Sensitivity and specificity of thallium-201 single-photon emission tomography in the functional detection and differential diagnosis of brain tumours

Value of Thallium-201 SPECT and SPECT/CT Brain Imaging in Differentiating Malignant From Nonmalignant Lesions: A Comparative Case-Series Study With Pathologic and/or Clinical Correlation

BACKGROUND

Thallium-201 single-photon emission computed tomography/computed tomography (SPECT/CT) brain scan is an imaging modality which can be done to differentiate between malignant and nonmalignant lesions among patients with nonconclusive findings on conventional neuroimaging. This study describes the results of thallium-201 SPECT/CT brain imaging and relate it to histopathologic and/or clinical findings and evaluate the value of thallium-201 SPECT/CT brain imaging in differentiating malignant from nonmalignant lesions.

METHODS

This is a retrospective case series study of 10 patients with cerebral lesions who underwent thallium-201 SPECT/CT brain imaging in a hospital in the Philippines from 2010 to 2021.

RESULTS

A total of 10 patients underwent thallium-201 SPECT/CT brain scan. Six had negative results while 4 had positive results. All of the patients who had positive results were found to have malignancy, whether recurrent or newly diagnosed. All of the patients with negative scan were found to have either an infectious and inflammatory disease and responded to treatment albeit in different degrees. Two of the 10 patients underwent biopsy whose results were consistent with the thallium-201 SPECT/CT brain scan results.

CONCLUSION

Thallium-201 brain scan combined with SPECT and SPECT/CT has been demonstrated to be useful in distinguishing malignant from nonmalignant lesions and is more cost-effective versus other imaging techniques. The findings in this study support the role of thallium scintigraphy in the diagnosis of patients with brain lesions most significantly when there is a need to differentiate between a malignant and benign condition.

PET and SPECT Imaging of Brain Tumors

Neuroimaging plays a vital role in the diagnosis and post-treatment assessment of brain tumors, aiding in treatment optimization, prognostication, and patient management. New clinical treatments have resulted in increased complexity of imaging interpretation, thus integrating complementary information from multiple imaging modalities (computed tomography, magnetic resonance imaging, and nuclear medicine) contributes to a thorough and more accurate evaluation. In review, we discuss current strategies of brain tumor imaging, specifically detailing the role of nuclear medicine single-photon emission computed tomography and positron emission tomography with utilization of both common and uncommon radiotracers in tumor grading, diagnosis, and treatment response.

Differential diagnosis of posterior fossa brain tumors: Multiple discriminant analysis of Tl-SPECT and FDG-PET

This study investigated the combined capability of thallium-201 (Tl)-SPECT and fluorine-18-fluoro-deoxy-glucose (FDG)-PET for differential diagnosis of posterior fossa brain tumors using multiple discriminant analysis.This retrospective study was conducted under approval of the institutional review board. In the hospital information system, 27 patients with posterior fossa intra-axial tumor between January 2009 and June 2015 were enrolled and grouped as the following 7 entities: low grade glioma (LGG) 6, anaplastic astrocytoma (AA) 2, glioblastoma (GBM) 3, medulloblastoma (MB) 3, hemangioblastoma (HB) 6, metastatic tumor (Mets) 3, and malignant lymphoma (ML) 4. Tl and FDG uptakes were measured at the tumors and control areas, and several indexes were derived. Using indexes selected by the stepwise method, discriminant analysis was conducted with leave-one-out cross-validation.The predicted accuracy for tumor classification was 70.4% at initial analysis and 55.6% at cross-validation to differentiate 7 tumor entities. HB, LGG, and ML were well-discriminated, but AA was located next to LGG. GBM, MB, and Mets largely overlapped and could not be well distinguished even applying multiple discriminant analysis. Correct classification in the original and cross-validation analyses was 44.4% and 33.3% for Tl-SPECT and 55.6% and 48.1% for FDG-PET.

Brain tumors

This review addresses the specific contributions of nuclear medicine techniques, and especially positron emission tomography (PET), for diagnosis and management of brain tumors. (18)F-Fluorodeoxyglucose PET has particular strengths in predicting prognosis and differentiating cerebral lymphoma from nonmalignant lesions. Amino acid tracers including (11)C-methionine, (18)F-fluoroethyltyrosine, and (18)F-L-3,4-dihydroxyphenylalanine provide high sensitivity, which is most useful for detecting recurrent or residual gliomas, including most low-grade gliomas. They also play an increasing role for planning and monitoring of therapy. (18)F-fluorothymidine can only be used in tumors with absent or broken blood-brain barrier and has potential for tumor grading and monitoring of therapy. Ligands for somatostatin receptors are of particular interest in pituitary adenomas and meningiomas. Tracers to image neovascularization, hypoxia, and phospholipid synthesis are under investigation for potential clinical use. All methods provide the maximum of information when used with image registration and fusion display with contrast-enhanced magnetic resonance imaging scans. Integration of PET and magnetic resonance imaging with stereotactic neuronavigation systems allows the targeting of stereotactic biopsies to obtain a more accurate histologic diagnosis and better planning of conformal and stereotactic radiotherapy.

