Comparative assessment of four different Tl-201 tumor uptake indices in the evaluation of brain tumors

Thallium-201 versus Tc99m-glucoheptonate SPECT for evaluation of recurrent brain tumours: a within-subject comparison with pathological correlation

BACKGROUND

Thallium-201 (Tl-201) is the most commonly used tracer for functional imaging of recurrent brain tumours. However, the physical properties of Tl-201 are not particularly suitable for this application, thus, a technetium-99 (Tc99m) labelled alternative with more favourable physical properties has been sought. The aim of this study was to compare the ability of Tl-201 and Tc99m-glucoheptonate single photon emission computed tomography (SPECT) to detect viable recurrent tumour and differentiate post-radiation gliosis.

METHOD

Brain SPECT with Tl-201 and Tc99m-glucoheptonate was performed in 20 patients with malignant brain tumour in whom recurrent disease was suspected. Tracer uptake in the mass was defined as high, moderate or low and was correlated with histological verification of the lesion in all cases.

RESULTS

Recurrent tumour was demonstrated in 17 patients by both Tl-201 and Tc99m-glucoheptonate SPECT and confirmed by surgical resection in all 17 patients. Three patients had no tracer uptake on either Tl-210 or Tc99m-glucoheptonate SPECT and surgical resection revealed only fibrotic tissue with areas of necrosis. Tc99m-glucoheptonate images were found to correlate more closely with the surgical findings with regard to the location of tumour margin, extent of tumour invasion and intratumoural necrosis.

CONCLUSION

Tc99m-glucoheptonate brain SPECT is an accurate agent for SPECT imaging of recurrent brain tumours and may provide more information about the location of the tumour margin and its extent and intratumoural necrosis than Tl-201. Tc99m-glucoheptonate may be a viable replacement for Tl-201.

Sestamibi technetium-99m brain single-photon emission computed tomography to identify recurrent glioma in adults: 201 studies

OBJECT

In the follow-up of treated gliomas, CT and MRI can often not differentiate radionecrosis from recurrent tumor. The aim of this study was to assess the interest of functional imaging with (99m)Tc-MIBI SPECT in a large series of 201 examinations.

METHOD

MIBI SPECT were performed in 81 patients treated for brain gliomas. A MIBI uptake index was computed as the ratio of counts in the lesion to counts in the controlateral region. SPECT was compared to stereotactic biopsy in 14 cases, or in the others cases to imaging evolution or clinical course at 6 months after the last tomoscintigraphy Two hundred and one tomoscintigraphies were performed. One hundred and two scans were true positive, 82 scans were true negative. Six scans were false positive (corresponding to 3 patients): 2 patients with an inflammatory reaction after radiosurgery, 1 with no explanation up to now. Eleven scans were false negative (5 patients): 1 patient with a deep peri-ventricular lesion, 2 patients with no contrast enhancement on MRI, 2 patients with a temporal tumor. The sensitivity for tumor recurrence was 90%, specificity 91.5% and accuracy 90.5%. We studied separately low and high grade glioma: sensitivity for tumor recurrence was respectively 91% and 89%, specificity 100% and 83% and accuracy 95% and 87%. MIBI SPECT allowed the diagnose of anaplasic degenerence of low grade sometimes earlier than clinical (5 cases) or MRI signs (7 cases).

CONCLUSIONS

Our results confirm the usefullness of MIBI SPECT in the follow-up of treated gliomas for the differential diagnosis between radiation necrosis and tumor recurrence.

Brain neoplasms: epidemiology, diagnosis, and prospects for cost-effective imaging

Currently, the literature lacks a solid body of research on decision and cost-effectiveness analysis of imaging strategies for adults and children suspected of having a brain neoplasm. This article describes the epidemiology and clinical presentation of brain neoplasms, reviews current diagnostic strategies, highlights gaps in the literature on decision and cost-effectiveness analysis, and suggests directions for future research.

Comparison of thallium-201 uptake and retention indices for evaluation of brain lesions with SPECT

Thallium-201 chloride single photon emission computed tomography ((201)TlCl SPECT) has been applied extensively for studies of human tumors. To assess which indices for (201)TlCl SPECT are most useful for diagnosing brain lesions, a total of 82 patients (98 images) with intracranial abnormalities were investigated. Seventy-six cases with abnormal (201)Tl uptake were evaluated in terms of six different (201)Tl uptake and retention indices: (1) average early (201)Tl uptake = Av.Le/Av.Be; (2) maximum early (201)Tl uptake = Mx.Le/Av.Be; (3)(201) Tl retention A = Av.Ld/Av.Le; (4) (201)Tl retention B = Mx.Ld/Mx.Le; (5) (201)Tl retention C = (Av.Ld/Av.Bd)/(Av.Le/Av.Be); (6) (201)Tl retention D = (Mx.Ld/Av.Bd)/(Mx.Le/Av.Be), where Av.Le and Mx.Le are average and maximum early counts for lesions, Av.Be and Av.Bd are average early and delayed counts for contralateral normal brains, and Av.Ld and Mx.Ld are average and maximum delayed counts for lesions. Comparison of patients with benign and malignant lesions did not demonstrate significant differences with any of the indices. However, low (I-II) and high (III-IV) grade astrocytomas varied in their average and maximum early (201)Tl uptake indices (both P = 0.0026). For patients with and without meningiomas, P values for indices of maximum early(201) Tl uptake and (201)Tl retention A and B were 0.0338, 0.0005, 0.0002, respectively. While comparison of patients with metastatic brain tumors and gliomas again showed no significant differences between the groups, the presence or absence of calcification was associated with significant variation in all the indices. With (201)TlCl-SPECT imaging, the average and maximum early (201)Tl uptake indices are appropriate for the assessment of tumor viability or malignancy, while (201)Tl retention indices (A,B) are useful for tumor differentiation, especially with meningiomas. Choice of suitable indices should enhance the utility of (201)TlCl-SPECT imaging in pre- and postoperative evaluation of intracranial lesions.

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.