99mTc-MIBI brain SPECT as an indicator of the chemotherapy response of recurrent, primary brain tumors

Clinical Significance of Incidental Pituitary TC-99m MIBI Uptake on Parathyroid Spect and Factors Affecting Uptake Intensity

OBJECTIVE

(1)To define a quantitative cutoff value for incidental pituitary Technetium-99m methoxyisobutylisonitrile (Tc-99m MIBI) uptake above which is of clinical importance and (2) to investigate possible factors affecting the intensity of uptake in pituitary adenoma.

MATERIALS AND METHODS

A retrospective analysis of 55 patients with a simultaneous parathyroid single-photon emission computed tomography and pituitary magnetic resonance imaging were included. Twenty-four patients with pituitary adenoma were chosen as the study group and 31/55 patients who had no signs of a pituitary adenoma were included in the control group. Mean count values (count/pixel) for pituitary region of interest (ROI)/mean value for normal cortical region ROI (P/C) were calculated in both groups. Median P/C values were compared. A cutoff value for P/C was calculated as a quantitative parameter to indicate pituitary tumors. Possible contributing factors in intensity of pituitary Tc-99m MIBI uptake were investigated.

RESULTS

Median P/C ratios were significantly higher in the study group (p < 0.001). A cutoff value of 7.675 was found for P/C to have a sensitivity, spesificity, positive predictive value, and negative predictive value 100%, 96.8%, 96%, and 100%, respectively. There was no correlation between investigated factors and degree of pituitary Tc-99m MIBI uptake.

CONCLUSIONS

Incidental pituitary Tc-99m MIBI uptake values above 7.675 for P/C are suspicious for pituitary adenoma and can be further investigated clinically and radiologically. Tc-99m MIBI uptake is not affected from the biochemical nature of the adenoma, the therapies received, size, local invasion, or cystic necrotic component of the tumor.

A framework using multimodal imaging for longitudinal monitoring of patients in neuro-oncology. Application to a SPECT/MRI study

This paper proposes a framework to assess the potential value of 99mTc Sestamibi SPECT in addition to Gadolinium-enhanced MRI for the monitoring of patients with high grade gliomas under antiangiogenic treatment. It includes: 1) multimodal and monomodal high precision registration steps achieved thanks to a registration strategy which selects the best method among several ones for each dataset, 2) tumor segmentation steps dedicated to each modality and 3) a tumor comparison step which consists in the computation of some global (volume, intensity) and local (matching and mismatching) quantitative indices to analyze the tumor using different imaging modalities and at different times during the treatment. Each step is checked via 2D and 3D visualization. This framework was applied to a database of fifteen patients. For all patients, except one, the tumor volumes decrease globally and locally. Furthermore, a high correlation (r=0.77) was observed between MRI and Sestamibi tumor volumes. Finally, local indices show some possible mismatches between MRI Gadolinium uptake and Sestamibi uptake, which need to be further investigated.

Assessing response using 99mTc-MIBI early after interstitial chemotherapy with carmustine-loaded polymers in glioblastoma multiforme: preliminary results

Introduction. Early signs of response after applying wafers of carmustine-loaded polymers (gliadel) are difficult to assess with imaging because of time-related imaging changes. (99m)Tc-sestamibi (MIBI) brain single-photon emission tomography (SPET) has reportedly been used to reveal areas of cellularity distinguishing recurrent neoplasm from radionecrosis. Our aim was to explore the role of MIBI SPET in assessing response soon after gliadel application in glioblastoma multiforme (GBM). Methods. We retrospectively reviewed the charts on 28 consecutive patients with a radiological diagnosis of GBM who underwent MIBI SPET/CT before surgery (with intracavitary gliadel placement in 17 patients), soon after surgery, and at 4 months. The area of uptake was selected using a volume of interest that was then mirrored contralaterally to obtain a semiquantitative ratio. Results. After adjusting for ratio at the baseline, the effect of treatment (gliadel versus non-gliadel) was not statistically significant. Soon after surgery, however, 100% of patients treated with gliadel had a decreased ratio, as opposed to 62.5% of patients in the non-gliadel group (P = 0.0316). The difference between ratios of patients with radical versus partial resection reached statistical significance by a small margin (P = 0.0528). Conclusions. These data seem to suggest that the MIBI ratio could be a valuable tool for monitoring the effect of gliadel early after surgery.

Pituitary incidentalomas detected with technetium-99m MIBI in patients with suspected parathyroid adenoma: preliminary results

Tc-99m MIBI (MIBI) is a cationic lipophilic agent, which has traditionally been used for myocardial perfusion scintigraphy, detection and monitoring of different benign and malignant tumors. The objective of this study was to evaluate the frequency of pituitary incidentalomas detected on MIBI scans performed on patients with suspected parathyroid adenomas and to provide semiquantitative analysis of tracer uptake in the pituitary region. Tomographic images of MIBI scans on 56 patients with suspected parathyroid adenomas (2006–2007) were analyzed retrospectively. Semiquantitative analysis of abnormal uptake was performed by drawing identical regions of interest (ROI) over the pituitary area and the normal brain on one transverse section that demonstrates the lesion most clearly. Pituitary uptake to normal brain uptake ratio was calculated in all cases. We found statistically significant differences of MIBI uptake in patients with pituitary adenomas, mean ratio: 29.78±12.17 (median 29.77, and range 19-41), compared with patients with no pathologic changes in this region, mean ratio was 5.88±1.82 (median was 5.95 and range 2.0- 9.2). As the groups are too small for statistical analysis, these results need to be confirmed in a larger cohort and should include more detailed biochemical correlation. MIBI parathyroid scintigraphy should be taken into account as a potential source of identifying pituitary incidentalomas. Clinical significance of these findings needs further evaluation.

