We usually measure the size of organs or other things with a caliper in the ultrasonographic diagnosis. However, it is difficult to measure the size of organs correctly, because the images obtained by U.S. are deformed or showed a false image as a result of the attenation beam and interference of the relection beam. In this examination, we studied the precision of measuring with ultrasonographic diagnostic machines, a linear, compound and sector scan system, by using trial phantom production. The result we got, comparing lateral direction with the axial direction of error, was more accurate measuring in axial direction than in the lateral direction, and in the event the phantom is more deeply positioned, the precision becomes worse for every system. Comparing each system, the compound scan system has the best precision, the linear scan system second best, the sector scan system the worst.
It is said that temporal lobe epilepsy (TLE), one of the incurable epilepsies, results from the lesions of various structrues located in the medial and deep portion of the temporal lobe such as the hippocampus and amygdaloid nucleus. Routine CT scanning techniques cannot adequately delineate these structures in the assessment of TLE. The anatomical relationship between these medial temporal structures and the inferior horn of lateral ventricle which is lateral to them and easily identified by CT lead us to believe that the sections through the longitudinal plane of the inferior horn may clearly delineate them. The present experimental study was undertaken to develop the CT scan technique of the inferior horn of lateral ventricle, which results in the clear delineation of the region of the hippocampus and amygdaloid nucleus. As a result, A total of the 3-4 reversed axial 5 mm-thick section centered at 2.5 cm cephalad to the roof of the external auditory canal at a reversed 25° angle to ABL are adequate to delineate the inferior horn and the medial temporal structures. This scan technique is considered to be useful in the assessment of TLE.
The CT scan techniques appear to have been well established in the diagnosis of neurosurgical diseases. The assessment of the disease in the region of posterior cranial fossa or hydrocephalus often requires detailed information on the circulatory process of cerebrospinal fluid (CSF) from the third ventricle to the cisterna magna via the cerebral aqueduct. However, it is too difficult to visualize this part of the ventricular system on a slice view when the usual scan techniques are used. The purpose of this study is to develop a scan technique which can display the ventricular system from the third ventricle to the cisterna magna on the same slice level. The present study revealed that the aiming CT image is obtained by the following "overlapping" technique ; 5 mm-thick sections are taken every 1.5 mm between 2 and 3 cm posterior to the external auditory meatus with a scan angle of 65° to the Anthropological basal line (ABL). This technique is very useful in assessing patients with an abnormal circulation of CSF and tumors in the posterior cranial fossa.
Recently computed tomography (CT) scanners have become popular among hospitals, and they are in the process of changing from the first generation to the third or fourth generation. Exposure has been increased due to an increase in the matrics by which to obtain better image quality. We have researched how to decrease patient dose by changing X-ray tube current (mA) and adding additional filters and by combining these two methods with better quality due to less deterioration. As a result of the experiment, we discovered that it was possible to decrease about 10% of patient dose with less deterioration in image quality by reducing mA up to 29 mA and by adding 1mm thick Al to 33 mA.
Digital Subtraction Angiography (DSA) digtizes conventional X-ray images produced by the image intensifier TV system, and shows analogue vascular images on the monitor simultaneously. This modality is more sensitive to a contrast medium than the conventional angiography and can visualize vessels filled with a low concentration of a contrast medium very clearly. About two years has passed since the Philips DSA unit (DVI-1) was installed in Osaka University Hospital. During this period, about 600 cases were examined using the DSA. Factors that influenced the quality of the DSA imagies were divided into three categories as follows. 1) X-ray system (x-ray dose, tube voltage) 2) Display and recording system (film, multiformat camera) 3) Clinical problems (e.g., patients movement during X-ray exposure) We studied the relation between these factors and quality of the DSA images in this report. The most adequate X-ray dose was about 2,500 μR and tube voltage was 60 to 80 kVp. The result of evaluation of the film was that the film with wide latitude gave goodimages, because the specificity of the images could be changed by adjusting the brightness and contrast of the multiformat camera to get the best image. The multiformat camera that we used in this report could not give satisfactory imagies and should be designed fit to the specificity of the DSA images. Misregistration was mostly caused by patient movement, in many cases ; the movement was caused because of an inadequate explanation of the DSA examination to the patients. However, the current DSA system is limited because of the temporal subtraction method. One of the solutions for the misregistration is to decrease the patient's heat sensation by using a contrast medium having a low osmotic pressure. The contrast medium having a low osmotic pressure seems to be warking well. The other way is to use the dual energy subtraction method to decrease the misregistration. This system will become popular in the future. We discussed the major problems and some solutions for the DSA images by using our clinical experience.