Brain tumour recurrence: brain single-photon emission computerized tomography, PET and proton magnetic resonance spectroscopy

Recurrence is a frequent clinical problem in the follow-up of brain tumours. Single-photon emission computerized tomography, positron emission tomography (PET) and proton magnetic resonance spectroscopy (1H-MRS) represent significant diagnostic options to investigate recurrence. Many authors studied the separate and associate significance of these modalities in investigating relapsing brain tumours. In this study, the current role and the perspectives of these functional diagnostic tools are presented, evidencing the valuable results provided by their association. Finally, future development of new radiopharmaceuticals and advanced MRS technique can reliably contribute to improve the diagnostic process of recurrent brain neoplasms.

Differentiation of tumor recurrence from radiation necrosis in high-grade gliomas using 201Tl-SPECT

MRI is routinely performed to detect recurrence in patients with primary brain tumors, but it may not differentiate recurrent tumor from radiation-induced necrosis reliably. Thallium-201 single-photon emission computed tomography ((201)Tl-SPECT) might be useful in distinguishing between these two clinical entities. In a retrospective study (201)Tl-SPECT studies with corresponding MRI studies in 19 patients with clinical or radiological suspicion of high-grade tumor recurrence were reviewed. The diagnostic accuracies of both modalities were based on the subsequent histology or clinical course where biopsy was not performed. Post-scan histology was available in nine patients (43%) who underwent re-resection. The SPECT result determined management in six patients (29%). Post-SPECT survival was significantly better in patients with negative (201)Tl-SPECT studies compared to patients with positive studies (median survival 15+vs. 6 months) (p=0.04, log-rank test). The sensitivity and specificity of (201)Tl-SPECT in diagnosing tumor recurrence were 83% and 100%, respectively. (201)Tl-SPECT can accurately differentiate tumor recurrence from radiation necrosis in patients with high-grade gliomas and abnormal MRI findings post irradiation. This is reflected in a significantly longer post-scan survival time in patients with a negative (201)Tl-SPECT result.

Does supplementation of contrast MR imaging with thallium-201 brain SPECT improve differentiation between benign and malignant ring-like contrast-enhanced cerebral lesions?

OBJECTIVE

To determine whether thallium-201 ((201)Tl) brain single photon emission computed tomography (SPECT) could supplement magnetic resonance (MR) imaging diagnostic information by visual comparison of two separate data sets from patients with ring-like contrast-enhanced cerebral lesions.

METHODS

A combination of MR imaging and (201)Tl brain SPECT sets obtained from 13 patients (10 men, 3 women) ranging in age from 26 years to 86 years (mean 61.0 years) were retrospectively reviewed. A total of 12 patients had a solitary lesion, and the others had multiple lesions. All but two intracranial foci were pathologically confirmed. The final diagnoses were six glioblastomas, two cerebral metastases from lung cancer, and one each of abscess, resolving hematoma, primary central nervous system lymphoma, toxoplasmosis, and radiation necrosis. The two separate image formats (MR images and SPECT) were shown to ten readers with practical experience. All of the MR images for each patient were shown to each reader first. After interpreting them, the readers were shown the SPECT images. Images were scored in terms of how benign or malignant the foci were on a 5-point scale from "definitely benign" to "definitely malignant."

RESULTS

The improvement in the performance of all ten readers was from 67.7% to 93.8% in mean accuracy (P = 0.0028) and from 0.730 to 0.971 in mean Az value (P = 0.0069) after they were shown the (201)Tl brain SPECT images.

CONCLUSIONS

(201)Tl brain SPECT should substantially increase confidence in the diagnosis of intracranial lesions with ring-like contrast enhancement when MR imaging does not permit differentiation between benign and malignant disease.

The value of Tc-99m tetrofosmin in the imaging of pituitary adenomas

AIM

Magnetic resonance imaging (MRI) and computerized tomography (CT) are used in the diagnosis and follow-up of pituitary adenoma cases. Sometimes, these methods cannot display the post-operative residual tissue. It has been shown that some radionuclides were taken up by the pituitary adenomas. The aim of this study was to evaluate the uptake of the technetium-99m (Tc-99m) tetrofosmin (TF) in the pituitary adenoma and normal pituitary tissue and assess the ability of Tc-99m TF to predict tumor malignancy in pituitary gland.

METHODS

The patients with pituitary adenoma (7 invasive and 8 non-invasive) were compared with control group (no. 13). Single-photon emission computed tomography (SPECT) imaging of pituitary gland was performed in both groups. Tc-99m uptake indices were evaluated statistically with the use of Mann-Whitney U test.

RESULTS

The average tetrofosmin uptake index of pituitary adenoma is 2.44+/-1.54 for the patients and 1.69+/-0.71 for the control group. Any significant difference was not observed between the groups (p 0.3). The average index was calculated as 3.04+/-2.15 for invasive adenomas and 1.92+/-0.33 for the non-invasive group, and there was no significant difference between the two groups regarding uptake of the agent (p 0.53). Furthermore, it was determined that the invasive and non-invasive adenomas displayed an uptake of Tc-99m TF similar to normal pituitary tissue.

CONCLUSIONS

Since the pituitary adenoma and normal pituitary tissue gave similar results regarding Tc-99m TF uptake, it was concluded that this agent would not be useful in the diagnosis of pituitary adenoma.

Early dynamic 201Tl SPECT in the evaluation of brain tumours

OBJECTIVE

To estimate the usefulness of early dynamic 201Tl single photon emission computed tomography (SPECT) studies in distinguishing the histological malignancy of brain tumours.

