SU-E-T-497: Study of Restricted Mass Stopping Power Ratio in Small Electron Tube Fields.

PURPOSE: Electron tubes with small radii are useful to treat narrow regions which cannot accommodate normal electron applicators. In small electron fields, it is not trivial to estimate restricted mass stopping power ratio (MSR), which is needed to evaluate dose from ion chamber measurement. We studied MSRs in small electron tube fields using the Monte Carlo simulation. METHODS: Electron tubes with radii, 3 and 2.5 cm, were used in this study. Nominal electron energies were 6 and 9 MeV. There were two types of tubes. One has a normal cut but the other has a 45-degree cut. For the normal cut tube, percent depth dose (PDD) in water was evaluated along the center of axis (CAX) of a beam. For the 45-degree cut tube, PDD was evaluated along the vertical line from the intersection of the CAX and the phantom surface with 45-degree gantry angle. The MSRs and mean electron energies were calculated using the Monte Carlo simulation. RESULTS: We found good agreement between the measured and calculated PDDs. The changes of mean energies from those in the 10×10 cm2 field at the depth of maximum dose (dmax) were very small for the normal cut electron tubes. For the 45-degree cut tubes, the changes of mean energies at dmax were less than 1 MeV. The MSRs in the normal cut tube fields were almost the same as those in the 10×10 cm2 field at the corresponding depths. The MSRs for the 45-degree cut tubes deviated from those in the 10×10 cm2 by about 1% (1.5 % at most). CONCLUSIONS: We evaluated the mean energies and MSRs in small electron tube fields. The deviations of them from the values in the 10×10 cm2 were small. The maximum difference of MSR was 1.5% in 45-degree cut tube fields. This work was supported by KAKENHI (23791449), Japan Society for the Promotion of Science, and Cancer Professional Training Plan, The Ministry of Education, Culture, Sports, Science and Technology, Japan.

Post-release feeding and growth of hatchery-reared Japanese flounder Paralichthys olivaceus: relevance to stocking effectiveness.

The feeding and growth of hatchery-reared (HR) Japanese flounder Paralichthys olivaceus of c. 100 mm total length (L(T) ) released off the coast of Fukushima, Japan, were investigated. From 2 to 15 days after release, the HR P. olivaceus frequently exhibited high empty-stomach frequency (>40%), low stomach-content mass (<1% of body mass), reduced somatic condition from release (c.-10%) and negligible growth. Thereafter, empty-stomach frequency decreased, the stomach-content mass of HR fish increased to 2-8% of body mass, the somatic condition recovered and growth rate increased to 0·5-1·5 mm day(-1) . Prey items were initially mysids, shifting thereafter to fishes such as the Japanese anchovy Engraulis japonica, as observed similarly in wild counterparts. The proportion of mysids decreased with time after release irrespective of size at release, indicating the importance of mysids for adaptation to natural food. Recapture rates at age 1 year, derived from fish market surveys, varied greatly among release years (4-11%). The variation in the recapture rates was largely accounted for by the post-release growth rates (r(2) = 0·5), suggesting a relationship between the post-release growth of HR fish and their survival and subsequent stocking effectiveness.

Post-release predation on hatchery-reared Japanese flounder Paralichthys olivaceus in the coast of Fukushima, Japan.

To determine the predators of 100 mm total length hatchery-reared juvenile Japanese flounder Paralichthys olivaceus, fishes and crabs were collected using gillnets and a small trawl net off the coast of Fukushima Prefecture, Japan. Predation on juvenile P. olivaceus by older conspecifics, the snailfish Liparis tanakai, ocellate spot skate Okamejei kenojei and the swimming crab Ovalipes punctatus, was detected based on analogical observation and molecular techniques. These predators are nocturnal feeders except for P. olivaceus. Liparis tanakai with body sizes large enough to consume juveniles only appeared in winter, whereas the large O. punctatus was abundant in early summer and in late autumn. Such seasonal variation in predator abundance indicates that the release season can be optimized for reducing predation mortality.

Factors affecting static seat cushion comfort.

