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We compared preoperative regular activity and low-activity radiology-based predictions with real surgical and pathological findings for parathyroidectomy surgery. The study retrospectively analyzed 54 consecutive cases (2009–2016) for benign tumor removal. Technetium-99m (Tc-99m)-sestamibi was used as a diagnostic radiopharmaceutical for diagnostic dual-phase parathyroid scintigraphy and single-photon emission computed tomography/computed tomography. We assessed images obtained with the radiation activity of 925 megabecquerel (MBq) and images obtained with the activity of 185 MBq. The study compared preoperative evaluation of tumor presence, multiplicity, location, and the type of pathology with actual data that were revealed during the operation and pathological investigation. The agreement between preoperative radiological prediction and actual location, number, and type of the parathyroid lesions was achieved in 98.4% (n = 61/62 lesions). The agreement between 925 MBq-based and 185-MBq based investigations was 100%. The agreement between radiological and pathological findings was 100% for both investigations. Our data suggest that the radioactivity of 185 MBq applied in the evaluation of the parathyroid glands provides results similar to the currently used 925–1110 MBq if used for diagnostic dual-phase parathyroid scintigraphy with Tc-99m-sestamibi. Such radioactivity may reduce the exposure to radiation of the patients and the staff without compromising results of the investigation.

OBJECTIVE. The purpose of this study is to evaluate a new device using molecular breast imaging (MBI) for 99mTc-sestamibi-guided stereotactic lesion localization as a complementary biopsy tool. MATERIALS AND METHODS. From December 2012 to May 2016, a total of 38 consecutive women (mean age, 59 years; range, 41-77 years) underwent 99mTc-sestamibi-guided biopsy using a new MBI-based device and were retrospectively reviewed. The biopsy modality used five steps: Stereotactic localization of the 99mTc-sestamibi-avid lesion, calculation of coordinates of the lesion location using dedicated software, placement of the needle, verification of the correct needle position, and tissue sampling with a vacuum-assisted device followed by placement of a radiologic marker at the biopsy site and ex vivo measurement of the biopsy specimens. RESULTS. The procedure was technically successful in all 38 lesions. In all cases, biopsy samples were radioactive and adequate for histopathologic analysis. Nineteen lesions (50%) were found to be malignant, and the remaining lesions were found to be benign. The mean procedure time was 71 minutes (range, 44-112 minutes). The radiologic marker was successfully deployed in 37 lesions (97%). Two hematomas and three vasovagal reactions were observed. CONCLUSION. Technetium-99m sestamibi-guided biopsy performed using a dedicated MBI-based device is technically feasible and represents a valuable complementary biopsy tool in breast lesion diagnosis.

In breast cancer, interest in technetium-99m (Tc-99m) sestamibi-based therapy monitoring is increasing owing to the growing use of Tc-99m-sestamibi-based molecular breast imaging. In the present meta-analysis of 529 patients, Tc-99m-sestamibi planar imaging showed low sensitivity for predicting a pathologic nonresponse to neoadjuvant chemotherapy. In contrast, Tc-99m-sestamibi imaging performed during treatment seemed highly sensitive for the prediction of nonresponse. New tools incorporating quantitative single photon emission computed tomography/computed tomography need to be explored.Background: Interest in technetium-99m (Tc-99m)-sestamibi imaging for neoadjuvant chemotherapy (NAC) response monitoring in locally advanced breast cancer (LABC) is increasing but remains matter of discussion. The present study conducted a meta-analysis of the diagnostic performance of Tc-99m-sestamibi to predict pathologic nonresponse to NAC for primary LABC. Materials and Methods: A systematic data search was performed. Studies with a minimum of 10 LABC patients that had evaluated Tc-99m-sestamibi imaging for NAC nonresponse using conventional planar scintimammography, breast-specific gamma-imaging, and/or single photon emission computed tomography/computed tomography (SPECT/CT) were included. The histopathologic findings were the reference standard. The meta-analysis was performed using a mixed logistic regression model. Results: The search revealed 14 eligible studies with 529 patients. Of the 14 studies, 11 had evaluated scintimammography and 3 breast-specific gamma-imaging. No studies examining SPECT or SPECT/CT were found. The overall estimated pooled sensitivity, specificity, and positive and negative likelihood ratios of Tc-99m-sestamibi imaging to predict nonresponsiveness to NAC were 70.3% (95% confidence interval [CI], 56.5%-81.3%%), 90.1% (95% CI, 77.5%-96.0%), 7.13 (95% CI, 3.08-16.53), and 0.33 (95% CI, 0.22-0.49), respectively. Only 3 studies (107 patients) evaluated Tc-99m-sestamibi imaging during NAC, reported an estimated pooled sensitivity of 87% (95% CI, 72%-100%) and specificity of 93% (95% CI, 85%-100%). Conclusion: Only planar Tc-99m-sestamibi imaging has been investigated for NAC nonresponse in LABC but showed low sensitivity to predict pathologic nonresponse. However, most studies focused on the prediction of pathologic complete response after NAC. Although experience is limited, Tc-99m-sestamibi uptake during NAC seems highly sensitivity for the prediction of nonresponsiveness. Features such as SPECT/CT imaging, standardized quantification, relation to tumor subtypes, and proper timing have been insufficiently evaluated and require further investigation. (C) 2017 Elsevier Inc. All rights reserved.

