WE-G-BRCD-04: Development of Automated Determination Method of Robust Beam Directions against Patient Setup Errors Based on Spatial Distribution of Electron Density in Particle Therapy.

PURPOSE: The three-dimensional (3D) dose distribution covering a tumor region tends to be more breakable if the beam's eye view (BEV) of the 3D electron density (ED) map in a beam direction changes more abruptly with large fluctuations. Our aim of this study was to develop an automated determination method of robust beam directions against the patient setup error based on the ED-based BEV in the beam direction in the particle therapy. METHODS: The basic idea of our proposed method was to find the robust beam directions, whose the ED-based BEV has the spatial fluctuations with low special frequency and small amplitude. For evaluation of the spatial fluctuation in the ED-based BEV in a beam direction, we obtained power spectra of the ED-based BEVs in all directions, i.e., 0 to 355 degree, with an interval of 5 degree. It was assumed that as the average spatial frequency and amplitude of the fluctuation in the ED-based BEV in a beam direction is lower and smaller, respectively, the absolute value of a gradient of the power spectrum becomes larger. Therefore the gradient of the power spectrum was calculated for determination of the robust beam direction. The ED-based BEV was produced by projecting a 3D electron density map derived from the computed tomography (CT) image from a beam source to the distal end of a planning target volume (PTV). Four cases of head and neck cancer patients were selected for evaluation of the proposed method. RESULTS: As a preliminary result, radiation oncologists agreed with most beam directions, which seem to be robust against patient setup errors, suggested by the proposed method. CONCLUSIONS: Our proposed method could be feasible to suggest the robust beam directions against patient setup errors in hadron particle therapy.

Carbon-ion radiotherapy: clinical aspects and related dosimetry.

The features of relativistic carbon-ion beams are attractive from the viewpoint of radiotherapy. They exhibit not only a superior physical dose distribution but also an increase in biological efficiency with depth, because energy loss of the beams increases as they penetrate the body. This paper reviews clinical aspects of carbon-beam radiotherapy using the experience at the National Institute of Radiological Sciences. The paper also outlines the dosimetry related to carbon-beam radiotherapy, including absolute dosimetry of the carbon beam, neutron measurements and radiation protection measurements.

Improved motion compensation in 3D-CT using respiratory-correlated segment reconstruction: diagnostic and radiotherapy applications.

Conventional respiratory-gated CT and four-dimensional CT (4DCT) are disadvantaged by their low temporal resolution, which results in the inclusion of anatomic motion-induced artefacts. These represent a significant source of error both in radiotherapy treatment planning for the thorax and upper abdomen and in diagnostic procedures. In particular, temporal resolution and image quality are vitally important to accurate diagnosis and the minimization of planning target volume margin due to respiratory motion. To improve both temporal resolution and signal-to-noise ratio (SNR), we developed a respiratory-correlated segment reconstruction method (RS) and adapted it to the Feldkamp-Davis-Kress algorithm (FDK) with a 256 multidetector row CT (256MDCT). The 256MDCT scans approximately 100 mm in the craniocaudal direction with a 0.5 mm slice thickness in one rotation. Data acquisition for the RS-FDK relies on the assistance of a respiratory sensing system operating in cine scan mode (continuous axial scan with the table stationary). We evaluated the RS-FDK for volume accuracy and image noise in a phantom study with the 256MDCT and compared results with those for a full scan (FS-FDK), which is usually employed in conventional 4DCT and in half scan (HS-FDK). Results showed that the RS-FDK gave a more accurate volume than the others and had the same SNR as the FS-FDK. In a subsequent animal study, we demonstrated a practical sorting process for projection data which was unaffected by variations in respiratory period, and found that the RS-FDK gave the clearest visualization among the three algorithms of the margins of the liver and pulmonary vessels. In summary, the RS-FDK algorithm provides multi-phase images with higher temporal resolution and better SNR. This method should prove useful when combined with new radiotherapeutic and diagnostic techniques.

Respiratory gated irradiation system for heavy-ion radiotherapy.