To improve the understanding of factors affecting automobile seat cushion comfort in static conditions (i.e. without vibration), relationships between the static physical characteristics of a seat cushion and seat comfort have been investigated. The static seat comfort of four automobile cushions, with the same foam hardness but different foam compositions, was investigated using Scheffe's method of paired comparisons. The comfort judgements were correlated with sample stiffness, given by the gradient of a force-deflection curve at 490 N (= 50 kgf). Samples with lower stiffness were judged to be more comfortable than samples with greater stiffness. A similar comfort evaluation was conducted using five rectangular foam samples of the same composition but different foam hardness (and a wider range than in the first experiment). There was no linear relationship between the sample stiffness and seat comfort for these samples. Static seat cushion comfort seemed to be affected by two factors, a 'bottoming feeling' and a 'foam hardness feeling'. The bottoming feeling was reflected in the sample stiffness when loaded to 490 N, while the foam hardness feeling was reflected in foam characteristics at relatively low forces. The pressures underneath the buttocks of subjects were compared with the comfort judgements. The total pressure over a 4 cm x 4 cm area beneath the ischial bones was correlated with static seat comfort, even when the differences among samples were great; samples with less total pressure in this area were judged to be more comfortable than samples with greater total pressure. It is concluded that the pressure beneath the ischial bones may reflect both comfort factors: the bottoming feeling and the foam hardness feeling.

Discrepancy between inducibility of ventricular tachycardia and activity of cardiac sarcoidosis. Requirement of defibrillator implantation for the inactive stage of cardiac sarcoidosis.

Monomorphic ventricular tachycardia (VT) developed in two patients with cardiac sarcoidosis. Before treatment with prednisolone, technetium or gallium scintigram revealed abnormal accumulation in the heart and bilateral hilar lymph nodes, but programmed electrical stimulation failed to induce VT in either case. Prednisolone was administered and the abnormal accumulation of the scintigra ms disappeared. However, VT became reproducibly inducible, and in one of the patients, transient entrainment was demonstrated in clinical VT morphology. Defibrillators were implanted in both patients. Some VTs associated with cardiac sarcoidosis are due to reentry, and inducibility of VT is not associated with the activity of cardiac sarcoidosis. Even though steroid therapy suppresses the activity of cardiac sarcoidosis, defibrillator implantation is necessary to prevent a possible arrhythmic event during the follow-up.

Combined immunodeficiency, chromosomal instability, and postnatal growth deficiency in a Japanese girl.

We report on an 11-year-old Japanese girl with combined immunodeficiency and chromosomal instability. She had postnatal growth deficiency and microcephaly, preaxial polydactyly of the left hand, and susceptibility to infections. Immunological studies showed marked lymphocytopenia (around 500/ll), reduced lymphocyte response to various mitogens, and reduced or absent serum IgA, IgG, and IgM. Cell biological studies of her primary skin fibroblasts demonstrated spontaneous chromosome aberrations and radiation hypersensitivity. The combination of immunodeficiency, chromosomal instability, and radiation hypersensitivity as seen in the girl is present in both ataxia-telangiectasia and Nijmegen breakage syndrome. Ataxia-telangiectasia was excluded because of differences in clinical features and laboratory data. Likewise, Nijmegen breakage syndrome is unlikely to be the case because the characteristic face, hyperpigmented spots, and mental retardation present in the syndrome were missing in the girl. Sequence analysis of a Nijmegen breakage syndrome responsible gene, NBS1, revealed no mutations. A normal NBS1 product was also demonstrated by immunoblot analysis using an anti-NBS1 antibody. We propose that the disorder in the girl represents a new combination of combined immunodeficiency and chromosomal instability.

Phase Ia study of a hypoxic cell sensitizer doranidazole (PR-350) in combination with conventional radiotherapy.

A phase Ia study of a 2-nitroimidazole nucleoside analog radiosensitizer doranidazole was conducted to evaluate its toxicity and pharmacokinetics in patients undergoing conventional external beam radiotherapy. Twenty-nine patients, aged 40-74 years, with a WHO performance status of 0-2 and with adequate organ functions, were entered in the study. Single administration of doranidazole was investigated first with 13 patients and then a course of five consecutive daily administrations was tested in 16 patients. Doranidazole was given i.v. 25 min before irradiation. Doranidazole doses of 400, 800, 1300 and 2000 mg/m2 were evaluated in the former study, and daily doses of 800, 1300 and 2000 mg/m2 were investigated in the latter study. All patients tolerated doranidazole administration. Although a transient decrease in the 24-h creatinine clearance rate was observed in five patients (one in the single administration study and four in the repeat administration study), this was not considered to be the dose-limiting toxicity. Other toxicities (hematological and gastrointestinal), which may not be related to doranidazole administration, were also mild and were not dose limiting. No neurotoxicity was observed. The average maximum concentration, area under the time-concentration curve and half-life of doranidazole in serum were 172-194 microg/ml, 502-582 microg x h/l and 4.2-4.6 h, respectively, at 2000 mg/m2. At the tested doses, administration of doranidazole was tolerable and achieved serum concentrations at which reasonable radiosensitization could be expected. A phase Ib/II study to evaluate the feasibility and efficacy of up to 30 repeat administrations seems to be warranted.