Purpose This review aims to discuss the methodological aspects of dedicated molecular breast imaging (MBI) using 99mTc-sestamibi as radiotracer to guide biopsy of occult or unclear breast lesions on mammography (MG) and ultrasound (US) that are suspicious on MBI (BI-RADS criteria 4 and 5), including its advantages, limitations and future clinical applications. Methods Literature search was performed using the PubMed/MEDLINE database and “99mTc-sestamibi”, “biopsy” and “breast cancer” as keywords. The search was restricted to English language. Results There are few studies on 99mTc-sestamibi guided biopsy methods; to our knowledge, no full studies have yet been reported on clinical validation of this new biopsy procedure. This review describes technical aspects of 99mTc-sestamibi guided biopsy and discusses the advantages and limitations of this procedure in comparison with MG, US and MRI-guided biopsy. Conclusions MBI-guided biopsy appears to be a complementary modality and is principally indicated in the case of occult or unclear breast lesions on MG/US, that are suspicious on MBI. The future indication is in targeted biopsies in patients with large heterogeneous tumours. Further studies are needed to define the accuracy of this biopsy procedure.

Background Only few data are available regarding the prognostic impact of myocardial perfusion scintigraphy with 99mTc-sestamibi (MPS) regarding emerging cardiac events in elderly patients Purpose To evaluate the prognostic value of MPS regarding emerging cardiac events in patients aged ≥70 years with known or suspected coronary artery disease (CAD). Material and Methods One hundred and thirty-three patients (74.6 ± 3.7 years) who underwent exercise or pharmacological stress/rest MPS were included in this analysis. Semi-quantitative visual interpretation of MPS images was performed and Summed-Stress- (SSS), Summed-Difference- (SDS), and Summed-Rest Scores (SRS) were calculated. Multivariate logistic regression analyses were calculated for evaluation of the independent prognostic impact of MPS results and several cardiac-related patient characteristics with regard to emerging cardiac events. Kaplan-Meier survival- and log rank analyses were calculated for assessment of cardiac event-free survival. Results Pathological SSS (OR: 3.3), angina (OR: 2.7) and ischemic ECG (OR: 3.0) were independently associated with cardiac events. Patients with pathological SSS (p = 0.005) and ischemic ECG (p = 0.012) had a significantly lower incidence of cardiac event-free survival. Conclusion Pathological MPS is independently associated with emerging cardiac events predicting a significantly lower incidence of cardiac event-free survival in patients aged ≥70 years.

Objectives: Brain single-photon emission computed tomography (SPECT) has been proposed as a potentially useful modality for the metabolic assessment of various brain tumors. Material and methods: In a 10-patient prospective pilot study we evaluated whether (99m)Tc-Tetrofosmin ((99m)Tc-TF) uptake correlates with glioma proliferative activity assessed by flow cytometric analysis. (99m)Tc-TF brain SPECT was performed shortly before surgical tumor excision. Results: Eight patients were diagnosed with glioblastoma multiform and 2 with anaplastic astrocytoma. All tumors were aneuploid. We found a significant positive linear correlation between 99mTc-TF uptake and percentage of tumor cells on the S-phase of the cell cycle (r=0.92, P=0.001). Conclusion: Initial evidence suggests that 99mTc-TF could provide a non-invasive indicator of glioma proliferative activity. (C) 2009 Elsevier B.V. All rights reserved. Clin Neurol Neurosurg