PURPOSE: In order to reduce the treatment margin of the moving target due to breathing, we developed a gated irradiation system for heavy-ion radiotherapy. METHODS AND MATERIALS: The motion of a patient due to respiration is detected by the motion of the body surface around the chest wall. A respiratory sensor was developed using an infrared light spot and a position-sensitive detector. A timing signal to request a beam is generated in response to the respiration waveform, and a carbon beam is extracted from the synchrotron using a RF-knockout method. CT images for treatment planning are taken in synchronization with the respiratory motion. For patient positioning, digitized fluoroscopic images superimposed with the respiration waveform were used. The relation between the respiratory sensor signal and the organ motion was examined using digitized video images from fluoroscopy. The performance of our gated system was demonstrated by using the moving phantom, and dose profiles were measured in the direction of phantom motion. RESULTS: The timing of gate-on is set at the end of the expiratory phase, because the motion of the diaphragm is slower and more reproducible than during the inspiratory phase. The signal of the respiratory sensor shows a phase difference of 120 milliseconds between lower and upper locations on the chest wall. The motion of diaphragm is delayed by 200 milliseconds from the respiration waveform at the lower location. The beam extraction system worked according to the beam on/off logic for gating, and the gated CT scanner performed well. The lateral penumbra size of the dose profile along the moving axis was distinguishably decreased by the gated irradiation. The ratio of the nongated to gated lateral fall-off was 4.3, 3.5, and 2. 0 under the stroke of 40.0, 29.0, and 13.0 mm respectively. CONCLUSION: We developed a total treatment system of gated irradiation for heavy-ion radiotherapy. We found that with this system the target margin along the body axis could be decreased to 5-10 mm although the target moved twice or three times. Over 150 patients with lung or liver cancer had already been treated by this gated irradiation system by the end of July 1999.

Breathing-synchronized radiotherapy program at the University of California Davis Cancer Center.

In this paper we present a complete description of the breathing synchronized radiotherapy (BSRT) system, which has been jointly developed between the University of California Davis Cancer Center and Varian Associates. BSRT is a description of an emerging radiation oncology procedure, where simulation, CT scan, treatment planning, and radiation treatment are synchronized with voluntary breath-hold, forced breath-hold, or breathing gating. The BSRT system consists of a breathing monitoring system (BMOS) and a linear accelerator gating hardware and software package. Two methods, a video camera-based method and the use of wraparound inductive plethysmography (RespiTrace), generate the BMOS signals. The BMOS signals and the synchronized fluoroscopic images are simultaneously recorded in the simulation room and are later analyzed to define the ideal treatment point (ITP) where organ motion is stationary. The BMOS signals at ITP can be used to gate a CT scanner or a linear accelerator to maintain the same organ configuration as in the simulation. The BSRT system allows breath-hold or gating. This dual role allows the system to be applicable for a variety of patients, i.e., the breath-hold method for those patients who can maintain and reproduce the ITP, and the forced breath-hold or gating method for those who are not ideal for voluntary breath-hold.

Patient position verification using CT images.

The use of ions in the radiotherapy of cancer patients requires an accurate patient positioning in order to exploit its potential benefits. Using CT images as the basis for the setup verification offers the advantage of a high in-plane resolution in combination with a geometrically accurate, volumetric information. Before each fraction a single CT slice is acquired at the isocenter level after the positioning procedure. This single slice is registered to the planning CT cube using automated image registration algorithms. Thus any erreonous translation or rotation can be detected and quantified. The registration process involves the interpolation of the volumetric data, the calculation of an energy function, and the minimization of this energy function. Several data interpolation functions as well as minimization algorithms were compared. CT studies with a head phantom were performed in which defined translations and rotations were simulated by moving a motor-driven treatment chair. Different slice thicknesses and anatomical sites were studied to investigate their potential influence on the registration accuracy. The accuracy of the registration was found to be a fraction of a voxel size for suitable combinations of algorithms (typically better than 0.16 mm/deg). A significant dependancy of the registration accuracy on the CT slice thickness and the anatomical site was found (the accuracy ranges from 0.05 mm/deg to 0.16 mm/deg depending on the site). The calculation time is dependant on the used algorithms and the magnitude of the setup error. For the standard combination of algorithms as proposed by the authors (Downhill Simplex minimization with Trilinear interpolation) the typical calculation time is about 20 s for a Sun UltraSPARC processor. Taking into account the mechanical accuracy of the setup device (motor-driven chair) the registration of CT images is thus a useful tool for detecting and quantifying any significant error in the patient position.

A horizontal CT system dedicated to heavy-ion beam treatment.

A horizontal helical CT system to be used for 3-D treatment planning and for positioning verification of patients in seated position was installed in the treatment room with a fixed horizontal heavy-ion beam line. The system achieved the expected mechanical consistency and reliability.

Biophysical characteristics of HIMAC clinical irradiation system for heavy-ion radiation therapy.

