in patients unable to achieve maximal dynamic exercise test. The purpose of the current study was to document the dobutamine induced false-positive septal defect in terms of its frequency and extent on 201Tl myocardial SPECT in patient with left bundle branch block (LBBB). METHODS: Twenty-five symptomatic patients with LBBB underwent dobutamine and redistribution 201Tl myocardial SPECT studies. Coronary angiographies were also performed. Only those patients with normal coronaries (n = 19) were included in the study. For each study, tomograms were divided into 19 segments, and each segment was analyzed qualitatively as to presence and type of perfusion defect (reversible or fixed). In addition, septal perfusion was scored in each patient (1 = markedly, 2 = moderately reduced, 3 = normal uptake). RESULTS: Sixteen of 19 patients (84.21%) had false-positive septal reversible perfusion defect, and the remaining 3 had normal images. Perfusion defects were confined to only the septum in 5 of 16 patients (31.25%), whereas a greater proportion of patients had septal defect extending to the contiguous myocardial areas, mainly to the anterior wall. Five of 16 patients with false-positive defects had a septal perfusion score of 1, while the remaining 11 had a score of 2. CONCLUSION: Dobutamine myocardial scintigraphy in patients with LBBB was misleading for the diagnosis of coronary artery disease, since up to 84.21% of patients had false-positive septal perfusion defects.

Pre- and post-therapy thallium-201 and technetium-99m-sestamibi SPECT in nasopharyngeal carcinoma.

UNLABELLED: We prospectively studied the diagnostic potential of 201Tl and 99mTc-sestamibi (MIBI) SPECT for evaluating the extent of primary disease and differentiating residual/recurrent disease from post-therapy changes in patients with nasopharyngeal carcinoma (NPC). METHODS: Fifty patients (20 initial presentation, 30 post-therapy evaluation) underwent 201Tl and MIBI imaging. The findings were correlated with CT/MRI results. Tumor-to-background ratios were obtained. Biopsy confirmation (14 patients) and/or 6-12 mo clinical follow-up data (16 patients) were available in the post-therapy group. RESULTS: All primary disease sites were accurately detected by both imaging studies in the pretherapy group. However, MIBI-SPECT was superior to 201Tl SPECT (p = 0.0057) in detecting regional metastases (sensitivities of 95% versus 68%). In the post-therapy group, MIBI and 201Tl imaging were true-positive in 14 of 16 patients with proven residual/recurrent. In 17 patients who had no evidence of residual/recurrent tumor. CT/MRI was false-positive in 13 when MIBI and 201Tl imaging were true-negative in 10 and false positive in 3. MIBI, 201Tl and CT/MRI had sensitivities of 87.5%, 87.5%, 100%, specificities of 82.4%, 76.5%, 23.5% and accuracies of 85%, 82%, 61%, respectively. Tumor-to-background ratios were < or = 1.5 in all false-positive cases except one. CONCLUSION: MIBI-SPECT proves more accurate than 201Tl SPECT in detecting regional metastases at initial presentation. MIBI and 201Tl imaging have higher specificity and accuracy than CT/MRI and MIBI-SPECT is slightly more specific than 201Tl SPECT in differentiating residual/ recurrent disease from post-therapy changes in patients with NPC.

Monitoring response to therapy with thallium-201 and technetium-99m-sestamibi SPECT in nasopharyngeal carcinoma.

UNLABELLED: This study prospectively assessed the value of 201Tl and 99mTc-sestamibi (MIBI) SPECT in monitoring disease regression/progression as compared with MRI findings in patients with nasopharyngeal carcinoma (NPC) having radiotherapy with or without chemotherapy. METHODS: Eighteen patients (age range 15-78 yr, mean 45 yr) had consecutive SPECT imaging using a dual-head gamma camera after the injection of 111 MBq 201Tl and 555 MBq MIBI before therapy and at 3 mo and 6 mo after completion of therapy. A total of 106 SPECT studies was correlated with contemporaneous MRI studies. Tumor-to-background ratios were obtained on coronal slices. Visually detectable lesions in the region of the nasopharynx and cervical lymph nodes were considered positive for residual disease. The gold standard for the presence of disease was the combination of repeat MRI scans, endoscopic examination and clinical evaluation performed 12-15 mo after completion of therapy. RESULTS: MIBI-SPECT proved superior to both 201Tl SPECT and MRI after 3 or 6 mo follow-up in predicting complete response. Accuracy rates in the detection of residual disease in the nasopharynx are 39%, 72% and 89% for MRI, 201Tl and MIBI, respectively, for the 3-mo evaluation; 71%, 71% and 94% for MRI, 201Tl and MIBI, respectively, for the 6-mo evaluation. CONCLUSION: MIBI SPECT could be used as a screening test in predicting response to therapy in patients with NPC.