BACKGROUND: In primary hyperparathyroidism the gamma probe is effective, but its role in secondary hyperparathyroidism is unclear. We investigated the utility of the probe in the surgical management of secondary and tertiary hyperparathyroidism.METHODS: The value of the probe in guiding resection of parathyroids was determined prospectively in 29 patients with secondary or tertiary hyperparathyroidism. Resected tissues with radioactivity of greater than 20% as compared with the wound bed was considered hyperfunctional parathyroid and was confirmed histologically.RESULTS: The probe was helpful in guiding resection in 13% of the hyperplastic glands, including ectopic glands and those not detected preoperatively. The gamma probe confirmed the presence of hyperfunctional parathyroid after resection with a sensitivity and specificity of 97% and 92%, respectively.CONCLUSIONS: The probe is particularly useful in confirming the presence of hyperfunctional parathyroids after resection. It also is useful in identifying ectopic localizations, but its value is limited in guiding surgery for secondary or tertiary disease. (c) 2008 Elsevier Inc. All rights reserved.

We aimed to evaluate the diagnostic and preoperative localization capacity of Tc-99m methoxyisobutylnitrile (MIBI) parathyroid scintigraphy and ultrasonography (USG) in enlarged parathyroid glands in the primary hyperparathyroidism (pH PT), as well as the relationship between the success rate of these techniques and biochemical values. We retrospectively evaluated 39 patients with clinical and biological evidence of pHPT who referred to the university hospital for MIBI parathyroid scintigraphy. Patients were examined with USG and double-phase MIBI parathyroid scintigraphy for the detection of enlarged parathyroid glands. Preoperative serum intact parathyroid hormone (iPTH) levels, calcium (Ca), phosphate and alkaline phosphatase measurements were obtained. A total of 45 parathyroid lesions in 39 patients were reviewed. Thirty-four patients had a single adenoma and five patients with multi-gland disease had 11 abnormal parathyroid glands including three adenomas, whereas the remaining 8 glands showed hyperplasia. The overall sensitivities of MIBI parathyroid scintigraphy, USG, and combined techniques were 85.3%, 72.5% and 90.4%, respectively; the positive predictive values (PPV) were 89.7%, 85.2%, and 92.6%, respectively. The most successful approach for detection of enlarged parathyroid glands in hyperparathyroidism is the concurrent application of USG and MIBI parathyroid scintigraphy modalities. The concomitance of thyroid diseases decreases the sensitivity of both MIBI parathyroid scintigraphy and USG in enlarged parathyroid glands.

Objectives: Fluorine-18 fluorodeoxyglucose (FDG) SPECT has emerged as an alternative to dedicated PET imaging. However, it remains uncertain whether FDG SPECT is an as accurate for viability assessment as FDG PET in patients with severely reduced left ventricular function. The aim of the study was to assess the diagnostic accuracy of FDG SPECT in a head-to-head comparison with FDG PET, and divide the patients according to the severity of left ventricular dysfunction. Methods: A total of 47 patients, with a history of myocardial infarction underwent FDG/perfusion (Tc-99m-sestamibi or Tl-201) SPECT as well as FDG/N-13-ammonia PET. The patients were divided into 2 subgroups based on the left ventricular ejection fraction (LVEF) (35% cutoff). The left ventricular myocardium was divided into 13 segments, and each segment was classified as viable or scar using a semi-quantitative scoring system based on defect severity and the presence or absence of perfusion-FDG mismatch. Results: Of the 47 patients studied, 23 had LVEF = 35% (high LVEF group; mean 47 +/- 6%). In the low LVEF group, 213 segments (71%) were dysfunctional, as compared to 102 (33%) in the high LVEF group. The agreement for detection of viability between PET and SPECT in the low LVEF group was 82% (kappa 0.63), which was not different from the agreement in the high LVEF group (85%, kappa 0.66, p = 0.42 versus low LVEF group). Conclusions: The results indicate that FDG SPECT can be used for tissue viability assessment regardless of the severity of left ventricular dysfunction.