Qualitative models of seat discomfort including static and dynamic factors.

Judgements of overall seating comfort in dynamic conditions sometimes correlate better with the static characteristics of a seat than with measures of the dynamic environment. This study developed qualitative models of overall seat discomfort to include both static and dynamic seat characteristics. A dynamic factor that reflected how vibration discomfort increased as vibration magnitude increased was combined with a static seat factor which reflected seating comfort without vibration. The ability of the model to predict the relative and overall importance of dynamic and static seat characteristics on comfort was tested in two experiments. A paired comparison experiment, using four polyurethane foam cushions (50, 70, 100, 120 mm thick), provided different static and dynamic comfort when 12 subjects were exposed to one-third octave band random vertical vibration with centre frequencies of 2.5 and 5.5 Hz, at magnitudes of 0.00, 0.25 and 0.50 m x s(-2) rms measured beneath the foam samples. Subject judgements of the relative discomfort of the different conditions depended on both static and dynamic characteristics in a manner consistent with the model. The effect of static and dynamic seat factors on overall seat discomfort was investigated by magnitude estimation using three foam cushions (of different hardness) and a rigid wooden seat at six vibration magnitudes with 20 subjects. Static seat factors (i.e. cushion stiffness) affected the manner in which vibration influenced the overall discomfort: cushions with lower stiffness were more comfortable and more sensitive to changes in vibration magnitude than those with higher stiffness. The experiments confirm that judgements of overall seat discomfort can be affected by both the static and dynamic characteristics of a seat, with the effect depending on vibration magnitude: when vibration magnitude was low, discomfort was dominated by static seat factors; as the vibration magnitude increased, discomfort became dominated by dynamic factors.

Quantitative prediction of overall seat discomfort.

Static seat characteristics (seat stiffness) and dynamic seat characteristics (vibration magnitude) can both influence judgements of seat comfort. It is proposed that seat comfort can be predicted on the basis of Steven's psychophysical law: psi = kphi(n), where psi is a sensation magnitude, phi is the stimulus magnitude and k is a constant. The law is modified to: psi = a + bphis[n(s)] + cphiv[n(v)], where phis and phiv represent seat stiffness and vibration magnitude, n(s) and n(v) are exponents determined by the rate of increase in discomfort associated with the stiffness and vibration magnitude, and a, b and c are constants. The stiffness of foam loaded to 490 N may indicate static seat comfort, while the vibration dose value (VDV) on the seat surface may indicate vibration discomfort. Two experiments with 20 subjects investigated this approach. The first experiment with five magnitudes of vibration, three foams and a rigid wooden flat seat yielded 0.929 for the exponent, n(v), for VDV. In the second experiment subjects judged the overall seat discomfort while exposed six vibration magnitudes with the same four seating conditions. This experiment yielded 1.18 for the exponent, n(s), for seat stiffness. The overall prediction of seat discomfort was given by: psi = -50.3 + 2.68phis1.18 + 101phiv0.929. The prediction equation provided more accurate estimates of subject discomfort than models using either the VDV alone or the stiffness alone, especially when the vibration magnitude was low or the seats were similar. An interaction variable between the VDV and the stiffness slightly improved the prediction. The equivalence of the two stimuli was given by log10 (stiffness) = 0.787 log10 (VDV) + 1.34, or log10 (VDV) = 1.27 log10 (stiffness) - 1.70.

Prototype system for an MR simulation of intracavitary brachytherapy for cervical cancer: preliminary results in six cases.

We report a newly developed MR simulation system for intracavitary brachytherapy for cervical cancer and subsequent treatment results. MR simulation was performed on six patients. The spatial relationship of the tumor to the bladder, rectum, bowel, applicators, etc. was depicted well. Doses to the tumor and surrounding normal tissues were read from isodose curves superimposed on the T2-weighted sagittal image. This system promises to be useful in customizing the dose distribution.

Evaluation of the radiosensitizing effects of RK28 intravenous, intraarterial, and intratumoral injections on the rabbit VX2 tumor system.

