New Stepwedge for Bootstrap Sensitometry in Medical Radiography

A new stepwedge has been developed for bootstrap sensitometry, which is used for determining the characteristic curve of radiographic screen/film systems. Since each step of the stepwedge is separated by the lead septum, flare generated under one step will not penetrate the region of another step. The metal of the stepwedge can be changed with various materials. Characteristic curves obtained with new stepwedge bootstrap (NSB) and conventional stepwedge bootstrap (CSB) techniques were compared with those obtained for screen/film systems with inverse sqare sensitometry. The inverse square method was used as the reference standard for accuracy. The NSB method provided characteristic curves that agreed well with those obtained using the inverse square method. The slope of the curve in the CSB method was lower than that in the inverse square or NBS method, because of scatter radiation. The shape of the characteristic curve from the NSB method did not vary with the materials of step metals (aluminum and copper). The cumulative error involved when using the bootstrap method is also discussed

Report of a study using phantom materials, and clinical experience with simultaneous radio-hyperthermotherapy.

Simultaneous radiohyperthermotherapy (SRH) is a combined hyperthermia-radiation therapy in which irradiation is given during heating. Mutual interference between the high energy radiotherapy system (Toshiba LMR-15A) and the 13.56 MHz capacitive heating system (Omron HEH-500C) was tested with phantom materials prior to a clinical trial with SRH. The energy and flatness of irradiation were not affected by the heating system within the range of clinical use. The high energy radiotherapy system did not affect the increase or distribution of temperature during simultaneous treatment. The results of this phantom study indicated that these apparatuses would not produce clinically significant mutual interference during SRH. A clinical trial was performed on a 57-year-old woman with postoperative recurrence of rectal cancer. This is the first reported clinical case treated with true SRH in which external irradiation was administered during mid capacitive heating. Twelve SRH treatments were performed on the recurrent lesion at a frequency of twice a week for six weeks using the apparatuses described above. There was a significant reduction in pain after treatment. The tumor marker carcinoembryonic antigen (CEA) level decreased after treatment. On CT images taken after treatment, the tumor site became a low density area which indicated necrosis. There were no side effects. These results suggest that further clinical study of SRH should be performed to clarify its advantages.</p

Physical Image Quality of Rapid Processing Films

The imaging properties of Konica "new" SR series films and "old" MG-SR series films for rapid processing were measured in combination with green-emitting intensifying screens. The measured image quality prarameters include: characteristic curve, modulation transfer function (MTF) and Wiener spectrum. The relative speeds of the new SR series systems were slower than those of the old MG-SR series systems from 10 to 25%. The MTF's of the new systems were generally comparable to those of the old systems, except that SR-G system was improved with an increase of approximately 10%. In the Wiener spectrum measurement, however, the new systems showed from 10 to 35% decrease in low-frequency noise

The contrast media containing soft drinks for X-ray examination of the stomach

胃検診の受診者を増やし、検査を円滑に行う上で、造影剤である硫酸バリウム懸濁液の飲みにくさが障害の一つとなっている。これを改善する試みとして、懸濁液に市販の粉末清涼飲料を混入し検討したところ72.1％の人から通常のものよりも飲みやすいという回答を得た。今後、臨床的な検討を加えながら、さらに創意工夫していく必要がある。Barium sulfate suspensions are disliked to drink by many people. That is one of the obstacles to increse person who consult doctors and to have medical examinations smoothly. We mixed soft drinks into the suspensions to improve this problem. As a result they were popular among 72.1% people. We need to study about these suspensions further, adding the clinical matters

Dose Distributions at Standard Diagnostic X-Ray Energy

Exposure dose has been indicated by surface dose or transit dose, but they could not indicate dose distributions inside the body. Modulex as the radiation therapy planning system was used for dose distributions at standard diagnostic X-ray energy. X-ray is low energy X-ray at standard diagnostic radiography, so alterations of the energy and the scattering dose distribution by absorbers are quite different from those at high energy X-rays. Mix-DP was put to the homogeneous tissue use, then Bone equivalent phantom or Lung equivalent phanton was put to the inhomogeneous tissue use. Density correction factors for inhomogeneous phantoms were gotten by the calculation of the water equivalent thickness. In Bone the inhomogeneous correction depended strongly on the bone thickness. In Lung it was in need of one density correction factor and the scattering correction method for the decrease of the back scattering. The calculated dose distributions by Modulex agreed with measured data when each correction was carried out, and it was indicated that those data apply to inclinical situations

Analysis of Tempormandibular Joint by Image Processing -Discrimination of Condylar Position-

Tomography is clinically useful in the diagnosis of the temporomandibular joint (TMJ) syndrome. The TMJ is formed by the condyle and the glenoid fossa, and there exists TMJ space between them. Image processing was employed in the present study, and the reference points of the condyle and the glenoid fossa were determined from the tomogram. Subsequently, the TMJ space was measured automatically in the image analysis. The TMJs of 98 patients were examined practically and the characteristics of each result were studied. There is a possibility of discriminating an abnormal condylar position from a normal one by making use of the TMJ space and the distance between two reference points