WOS: 000179279000014 PubMed: 12397470 Oxygen (O-2) inhalation after acute myocardial ischaemia has long been a part of standard therapy in cardiology. It has also been demonstrated that therapeutic hyperoxia diminishes myocardial stunning. The aim of this pilot study was to investigate whether the uptake kinetics of the myocardial perfusion agent technetium-99m sestamibi (MIBI) during O-2-enriched breathing is modified in comparison with the kinetics observed under conventional rest imaging performed after injection during inhalation of room air. Nine patients scheduled for coronary intervention (CI) with a documented significant stenosis (greater than or equal to50%) of at least one epicardial coronary vessel and one patient with slow flow on coronary angiography were investigated. First, rest MIBI electrocardiogram-gated single-photon emission tomography (G-SPET) with 740 MBq was performed. Two days later, the tracer was injected following a 5-min period of 100% O-2-supported (nasal catheter) breathing at rest (6 1/min) and a second G-SPET acquisition (O-2+MIBI G-SPET) was carried out. Patients' medication was not withdrawn and was matched throughout the study. The mean elevation of arterial oxygen saturation achieved was 2.95%. No significant changes in arterial blood pressure or heart rate could be detected at any time during the procedure. Compared with the results of baseline G-SPET, on O-2+MIBI G-SPET five patients scheduled for CI and the patient with slow flow showed increased tracer uptake in initially ischaemic regions without any alterations in other myocardial regions. In three of these five patients, post-CI imaging could be performed and showed increased tracer uptake in all additional areas detected previously by O-2+MIBI imaging. In three patients, besides improvement in ischaemic regions, a mild reduction in tracer uptake was observed in myocardium that initially appeared normal. In one of these patients, thallium-201 rest-redistribution SPET was performed and showed an uptake pattern more similar to that seen on O-2+MIBI images than that on baseline MIBI G-SPET.In one patient, no difference in tracer uptake was observed in pre- and post-CI studies. Improvement was detected in the wall thickening images of the O-2+MIBI study in seven of the ten patients. Four of these patients showed improvement in the same regions after CI. In this pilot study, it was demonstrated that MIBI injection during O-2-enriched breathing can be a useful technique for enhancing the detection of viable myocardial tissue. The possible mechanisms of altered tracer kinetics are discussed.

Background: Our aim was to determine the value of 99mTc-Sestamibi scanning as functional detection method of P-glycoprotein (Pgp) blockade by PSC 833 in solid tumour patients. Patients and methods: Day 1 and day 4 after 2,200 mg orally administered PSC 833 the tumour area was scanned after intravenous (iv) administration of 400 MBq Tc-99m-Sestamibi. In rumours with net Tc-99m-Sestamibi uptake and in the hepatic region K-efflux was determined. Whole blood was analyzed for Tc-99m-Sestamibi, and PSC 833 levels. Results: Fourteen patients were included. In the only Pgp-positive tumour with positive Tc-99m-Sestamibi scanning K-efflux of Tc-99m-Sestamibi decreased significantly after PSC 833 intake. A net inhibition of liver efflux of Sestamibi after PSC 833 intake was observed in all evaluable patients. PSC 833 blood levels were all above 2 mg/L during scanning; Tc-99m-Sestamibi blood levels post versus pre PSC 833 were unchanged Conclusions: PSC 833 induced modulation of K-efflux of Tc-99m-Sestamibi in a Pgp positive tumour and in all patients in the liver.