Selective spleen scintigraphy in the diagnosis of polysplenia syndrome.

This report describes a case of polysplenia syndrome diagnosed by selective spleen scintigraphy. This syndrome is rarely encountered in the elderly. It is characterized by multiple splenuncules with a number of associated congenital anomalies involving the cardiovascular system and the viscera. The differential diagnosis of these intra-abdominal masses can sometimes be difficult and can be confused with lymphadenopathy or metastases. Furthermore, biopsy of the splenuncules may be hazardous. The diagnosis of polysplenia can be established in most instances by (99)Tc(m) labelled heat-denatured red blood cell selective spleen scintigraphy without biopsy.

Accumulation of 99mTc-Cysteine in experimental inflammatory lesions in comparison to 99mTc-glutamine and 99mTc-HIG.

AIM: The aim of this experimental work was to investigate the efficacy of 99mTc-L-Cysteine (Cys) in scintigraphic visualization of inflammatory lesions in comparison to 99mTc-L-glutamine (G), and 99mTc-HIG. METHODS: In mice abscesses were induced by intramuscular injection of turpentine. Six days later mice were injected with 3.7 MBq of each agent and sacrificed in groups of three at 1, 3, 6 and 24 h. Scintigrams were obtained with a gamma camera. The organs, some blood, abscesses, some muscle and urine were removed, weighed and counted in a gamma counter. Percentage of uptake by organs and per gram tissues and abscess/normal tissue concentration ratios were calculated. Experimental arthritis was produced in 6 New Zealand rabbits by intraarticular injection of ovalbumin. Four days later 37 MBq of 99mTc-Cys and 99mTc-HIG were each i.v. administered to 3 rabbits. Scintigrams obtained at 1, 3, 6, and 24 h demonstrated the arthritic joints very well. ROI's over arthritic joints were compared to contralateral normal joints (A/C). RESULTS: In mice the abscesses were well visualized on all scintigrams. The maximum abscess/muscle ratios were 5.21 +/- 1.09 (6 h), 3.73 +/- 0.81 (3 h) and 5.98 +/- 1.17 (24 h) and the maximum abscess/blood ratios were 3.46 +/- 1.33 (24 h), 1.81 +/- 0.10 (6 h) and 0.914 +/- 0.351 (24 h) for 99mTc-Cys, 99mTc-G, and 99mTc-HIG, respectively. In rabbits the maximum A/C ratios were 2.61 +/- 0.53 (3 h) and 2.92 +/- 0.99 (24 h) for 99mTc-Cys and 99mTc-HIG, respectively. CONCLUSION: Our results indicate that 99mTc-Cys is a promising agent for imaging inflammatory lesions. It is preferred to 99mTc-HIG, because of higher concentration ratios attained earlier, lower blood background, lower cost and a simpler in-house preparation method.

Effect of an additional atropine injection during dobutamine infusion for myocardial SPET.

