In single-photon emission computed tomography (SPECT) and X-ray CT one-dimensional (1-D) convolution method is used for their image reconstruction from projections. The method makes a 1-D convolution filtering on projection data with a 1-D filter in the space domain, and backprojects the filtered data for reconstruction. Images can also be reconstructed by first forming the 2-D backprojection images from projections and then convoluting them with a 2-D space-domain filter. This is the reconstruction by the 2-D convolution method, and it has the opposite reconstruction process to the 1-D convolution method. Since the 2-D convolution method is inferior to the 1-D convolution method in speed in reconstruction, it has no practical use. In the actual reconstruction by the 2-D convolution method, convolution is made on a finite plane which is called convolution window. A convolution window of size N×N needs a 2-D discrete filter of the same size. If better reconstructions are achieved with small convolution windows, the reconstruction time for the 2-D convolution method can be reduced. For this purpose, 2-D filters of a simple function form are proposed which can give good reconstructions with small convolution windows. They are here defined on a finite plane, depending on the window size used, although a filter function is usually defined on the infinite plane. They are however set so that they better approximate the property of a 2-D filter function defined on the infinite plane. Filters of size N×N are thus determined. Their value varies with window size. The filters are applied to image reconstructions of SPECT. The results show that the filters give good reconstructions almost comparable to the 1-D convolution method for small convolution windows such as 9×9. It can result in the reduction in the reconstruction time for the 2-D convolution method. Thus, with filters proposed in the present work, an appreciable improvement on the 2-D convolution method is achieved. It will encourage person to use the method.
N-Isopropyl-p- [123I] iodamphetamine (123I-IMP) has been widely used in patients with cerebral vascular damage and epilepsy. The potential of123I-IMP accumulation in the melanin producing cells has been reported since early stage of its development. Some authors reported the accumulation of123I-IMP in the malignant melanoma of human and animals. We evaluated the123I-IMP scintigraphy in 9 patients with malignant melanoma. Patients were classified into two groups: A, 4 patients with 8 lesions; B, 5 post-operative parients without lesions. In group A, the123I-IMP uptake was seen in 4 of 8 lesions. The smallest true positive lesion was located at skin and its size was 15 mm in diameter. Two of the visualized 4 lesions were amelanotic malignant melanomas. This fact suggests that uptake of123I-IMP in malignant melanoma may be related to the processes of melanin synthesis. In group B, two abnormal deposits had been seen in the right thigh of a femal patient. However no abnormality was seen in the following67Ga scintigraphy, TCT, MRI, and repeated123I-IMP scintigraphy. Therefore the abnormal deposits were considered to be the false positive lesions due to urinary contamination.
The synthesis of 6-nitroquipazine, a very potent and selective 5-hydroxytryptamine (5-HT; serotonin) uptake inhibitor, labeled with tritium is described. High specific activity [3H] 6-nitroquipazine could be prepared by the nitration of [3H] quipazine using a mixture of equal volumes of sulfuric acid and nitric acid. The radiochemical yield was approximately 50% based on [3H] quipazine. The radiochemical purity was more than 95% from high performance liquid chromatography (HPLC) and thin layer chromatography (TLC) determinations. [3H] 6-Nitroquipazine would be a new suitable radioligand for studying 5-HT transporter complex in brain and platelets.
This note describes a method of direct measurement of airborne gamma-rays primarily from222Rn daughters using a NaI (Tl) scintillation spectrometer with lead shields. This method has the advantage of being able to maintain the system easily compared to other usual systems including a pump. The pulse-height distributions are successively fed to a floppy disk in a personal computer every unit time. The gain shifts can be corrected automatically by a computer program. This technique would be applicable to the estimation of222Rn daughters concentration and to examination of disequilibrium between214Pb (RaB) and214Bi (RaC) and of those height distribution up to about 200 m. The accuracy for estimating the concentration is as good as that of the filter method.
A new procedure was developed for the waste treatment of radioactive phenol on a laboratory scale. Waste phenol was dissolved in water (2 % as phenol), and ferrous ion (10 mg/l as Fe2+) was added. Hydorgen peroxide (6 % as H2O2) was added seperately in three steps, 20, 30, and 50% of the volume, in order to avoid rapid reaction. The solution was heated at 80-90 °C for several hours in a beaker covered with a watch glass till the color of the solution changes from red purple to pale yellow. Then, the solution was neutralized with sodium hydroxide and heated for 1 h to decompose excess hydrogene peroxide. When the procedure is carried out with four 2 l beakers on a hot plate, 100 ml of phenol (1200 ml of the aqueous solution saturated with phenol) can be oxidized simultaneously.