Made available in DSpace on 2013-08-12T18:17:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-01 Made available in DSpace on 2013-09-30T18:20:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:33:15Z No. of bitstreams: 0 Made available in DSpace on 2014-05-20T13:33:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-01 To evaluate the tumor response to neoadjuvant chemotherapy, Tc-99m-sestamibi breast scintigraphy was proposed as a quantitative method Fifty-five patients with ductal carcinoma were studied They underwent breast scintigraphy before and after neoadjuvant chemotherapy, along with clinical assessment and surgical specimen analysis The regions of interest on the lesion and contralateral breast were identified, and the pixel counts were used to evaluate lesion uptake in relation to background radiation The ratio of these counts before to after neoadjuvant chemotherapy was assessed The decrease in uptake rate due to chemotherapy characterized the scintigraphy tumor response The Kruskal-Wallis test was used to compare the mean scintigraphic tumor response and histological type Dunn's multiple comparison test was used to detect differences between histological types The Mann-Whitney test was used to compare means between quantitative and qualitative variables scintigraphic tumor response vs clinical response and uptake before chemotherapy vs scintigraphic tumor response The Spearman's test was used to correlate the quantitative variables of clinical reduction in tumor size and scintigraphic tumor response All of the variables compared presented significant differences The change in Tc-99m-sestamibi uptake noted on breast scintigraphy, before to after neoadjuvant chemotherapy, may be used as an effective method for evaluating the response to neoadjuvant chemotherapy, since this quantification reflects the biological behavior of the tumor towards the chemotherapy regimen Furthermore, additional analysis on the uptake rate before chemotherapy may accurately predict treatment response São Paulo State Univ UNESP, Botucatu Med Sch, Dept Nucl Med, São Paulo, Brazil São Paulo State Univ UNESP, Botucatu Med Sch, Dept Obstet & Gynecol, São Paulo, Brazil São Paulo State Univ UNESP, Botucatu Med Sch, Dept Clin Med, São Paulo, Brazil São Paulo State Univ UNESP, Botucatu Med Sch, Dept Pathol, São Paulo, Brazil Barretos Canc Hosp, Dept Nucl Med, São Paulo, Brazil Barretos Canc Hosp, Dept Physiotherapy, São Paulo, Brazil Barretos Canc Hosp, Ctr Researcher Support, São Paulo, Brazil São Paulo State Univ UNESP, Botucatu Med Sch, Dept Nucl Med, São Paulo, Brazil São Paulo State Univ UNESP, Botucatu Med Sch, Dept Obstet & Gynecol, São Paulo, Brazil São Paulo State Univ UNESP, Botucatu Med Sch, Dept Clin Med, São Paulo, Brazil São Paulo State Univ UNESP, Botucatu Med Sch, Dept Pathol, São Paulo, Brazil

Made available in DSpace on 2013-08-12T18:51:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-01 Made available in DSpace on 2013-09-30T18:20:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:33:15Z No. of bitstreams: 0 Made available in DSpace on 2014-05-20T13:33:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-01 Scintimammography using Tc-99m-sestamibi is a noninvasive and painless diagnostic imaging method that is used to detect breast cancer when mammography is inconclusive Because of the advantages of labeling v '7,ith Tc-99m-sestamibi and its high efficiency in detecting carcinomas, it is the most widespread agent for this purpose Its accumulation in the tumor has multifactorial causes and does not depend on the presence of architectural distortion or local or diffuse density variation in the breast The objective of tfiis study was to evaluate the accuracy of scintimammography 1 for detecting breast cancer One hundred and fifty-seven patients presenting 158 palpable and non-palpable breast nodules were evaluated Three patients were male and 154 were female, aged between 14 and 81 years All patients underwent scintimammography, and the nodule was subjected i to cytological or histological study, i e, the gold standard for diagnosing cancer One hundred and eleven malignant and 47 benign nodules were detected, with predominance of ductal carcinomas (n=94) and fibroadenoma/fibrocysiic condition (n=11/n=11), respectively The mean size was 3 11 cm (7-10 cm) among the malignant nodules and 2 07 cm among the benign nodules (0 5-10 cm) The sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 89, 89, 95, 78 and 89%, respectively Analysis on the histological types showed that the technique was more effective on tumors that were more aggressive, such as ductal carcinoma In this study, Tc-99m-sestamibi scintim immography was shown to be an important tool for diagnosing breast cancer when mammography was inconclusive Barretos Canc Hosp, Dept Nucl Med, BR-14784400 São Paulo, Brazil São Paulo State Univ UNESP, Dept Nucl Med, Botucatu Med Sch, BR-18618970 São Paulo, Brazil São Paulo State Univ UNESP, Dept Obstet & Gynecol, Botucatu Med Sch, BR-18618970 São Paulo, Brazil São Paulo State Univ UNESP, Dept Nucl Med, Botucatu Med Sch, BR-18618970 São Paulo, Brazil São Paulo State Univ UNESP, Dept Obstet & Gynecol, Botucatu Med Sch, BR-18618970 São Paulo, Brazil