METHODS

Dynamic 201Tl SPECT was performed for 3 min per scan for 15 min immediately after the administration of 201TlCl in 110 patients with brain tumours (111 lesions). The data obtained each 3 min were used for dynamic SPECT, and the five sets of data obtained were added to acquire static SPECT data. For static SPECT, the static thallium index (STI) was calculated as the ratio of 201Tl uptake in the tumour to that of the contralateral normal brain. The ratio of the 201Tl uptake for each 3 min was defined as the dynamic thallium index (DTI). The dynamic thallium rate (DTR), as a per cent, was calculated as DTR=(DTI for every 3 min)/STI H 100. The five values were approximated as a linear function and the slope (%/min) was calculated.

RESULTS

In static SPECT, there was no significant difference between the STI of malignant tumours (glioblastoma and anaplastic astrocytoma) and that of benign tumours (low-grade glioma, meningioma, pituitary adenoma, neurinoma and haemangioblastoma) (3.7+/-1.5, 5.0+/-3.5, respectively). On dynamic SPECT, DTI increased markedly over 15 min for malignant tumours. In contrast, the DTI of benign tumours increased slightly, steadily or decreased. The slope of the linear functions calculated from the DTRs was much higher in the malignant tumour group than in the benign tumour group (P<0.001).

CONCLUSIONS

We suggest that the performance of 201Tl dynamic SPECT for 15 min is useful for distinguishing malignant brain tumours from benign brain tumours and reduces the examination stress of patients.

Technetium-99m sestamibi single photon emission computed tomography findings correlated with P-glycoprotein expression in pituitary adenoma

The aim of this study is to evaluate whether the technetium-99m sestamibi ((99m)Tc-MIBI) single photon emission computed tomography (SPECT) characteristics of pituitary adenomas might be correlated with cavernous sinus invasion, proliferative potential or the multidrug-resistance (MDR-1) gene product P-glycoprotein (Pgp) expression in pituitary adenomas. Fifteen patients with pituitary adenomas, including 10 nonfunctioning adenomas, two prolactinomas, two GH producing adenomas, and one ACTH producing adenomas was investigated for this study. SPECT images with (99m)Tc-MIBI were acquired 15 minutes (early) and 3 hours (delayed) after injection. The tumor-to-normal brain ratio was calculated both early (ER) and delayed (DR) images. Retention index (RI) was calculated using the following formula: (DR-ER)/ERx100%. The pituitary adenomas specimens were examined by immunohistochemistry using anti-Pgp and MIB-1 monoclonal antibodies.(99m)Tc-MIBI SPECT findings were not related to MIB-1 labeling index or cavernous sinus invasion. (99m)Tc-MIBI SPECT RI (-38.55+/-20.77) of the Pgp-positive group was significantly lower than that (-15.78+/-19.40) of Pgp-negative group (p=0.0494). No significant difference was observed in the ER and DR of (99m)Tc-MIBI SPECT between Pgp-positive and negative groups. Our study suggests that although (99m)Tc-MIBI SPECT is not useful to evaluate the proliferative potential or cavernous sinus invasion of pituitary adenomas. (99m)Tc-MIBI SPECT could predict anti-cancer drug resistance related to the expression of Pgp in pituitary adenomas.

[Value of thallium 201-SPECT in typing brain space-occupying lesions]

OBJECTIVE

This study was designed to assess the diagnostic accuracy of single photon emission computed tomography with Tl-201 (SPECT Tl-201) to establish the tumoral or non-tumoral nature of brain space occupying lesions in comparison with usual diagnostic techniques.

MATERIAL AND METHODS

The study population consisted of 37 patients, 24 men (64.9 %) and 13 women (35.1 %), mean age 48 +/- 16 years. After establishing the clinical and radiological diagnosis of brain lesion, all patients underwent SPECT Tl-201, evaluating it only by subjective analysis and blinded to neuroestructural techniques. After surgical resection all patients were evaluated anatomopathologically to establish the histologic nature.

RESULTS

The sensitivity of SPECT Tl-201 (0.87) was higher than standard neuroimaging techniques (0.78). Specificity (0.43), positive (0.87) and negative (0.43) predictive values of SPECT were similar to neuroestructural procedures (MRI and CT scan) with 0.43, 0.82 and 0.38 values. Tumoral disease prevalence was 0.81. Neuroestructural procedures were non-conclusive in 18.9 % of the studies. No non-conclusive results were obtained with SPECT Tl-201.

CONCLUSIONS

SPECT Tl-201 is a diagnostic procedure of high sensitivity to establish the tumoral nature of brain lesions, with poor specificity, similar to structural X-ray techniques.