PURPOSE: To evaluate the differences in the radiosensitizing effects of intravenous (i.v.) injection, intraarterial (i.a.) injection, and intratumoral (i.t.) injections of the hypoxic cell radiosensitizer RK28 ([1-(4'-hydroxy-2'-butenoxy)methyl-2-nitroimidazole], a 2-nitroimidazole with an acyclic sugar analogue substituted at the N-1 position of the imidazole ring) using an animal experimental system. METHODS AND MATERIALS: Rabbit VX2 tumors, which were implanted in the muscle of left hind legs and grown to 3 cm in diameter, were treated with RK28 (80 mg/kg x b.wt.) before 15 Gy of local x-ray irradiation. The auricular vein and the left saphenous artery were used for systemic injection and regional injection, respectively. For i.t. injection, a 21-gauge needle with three lateral holes was positioned in the central area of the tumor. Tumor regression was precisely evaluated by computed tomograpy (CT), and survival time was also studied. Using high-performance liquid chromatography (HPLC), pharmacokinetic studies for RK28 and its seven major metabolites were performed in tumor and serum at 0, 10, 20, 30, and 60 min after drug injection was completed. RESULTS: Radiosensitizing effects of RK28 were considered present after i.a. injection (p < 0.05) and i.t. injection (p < 0.05) after analyzing tumor volumes on day 21 after treatment. Increased survival was not observed in any group with RK28 injection compared with survival in the group treated by x-ray irradiation alone. Pharmacokinetic studies showed the average concentration of RK28 in the tumor during x-ray irradiation was 1.3 times higher after i.a. injection and 3.5 times higher after i.t. injection than that after i.v. injection. The time modifying factor50 (TMF50: ratio of time for tumor to decrease by 50%, radiation alone vs. radiation plus drug) was calculated to be 1.5 after i.v. injection, 1.7 after i.a. injection, and 2.3 after i.t. injection. The values of TMF50 correlated to the average concentrations of RK28 in the tumor. As to metabolites of RK28, beta-glucuronated compound and cysteine conjugate were highly detected. The concentrations of cysteine conjugate were higher in the tumor than in serum via i.v. injection. CONCLUSIONS: Radiosensitizing effects of RK28 were observed on the rabbit VX-2 tumor system after i.a. or i.t. injection. Pharmacokinetic studies proved that radiosensitizing effects depended on the concentration in the tumor, though the administration routes were different. Combined forms with nonprotein thiols were detected. However, survival benefits were not obtained by RK28. For clinical applications of RK28, i.a. or i.t. injection could facilitate better local control of cancer.

Primary brain tumors in two dogs treated by surgical resection in combination with postoperative radiation therapy.

Primary brain tumors in two dogs were surgically removed followed by postoperative radiation therapy. The two tumors were confirmed histologically to be astrocytoma and meningioma, respectively. After the surgery, the neurological status of each dog improved dramatically and a total dose of 40 Gy was delivered to the surgical site to treat residual tumor tissue. Although the dog with astrocytoma died 6 months after surgery due to unknown causes, the dog with meningioma has lived for over 24 months with a degree of neurological disorder less severe than that before treatment. These results suggested the effectiveness of this type of therapy on brain tumor in dogs and therapeutic modality should be positively planned to treat canine brain tumors.

Clinical characteristics and EPS-guided therapy in 142 cases of sustained ventricular tachycardia.

One hundred and forty-two consecutive patients with sustained monomorphic ventricular tachycardia (VT) were investigated. Only 26.1% of VTs were associated with ischemic heart disease (IHD). The induction rate of sustained VT upon electrophysiologic study (EPS) was 82.9% in patients with IHD and 65.3% in non-IHD. Of 76 inducible sustained VTs, pharmacologic therapy was finally selected in 35 cases, ablative therapy in 25 and surgical therapy in 12. Long-term prognosis was compared between groups divided according to type of ventricular arrhythmia induced at final EPS after antiarrhythmic therapy as follows: Group A: complete suppression of VT, Group B: clinical or non-clinical nonsustained VT, Group C: clinical sustained VT. The event rate in IHD was 6.3% in Group A, 44.4% in Group B and 100% in Group C. In non-IHD, the event rate was 24.0%, 25.0% and 75.0% (Groups A, B and C, respectively). Complete suppression of VT showed a good prognosis in IHD, however, a slightly higher recurrence rate was observed in non-IHD. In ablative therapy, some recurrences and sudden deaths were observed in spite of complete suppression of both VTs in both the IHD and non-IHD groups. Review of the efficacy of antiarrhythmic procedures is recommended during the follow-up period.

