Pedigree study of the heredity of copper-associated hepatitis in Dalmatians in Japan.

The pedigrees of 3 Dalmatian dogs afflicted with copper-associated hepatitis were investigated to discover the mode of inheritance. A composite family pedigree showed that the 3 affected Dalmatians were related. None of the parents of the affected dogs showed clinical symptoms of liver disease, and the disease had no sex predisposition. The estimated segregation ratio was approximately 3:1 based on surviving littermates. These findings suggested that the copper-associated hepatitis in these Dalmatians was an autosomal recessive mode of inheritance. In addition, some male Dalmatians imported from abroad might have been involved in the occurrence of this disease in Japan.

Étude généalogique de l'hérédité de l'hépatite associée au cuivre chez des Dalmatiens au Japon. Les pedigrees de trois chiens dalmatiens atteints d'hépatite associée au cuivre ont été étudiés pour découvrir le mode de transmission. Un pedigree familial composite a montré que les trois Dalmatiens affectés étaient apparentés. Aucun des parents des chiens affectés n'a présenté de symptômes cliniques de maladie du foie et la maladie n'avait aucune prédisposition associée au genre. Le ratio de ségrégation estimé était d'environ 3:1 sur la base des compagnons de portée survivants. Ces résultats suggèrent que l'hépatite associée au cuivre chez ces Dalmatiens était un mode de transmission autosomique récessif. De plus, certains dalmatiens mâles importés de l'étranger pourraient avoir été impliqués dans l'apparition de cette maladie au Japon.(Traduit par Dr Serge Messier).

Isolation of Aspergillus caninus (Synonym: Phialosimplex caninus) from a Canine Iliac Lymph node.

Aspergillus caninus (synonym: Phialosimplex caninus) is an anamorphic fungus species associated with systemic infections in dogs that has been transferred from the genus Phialosimplex to Aspergillus. Here, we report the first case of canine A. caninus infection in Japan. A castrated Japanese Shiba Inu (6 years old; weight, 12.5 kg) was referred to the Yamaguchi University Animal Medical Center, Yamaguchi, Japan, in June 2017 showing vitality loss and depression. Computed tomography revealed iliac and splenic hilum lymphopathies, and histologic examination of an iliac lymph node by biopsy revealed granulomatous lesions with numerous oval to round yeast-like fungal cells. Aspergillus caninus was isolated from the biopsy samples, and in vitro susceptibility tests of the isolate to the antifungal drugs amphotericin B (AMB), fluconazole (FLZ), itraconazole (ITZ), voriconazole (VRZ), and micafungin (MCF) were performed by the E-test method. The isolate from this dog exhibited a minimal inhibitory concentration of < 0.002 µg/ml to AMB, > 256 µg/ml to FLZ, < 0.002 µg/ml to ITZ, < 0.002 µg/ml to VRZ, and < 0.002 µg/ml to MCF, indicating that the isolate was not susceptible to FLZ and susceptible to AMB, ITZ, VRZ, and MCF. Since the response of the patient dog to ITZ and VRZ treatments was poor, more aggressive management using combination therapies of ITZ with other antifungals may be necessary for treating canine A. caninus infection in dogs.

Transcatheter arterial embolization in normal canine liver.

OBJECTIVE: To determine the effects of selective transcatheter arterial embolization (TAE) in the normal canine liver. STUDY DESIGN: Experimental study. ANIMALS: Adult Beagle dogs (n = 5). METHODS: Gelatin sponge particles (GSPs) were injected through a microcatheter for selective embolization of the left hepatic artery in normal dogs. Computed tomography (CT) and histology were performed during an 8-week observation period; biochemical analysis data were obtained during a 12-week observation period after TAE. RESULTS: Embolization was successful in all dogs and did not induce any change in the clinical appearance of dogs. Postoperative CT was consistent with recanalization of the artery within 2 weeks of embolization in all dogs. Hepatic enzyme levels increased temporarily after embolization but gradually returned to normal ranges. Histological examinations did not differ between treated and untreated liver tissues. CONCLUSION: TAE appears safe in normal dogs observed for 12 weeks. Arterial recanalization seems to occur within 2 weeks after injection of GSPs in the left hepatic artery. IMPACT/CLINICAL RELEVANCE: Selective TAE of the hepatic artery was well tolerated in normal dogs. Selective TAE may be applicable to canine hepatocellular carcinoma.

