ro-16-0154 and Brain-Neoplasms

Intracranial meningiomas are the most common types of neoplasms that cause mental disorders. Although higher brain function can be restored and even improved in some patients after tumor resection, the mechanisms remain unclear. We investigated changes in the brains of patients after resection of an intracranial meningioma using (123)I-Iomazenil (IMZ)-single photon emission computed tomography (SPECT). Ten patients underwent IMZ-SPECT within 4 weeks before and 3 months after intracranial meningioma resection. Changes in IMZ accumulation in brain parenchyma were assessed as ratios of counts in the lesion-to-contralateral hemisphere (L/C ratios). Mean Mini-Mental State Examination scores before and after resection of 19.9±11.4 vs. 26.5±3.8, respectively (p=0.03) indicated that the cognitive function of these patients was significantly improved after tumor resection. The average L/C ratios calculated from image counts of IMZ were 0.92±0.05 and 0.98±0.02 before and after surgery, respectively. The L/C ratio of IMZ accumulation was significantly decreased after tumor resection (p=0.0003). In contrast, regional cerebral blood flow calculated from (123)I-Iodoamphetamine-SPECT images did not significantly differ after tumor resection. The recovered binding potential of IMZ in brain parenchyma surrounding the tumor bulk after resection indicates that the viability of central benzodiazepine receptors was reversibly depressed and recoverable after release from compression by the tumor. The recovered neuronal viability revealed by IMZ-SPECT might be responsible for the improved cognitive function after intracranial meningioma resection.

Topics: Aged; Aged, 80 and over; Brain; Brain Neoplasms; Cell Survival; Cerebrovascular Circulation; Cognition Disorders; Female; Flumazenil; Humans; Iodine Radioisotopes; Magnetic Resonance Imaging; Male; Meningioma; Mental Status Schedule; Middle Aged; Neurons; Radiopharmaceuticals; Receptors, GABA-A; Tomography, Emission-Computed, Single-Photon; Treatment Outcome

Iodine-123-iomazenil (Iomazenil) is a ligand of central type benzodiazepine receptors for single photon emission computed tomography (SPECT). Previously we reported a simple, table look-up method for quantification of its binding potential (BP) by using two SPECT scans and calibrated standard input function with one blood sampling. This method is based on a two-compartment model (K1: influx rate constant; k2: efflux rate constant; Vd (= K1/k2): the total distribution volume corresponding BP), and requires two SPECT scans for calculating both K1 and Vd values. If the K1 value in the two-compartment model can be assumed to be constant, the radioactivity of one SPECT scan at 180 min after injection can be considered to tabulate as a function of Vd for a given K1 value and a given input function, and a table look-up procedure provides the corresponding Vd value. The purpose of this study was to develop a simple, autoradiographic method for quantification of BP by using one SPECT scan and calibrated standard input function with one blood sampling. SPECT studies were performed on 14 patients. A dynamic SPECT scan was initiated following an intravenous bolus injection of Iomazenil. A static SPECT scan was performed at 180 min after the injection. Frequent blood sampling from the brachial artery was performed on all subjects to determine the arterial input function. Simulation studies revealed that errors in calculated Vd values were around +/-10-15% for varied K1 values. A good correlation was observed between total distribution volume values calculated by three-compartment model analysis and those calculated by the present method (r = 0.90), supporting the validity of this method. The present method is simple and applicable for clinical use, and will be able to provide images of BP.

Topics: Adult; Aged; Autoradiography; Brain; Brain Neoplasms; Cerebrovascular Disorders; Computer Simulation; Dementia; Evaluation Studies as Topic; Flumazenil; Humans; Iodine Radioisotopes; Middle Aged; Models, Biological; Nonlinear Dynamics; Receptors, GABA-A; Reproducibility of Results; Tomography, Emission-Computed, Single-Photon

Iodine-123 iomazenil (Iomazenil) is a ligand for central type benzodiazepine receptors that is suitable for single-photon emission tomography (SPET). The purpose of this study was to develop a simple method for the quantification of its binding potential (BP). The method is based on a two-compartment model (K1, influx rate constant; k2', efflux rate constant; VT' (=K1/k2'), the total distribution volumes relative to the total arterial tracer concentration), and requires two SPET scans and one blood sampling. For a given input function, the radioactivity ratio of the early to delayed scans can be considered to tabulate as a function of k2', and a table look-up procedure provides the corresponding k2' value, from which K1 and VT' values are then calculated. The arterial input function is obtained by calibration of the standard input function by the single blood sampling. SPET studies were performed on 14 patients with cerebrovascular diseases, dementia or brain tumours (mean age+/-SD, 56.0+/-12.2). None of the patients had any heart, renal or liver disease. A dynamic SPET scan was performed following intravenous bolus injection of Iomazenil. A static SPET scan was performed at 180 min after injection. Frequent blood sampling from the brachial artery was performed on all subjects for determination of the arterial input function. Two-compartment model analysis was validated for calculation of the VT' value of Iomazenil. Good correlations were observed between VT' values calculated by three-compartment model analysis and those calculated by the present method, in which the scan time combinations (early scan/delayed scan) used were 15/180 min, 30/180 min or 45/180 min (all combinations: r=0.92), supporting the validity of this method. The present method is simple and applicable for clinical use.

Topics: Brain; Brain Neoplasms; Cerebrovascular Disorders; Computer Simulation; Dementia; Flumazenil; Humans; Iodine Radioisotopes; Middle Aged; Receptors, GABA-A; Reproducibility of Results; Tomography, Emission-Computed, Single-Photon