Technetium-99m sestamibi single photon emission computed tomography findings correlated with P-glycoprotein expression, encoded by the multidrug resistance gene-1 messenger ribonucleic acid, in intracranial meningiomas

The present study evaluated whether technetium-99m sestamibi (99mTc-MIBI) single photon emission computed tomography (SPECT) characteristics of intracranial meningioma are correlated with the histological malignancy, proliferative potential, and P-glycoprotein (Pgp) expression, encoded by the multidrug resistance gene-1 (MDR-1) messenger ribonucleic acid (mRNA). Twenty-one patients with intracranial meningiomas, including 17 benign and four nonbenign meningiomas, underwent 99mTc-MIBI SPECT imaging at 15 minutes (early) and 3 hours (delayed) after injection. The tumor-to-normal pituitary gland ratio was calculated on both early (ER) and delayed (DR) images. Retention index (RI) was calculated using the following formula: (DR - ER)/ER x 100%. Meningioma specimens were examined by immunohistochemistry using anti-Pgp and MIB-1 monoclonal antibody. MDR-1 mRNA expression was also investigated using reverse transcription-polymerase chain reaction assay. 99mTc-MIBI was highly accumulated and retained in the tumors. 99mTc-MIBI SPECT findings were not related to MIB-1 labeling index. 99mTc-MIBI SPECT RI of the Pgp-positive group (-9.12 +/- 22.27%) was significantly lower than that of the Pgp-negative group (28.79 +/- 22.80%) (p = 0.0016). No significant difference was seen in ER and DR between the positive and negative groups. These results show that 99mTc-MIBI may not be useful for determining proliferative potential and histological malignancy, but could predict anticancer drug resistance related to the expression of MDR-1 mRNA and its gene product Pgp in patients with intracranial meningiomas.

Usefulness of Thallium-201 Chloride Single Photon Emission Computed Tomography for the Preoperative Diagnosis of Fourth Ventricle Meningioma-Case Report-

A 51-year-old woman presented with a fourth ventricle meningioma manifesting as a 2-week history of dizziness and vomiting. Computed tomography (CT) and magnetic resonance (MR) imaging revealed a round mass lesion in the fourth ventricle. Thallium-201 chloride single photon emission computed tomography (201TlCl SPECT) showed high and rapid uptake on the early image and rapid washout on the delayed image. The preoperative diagnosis of meningioma could be established based on these findings. Total removal of the tumor was successfully performed. 201TlCl SPECT is useful for the preoperative diagnosis of fourth ventricle meningioma combined with CT, MR imaging, and angiography.

Unexpected accumulation of thallium-201 in bilateral thalamic venous infarction induced by arteriovenous fistula in the posterior fossa: report of a case

We encountered unexpected accumulation of thallium-201 in a patient with thalamic dementia resulting from bithalamic venous infarction induced by arteriovenous fistula in the posterior fossa The site and degree of abnormal accumulation varied between early and delayed thallium-201 SPECT images. This unexpected and complicated accumulation of thallium-201 appeared to depend on not only breakdown of the blood-brain barrier but also on the hemodynamics of this type of venous infarction.

Imaging gliomas with positron emission tomography and single-photon emission computed tomography

Over the last two decades the large volume of research involving various brain tracers has shed invaluable light on the pathophysiology of cerebral neoplasms. Yet the question remains as to how best to incorporate this newly acquired insight into the clinical context. Thallium is the most studied radiotracer with the longest track record. Many, but not all studies, show a relationship between (201)Tl uptake and tumor grade. Due to the overlap between tumor uptake and histologic grades, (201)Tl cannot be used as the sole noninvasive diagnostic or prognostic tool in brain tumor patients. However, it may help differentiating a high-grade tumor recurrence from radiation necrosis. MIBI is theoretically a better imaging agent than (201)Tl but it has not convincingly been shown to differentiate tumors according to grade. MDR-1 gene expression as demonstrated by MIBI does not correlate with chemoresistance in high grade gliomas. Currently, MIBI's clinical role in brain tumor imaging has yet to be defined. IMT, a radio-labeled amino acid analog, may be useful for identifying postoperative tumor recurrence and, in this application, appears to be a cheaper, more widely available tool than positron emission tomography (PET). However, its ability to accurately identify tumor grade is limited. 18 F-2-Fluoro-2-deoxy-d-glucose (FDG) PET predicts tumor grade, and the metabolic activity of brain tumors has a prognostic significance. Whether FDG uptake has an independent prognostic value above that of histology remains debated. FDG-PET is effective in differentiating recurrent tumor from radiation necrosis for high-grade tumors, but has limited value in defining the extent of tumor involvement and recurrence of low-grade lesions. Amino-acid tracers, such as MET, perform better for this purpose and thus play a complementary role to FDG. Given the poor prognosis of patients with gliomas, particularly with high-grade lesions, the overall clinical utility of single photon emission computed tomography (SPECT) and PET in characterizing recurrent lesions remains dependent on the availability of effective treatments. These tools are thus mostly suited to the evaluation of treatment response in experimental protocols designed to improve the patients' outcome.

99mTc-MIBI and 201Tl SPET in the detection of recurrent brain tumours after radiation therapy

The purpose of this study was to evaluate whether Tc-hexakis-2-methoxyisobutylisonitrile ( Tc-MIBI) or Tl single photon emission tomography (SPET) could detect recurrent tumours in patients with previous radiation therapy for brain tumours. Dual SPET with Tc-MIBI and Tl was performed in 21 patients suspected of having recurrent brain tumours. SPET images were acquired 15 min (early) and 2 h (delayed) after injection. The ratio of the average counts for the region of interest in the lesion area and its mirror image in normal brain tissue was obtained. Early and delayed ratios were calculated. On the basis of histological and/or clinical findings, the final diagnosis was considered as recurrent tumours in 15 patients and radiation necrosis in six. Both ratios using Tc-MIBI and Tl were significantly higher in recurrent tumours than in radiation necrosis. Based on a cut-off of 5.89 of the early ratio using Tc-MIBI to distinguish between recurrent tumours and radiation necrosis, the accuracy was 90%. Based on a cut-off of 6.77 of the delayed ratio using Tc-MIBI, the accuracy was 86%. The corresponding values using cut-offs of 2.40 and 1.85 with Tl were 90% and 86%, respectively. However, within recurrent tumours, both ratios for Tc-MIBI were significantly higher than those for Tl. Early Tc-MIBI SPET may be especially useful for the detection of recurrent tumours in patients who have previously undergone radiation therapy for brain tumours.