PURPOSE: The irradiation system and biophysical characteristics of carbon beams are examined regarding radiation therapy. METHODS AND MATERIALS: An irradiation system was developed for heavy-ion radiotherapy. Wobbler magnets and a scatterer were used for flattening the radiation field. A patient-positioning system using X ray and image intensifiers was also installed in the irradiation system. The depth-dose distributions of the carbon beams were modified to make a spread-out Bragg peak, which was designed based on the biophysical characteristics of monoenergetic beams. A dosimetry system for heavy-ion radiotherapy was established to deliver heavy-ion doses safely to the patients according to the treatment planning. A carbon beam of 80 keV/microm in the spread-out Bragg peak was found to be equivalent in biological responses to the neutron beam that is produced at cyclotron facility in National Institute Radiological Sciences (NIRS) by bombarding 30-MeV deuteron beam on beryllium target. The fractionation schedule of the NIRS neutron therapy was adapted for the first clinical trials using carbon beams. RESULTS: Carbon beams, 290, 350, and 400 MeV/u, were used for a clinical trial from June of 1994. Over 300 patients have already been treated by this irradiation system by the end of 1997.

Relationship between CT number and electron density, scatter angle and nuclear reaction for hadron-therapy treatment planning.

The precise conversion of CT numbers to their electron densities is essential in treatment planning for hadron therapy. Although some conversion methods have already been proposed, it is hard to check the conversion accuracy during practical therapy. We have estimated the CT numbers of real tissues by a calculational method established by Mustafa and Jackson. The relationship between the CT numbers and the electron densities was investigated for various body tissues as well as some tissue-equivalent materials used for a conversion to check the accuracy of the current conversion methods. The result indicates a slight disagreement at the high-CT-number region. A precise estimation of the multiple scattering, nuclear reaction and range straggling of incident particles has been considered as being important to realize higher-level conformal therapy in the future. The relationship between these parameters and the CT numbers was also investigated for tissues and water. The result shows that it is sufficiently practical to replace these parameters for real tissues with those for water by adjusting the density.

Surgical treatment of discrete subaortic stenosis in an adult.

We report on an adult patient with discrete-type subaortic stenosis. A 48-year-old man who had progressed asymptomatically since childhood despite heart murmur was transferred to our hospital. The patient was diagnosed as having severe aortic stenosis with a pressure gradient of 100 mmHg across the aortic valve, associated with a grade II aortic regurgitation. A conventional aortic valve replacement was scheduled. During surgery, the aortic valve was found to be tricuspid but incompetent as a result of shrinking and thickening of the left coronary cusp. A circumferential fibromuscular ridge was observed under the cusps, which corresponded to Kelly's type II discrete subaortic stenosis. Because of the small subaortic area and deformity of the cusp, we performed aortic valve replacement after excision of all cusps and the fibromuscular ridge. Early corrective surgery is recommended for discrete subaortic stenosis to prevention regurgitation progression.

[A case report of coronary artery bypass grafting in a patient with ankylosing spondylitis].

We reported a case of ankylosing spondylitis who successfully underwent coronary artery bypass grafting (CABG) for unstable angina pectoris. A 67-year-old man was admitted with symptom of anginal pain. Selective coronary angiography revealed coronary artery stenoses; 90% in seg 6, 90% in seg 11, proximal 75%, distal 90% in seg 3, 99% in 4 PD and 99% with delay in 4 AV. The left internal thoracic artery was anastomosed to seg 7 and saphenous vein (SVG) to PL-2, PL-1 sequentially, and another SVG to 4 PD. His postoperative course was uneventful. Cardiac lesions accompanied by ankylosing spondylitis are rare in Japan. Perioperative problems of these lesions therefore, are discussed.

[A case of mobile left atrial thrombus without mitral valve disease].

A 70-year-old woman who had a left atrial thrombus without mitral valve disease was reported. On admission her electrocardiogram showed atrial fibrillation, but there was no cardiac murmur. Transthoracic echocardiogram revealed a dilated left atrium and an intact mitral valve, but did not detect any thrombus. Transesophageal echocardiogram, however, demonstrated the thrombus attaching to the left atrial appendage. Removal of the thrombus and maze procedure were performed at the same time. Although a pacemaker (DDDR mode) was required postoperatively, she spends uneventful daily life at two years after the surgery.

[Effect of aprotinin on bleeding during and graft patency after coronary artery bypass grafting].

The purpose of this study was to evaluate the effect of aprotinin on intraoperative bleeding and graft patency in 200 patients undergoing elective CABG. Patients were classified into three groups; patients receiving 1500000 KIU of aprotinin (group A), 300000 KIU of aprotinin (group B) and no aprotinin as the control (group C). The groups were almost the same as to age, sex, number of grafts and use of ITA. Intraoperative bleeding and reexploration were significantly decreased in group A compared with group B and C. All patients underwent coronary angiography between the 4th and 8th post-operative weeks. Graft patency was significantly decreased in group A (SVG: 90.4%, ITA: 91.1%) compared with group B (SVG: 95.3%, ITA: 100%) and C (SVG: 95.5%, ITA: 99.2%). Perioperative myocardial infarction increased in group A (3.7%). Aprotinin was effective in reducing intraoperative bleeding in CABG, but decreased early graft patency after CABG. It is suggested that aprotinin should not be used routinely in CABG unless a patient has bleeding tendency which is likely to be seen in emergency and redo surgery.

