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.

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.

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.

Dosimetry and measured differential W values of air for heavy ions.

Heavy-ion irradiation systems were designed and constructed at two cyclotron facilities in Japan for use in various fields of radiation physics and radiation biology. A 135 MeV/u carbon beam as well as 12 MeV/u carbon and helium-3 beams were first used in experiments. We have established a systematic method for heavy-ion dosimetry at both high and low incident energies involving measurements of fluences. We also obtained differential W values (w) of air for those beams by comparing the results of fluence measurement dosimetry with ionization chamber dosimetry. The differential W values of air were found to be 36.2 +/- 1.0, 34.5 +/- 1.0, and 33.7 +/- 0.9 eV for 6.7 MeV/u carbon ions, 10.3 MeV/u 3He ions, and 129.4 MeV/u carbon ions, respectively. The w value for high-energy heavy ions approaches the W value for high-energy electron or photon beams. In ionization chamber dosimetry for a heavy-ion beam, we found a track-size effect. A difference in the track sizes of heavy ions in the gas and solid phases affected the output current of the ion chamber in the case of high-energy heavy ions.

Easy dissection of hard and thickened pericardium on constrictive pericarditis.

The keys to successful pericardiectomy for constrictive pericarditis are early operation and as complete a pericardiectomy as possible. With the high-speed burr it is easy and safe to dissect the calcified pericardium and define the epicardium even in a small operative field such as the inferior or posterior portion of the heart. This method has the important ability to perform very complete pericardiectomy.

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.

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.

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.

[Successful repair of post-operative rupture of the left ventricular wall after mitral valve replacement].

Rupture of the left ventricular wall after mitral valve replacement (MVR) is a rare but lethal complication, particularly in delayed type. We have encountered five cases of this complication, and the last case who was suffered 6 hours after MVR was successfully repaired. This case is a 56-year-old woman with MS. She underwent MVR with a Duromedics 25 M. She was transferred to the ICU and the postoperative course was uneventful until 6 hours after the operation, then bleeding from chest drainage tubes increased suddenly. She was promptly brought to the operating room, and the cardiopulmonary bypass was restarted. A tear and hematoma at the posterior wall of the left ventricle (Type II perforation) were found. The rupture was closed with three interrupture mattress sutures with a teflon felt strip. Bleeding was decreased, but oppression with sponge was applied to small but continuous bleeding. At present, she is in a good condition without occurrence of pseudoaneurysm of the left ventricle. We investigated our own five cases and sixty cases reported in Japan, and etiology, surgical repair and prevention of this complication were discussed.

[The results and problems of reoperation for coronary artery disease].

In six hundred and six consecutive patients undergoing coronary artery bypass grafting (CABG) within the past 17 years (May 1974 to March 1991), repeated CABG were performed on 10 patients (1.65%). The main reasons for repeated CABG were graft failure (GF) in 8, progression of native disease (NP) in 5 and incomplete revascularization (IR) in 3 patients. The incidence of GF was high either within a half year or around 5 years after CABG. Although all patients survived from reoperation, four patients continued to have mild angina pectoris. When the recurrence of angina is noted after CABG, coronary arteriography and if necessary PTCA should be done as soon as possible. If a second surgery is inevitable, maximum utilization of arterial graft and accomplishment of complete revascularization are emphasized.

[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.

[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.

[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.

[A case report of aorto-pulmonary window associated with atrial septal defect].

The patient was a one-year-old boy, who underwent surgery with a diagnosis of atrial septal defect (ASD). During operation, aorto-pulmonary window (A-P window) which had not been detected by the preoperative examinations, was found. Therefore, the A-P window was divided prior to closing ASD. The patient is in good condition six months after the operation. The causes of the inaccurate preoperative diagnosis were discussed.

[Coronary artery bypass utilizing vein grafts: why didn't we use an arterial graft?].

Internal thoracic artery (ITA) grafts for coronary artery bypass grafting (CABG) are superior to SVG in the long-term patency and survival. In spite of our effort to utilize ITA whenever possible, we still have some cases which have to receive only vein grafts. Among the consecutive 201 patients undergoing CABG in the past three years, 32 patients (16%) received only vein grafts. We compared these patients (SVG group) with those who received ITA grafts (ITA group). The SVG group consisted of all emergency cases and many cases with single and double vessel disease. In the SVG group, perioperative use of IABP was more frequent and operative mortality was higher, although the number of grafts was fewer (2.66 vs 3.61) and aortic cross clamping time was shorter in this group. Main reasons for selecting only vein grafts were emergency surgery, inadvertent injury of ITA, inadequate ITA free flow etc. Technical refinement in the preparation of ITA is important to make possible wider application of arterial grafts for CABG.

[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.

[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.

[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.

[Reoperation for mitral valve disease].

From 1978 to March 1994, 95 patients underwent repeated open heart surgery for mitral valve diseases. There were 48 men and 47 women. The mean age was 50 and the mean interval between initial and second operation was 8 years. The initial operations were OMC in 39, MAP in 13, OMC+MAP in 11, MVR in 30 and AVR in 2 patients. The hospital death occurred in 31 cases (32.6%). In recent cases, however the hospital death were reduced to 4 (14.8%). This was attributed to the change in myocardial protection from previous intermittent antegrade crystalloid to recent continuous combined antegrade and retrograde cardioplegia.