Use of 201Tl SPECT imaging to assess the response to therapy in patients with high grade gliomas

PURPOSE

To assess the potential role of 201Tl single photon emission tomography (201-Thallium SPECT) when compared to other imaging modalities in the evaluation of the response to therapy in high grade gliomas.

MATERIALS AND METHODS

Twenty patients with histologically proved high grade glioma have been included: 15 with glioblastoma (GBM), 3 with anaplastic astrocytoma (AA) and 2 with anaplastic oligoastrocytoma (AOA). Patients were assessed by 201Tl SPECT, computed tomography (CT) and magnetic resonance imaging (MRI) at (a) either at the moment of maximum response to first line chemotherapy, or after the completion of radiotherapy and chemotherapy if post-surgical residual disease was present, and (b) after the completion of second line chemotherapy if disease persisted, or either a relapse or disease progression was confirmed. Final response was evaluated according to the McDonald criteria, and by comparing SPECT, CT and MRI results.

RESULTS

According to the McDonald criteria, clinical response after first line chemotherapy was 5 partial response, 7 stable disease and 8 progressive disease. Evaluation by 201Tl SPECT was in agreement with such criteria in nearly all patients (90%). MRI findings closely agreed with the clinical follow-up. CT findings clearly differed from those observed by SPECT and MRI. After second line therapy, 10 patients progressed, 3 had stable disease and 7 had partial response. 201Tl SPECT agreed with the clinical status in 89% cases, whereas MRI and, specially CT, fared significantly lower.

CONCLUSION

Compared to conventional neuroimaging, 201Tl SPECT added valuable information in the assessment of the response to therapy in our patient population; whenever findings were not conclusive and in the case of disagreement between CT and MRI findings.

Quantitative MR spectroscopic imaging of brain lesions in patients with AIDS: correlation with [11C-methyl]thymidine PET and thallium-201 SPECT

RATIONALE AND OBJECTIVES

The purpose of this study was to examine the metabolic basis for magnetic resonance (MR) spectroscopic imaging findings in focal brain lesions of patients with acquired immunodeficiency syndrome (AIDS).

MATERIALS AND METHODS

The authors combined MR spectroscopic imaging with [11C-methyl]thymidine positron emission tomography (PET) and thallium-201 single photon emission computed tomography (SPECT) in 10 patients. They sought a characteristic metabolite profile that would enable differentiation of benign lesions from primary central nervous system lymphoma and determined whether PET and SPECT results supported the MR spectroscopic imaging findings.

RESULTS

Metabolite compositions of the lesions were similar, likely because the lesions were late stage and tended to be necrotic. Brain lesions in patients with AIDS were nonspecific regarding metabolic profile as determined with MR spectroscopic imaging. All patients with positive PET and SPECT studies had primary central nervous system lymphoma.

CONCLUSION

PET and SPECT may be more reliable than MR spectroscopic imaging for differentiating benign lesions from primary central nervous system lymphoma in patients with AIDS.

Inaccuracy of Tl-201 brain SPECT in distinguishing cerebral infections from lymphoma in patients with AIDS

PURPOSE

Studies have suggested using Tl-201 brain SPECT to differentiate lymphoma from infectious processes and to determine the timing for biopsy or empirical therapy for patients with AIDS-related brain lesions. This study prospectively investigated the utility of Tl-201 SPECT in distinguishing central nervous system lymphoma from non-neoplastic disease in patients with AIDS.

MATERIALS AND METHODS

Fourteen patients with AIDS and focal abnormalities on computed tomography or magnetic resonance imaging underwent brain SPECT before diagnosis (12 by biopsy, 2 by clinical course and response to therapy). A an uptake ratio (UR) was obtained by drawing a region of interest around the lesion, measuring average counts per pixel, and dividing this value by the value of a non-lesion-containing contralateral region of interest. The UR cutoff producing the highest accuracy (TP+TN/TP+TN+FP+FN) in discriminating lymphoma from another condition was determined from URs generated from these 14 patients.

RESULTS

Five patients had lymphoma, five had toxoplasmosis, one had Herpes simplex virus encephalitis, two had progressive multifocal leukoencephalopathy, and one had gliosis (UR, 0.8). Patients were separated into categories of lymphoma or nonlymphoma. The mean UR was 2.2 +/- 1.6 (range, 1.0 to 3.85) for lymphoma and 1.7 +/- 0.8 (range, 0.7 to 3.2) for nonlymphoma. Only a UR of 1.63 resulted in sensitivity and specificity better than 50% (60% and 55%, respectively), with an accuracy of 57%, positive predictive value of 43%, and negative predictive value of 71%.

CONCLUSIONS

Tl-201 brain SPECT appears unreliable for differentiating primary lymphoma from nonmalignant brain lesions in patients with AIDS. Early brain biopsy is necessary to establish a definitive diagnosis when appropriate.