The aim of this study was to examine the value of an additional atropine injection in patients who do not achieve an adequate heart rate during dobutamine infusion for myocardial perfusion SPET (single photon emission tomography). Patients undergoing dobutamine myocardial SPET who failed to achieve > or = 85% of their age-predicted maximal heart rate at the end of dobutamine infusion (D protocol) had a second dobutamine myocardial SPET study on a separate day with the addition of an atropine injection during the dobutamine infusion (D + A protocol). Twenty-nine patients were studied. 201Tl was used in 27 patients and 99Tc(m)-MIBI in two patients. All patients underwent coronary angiography and significant coronary artery disease was found in 19 of 29 patients. The mean heart rate obtained at the peak of dobutamine infusion in the D + A protocol was significantly higher than that in the D protocol (153.8 +/- 13.8 vs 117.5 +/- 15.3 beats min[-1]). The D + A protocol resulted in a higher diagnostic sensitivity for the detection of stenosed coronaries compared with the D protocol (87 vs 80%, P > 0.05) without changing the specificity (89% for both protocols). On the other hand, the frequency of side-effects and ECG changes during the D + A protocol was higher than that with the D protocol (32 vs 47). In conclusion, the addition of an atropine injection during dobutamine infusion resulted in a higher diagnostic sensitivity for identifying stenosed coronaries compared to dobutamine alone.

Comparison of 201Tl, 99Tcm-MIBI and 131I imaging in the follow-up of patients with well-differentiated thyroid carcinoma.

Problems stemming from the withdrawal of TSH suppressing doses of T4 or T3 and false-negative studies associated with 131I scintigraphy have justified the search for other radionuclides in the follow-up of patients with well-differentiated thyroid carcinoma. Although 201Tl and 99Tcm-MIBI (MIBI) have been suggested as alternatives, their role in the detection of residual and recurrent disease has yet to be established. We therefore studied 36 patients who had undergone total or near total thyroidectomy for well-differentiated thyroid carcinoma to determine the imaging potential of 201Tl, MIBI and 131I in the detection of residual or recurrent disease. Eighteen of the 36 patients had undergone 131I ablation. Imaging was performed 20 min following the intravenous injection of 111 MBq 201Tl or 555 MBq MIBI, or 48 h after the oral ingestion of 185 MBq 131I. The overall concordance between the 201Tl, MIBI and 131I scans was 70%. The concordance between thyroglobulin (TG) levels and the 131I scans was 78%; that between the 201Tl and MIBI scans and TG levels was 83%. Among the group of pre-ablative patients, there were six false-negative results with 201Tl and three false-negative results with MIBI. Among the post-ablation group, the 201Tl and MIBI scans were falsely negative in five patients. The 131I scans revealed all known residual or recurrent diseases. In conclusion, 201Tl, MIBI or TG levels should not be used in the place of 131I for the detection of residual or recurrent thyroid cancer. However, in patients who have not had their TSH suppressing doses of T4 or T3 withdrawn, the role of 201Tl and MIBI is debatable.

Impact of radiotherapy on normal brain tissue: semi-automated quantification of decrease in perfusion.

PURPOSE: We attempted to ascertain the impact of Co-60 conventional external radiotherapy (cRT) on the perfusion of normal brain tissue in relation to the radiation doses delivered to the tumors in patients with primary brain tumors. MATERIALS AND METHODS: After surgery 18 patients (pts) were due to undergo cRT with a total dose of 5400- 6400 cGy. All the patients had a Tc-99m-HMPAO SPECT study prior to cRT (basal), 15th and 30th days of cRT as well as 1 (in 6 pts), 3 (in 9 pts), and 6 (in 3 pts) months after cRT. For quantitative evaluation, the entire set of transverse slices were divided into 4 regions as frontal, parietal, occipital and temporal regions by means of a computer software program. Semi-automated quantification was performed on a total of 1392 regions in 87 studies to determine left to right ratios. An interregional difference of at least 10% was considered abnormal. RESULTS: After elimination of tumor sites, 80 normal brain regions showed decreased perfusion after cRT. The percent decrease in perfusion was (mean 22.5+/-9.9) significantly higher in areas irradiated with doses > 3000 cGy (p < 0.05). CONCLUSION: cRT has adverse effects on the perfusion of normal brain tissue for doses > 500 cGy. Our findings justify treating patients with small and limited lesions with stereotactic radiotherapy in order to minimize the adverse effects of cRT on normal tissues.

Can bone scintigraphy detect additional metastatic sites unrevealed by CT in patients with recurrent ovarian carcinoma?