Total Skin Electron Beam Therapy

The peripherally T-cell lymphoma; Mycosis fungoides etc, has the good radiation sensitivity, and has been adapted for total skin electron beam therapy. In this study the pendular irradiation method was used for the purpose of total skin electron beam therapy in Mycosis fungoides, and physical data on the radiation field and the electron beam energy were useful clinically.皮膚に限局した一連の末梢型T細胞リンパ腫は放射線に対する感受性が高く、電子線治療の適応となる疾患である。こららの疾患は一般的に全身の皮膚に浸潤するため、治療に際してはTarget Volumeの深さに合わせた最小限のエネルギーで全身隈なく照射する必要がある。筆者等は最近臨床で遭遇した菌状息肉症の患者を治療するため、その患者に合った物理的なデータを測定した。照射野の拡大には振子照射法を用い、エネルギー低減方法は装置に装備されている鉛のスキャタラーを低原子番号で、しかも加工のしやすい塩化Vinyl板に交換する方法を工夫した。データとして治療効果、副作用に関係する線量率、エネルギー、及び照射野内平坦度について測定した結果、距離が長くなる関係から線量率が低下する全身照射法の欠点は解消できなかったが、エネルギー及び平坦度については使用可能なデータを得ることができた

Granularity of Asymmetric Screen-Film System

非対称増感紙フィルム系について、両面乳剤フィルムのウィナースペクトル測定に及ぼす影響を検討した。濃度0.5～2.5のノイズ試料のフロント乳剤、バック乳剤、支持体層それぞれで測定したスペクトルの和と、両面同時に測定した全スペクトルとを比較した。その結果、全ウィナースペクトルの値は、フロント乳剤、バック乳剤の和より高くなった。また、試料濃度が高いほど、その差は大きくなった。これらは、マイクロデンシトメータの光学系の配置と両面乳剤フィルムの構造に起因している。したがって、非対称システムのようにフィルムの前面と後面で特性を分けて考える場合、注意を要する。We have examined a factor affecting the Wiener spectrum measurement of double-emulsion film. An asymmetric screen-film system (Kodak HC/INSIGHT system) was used in this study. The results indicated that the total Wiener spectra of double-emulsion films are higher than the sum of spectra obtained with the front emulsion and back emulsion separately. These differences are attributed to the arrangement of the optical system of the microdensitometer used to measure and the structure of double-emulsion film

Statistics and analysis on the troubles of linear accelarator.

放射線治療の成否は厳密に設定されたTarget Volumeに如何に正確な線量を照射するかによって決まる。治療術式の過程において、最も大きな誤差を生む要因は照射機器である。誤差の少ない治療を目指す第一歩は機器を正確に作動させることであり、日常からの保守点検および整備が必要である。今回、岡山大学附属病院で1976年から1991年までに使用されたリニアックについて、その故障状況を集計し、部位別故障件数、管球の寿命、稼動率などを分析検討した。その結果、故障件数では設置され稼動を始めた1976年、装置の老朽化が進んだ1990、1991年に多かった。部位別集計では加速部に圧倒的に多く、次いで照射口、高圧部の順であった。稼動率は設置年および1987年を除いてはいずれも96％以上とよい結果であった。この結果は全国に稼動している同型の装置の保守点検に役立つものと考える。The Accuracy of radiation dose exposed the rigidly selected target volume is one of significant factors that have an influence upon the efficiency of treatment in the radiotherapy techniques. Therefore, it is necessary to daily maintain and check irradiation equipment for the radiotherapy. For the radiotherapy, the electron linear accelerator, Toshiba LMR-15A, had worked from 1976 to 1991 in Okayama University Hospital. On this study, all records regarding the operating condition were analyzed concerning parts of trouble, life of a tube and operating efficiency for these sixteen years. In a high frequency of trouble, an accelerating structure ranked first, followed by a collimator and a high voltage generator. The operating efficiency was 95% or greater. This report should be helpful to maintain and check a same model in other hosptals

Photon background caused by the reduction of the electron beam energy - Materials of scattering foil -

The total skin electron beam therapy has been one of the clinical treatment for peripherally T-cell lymphoma; Mycosis fungoides, adult T-cell lymphoma, and so on. The crucial points in this treatment are not only having an optimum energy level of electron beam for a target volume (a tissue) but also keeping the photon back ground low. It is not easy to regulate those points by the control panel, however, for the equipment that is conventinally used for electron beam, theoretically, is to exchange lead (Pb), which is ordinarily used, to a low atomic number material as a scattering foil. We examined several different kinds and / or various thickness as a scattering foil material that can make the electron beam lower without an increase of the contaminant as X-ray. We hereby reported the results, and strongly suggested the following two materials in use; acrylic plate, carbon board, and so on, which are easily available and worked, would be practically useful for the total skin electron beam therapy