The modified corneocyte surface area measurement as an index of epidermal barrier properties: inverse correlation with transepidermal water loss.

BACKGROUND: Corneocyte surface area (CSA) is as established parameter for skin barrier function in humans. Measurement of canine CSA has been previously reported but has not been validated. HYPOTHESIS/OBJECTIVES: The aim of this study was to evaluate the validity of CSA as a barrier function parameter in dogs. ANIMALS: Six clinically normal beagle dogs. METHODS: CSA was measured and compared with transepidermal water loss (TEWL) using sequential tape stripping of the stratum corneum as a model of acute barrier disruption. Then, CSA and TEWL were measured at four anatomical sites (groin, lower back, nasal bridge and pinna). The correlation between the two indices was also evaluated. RESULTS: From the results of sequential tape stripping, CSA values gradually decreased with increasing number of tape strippings. The CSA values were inversely correlated with the TEWL ones. The two indices at different sites were variable and were strongly correlated. CONCLUSIONS AND CLINICAL IMPORTANCE: Canine CSA was demonstrated to be a useful parameter for the canine skin barrier function. The results from the anatomical sites imply that the cephalic sites (nasal bridge and pinna) were lower than others in skin barrier function.

Establishment of a novel canine soft tissue sarcoma cell line and comparison of its characteristics with other soft tissue sarcoma cell lines.

Soft tissue sarcoma (STS) is a relatively common tumor in dogs. However, very few canine STS cell lines are available. This study aimed to establish a new cell line, STS-YU1, derived from a recurrence of myxosarcoma in an 11-year-old mixed-breed dog. We examined STS-YU1 for in vitro cell proliferation, migration, anticancer drug sensitivity, transcriptome analysis using next-generation sequencing (RNA-seq), and in vivo tumorigenicity in mice and compared it with previously established STS cell lines, MUMA-G and A72. The cell proliferation and migration of STS-YU1 were higher than MUMA-G although MUMA-G only exhibited tumorigenicity in mice. STS-YU1 showed dose-dependent cytotoxicity to anticancer drugs, but with weak effects. RNA-seq analysis revealed the molecular phenotype of STS-YU1 was different from that of a previously reported cell line, A72. Hence, the use of STS-YU1 would help in efficient drug screening against canine STS in vitro.

Finite element study on post-screw removal stress in toy poodle radius with different plate designs and screw arrangements.

Background: The study employs finite element analysis to investigate stress distribution in the radius of toy poodles after screw removal. The examination focuses on the biomechanical implications of varied screw hole configurations using 1.5 and 2.0-mm locking compression plates (LCPs) with notched head T-Plates. Aim: To provide a noninvasive approach to analyzing the immediate consequences of screw removal from the radius bone in toy poodles. Specifically, it explores the impact of varied plate designs and screw arrangements on stress distribution within the forelimb bones. Methods: The study constructs a three-dimensional bone model of the toy poodle's forelimb based on computed tomography (CT) images. Simulations were designed to replicate jumping and landing from a 40 cm height, comparing stress distribution in the radius post-screw removal. Results: The analysis reveals significant variations in stress distribution patterns between the two LCPs. The radius implanted with the 2.0-mm LCP displays a uniform stress distribution, contrasting with the 1.5-mm plates. Localized stress concentration is observed around the screw holes, while trabecular bone regions near the screw holes exhibit lower stress levels. Conclusion: The study highlights the plate designs and screw configurations that affect bone stress in toy poodle forelimbs post-screw removal. The findings provide valuable insights for veterinarians, aiding informed decisions in veterinary orthopedic practices.

Relationship between clinical parameters and malformations in dogs diagnosed with atlanto-axial instability.