A patient who presented with recurrent ovarian carcinoma with elevated levels of CA 125 was evaluated for skeletal metastases by routine whole body bone scintigraphy. Although no bone metastasis was visualized, there was intense accumulation of tracer in the soft tissues corresponding to the liver, pelvis, and intestinal/peritoneal surface, suggestive of metastatic disease. Although liver and pelvic soft tissue metastases were confirmed by CT and USG, intestinal/peritoneal metastases could not be disclosed by either modality.

Influence of immediate post-therapy bone scintigraphy in the assessment of response to therapy in a case of nasopharyngeal carcinoma.

A patient with undifferentiated stage IV (T3N3M0) nasopharyngeal carcinoma (WHO type III) underwent pre- and one-month post-therapy bone scintigraphy as part of an ongoing trial combining scintigraphic and radiographic modalities. The patient had advanced disease in the nasopharynx and bulky cervical lymph nodes at presentation. Initial bone scintigraphy performed 10 days prior to therapy was negative for bone metastases. Immediately after concomitant chemoradiotherapy, bone scintigraphy revealed distant metastases, whereas clinical assessment of disease disclosed complete response to therapy in the nasopharynx and cervical lymph nodes. The scintigraphic findings were also confirmed by a subsequent MRI scan of the corresponding regions.

A comparative study of technetium-99m sestamibi and technetium-99m tetrofosmin single-photon tomography in the detection of nasopharyngeal carcinoma.

The intention of this prospective study was to compare the diagnostic potential of technetium-99m sestamibi (MIBI) and a novel radiotracer, 99mTc-Tetrofosmin (Tetro), for the assessment of primary nasopharyngeal carcinoma (NPC) and the differentiation of residual disease from post-therapy changes. A total of 38 patients underwent MIBI and Tetro single-photon emission tomography (SPET) imaging at initial presentation (n=22) or following therapy (n=16). The findings were correlated with computed tomography or magnetic resonance imaging (MRI) on a site-by-site basis. Tumour/background (Tm/Bkg) ratios were obtained on coronal sections. Biopsy (nine patients) and/or 12- to 24-month clinical follow-up data were available in the post-therapy group. All primary disease sites were accurately detected by both imaging studies. Although there was no statistical difference between the two imaging techniques in the detection of primary disease, MIBI was superior to Tetro in the detection of regional lymph node metastases (sensitivity: 95% vs 79%). Tetro and MIBI SPET were true-positive in all patients (n=7) with proven residual/recurrent disease. In nine patients who had no evidence of residual/recurrent tumour, MRI was false-positive in five while Tetro and MIBI SPET were false-positive in two and three patients, respectively. Tm/Bkg ratios were

Comparison of 99mTc(V)-DMSA, 201Tl and 99mTc-MIBI imaging in the follow-up of patients with medullary carcinoma of the thyroid.

Radionuclide scanning with tumour-seeking agents such as pentavalent technetium-99m dimercaptosuccinic acid [99mTc(V)-DMSA], thallium-201 and technetium-99m sestamibi (MIBI) has been reported to be useful in the detection of medullary thyroid carcinoma (MTC). We undertook a study in 14 MTC patients to determine the comparative imaging potential of 201Tl, MIBI and 99mTc(V)-DMSA in the detection of recurrent or metastatic MTC. All patients underwent total thyroidectomy and had persistently elevated serum calcitonin levels after the surgery. Scintigraphic studies were carried out 20 min after the injection of 111 MBq of 201Tl or 555 MBq of MIBI and 2 h following the injection of 370 MBq of 99mTc(V)-DMSA. All scintigraphic findings were correlated with contemporaneous CT or MRI studies. CT, MRI and bone scans showed 42 (26 bone, 16 soft tissue) metastatic sites in 11 of the 14 patients. In the remaining three patients no lesions were detected during diagnostic evaluation. 99mTc(V)-DMSA showed all of the soft tissue metastases but could not show two bone lesions. On the other hand, MIBI imaging was false-negative in 22 (52%) sites and 201Tl was false-negative in 34 (80%) sites. Overall, lesion detection sensitivities for 99mTc(V)-DMSA, MIBI and 201Tl were 95%, 47% and 19% respectively. We conclude that 99mTc(V)-DMSA is clearly superior to MIBI and 201Tl in the follow-up of MTC patients.