Accurate radiation therapy delivery to the target volume depends on appropriate treatment planning, daily patient set-up with minimum localization errors and performed treatment equipments. The present report describes 1) acquisition of patient data by CT and transfers axial tomography, 2) physiological movements of target volume due to respiration and swallowing during irradiation and 3) quality control of radiation therapy delivery by detection of localization errors in daily set-up.
Precision in external beam therapy for target volume is estimated by the following three conditions : machine setting parameter error, movement of the portal skin and reproducibility as well as the exactness of the target absorbed dose calculated according to the transit dose including this information. Mismatch in setting treatment parameters is 1% (37/3,586). However, these setting errors can be prevented by the use of a verification and recording device. The movement during the radiotherapy for the head and neck regions is within 3 mm using a fixing device. The range of reproducibility is within 5mm in 83% of patients throughout the cource of the radiotherapy. Errors in expected target absorbed dose in pelvic irradiation is within 5% by means of the calculation from transit dose measurements during the radiotherapy.
In radiotherapy, the deliverly of an accurate absorbed dose to target volume in a patient is fundamental strategy. The ICRU Report 29 recommended to achieve the accuracy of ±5% to tumor points for certain type of tumor. Ideally the accuracy should be accomplished all over the target volume rather than a tumor point. The purpose of this paper is to describe an analysis of dose distributions in a target volume. The dose distribution obtained with a conformation technique were used and compared with one of the other technique. Newly developed software on a commercial RTP computer system (CMS, Modulex) calculated dose spectrum, which is similar to the histogram in a target area shown on the ICRU Report 29,in any regions predefined at planning procedures. The extent of dose cocentration to the target volume, the uniformity of doses in the target volume and doses given to normal tissues and to particular organs were obtained by utilizing this dose spectrum. Selected clinical examples were the treatment of cancer of the hypohysis, the maxillary, the esophagus and the pancreas. The conformation technique showed better results than the others with regard to the dose concentration in all cases. As for the dose homogeneity, no differences between two irradiation techniques were observed. Planning procedures in a conformation radiotherapy is not complicate as compared to another techniques, therefore the conformation technique is suitable method for fitting high dose region to the target volume. Use of rotational blocks with the conformation therapy, which are used for selective protection to organs at risk, accomplished the purpose of dose reduction at the organs, however the dose uniformity in a target volume becomes slightly worse. Carefull considerations will be required to avoid the poor dose uniformity in a target volume when a technique for selective protection is planned with another techniques.
As to the factors which affect the dose calculation in tissue heterogeneity for an electron beam, the energy of the beam and the anatomical information of the inhomogeneous region will be more significant than the field size of the beam or the electron density of the tissue. It will be possible to calculate the dose at a point up to 10 cm depth in the lungs for 12 to 25 Mev (up to 7 cm for 12 Mev) electron beams with an accuracy of ±5% if the electron density has an accuracy of ±15%. As the result of our study, the accuracy of the dose calculation using the AET method and the Fermi-Eyges pencil beam method proposed by Hogstrom was X^^-=0.982±0.424,σn/X^^-×100=43.2% and X^^-=1.01±0.08,σn/X^^-×100=7.9%, respectively.
Recently, The radiological technology has a remarkable progress. The modernistic medical treatment contains many factor, that is advice of ICRP, WHO, medical economy and so on. Therefore, it is the experimental approach of the radiological technology in quality control, quality assurence, and product liability. This report show to comprehend that is the foundation of QC, QA, PL and enforcement is radiological technology.