Exercise-induced angina with intermittent ST-segment elevation.

A 59-year-old man was admitted for evaluation of mild exertional angina in the morning. During graded treadmill exercise stress testing, the patient had reproducibly intermittent chest pains associated with ST-segment elevations in leads II, III and aVF. A baseline coronary angiogram showed a coronary narrowing of 90% in the middle segment of the right coronary artery. The coronary narrowing was immediately resolved by an intracoronary injection of nitroglycerin. This was a very rare case of variant angina with intermittent ST-segment elevations and chest pains which were reproducibly demonstrated during exercise and the recovery phase of treadmill testing.

[A case of sudden death three months after successful PTCA].

A case report of the sudden death of a 64-year-old man, three months after successful percutaneous transluminal coronary angioplasty (PTCA). He was admitted because of non-Q-wave acute myocardial infarction. Coronary angiography showed 90% stenosis in the anterior descending artery (No. 6). PTCA was successful, but the proximal portion of anterior descending artery was dissected because the balloon slipped from the dilated site during inflation. Acute coronary occlusion was not observed. However, he died suddenly shortly after he complained of severe chest pain three months after PTCA. Histologically, the site of the dissecting artery showed that the intima and media of the arterial wall was disrupted and the lumen was severely stenotic with cellular proliferation. This dissection of the coronary artery is also important because rapid and severe stenosis was induced by the artery's being badly injured.

[Sudden death presenting cardiac tamponade in a case of coronary dissection].

A case is reported of a 56-year-old man with primary coronary dissection presenting as sudden death due to aortic rupture and cardiac tamponade. He was admitted because of loss of consciousness and chest pain. ECG showed complete atrioventricular block and myocardial infarction. Coronary angiography demonstrated coronary dissection and total obstruction of right coronary artery (RCA). Intracoronary injection of urokinase was not effective for recanalization of RCA. He died suddenly two days later. At autopsy, the proximal site of the ascending aorta was dissected locally and had ruptured into a pericardial space. RCA was torn off. The perivascular area around the torn coronary artery communicated with the dissecting space of the ascending aorta. Histologically, no degeneration or infiltration of inflammatory cells was observed in the media of the aorta and the right coronary artery. Histological change was observed only at the media of the torn site of the coronary artery. The thickness of the media was about half of that at the other site of the coronary artery. This is the third case reported in world medical literature of primary coronary dissection presenting as cardiac tamponade.

Experimental study about removal of the implanted tined polyurethane ventricular lead by radiofrequency waves through the lead.

Polyurethane pacemaker leads are widely used nowadays. However, only a few studies have been done to investigate the fixation mechanism of polyurethane leads. To elucidate how pacemaker leads are fixed at the early phase after implantation, polyurethane-insulated tined ventricular leads were implanted in seven mongrel dogs. One to 4 months later, tips of the leads were anchored among the trabeculae and the distal part of the leads were encapsulated by whitish fibrous tissue. It was found that not organized thrombi, but cell reaction with various stages of inflammatory cells was responsible for forming the fibrous tissue. We attempted to remove the lead by delivering radiofrequency wave through the lead. However, no lead could be removed.

Conduction through the reentrant circuit in recurrent sustained ventricular tachycardia evaluated by use of transient entrainment.

Using transient entrainment, the effect of the paced cycle length on the conduction through the reentrant circuit was assessed in recurrent sustained ventricular tachycardia (VT). Fourteen patients were included in the present study and their VTs were paced at multiple cycle lengths while the criteria of entrainment were confirmed at each paced cycle length. Then, the effect of the paced cycle length upon the conduction time, which was evaluated by the measurement of the time interval from stimulus to the entrained electrogram, was analyzed. In the overdrive pacings of VT, 3 response patterns in conduction time were observed: an increasing pattern (n = 8), a flat pattern (n = 5) and a decreasing pattern (n = 1) while the local conduction time outside the reentrant circuit remained unchanged at comparable paced cycle lengths. A decremental property is the likely mechanism responsible for the paced cycle length-dependent prolongation. As for the flat pattern, the existence of a fully excitable gap may be responsible. A paced cycle length related change in the reentrant circuit may account for the decreasing pattern. By using transient entrainment, the electrophysiological characteristics of the reentrant circuit can be evaluated and the information so gathered may be valuable in analyzing the action of antiarrhythmic drugs on the slow pathway.