Atlanto-axial instability is a common disease that affects toy-breed dogs. Most cases of atlanto-axial instability are congenital. Furthermore, patients with atlanto-axial instability are predisposed to other concurrent diseases. Therefore, this study aimed to retrospectively determine the presence of concurrent diseases in cases with atlanto-axial instability using imaging data and analyze the relationship between clinical parameters and the incidence of complex malformations. The clinical data and imaging findings of 41 toy-breed dogs diagnosed with atlanto-axial instability were analyzed using their medical records and imaging data. Occipital dysplasia (17/27), atlanto-occipital overlapping (22/34), dens dysplasia (27/41), Chiari-like malformation (8/34), syringomyelia (5/34), lateral ventricular enlargement (20/36), and intracranial arachnoid cyst (5/35) were observed in patients with atlanto-axial instability. The body weight of the patients in the groups with atlanto-occipital overlapping and lateral ventricular enlargement was lower than that of those in the groups without these diseases (1.78 ± 0.71 vs 2.71 ± 1.15 kg, P = 0.0269, 1.60 ± 0.40 vs 2.75 ± 1.08 kg, P = 0.001, respectively). Furthermore, when the correlation between the total number of concurrent diseases and the age at onset and body weight was examined, it became clear that lower body weight was associated with the incidence of a greater number of concurrent diseases. Thus, the findings of this study suggest that toy-breed dogs are more likely to present with complex malformations and should be evaluated carefully with additional examinations and treatment methods.

Elucidation of the radius and ulna fracture mechanisms in toy poodle dogs using finite element analysis.

Fractures occurring in the distal radius and ulna of toy breed dogs pose distinctive challenges for veterinary practitioners, requiring specialized treatment approaches primarily based on anatomical features. Finite Element Analysis (FEA) was applied to conduct numerical experiments to determine stress distribution across the bone. This methodology offers an alternative substitute for directly investigating these phenomena in living dog experiments, which could present ethical obstacles. A three-dimensional bone model of the metacarpal, carpal, radius, ulna, and humerus was reconstructed from Computed Tomography (CT) images of the toy poodle and dachshund forelimb. The model was designed to simulate the jumping and landing conditions from a vertical distance of 40 cm to the ground within a limited timeframe. The investigation revealed considerable variations in stress distribution patterns between the radius and ulna of toy poodles and dachshunds, indicating notably elevated stress levels in toy poodles compared to dachshunds. In static and dynamic stress analysis, toy poodles exhibit peak stress levels at the distal radius and ulna. The Von Mises stresses for toy poodles reach 90.07 MPa (static) and 1,090.75 MPa (dynamic) at the radius and 1,677.97 MPa (static) and 1,047.98 MPa (dynamic) at the ulna. Conversely, dachshunds demonstrate lower stress levels for 5.39 MPa (static) and 231.79 MPa (dynamic) at the radius and 390.56 MPa (static) and 513.28 MPa (dynamic) at the ulna. The findings offer valuable insights for modified treatment approaches in managing fractures in toy breed dogs, optimizing care and outcomes.

Quantitative evaluation of the biomechanical and viscoelastic properties of the dog patellar tendon in response to neuromuscular blockade at different stifle angles.

The patellar tendon (PT) is crucial for maintaining stability and facilitating movement in the stifle joint. Elastography has been recognized as a prominent method for evaluating PT properties in humans and dogs. The utilization of oscillation methods in canine studies remains limited despite their extensive documentation in human studies. Our study represents the first effort to quantitatively assess and compare the effects of muscle relaxant on the biomechanical and viscoelastic characteristics of the PT at varying stifle angles in living dogs. Five healthy female beagles were used in this study. Biomechanical (tone, stiffness, and decrement) and viscoelastic (relaxation time and creep) properties of the PT were measured using MyotonPRO (Myoton Ltd, Estonia) prior to and following administration of rocuronium (0.5 mg/kg/body weight) at normal, extended, and flexed positions. Rocuronium was selected for its safety, controllability, and widespread clinical use in veterinary anesthesia. Two-way analysis of variance showed that tone, stiffness, and decrement were significantly higher (P < 0.001) in the control group than in the muscle relaxation group. At the same time, relaxation time and creep were significantly lower (P < 0.001) in the control group than in the muscle relaxation group. The findings indicate that stifle angle position and muscle rexalant administration fundamentally alter the biomechanical loading conditions of the PT, leading to changes in its viscoelastic properties. Therefore, this novel quantitative data could benefit clinical settings that necessitate accurate and objective methods for risk identification and monitoring PT biomechanics in dogs.

