CASE REPORT Annals of Nuclear Medicine Vol. 12 No. 3, 161-164, 1998 Single photon emission CT images in a case of intraventricular neurocytoma Manabu OGUCHI, Kotaro HIGASHI, Mitsuru TANIGUCHI, Takahiro NISHIKAWA, Hiroyasu TAMAMURA, Tetsuro OKIMURA and Itaru YAMAMOTO Department of Radiology Kanazawa Medical University Although Tc-99m HMPAO uptakes in various brain tumors have been reported, SPECT images of neurocytoma have not been described. The authors report a patient with intraventricular neurocytoma (IN) who demonstrated significant uptake of Tc-99m HMPAO and Tl-201 Cl before brain biopsy. Residual tumor after biopsy showed significant uptake of I-123 IMP on early SPECT images, but this uptake was decreased on delayed images. The three radionuclides seem to have different uptake mechanisms. Key words: Tc-99m HMPAO, I-123 IMP, Tl-201 Cl, neurocytoma, SPECT INTRODUCTION TECHNETIUM-99m-hexamethyl-propyleneamine-oxime (Tc-99m HMPAO) is a lipophilic agent that can penetrate the blood brain barrier (BBB) and is used for regional cerebral blood flow studies. Most brain tumors show a decreased uptake of Tc-99m HMPAO on brain SPECT images, although in some brain tumors such as meningioma and glioblastoma increased uptakes have been reported.1,2 Intraventricular neurocytoma (IN), a recently recognized benign cerebral tumor of young adults, can be confused microscopically with oligodendroglioma. CT and MRI studies of IN have been reported.3,4 Although positron emission CT (PET) studies of IN have been reported, SPECT images of IN have not yet been demonstrated.5-7 CASE REPORT A 33-year-old woman had complained of occipitalgia for the last 6 months. She recently developed nausea, vomiting and muscle weakness. Severe memory disturbance was recognized on physical examination but there were no other neurological deficits. There was no history of epilepsy. MRI revealed a large intraventricular tumor Received December 10, 1997, revision accepted March 9, 1998. For reprint contact: Manabu Oguchi, M.D., Department of Radiology, Kanazawa Medical University, 1-1, Daigaku, Uchinada, Kahoku 92O-0293, JAPAN. with marked and homogenous enhancement with Gd-DTPA on a Tl-weighted image (Fig. 1A, B). CT also revealed well enhanced intraventricular tumor (Fig. 2A, B). A brain SPECT study was performed to evaluate cerebral blood flow with a triple-headed camera SPECT system 20 min after the i.v. injection of 740 MBq of Tc-99m HMPAO. The Tc-99m HMPAO SPECT image showed noticeably increased tracer uptake in the intraventrlcular tumor (Fig. 3). Tl brain SPECT images were obtained with a single head camera 15 min and 3 hours after the i.v. injection of Tl-201 Cl 111 MBq. Both early and delayed images showed significant Tl-201 uptake in the tumor (Fig. 4A, B). About 2 weeks later, the tumor biopsy was performed through right occipital craniotomy. The pathological finding confirmed the presence of neurocytoma (Fig. 5). Four weeks later, IMP SPECT was performed 20 min and 3 hours after the i.v. injection of 111 MBq I-123 IMP to evaluate regional brain perfusion with a single head camera. Early SPECT images showed a significant tracer uptake in the residual tumor, although tracer uptake was decreased on the delayed images (Fig. 6A, B). DISCUSSION Intraventricular neurocytoma (IN) is a relatively rare and benign brain tumor of young adults. Radiologically, CT and MRI studies of intraventricular neurocytoma have been reported with the tumors demonstrating a characteristic attachment to the lateral and third ventricles. Calcification and intratumoral vessels have also been commonly seen.3,4 Mineura et al. reported blood flow and metabolism of central neurocytoma by using C15O2, C15O, and 18F-fluorodeoxyglucose (FDG). They reported that tumor regional cerebral blood flow (r-CBF) and regional cerebral blood volume (r-CBV) were higher than comparable values in the contralateral gray matter but the oxygen extraction fraction (r-OEF), the cerebral metabolic rate of oxygen (r-CMRO2) and the cerebral metabolic rate of glucose (r-CMRGl) are significantly lower than those of the gray matter.5 Perfusion of brain tumors has been studied extensively with SPECT and I-123 IMP, Tc-99m HMPAO, and Tc-99m ECD. Most brain tumors show a low uptake or defect on SPECT images, although some such as meningioma and glioblastoma have been reported to show a high uptake.1.2,8.9 Recently, low-grade gliomas have been reported to show increased Tc-99m HMPAO or Tc-99m ECD uptake.10,ll The mechanism of Tc-99m HMPAO uptake is not known, but hypervascularity is thought to be one of the important factors. Suess et al, have demonstrated a correlation between the glutathione content of brain tumor and Tc-99m HMPAO uptakes.12 Winchell et al. have reported that I-123 IMP uptake is dependent on amine binding sites and that decreased uptake is due to a deficiency of binding sites in the brain tumors.13 In the case presented here, the neurocytoma showed significant uptake of Tc-99m HMPAO compared to normal brain parenchyma. Since the tumor was well enhanced by contrast media on CT and MRI images, it is more likely that hypervascularity or increased blood flow to the tumor is responsible for the phenomenon than other uptake mechanisms. PET study also demonstrated a relatively high r-CBF and r-CBV of IN.5 Histological finding for the biopsy specimen demonstrated that the tumor was composed of small, and uniform cells and that capillary dilatation contained red blood cells. A similar pattern has been reported in the case of meningioma.1 I-123 IMP SPECT also demonstrated high accumulation in the tumor on early images, though low radioactivity (washout from the tumor) was observed on the delayed images. This could be explained by the difference between the tumor and normal brain tissue in amine binding sites. Tl-201 Cl uptake is thought to reflect the viability of the tumor, and the degree of TlCl uptake has been repoted to correlate with cell growth rate and to represent tumor malignancy.11 Intraventricular neurocytoma is believed to be biologically benign. This seems to correlate with the cellular viability of the tumor and perfusion of the tumor. REFERENCES 1. Hoshi H. Jinnouchi S, Watanabe K, Nakano S, Kinoshita K. Mismatch between Iodine-123 IMP and Technetium-99m HM-PAO Brain Perfusion Imaging in a Patient with Meningioma. Clin Nucl Med 12: 737-740, 1987. 2. Babich JW, Keeling F, Flower MA, Repetto L, Whitton A, Fieding S, et al. Initial experience with Tc-99m-HM-PAO in the stud of brain tumors. Eur Nucl Med 14: 39-44, 1988. 3. Goergen SK, Gonzales MF, McLean C. Intraventricular Neurocytoma: Radiologic Features and Review of the Literature. Radiology 182: 787-792, 1992. 4. Chang KH, Han DG, Kim JG. Chi DC, Suh SJ, Kim SH, et al. MR Appearance of Central Neurocytoma. 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