Is technetium-99m-MIBI taken up by the normal pituitary gland? A comparison of normal pituitary glands and pituitary adenomas

PURPOSE

The aim of this study was to compare the behavioral uptake of a normal gland and a pituitary adenoma and to assess the ability to diagnose pituitary adenoma by means of technetium-99m-hexakis-2-methoxy-isobutyl-isonitrile (MIBI) single photon emission computed tomography (SPECT).

METHODS

The study included 15 patients with pituitary adenomas (mean age = 44.0 years, range 19-63) and 15 control subjects (mean age = 50.7 years, range 20-67). SPECT was performed 15 minutes after an intravenous injection of MIBI 600 MBq. The shape and location of MIBI uptake were evaluated on a magnetic resonance (MR) imaging/SPECT registration image. The shape patterns and location were classified as follows: Shape C (circular); LO (longitudinal oval); T/R (triangular or rectangular) and location P (pituitary gland or adenoma); D/C (dorsum sellae and/or clivus).

RESULTS

Analysis of the uptake showed that 10 (67%) adenomas were C, and 5 (33%) were LO. Of the controls, 5 (33%) were C, and 10 (69%) were T/R. With regard to location, all patients with pituitary adenomas were classified as P, and all control subjects (93%) but one showed uptake in the dorsum sellae and clivus (D/C).

CONCLUSION

MIBI was taken up in the dorsum sellae or clivus but not the normal pituitary gland and had a strong affinity for the pituitary adenoma. This result implies that MIBI SPECT may be a useful new auxiliary examination technique for the location diagnosis of pituitary adenoma.

Comparison of 99Tcm-MIBI with 201Tl chloride SPET in patients with malignant brain tumours

The purpose of this study was to evaluate the usefulness of 99Tcm-MIBI accumulation for the differentiation of histological diagnosis of malignant brain tumours in comparison with the findings obtained using 201Tl chloride. A total of 25 patients with malignant brain tumours were investigated. The histological categories of tumours included glioblastoma multiforme (n = 5), anaplastic astrocytoma (n = 4), malignant lymphoma (n = 5), and metastatic tumour (n = 11). Simultaneous dual single photon emission tomography (SPET) images with 99Tcm-MIBI and 201Tl were acquired 15 min (early) and 2 h (delayed) after injection, and the early ratio, delayed ratio and retention index were measured. The new indices 201Tl/99Tcm-MIBI ratios and 201Tl/99Tcm-MIBI retention index were also calculated. With respect to the histological type, a higher retention index using 99Tcm-MIBI was noted in glioblastoma multiforme compared with metastatic tumour. Higher values of both ratios using 201Tl were noted in glioblastoma multiforme compared to metastatic tumour. The value of the delayed ratio obtained using 201Tl was higher in glioblastoma multiforme than in anaplastic astrocytoma, and the value was also higher in malignant lymphoma than in metastatic tumour. The 201Tl/99Tcm-MIBI early ratio of glioblastoma multiforme was significantly higher than that of metastatic brain tumour. The 201Tl/99Tcm-MIBI retention index of malignant lymphoma was significantly higher than that of glioblastoma multiforme. In the histological type of tumour, 99Tcm-MIBI is not superior to 201Tl, but the combined indices using 201Tl/99Tcm-MIBI may add new information about differential diagnosis.

Detecting meningeal carcinomatosis from breast cancer with thallium-201 SPECT

Thallium-201 (201Tl) scintigraphy is one of the imaging methods used in the detection of various tumors including brain metastasis. We evaluated a patient with meningeal carcinomatosis from breast cancer by using 201Tl single-photon emission computed tomography (SPECT). Meningeal spread of a tumor was noted on enhanced CT. SPECT revealed tumor localization in meningeal carcinomatosis. These results suggest that SPECT with 201Tl may be useful in detecting meningeal carcinomatosis from breast cancer.

False positive thallium-201 SPECT imaging in brain abscess

Three cases of intracranial 201Tl uptake, reported as positive tumour activity in patients with a final diagnosis of abscess, are described. 201Tl has been proposed as a useful oncotropic radiotracer in the diagnosis of brain tumour activity. These cases suggest a note of caution in the interpretation of 201Tl brain images in the differential diagnosis of an intracranial expanding mass.

Childhood brain tumor: neuroimaging correlated with disease outcome

The authors explored the hypothesis that functional behavior of childhood brain tumors can be estimated by serial analysis of imaging (thallium-201 [201Tl] single-photon emission computed tomography and magnetic resonance imaging [MRI]) examinations. Seventy-five patients diagnosed on clinical or histologic grounds were monitored for a period of 1 day to 3.9 years (mean +/- S.D. = 1.39 +/- 1.10 years). Abnormal 201Tl uptake appeared to denote a subgroup of lesions with distinctly greater mortality and morbidity. Of 201Tl-positive patients, 17% died within the course of this study; no deaths occurred among the 201Tl-negative group. Other parameters of disease outcome also clearly separated the 201Tl-positive and 201Tl-negative groups, with the former demonstrating a 50% shorter period of recurrence-free survival from the time of diagnosis (two-tailed t test, P < 0.01). Significant enhancement with paramagnetic contrast agents paralleled 201Tl positivity in correlating with greater mortality but failed to predict duration of recurrence-free survival. The authors conclude that 201Tl activity provides significant predictive information of the expected biologic behavior of childhood brain tumors, both for duration of recurrence-free survival and for estimated life expectancy. This information complements and extends data provided by MRI enhancement patterns.