The perfusion index as a method of assessing epidural anaesthesia efficacy in healthy dogs.

Introduction: Perfusion index (PI) is used as assessment of epidural anaesthesia efficacy in human medicine, but its usefulness in dogs is unknown. The aim of this study was to evaluate the usefulness of PI in determining epidural anaesthesia effectiveness. Material and Methods: This is prospective cross-over experimental study. Five healthy adult beagle dogs were anaesthetised and an epidural catheter was inserted in the lumbosacral area and adjusted so that the end of the catheter was placed at the fourth lumbar vertebra. Single-port catheters were used in the control group and multiple-port catheters were used in the treatment group. A PI probe was placed on a hind leg, and the catheter placement was confirmed via computed tomography. The treatment group received a bolus dose of lidocaine, and the control group received saline, via epidural catheter. The PI value was recorded every 5 min until 30 min after lidocaine injection. Results: The PIs of the hind limbs were not significantly different over time, nor were they between the control and lidocaine-injected groups at any point in time. Conclusion: The PI is not useful in determining the efficacy of epidural anaesthesia in dogs under general anaesthesia. In the future, finding a reliable method to evaluate the success of regional anaesthesia, even in patients under general anaesthesia, will be necessary.

Proof-of-concept study of the caninized anti-canine programmed death 1 antibody in dogs with advanced non-oral malignant melanoma solid tumors.

BACKGROUND: The anti-programmed death 1 (PD-1) antibody has led to durable clinical responses in a wide variety of human tumors. We have previously developed the caninized anti-canine PD-1 antibody (ca-4F12-E6) and evaluated its therapeutic properties in dogs with advance-staged oral malignant melanoma (OMM), however, their therapeutic effects on other types of canine tumors remain unclear. OBJECTIVE: The present clinical study was carried out to evaluate the safety profile and clinical efficacy of ca-4F12-E6 in dogs with advanced solid tumors except for OMM. METHODS: Thirty-eight dogs with non-OMM solid tumors were enrolled prospectively and treated with ca-4F12-E6 at 3 mg/kg every 2 weeks of each 10-week treatment cycle. Adverse events (AEs) and treatment efficacy were graded based on the criteria established by the Veterinary Cooperative Oncology Group. RESULTS: One dog was withdrawn, and thirty-seven dogs were evaluated for the safety and efficacy of ca-4F12-E6. Treatment-related AEs of any grade occurred in 13 out of 37 cases (35.1%). Two dogs with sterile nodular panniculitis and one with myasthenia gravis and hypothyroidism were suspected of immune-related AEs. In 30 out of 37 dogs that had target tumor lesions, the overall response and clinical benefit rates were 6.9% and 27.6%, respectively. The median progression-free survival and overall survival time were 70 days and 215 days, respectively. CONCLUSIONS: The present study demonstrated that ca-4F12-E6 was well-tolerated in non-OMM dogs, with a small number of cases showing objective responses. This provides evidence supporting large-scale clinical trials of anti-PD-1 antibody therapy in dogs.

Factors associated with anxiety and depression among caregivers of patients receiving medical home visits.

In recent years, Japan has promoted home visits to support older adults, with caregivers playing an important role. However, caregivers generally experience a high frequency of anxiety and depression, and the factors associated with these conditions among home visit caregivers remain unknown. To identify the associated factors, we conducted a questionnaire-based cross-sectional study of home visit caregivers in Tokushima Prefecture, Japan. The survey included caregivers' Hospital Anxiety and Depression Scale;sociodemographic items of patients and caregivers;and caregivers' perceptions of the home care environment, patients, and themselves. The questionnaires were sent to 379 caregivers;203 responded (53.6% response rate), of which 173 were valid (85.2% valid response rate). The prevalence of anxiety and depression was 43.9% and 69.4%, respectively. Multiple logistic regression analysis of factors associated with anxiety and depression showed that stable family finances (OR:0.69, 95% CI:0.48-1.00, p=0.049) and stable caregiver health (OR:0.45, 95% CI:0.30-0.68, p<0.001) were associated with anxiety. Further, stable family finances (OR:0.60, 95% CI:0.38-0.93, p=0.022), stable caregiver health (OR:0.49, 95% CI:0.30-0.81, p=0.005), and stable patient condition (OR:0.51, 95% CI:0.29-0.92, p=0.025) were associated with depression. These findings demonstrate that caregiver wellbeing is essential in home care settings. J. Med. Invest. 70 : 443-449, August, 2023.