Strahlentherapie Und Onkologie

Objectives: Fluorine-18 fluorodeoxyglucose (FDG) SPECT has emerged as an alternative to dedicated PET imaging. However, it remains uncertain whether FDG SPECT is an as accurate for viability assessment as FDG PET in patients with severely reduced left ventricular function. The aim of the study was to assess the diagnostic accuracy of FDG SPECT in a head-to-head comparison with FDG PET, and divide the patients according to the severity of left ventricular dysfunction. Methods: A total of 47 patients, with a history of myocardial infarction underwent FDG/perfusion (Tc-99m-sestamibi or Tl-201) SPECT as well as FDG/N-13-ammonia PET. The patients were divided into 2 subgroups based on the left ventricular ejection fraction (LVEF) (35% cutoff). The left ventricular myocardium was divided into 13 segments, and each segment was classified as viable or scar using a semi-quantitative scoring system based on defect severity and the presence or absence of perfusion-FDG mismatch. Results: Of the 47 patients studied, 23 had LVEF = 35% (high LVEF group; mean 47 +/- 6%). In the low LVEF group, 213 segments (71%) were dysfunctional, as compared to 102 (33%) in the high LVEF group. The agreement for detection of viability between PET and SPECT in the low LVEF group was 82% (kappa 0.63), which was not different from the agreement in the high LVEF group (85%, kappa 0.66, p = 0.42 versus low LVEF group). Conclusions: The results indicate that FDG SPECT can be used for tissue viability assessment regardless of the severity of left ventricular dysfunction.

The aim of this study was to determine the yield of attenuation correction in myocardial perfusion imaging (MPI), before and after a 1-year experience period. In 48 consecutive patients referred for MPI, both non-corrected (NC) and attenuation-corrected (AC) images were analysed by three independent readers shortly after implementation of attenuation correction. The same images were re-analysed 1 year later, after having obtained experience in attenuation correction on a routine basis in >500 patients with clinical feedback. Results were compared with gold standards for ischaemia and infarction based on coronary angiography, follow-up, ultrasound and gated blood pool imaging. Sensitivity and specificity for the detection of coronary artery disease were 95% and 45% respectively for NC images and 77% and 70% respectively for AC images at first readings. After 1 year of AC experience, NC sensitivity/specificity was 100%/61%, and AC results were 89%/92%. It is concluded that attenuation correction improves the performance of MPI interpretation. With attenuation correction, specificity is increased and sensitivity is similar as compared with NC images. However, attenuation correction requires experience and is associated with a learning curve.

Background: Our aim was to determine the value of 99mTc-Sestamibi scanning as functional detection method of P-glycoprotein (Pgp) blockade by PSC 833 in solid tumour patients. Patients and methods: Day 1 and day 4 after 2,200 mg orally administered PSC 833 the tumour area was scanned after intravenous (iv) administration of 400 MBq Tc-99m-Sestamibi. In rumours with net Tc-99m-Sestamibi uptake and in the hepatic region K-efflux was determined. Whole blood was analyzed for Tc-99m-Sestamibi, and PSC 833 levels. Results: Fourteen patients were included. In the only Pgp-positive tumour with positive Tc-99m-Sestamibi scanning K-efflux of Tc-99m-Sestamibi decreased significantly after PSC 833 intake. A net inhibition of liver efflux of Sestamibi after PSC 833 intake was observed in all evaluable patients. PSC 833 blood levels were all above 2 mg/L during scanning; Tc-99m-Sestamibi blood levels post versus pre PSC 833 were unchanged Conclusions: PSC 833 induced modulation of K-efflux of Tc-99m-Sestamibi in a Pgp positive tumour and in all patients in the liver.

99mTc-sestamibi (99mTc-MIBI) is a substrate for the P-glycoprotein (P-gp) pump but it is not known whether it is a substrate for the multidrug resistance-associated protein (MRP) pump. Therefore, 99mTc-MIBI was evaluated in the GLC4 cell line and its doxorubicin-resistant MRP-, but not P-gp-, overexpressing GLC4/ADR sublines as well as in the S1 cell line and its MRP-transfected subline S1-MRP. 99mTC-MIBI concentration decreased in the GLC4/ADR sublines with increasing MRP overexpression and was lower in S1-MRP than in S1. 99mTC-MIBI plus vincristine increased 99mTc-MIBI concentration in GLC4 lines compared with 99mTc-MIBI alone. 99mTc-MIBI efflux raised with increasing MRP expression in the GLC4 lines. Glutathione depletion elevated 99mTC-MIBI concentration in GLC4/ADR(150x). Cross resistance for 99Tc-MIBI, used to test cytotoxicity of the Tc compound, was observed in GLC4/ADR(150x) vs GLC4. 99Tc-MIBI induced a synergistic effect on vincristine cytotoxicity in GLC4/ADR(150x). These results show that 99mTc-MIBI is involved in MRP-mediated efflux. The fact that 99mTc-MIBI efflux is influenced by MDR1 and MRP expression must be taken into account when this γ-rays-emitting complex is tested for tumour efflux measurements.