Recently, CT images are being used over a wide range in radiation therapy. CT data is used to calculate the dose in high dose rate intracavitary irradiation therapy. In conventional method it is difficult to place the sources upon the CT image correctly. Therefore, the metalic dummy source are inserted into the applicators and two directional scout views are taken. Location of the sources are calculated using twice enlarged scout views. CT images with 5mm spacing are taken after exchanging the dummy sources which do not cause artifact. Dose calculation points are obtained from CT image by pixel position. The calculation points are displayed on CT image by brightening the points and the doses are printed out to CRT and printer. The rectum sigmoid colon, bladder, intestine and arbitrary point dose are calculated using these data for each slice. About 20 patients have been computed with this method from Oct. 1982 to Jul. 1983 and from which the damage was tried to be guessed.
Recently, magnification angiography has become popular, because of improvement in X-ray tubes and development of sensitive filmscreen system. Blood vessel contrast is affected by scattered radiation, MTF of systems and taper effect. This time we introduced one of the new functions called P (ω) composed by content rate of direct radiation, MTF of direct radiation and absorption rate of contrast medium, and tried to obtain prediction of the contrast of blood vessel filled with contrast medium. On comparing the contrast calculated from P (ω) with the contrast of the clinical radiography, we got good result and found that P (ω) was very useful.
Recently, geometrical magnification using small focus has been noticed in coronary arteriography to obtain more improved resolving power. For this study, we made a device called "I.I. Zoom" with 20 changeable switch which could make up to two fold image enlargement, and investigated the size of the projectional image in "I・I Zoom"and the geometrical manification using MTF and ROC. Using this "I・I Zoom", we have been able to get more improved resolving power even in the case of large focal spot angiography and could select the fine visual size.
Low contrast resolution of X-ray CT scanners in the range of 0.1 to 3% is clinically important but difficult to measure accurately. The main obstacle for measurement has been the lack of a proper phantom. Presently available phantoms cannot be used to measure various contrasts, and they also have the problem of reproducibility. We have made a water and polystyrene phantom which overcomes these problems. The new phantom is made of the 3% lower attenuation coefficient of polystyrene in relation to water. By varying the thickness of the polystyrene disk in six different sectors, the partial volume effect of the disk and water allows six contrast differences between 0.3 and 3% to be detected. The disk is also provided with holes of various diameters. By measuring the minimum hole sizes of the phantom images, the threshold of perceptibility for each contrast difference can be determined. A contrast-detail-curve is drawn using the contrast and perceptible hole size as parameters. These curves allow for visualization of varing physical parameters and comparison of the performance of differing X-ray CT scanners.
Irregularly shaped fields are commonly used in radiation therapy in order to protect healthy tissue in a treatment field. The calculation methods of percentage depth dose or tissue-air ratio for irregularly shaped fields have been reported by many authors. However, there are few comments refered to the output used in depth dose calculations. We investigated the dose rate at reference depth (output) for the irregularly shaped fields on cobalt 60 gamma rays, Therateron 80. For obtaining the output of irregularly shaped fields, we measured the output both the equivalent square fields formed with lead blocks and the original collimators. With regard to the depth dose for some cases of irregularly shaped fields in clinical applications, we investigated to compare the measured values and calculated values obtained from our output study. In conclusion, it was shown that the values calculated by output of equivalent square fields formed with lead blocks would give the best accuracy for the depth dose of irregularly shaped fields.
In this report, we analyzed field factors, which are important parameter in dose calculations, for 60Co
irregularly shaped fields. Measured field factors for irregular fields were different from the field factors for equivalent square fields obtained from the standard field factor curve measured on square fields defined by installed collimator. They were almost settled on field factors for their open fields. From the result of this experiment, we consider that in dose calculations for irregular fields it is better to use field factors not for equivalent square fields but for the open fields.
In the first report, various characteristics of the multi-image camera were studied using the grey scale test pattern. To distinguish from the H & D curve, the density curve obtained by photographing the grey scale test pattern was named Film-CRT curve (F-C curve hereafter). Then it was reported that the F-C curve was dependent upon each of the three variables namely contrast, brightness and camera's exposure time. In the present report, two types of CRT with and without clamp circuit were surveyed by changing contrast while keeping the brightness and exposure time of the camera constant. The result showed that for CRT without the clamp circuit, the F-C curve was intersecting at one point near its shoulder, whereas for CRT with the clamp circuit, the F-C curve instead of intersecting with its shoulder, was converging to a single point, that is, in the case of CRT with clamp circuit, the highest density values for the F-C curve was independent of variation of contrast, hence dependent upon the 2 variables brightness and exposure time.
The radioimmunoassay (RIA) for parathyroid hormone (PTH) was reported at first by Berson & Yalow ; 1963. Since then their method of PTH assay have been modified by many authers and new methods have developed. PTH is polypeptide hormone composed of 84 amino acids and has a molecular weight of approximately 9,500. Cleavage of the native PTH yields two principal smaller peptides ; the amino (N) terminal fragment which consists of 34 residues and has its biological activity and the carboxyl (C) terminal which is composed of 50 amino acids residues. We have studied RIA of PTH for these 6 years, which contained following measurements ; c-terminal portion (c-PTH), n-terminal portion (n-PTH) and middle region fragment (MM). The results were as follows : 1) In RD24 RIA system, reproducibility was poor. 2) In EIKEN kit (old one), the recovery was poor. 3) In CIS kit, normal range (1 to 4 mIU/ml) was higher than those of the other c-terminal PTH kits. 4) In RIA-mat (65-84), there is possibility that obtained values included PTH and non functioning PTH like substance. 5) EIKEN (46-84) kit was supposed to be best for the measurement of c-PTH. 6) In n-PTH RIA, obtained values could not differentiate between healthy from various diseases. 7) In PTH-MM (44-68), obtained values seemed to be equal to or slightly higher than those of c-PTH. Measurement of the levels of the c-PTH (or MM) by radioimmunoassay in conjunction with serum calcium determination has become a definitive diagnostic test of parathyroid overactivity.
In the present study, uniform survey for commercially available RIA kits of AFP was performed. RIA kits surveyed were AFP RIA kit (RIABEAD), AFP RIA kit, RIAGNOST AFP (Tachisorb), AFP "Eiken"and SPAC AFP. Coefficient of variations (±2SD) of measured values by these five kits are 7.4〜9.3%, 5.2〜11.1%, 7.0〜13.4%, 5.5〜10.7% and 4.9〜7.2%, respectively. C.V. values were smaller in solid state RIA kits than in liquid phase RIA kits. Mean of measured values by SPAC kit was significantly higher than those by the other kits (p<0.005). The analysis of the standard curves of five RIA kits revealed that the best fitting statistical standard curve was different for each RIA kits. Thus it was sugested that the best fitting statistical standard curve should be selected for each RIA when computer analysis was used for the calculation of measured value.