Perfusion and thallium single photon emission computed tomography in herpes simplex encephalitis

This is the first report on 201thallium-single photon emission computed tomography (201Tl-SPECT) brain scan of a patient with herpes simplex encephalitis (HSE). The presented 201Tl-SPECT observations are correlated with 99mtechnetium hexamethylpropylene amine oxime (99mTc-HMPAO) perfusion SPECT and magnetic resonance imaging (MRI) findings. Brain 99mTc-HMPAO perfusion SPECT reveals a hyperperfusion in the right temporal lobe with extension to the parietal lobe and a hypoperfusion in the ipsilateral occipital lobe. 201Tl-SPECT shows a fixation in the right temporal lobe coinciding with the gadolinium enhancement on MRI. The right occipital lesion shown by gadolinium captation on MRI and hypoperfusion on 99mTc-HMPAO perfusion SPECT was not evident on the 201Tl SPECT. These findings could illustrate that the lesions might be different pathophysiologically.

[Is cerebral tomoscintigraphy with 99mTc-MIBI useful in the diagnosis of local recurrence in patients with malignant gliomas?]

PURPOSE

99mTc-MIBI, an alternative radiopharmaceutical for myocardial perfusion study has been proposed for use as a tumor imaging agent, including breast cancer, lung cancer, lymphomas, melanomas, and brain tumors. After routine radiation therapy, deteriorating clinical status or treatment failure may be due to either radiation changes or recurrent tumor. CT and MRI offer imperfect discrimination of tumor viability and radionecrosis.

MATERIALS AND METHODS

Thirty-five malignant glioma patients with clinical deterioration were studied retrospectively. Tomoscintigraphy was performed 15 minutes after intravenous injection of 1110 Mbq 99mTc-MIBI. The images were obtained from a dual headed gamma camera using fan beam collimator. Transverse, coronal and sagittal views were reconstructed.

RESULTS

A dramatic MIBI uptake was found in 31 patients. This uptake was correlated to tumor recurrence proven by histological fragments and/or the rapid, fatal evolution of these patients. Death occurred after the brain SPECT had been performed for those cases showing MIBI uptake, an average 5.48 months later. No MIBI uptake was found for these four remaining patients: their evolution can be currently considered to be a disease-free time.

CONCLUSIONS

According to our results, the sensibility and specificity of 99mTcMIBI brain SPECT seems to be high. Moreover, this investigation is more accurate for discriminating tumor recurrence from radionecrosis than a CT scan or MRI.

Chronic encapsulated intracerebral hematoma: contribution of thallium-201 single photon emission computed tomography in preoperative diagnosis: case report

OBJECTIVE AND IMPORTANCE

Chronic encapsulated intracerebral hematoma is a fairly rare clinical entity. This unique lesion is peculiar for its clinical onset, formation of a capsule, and progressive enlargement. The mechanism for capsule formation and self-perpetuating expansion still remains uncertain, as well as the causal relationship with vascular malformations. Because of their pseudotumoral course and misleading neuroradiological features, these lesions can be misdiagnosed preoperatively as cerebral neoplasms.

CLINICAL PRESENTATIONS

A 62-year-old man was referred with a 2-month history of generalized tonicoclonic seizures. There was no history of head injury or arterial hypertension. The results of a neurological examination were normal. Computed tomographic scans revealed a slightly hyperdense roundish area in the right parietotemporal region with ring-like enhancement after contrast medium injection, moderate mass effect, and perifocal low attenuation. With the provisional diagnosis of astrocytoma, the patient was admitted for a craniotomy. Before surgery, a thallium-201 single photon emission computed tomographic study was performed, which showed no abnormal uptake of the tracer, raising significant doubt regarding the presumptive diagnosis of a tumor.

INTERVENTION

Intraoperative findings revealed a hematoma, with a well-demarcated, thick, fibrous-elastic capsule. There was evidence of repeated intracapsular hemorrhages. The lesion was totally removed, and the patient recovered fully. No other pathological findings, including vascular malformations, were noted.

CONCLUSION

Chronic encapsulated intracerebral hematomas probably occur more frequently than the limited number of reported cases would indicate. This case represents a realistic clinical problem-solving setting in with thallium-201 single photon emission computed tomography was used because of its capacity for functional tumor detection and differential diagnosis.