Indications and problems of coronary artery bypass grafting without cardiopulmonary bypass.

As an alternative method of myocardial protection and to obviate the inherent risks of cardiopulmonary bypass (CPB), we have been performing coronary artery bypass grafting (CABG) without CPB in carefully selected patients. Since the first such operation was successfully performed in January 1995 on a patient with angina pectoris and lung cancer, four other patients have subsequently undergone this technique. This series of 5 patients, being 1 man and 4 women ranging in age from 68 to 80 years, is presented in this report. The reasons for the selection of this procedure were concomitant diseases including lung cancer, a calcified aorta, and myocardial infarction. The mean time of ischemia for each anastomosis was 15.3 +/- 5.3 min, and the maximum cardiac muscle creatine phosphokinase (CPK-MB) was less than 14 unit/l postoperatively. None of the patients required ventilatory support for longer than 24 h postoperatively, and oral intake was started within 24 h after extubation in all patients. Postoperative angiography confirmed graft patency and none of the patients developed any ischemic symptoms. All the patients were discharged between 1 and 2 months postoperatively. Thus, the off-pump technique is useful when concomitant diseases are present and will become an alternative method of treatment for coronary artery disease in selected patients.

[Surgical treatment of aortic stenosis with polycythemia vera: a case report].

We report a case of 67-year-old woman with severe aortic stenosis complicated by polycythemia vera (PV). She has been treated for PV with busulfan over the past three years. On admission, she had increase in white blood cell, red blood cell and platelet count. The pressure gradient between left ventricle and aorta was 170 mmHg. Aortic valve was bicuspid and replaced with a 21 mm Carpentier-Edwards pericardial xenoprosthesis. Ascending aorta with a diameter 6.0 cm was replaced simultaneously with a 30 mm Dacron graft (Hemashield). Post-CPB course was uneventful except for a tendency to the prolongation of activated clotting time. She was discharged from the hospital in good condition.

[Surgical treatment of active infective endocarditis].

Between August 1980 and December 1995, 29 patients have undergone valve replacement for active infective endocarditis (IE) at our institute. Twenty five patients had native valve endocarditis (NVE) and 4 had prosthetic valve endocarditis (PVE). The indication for surgery in 29 patients was congestive heart failure, septicemia or systemic embolization. Twenty six patients had vegetation. Eleven patients had AVRs, including one modified Bentall operation, 10 had MVRs and four had DVRs with mechanical prosthetic valve. There were eleven early death (38%) and one late death. Operative mortality rate has reduced to 24% after 1991. We conclude that early surgical intervention should be taken according to the hemodynamic state of the patients irrespective of the presence of septicemia.

Differences in heavy-ion-induced DNA double-strand breaks in a mouse DNA repair-deficient mutant cell line (SL3-147) before and after chromatin proteolysis.

DNA double-strand breaks induced by X- or neon beam-irradiation in a DNA double-strand break-repair-deficient mutant cell line (SL3-147) were examined. The increase in the number of DNA double-strand breaks was dose depend after irradiation with X-rays and neon beams and was enhanced by chromatin-proteolysis treatment before irradiation. These results suggest that the induction of DNA double-strand breaks by ionizing radiation, including heavy-ions, is influenced by the chromatin structure.

[Esophageal perforation after replacement of descending thoracic aorta for rupture mycotic aneurysm].

Primary mycotic aneurysm of the thoracic aorta has rarely been reported. The patient was a 61-year-old male who had a ruptured mycotic aneurysm of the descending thoracic aorta without any evidence of infectious disorders in his history. The patient developed esophageal perforation after graft replacement of the descending thoracic aorta. After continuous irrigation of the left pleural cavity and the mediastinum for one month, the thoracic esophagus was resected and reconstructed. However, the patient died of DIC following uncontrolled sepsis on the 98th postoperative day. Pathogenesis of the esophageal perforation and operative procedures that might have been effective in saving the patient were discussed.

[The causes and timing of reoperation for coronary artery disease].

In eight hundred and sixteen consecutive patients undergoing coronary artery bypass grafting (CABG) within the past 19 years (1974 to 1993), repeated CABG were performed on 12 patients (1.47%). The main reasons for repeated CABG were graft failure (GF), progression of native disease (NP) and incomplete revascularization (IR). The incidence of GF only and GF combined NP were high either within a half year or around 5 years after CABG. When the recurrence of angina is noted after CABG, the catheter intervention should be chosen at first but the reoperation should be done not so late. Although all patients survived from reoperation, three patients continued to have mild angina pectories. If a reoperation is inevitable, maximum utilization of arterial graft and accomplishment of complete revascularization are emphasized.