Imaging of multidrug resistance in cancer

Primary intrinsic and/or acquired multidrug resistance (MDR) is the main obstacle to successful cancer treatment. Functional molecular imaging of MDR in cancer using single photon or positron emitters may be helpful to identify multidrug-resistant tumours and predict not only those patients who are resistant to treatment, with a clinically unfavourable prognosis, but also those who are susceptible to the development of drug toxicity or even certain tumours . Variations in the mdr1 gene product may directly affect the therapeutic effectiveness, and single nucleotide polymorphisms for the mdr1 gene may be associated with altered oral bioavailability of MDR1 substrates, drug resistance, and a susceptibility to some human diseases. The challenge of translating the concept of MDR modulation in vivo involves a complex cellular interplay between both malignant and normal cells. Integration and correlation of functional single photon emission tomography or positron emission tomography imaging findings with mdr1 genotype and clinical data may contribute to efficient management by selecting cancer patients with the appropriate molecular phenotype for maximal individual therapeutic benefit, as well as those who are non-responders. This review describes a role for functional imaging of classical mechanisms of MDR with an emphasis on readily available [^99mTc]MIBI scintigraphy. MIBI scintigraphy has been shown to be a non-invasive cost-effective in vivo assay of ATP-binding cassette transporters associated with MDR in cancer, including P-glycoprotein, multidrug-resistant protein 1 and breast cancer resistant protein. New imaging agents for molecular targets such as vascular endothelial growth factor and HER2 receptors, may potentially be combined with MDR imaging substrates to more accurately predict the therapeutic response to anticancer drugs, guiding individualised treatment while minimising the economic health costs of ineffective therapy in an era of personalised medicine.

Investigation of blood perfusion and metabolic activity of brain tumours in adults by using 99mTc-methoxyisobutylisonitrile

OBJECTIVES

(i) To examine blood perfusion and metabolic activity of various brain tumours using radionuclide cerebral angiography (RCA) and single-photon emission tomography (SPET) after a single dose of Tc-methoxyisobutylisonitrile (MIBI). (ii) To examine if the inclusion of RCA can improve insight into the relative contribution of tumour perfusion to the uptake of MIBI shown by SPET, and to improve evaluation of tumour biology. (iii) To determine the value and the roles of MIBI in the management of brain tumour patients.

METHODS

Fifty adult patients (38 male, 12 female) with a total of 56 intracranial space-occupying lesions have been included prospectively, 37 of which were newly diagnosed and the remaining with signs of recurrence/rest of earlier resected and irradiated brain tumours. The control group consisted of nine volunteers with no evidence of organic cerebral disease. Scintigraphic examination consisted of a dynamic first-pass study lasting 60 s (3 s/frame) and two SPET studies (60 projections each, 25 s/projection), starting 15 min and 2 h after intravenous injection of MIBI. Regions of interest of the tumour and normal brain tissue were drawn on RCA and both early and delayed SPET slices. The following tumour/brain activity ratios have been calculated: (i) tumour perfusion index (P); (ii) early uptake index (E); (iii) delayed uptake index (D); and(iv) retention index (R). Analogous indices have been calculated from the same examinations performed in controls, reflecting maximal physiologic regional variations of perfusion and uptake in brain tissue.

RESULTS

Mean P of various brain tumours (low-grade gliomas 0.98, anaplastic gliomas 1.14, glioblastoma multiforme 1.20, metastases 1.09, lymphomas 1.08) differ little from each other and do not exceed maximal physiologic regional variations of cerebral perfusion (1.33), with the exception of meningioma (1.87, F=2.83, P=0.015). The receiver operating characteristics curve analysis of P showed that for the cut-off value of 1.45 the sensitivity for distinguishing meningioma from other tumours is 75%, specificity 87%, positive predictive value 33% and negative predictive value 97%. Mean E of malignant brain tumours (8.3, n=31, 23 primary, eight secondary), except anaplastic gliomas (3.5, n=5), differed significantly (P=0.02) from those of benign gliomas (3, n=9) but not from that of meningioma (11.9, n=4). The cut-off value for distinguishing malignant from benign lesions on the basis of E set at 4.8 resulted in sensitivity 67%, specificity 75%, accuracy 70%, positive predictive value 80% and negative predictive value 60%. D and R showed tendency of wash-out of MIBI from meningiomas, but otherwise did not improve the results substantially.

CONCLUSION

Integrated results of RCA and SPET with Tc-MIBI indicate that blood perfusion, blood-tumour barrier permeability and metabolic activity of the tumour are all very important for the resultant uptake shown by SPET. If the perfusion index is less than 1.45, then meningioma can be ruled out. Early SPET is recommendable for distinguishing glioblastoma from low-grade gliomas, as a complement to standard magnetic resonance imaging and/or computed tomography.

99mTc-sestamibi scan differentiates tumor from other contrast enhancing tissue in choroid plexus tumors

Choroid plexus tumors are rare brain tumors which account for 0.4% to 0.6% among brain tumors. Tumor resection is known to be of large prognostic impact, and re-resection of residual tumors is a part of standard care. However, after multiple resections it can become difficult to differentiate tumor from reactive tissue. 99mTC-sestamibi scans may assist in differentiating neoplastic (99mTC-sestamibi positive) from non-neoplastic tissue (99mTC-sestamibi negative). Previous literature showed sestamibi to be helpful in detecting residual choroid plexus tumors resulting in further resection. Here, we report the first case to show that sestamibi scans can also help with the opposite decision.