Different thallium-201 single-photon emission tomographic patterns in benign and aggressive meningiomas

To evaluate the possibility of preoperatively obtaining an index of aggressiveness for intracranial meningiomas, we prospectively studied 22 patients with computed tomographic or magnetic resonance imaging evidence of meningeal tumour, using single-photon emission tomography (SPET) of the brain and thallium-201 (201Tl). On a brain-dedicated SPET scanner, a rapid acquisition protocol with early, short scans was started simultaneously with the intravenous administration of 111 MBq 201Tl, covering the initial intratumoral distribution of the tracer. Twenty minutes post injection, a delayed SPET scan was also obtained. On the reconstructed and attenuation-corrected images we calculated the 201Tl concentration in tumour and normal contralateral brain tissue, and compared intratumoral tracer concentration in the initial and the final part of the rapid acquisition protocol. Benign and malignant meningiomas were classified as such based on histological examination. In malignant lesions, the ratio of the 201Tl concentration at 2-4 min post injection to that at 14-16 min was found to be significantly higher than in non-aggressive neoplasms (mean+/-1 SD: 1.14+/-0.31 and 0.56+/-0.13, respectively, P <0.01). Conversely, in the delayed scan, most lesions showed high tracer concentration, and the two groups could not be distinguished. In addition, three recurrent meningiomas displayed the same imaging behaviour as the malignant group, i.e. had similar 201Tl concentration values at 2-4 and at 14-16 min. Our findings suggest that the comparative assessment of intratumoral 201Tl concentration at 2-4 and at 14-16 min post injection could provide a fast, simple method to differentiate preoperatively intracranial meningiomas with different biological behaviour.

Functional characterization of brain tumors: an overview of the potential clinical value

Early detection and characterization are still challenging issues in the diagnostic approach to brain tumors. Among functional imaging techniques, a clinical role for positron emission tomography studies with [18F]-fluorodeoxyglucose and for single photon emission computed tomography studies with [201Tl]-thallium-chloride has emerged. The clinical role of magnetic resonance spectroscopy is still being defined, whereas functional magnetic resonance imaging seems able to provide useful data for presurgical localization of critical cortical areas. Integration of morphostructural information provided by computed tomography and magnetic resonance imaging, with functional characterization and cyto-histologic evaluation of biologic markers, may assist in answering the open diagnostic questions concerning brain tumors.

Relationship between thallium-201 uptake by supratentorial glioblastomas and their morphological characteristics on magnetic resonance imaging

Single-photon emission tomography (SPET) with thallium-201 is used in the assessment of patients with gliomas because the amount of 201Tl accumulated by the tumoral cells increases in proportion to the degree of tumour malignancy, thus making it possible to differentiate high-grade from low-grade gliomas or recurrences from radiation necrosis. However, in large areas of tissue such as those examined in 201Tl SPET studies, the uptake of 201Tl may vary considerably even in tumours with the same histological diagnosis, as occurs in glioblastomas (GBMs). In order to evaluate the possible influence of the macroscopic characteristics of tumours on 201Tl uptake, we studied a series of 13 patients with histologically proven GBMs, comparing magnetic resonance imaging (MRI) parameters such as tumour dimensions, perilesional oedema, intratumoral necrosis and contrast enhancement with the degree of 201Tl uptake. The patients underwent both 201Tl SPET and MRI before surgery. The 201Tl index (tumour/contralateral unaffected brain) was calculated using two different region of interest (ROI) methods: the first employed irregular large ROIs (3.2+/-13.9 cm2) including pixels with more than 50% maximum activity; the second employed regular square small ROIs (2.7 cm2) centered on the maximum activity of the lesion. Of the MRI morphological parameters studied, only necrosis significantly reduced the degree of 201Tl uptake in GBMs when larger ROIs were used. However, by using small regular ROIs the influence of necrosis on 201Tl uptake was found to be less relevant. Since necrosis is related to tumour proliferative activity and represents a negative prognostic factor in astrocytoma, a possible underestimation of 201Tl uptake due to intratumoral necrosis must be carefully evaluated.

Cerebral demyelination syndrome in a patient treated with 5-fluorouracil and levamisole. The use of thallium SPECT imaging to assist in noninvasive diagnosis--a case report

BACKGROUND

The use of 5-fluorouracil (5-FU) and levamisole in patients with Stage III adenocarcinoma of the colon has now become standard. There have been several reports of a multifocal cerebral demyelination syndrome following 5-FU and levamisole administration.

METHODS

We describe a patient who developed focal neurologic symptoms while being treated with levamisole and 5-FU in whom the diagnosis of central nervous system (CNS) metastases was considered.

RESULTS

A magnetic resonance imaging (MRI) scan showed a diffuse, multifocal white matter process. Diagnostic evaluation did not support a diagnosis of CNS metastasis. 201Thallium chloride single photon emission computed tomography (SPECT) study was cold. A stereotactic brain biopsy disclosed demyelination but not tumor. The patient had complete functional resolution of symptoms with 1 month of dexamethasone therapy, although follow-up MRI scans have shown persistent abnormality on T2-weighted images.

CONCLUSIONS

In patients receiving 5-FU and levamisole who develop focal neurologic symptoms with an abnormal MRI scan, the diagnosis of CNS metastasis should not be made without a thorough diagnostic evaluation. We suggest the use of 201thallium chloride SPECT imaging to support the diagnosis of multifocal leukoencephalopathy related to 5-FU and levamisole. In atypical cases, a stereotactic brain biopsy may be required for confirmation.

Where are we with nuclear medicine in pediatrics?

The practice of nuclear medicine in children is different from that in adults. Technical considerations including immobilization, dosing of radiopharmaceuticals, and instrumentation are of major importance. Image magnification and the capability to perform single-photon emission tomography are essential to performing state of the art pediatric nuclear medicine. New advances in instrumentation with multiple detector imaging, the possibility of clinical positron emission tomography imaging in children, and new radiopharmaceuticals will further enhance pediatric scintigraphic imaging. This review highlights advances in pediatric nuclear medicine and discusses selected clinical problems.