Thallium-201 Chloride Single Photon Emission Research Articles

NI-2 DUAL-ISOTOPE 123I-IMP/201TL SPECT FOR THE DIFFERENTIAL DIAGNOSIS OF PRIMARY CENTRAL NERVOUS SYSTEM LYMPHOMA AND GLIOBLASTOMA

Abstract Background Preoperative differential diagnosis between primary central nervous system lymphoma (PCNSL) and glioblastoma (GBM) is important because these tumors require different surgical strategies. This study investigated the usefulness of dual isotope, iodine-123-labeled N-isopropyl-p-iodoamphetamine (123I-IMP) and thallium-201 chloride single photon emission computed tomography (201Tl SPECT) for the differential diagnosis. Methods Sixteen PCNSL patients and 20 GBM patients who underwent dual isotope imaging, 123I-IMP and 201Tl SPECT, are included. Early and delayed SPECT images were obtained after 30 minutes and 4 hours, respectively. Tumor to normal (T/N) ratio was calculated from the ratio of maximum tracer counts in the lesion to the mean counts in the contralateral cerebral cortex. The mean and minimum apparent diffusion coefficient values (ADCmean and ADCmin, respectively) on magnetic resonance imaging were also analyzed for comparison of diagnostic accuracy. Results Delayed phase 123I-IMP SPECT was the most useful imaging examination for the differentiation between PCNSL and GBM compared with early phase 123I-IMP SPECT, early and delayed phase 201Tl SPECT, ADCmean and ADCmin. However, the median T/N ratios of PCNSL and GBM were 1.29 and 0.84, respectively, in the delayed phase 123I-IMP SPECT, and the tumor detection was inadequate. On the other hand, the median T/N ratios of PCNSL and GBM were 3.23 and 2.34, respectively, in the delayed phase 201Tl SPECT, with excellent tumor detection. Thirty-five of 36 patients (97.2%) showed a tracer retention rate of 201Tl SPECT 0.7 or higher, which indicates malignant property of brain tumors. Conclusion Delayed phase 123I-IMP SPECT could differentiate between PCNSL and GBM with high accuracy, but T/N ratio was low and tumor detection was poor. 201Tl SPECT was useful for estimation of the localization and the malignant property of the tumors. The combination of these isotopes was useful for the diagnosis of PCNSL and GBM.

Semiquantitative Analysis Using Thallium-201 SPECT for Differential Diagnosis Between Tumor Recurrence and Radiation Necrosis After Gamma Knife Surgery for Malignant Brain Tumors

Semiquantitative analysis of thallium-201 chloride single photon emission computed tomography (201Tl SPECT) was evaluated for the discrimination between recurrent brain tumor and delayed radiation necrosis after gamma knife surgery (GKS) for metastatic brain tumors and high-grade gliomas. The medical records were reviewed of 75 patients, including 48 patients with metastatic brain tumor and 27 patients with high-grade glioma who underwent GKS in our institution, and had suspected tumor recurrence or radiation necrosis on follow-up neuroimaging and deteriorating clinical status after GKS. Analysis of 201Tl SPECT data used the early ratio (ER) and the delayed ratio (DR) calculated as tumor/normal average counts on the early and delayed images, and the retention index (RI) as the ratio of DR to ER. A total of 107 tumors were analyzed with 201Tl SPECT. Nineteen lesions were removed surgically and histological diagnoses established, and the other lesions were evaluated with follow-up clinical and neuroimaging examinations after GKS. The final diagnosis was considered to be recurrent tumor in 65 lesions and radiation necrosis in 42 lesions. Semiquantitative analysis demonstrated significant differences in DR (P=.002) and RI (P<.0001), but not in ER (P=.372), between the tumor recurrence and radiation necrosis groups, and no significant differences between metastatic brain tumors and high-grade gliomas in all indices (P=.926 for ER, P=.263 for DR, and P=.826 for RI). Receiver operating characteristics analysis indicated that RI was the most informative index with the optimum threshold of 0.775, which provided 82.8% sensitivity, 83.7% specificity, and 82.8% accuracy. Semiquantitative analysis of 201Tl SPECT provides useful information for the differentiation between tumor recurrence and radiation necrosis in metastatic brain tumors and high-grade gliomas after GKS, and the RI may be the most valuable index for this purpose.

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.

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

Thallium-201 chloride single photon emission computed tomography (201TlCl SPECT) has been applied extensively for studies of human tumors. To assess which indices for 201TlCl 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 201Tl uptake were evaluated in terms of six different 201Tl uptake and retention indices: (1) average early 201Tl uptake=Av.Le/Av.Be; (2) maximum early 201Tl uptake=Mx.Le/Av.Be; (3)201 Tl retention A=Av.Ld/Av.Le; (4) 201Tl retention B=Mx.Ld/Mx.Le; (5) 201Tl retention C=(Av.Ld/Av.Bd)/(Av.Le/Av.Be); (6) 201Tl 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 201Tl uptake indices (bothP =0.0026). For patients with and without meningiomas, P values for indices of maximum early201 Tl uptake and 201Tl 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 201TlCl-SPECT imaging, the average and maximum early 201Tl uptake indices are appropriate for the assessment of tumor viability or malignancy, while 201Tl retention indices (A,B) are useful for tumor differentiation, especially with meningiomas. Choice of suitable indices should enhance the utility of 201TlCl-SPECT imaging in pre- and postoperative evaluation of intracranial lesions.

Value of Thallium-201 SPECT Imaging in Childhood Brain Tumors

Thallium-201 chloride single photon emission computed tomography (201Tl SPECT) has been proposed as a diagnostic tool in the assessment of patients with brain tumors. We performed SPECT scans coupled with magnetic resonance imaging (MRI) in children with brain tumors to determine the sensitivity and potential value of SPECT in neuro-oncology. Each patient was injected with 2.5-3.0 mCi of thallium chloride, followed by technetium-99m HMPAO (5-15 mCi) to assess cerebral perfusion. 201Tl uptake was imaged with triple-headed SPECT in 20/24 (83%) histologically and anatomically diverse neoplasms with MRI-measurable residual disease, including 13/16 (80%) posterior fossa tumors. 201Tl SPECT demonstrated uptake in tumors with MRI volumes ranging from 0.03 to 60 cm3. 201Tl SPECT imaging was not correlated with the following MRI features: gadolinium enhancement, necrosis, exophytic, unicentric and multicentric. 201Tl uptake was not detectable in patients with tumors of maldevelopmental origin or radionecrosis. It is suggested that 201Tl SPECT is an important imaging adjunct in the assessment of children with brain tumors.