In-silico decongested trial effects on the impaired breathing function of a bulldog suffering from severe brachycephalic obstructive airway syndrome.

BACKGROUND AND OBJECTIVE: Brachycephalic obstructive airway syndrome (BOAS) susceptible dogs (e.g., French bulldog), suffer health complications related to deficient breathing primarily due to anatomical airway geometry. Surgical interventions are known to provide acceptable functional and cosmetic results; however, the long-term post-surgery outcome is not well known. In silico analysis provides an objective measure to quantify the respiratory function in postoperative dogs which is critical for successful long-term outcomes. A virtual surgery to open the airway can explore the ability for improved breathing in an obstructed airway of a patient dog, thus supporting surgeons in pre-surgery planning using computational fluid dynamics. METHODS: In this study five surgical interventions were generated with a gradual increment of decongested levels in a bulldog based on computed tomography images. The effects of the decongested airways on the breathing function of a patient bulldog, i.e., airflow characteristics, pressure drop, wall shear stress, and air-conditioning capacity, were quantified by benchmarking against a clinically healthy bulldog using computational fluid dynamics (CFD) method. RESULTS: Our findings demonstrated a promising decrease in excessive airstream velocity, pressure drop, and wall shear stress in virtual surgical scenarios, while constantly preserving adequate air-conditioning efficiency. A linear fit curve was proposed to correlate the reduction in the pressure drop and decongested level. CONCLUSIONS: The in silico analysis is a viable tool providing visual and quantitative insight into new unexplored surgical techniques.

Does student evaluation of on-demand video lectures vary with student characteristics? A questionnaire survey of medical students at Tokushima University.

The popularity of online classes in university education has grown rapidly since the COVID-19 outbreak. This study aims to examine the association between the detailed characteristics/various contexts of students and the evaluation of online classes. An online questionnaire survey administered to third- and fourth-grade medical students of Tokushima University in September 2021-with 101 (42.8%) valid responses-showed the respondents' general impressions, comprehension, convenience, and desire for online classes even after the pandemic ends were significantly higher for the on-demand lectures than for simultaneous online classes. Notably, students who did not do other things while watching video lectures (10.9%) rated on-demand lectures as facilitating significantly higher impression, comprehension, and convenience than those who did other things (89.1%). A multivariate analysis revealed that students who did not do anything else while watching, whose waking time changed slightly, who commuted to school for shorter periods, who were not good at morning lectures, and who watched at high speed rated the video lectures highly. Thus, video lectures are appreciated by students who are committed to learning, which is a positive result for the future of on-demand education. J. Med. Invest. 70 : 483-493, August, 2023.

Comparison of therapeutic responses between polymyalgia rheumatica and remitting seronegative symmetrical synovitis with pitting edema syndrome.

Polymyalgia rheumatica (PMR) and remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome are common inflammatory rheumatic diseases in the elderly. In this study, we investigated the difference of the therapeutic responses between patients with PMR and RS3PE syndrome. Twenty-four patients with PMR and 12 patients with RS3PE syndrome were treated with initial dosages of 10-20 mg per day oral prednisolone, and the dosages were then tapered. Percentages of patients with negative c-reactive protein (CRP) after 8-week treatment were significantly more in RS3PE syndrome than in PMR. Percentages of patients with relapse during one-year treatment were less likely to be in RS3PE syndrome than in PMR. These differences observed between the two disorders were not associated with the level of initial CRP. There was no significant difference in percentages of patients with prednisolone-free remission after two-year treatment between PMR and RS3PE syndrome. These results indicate that the early response to the treatment is greater in RS3PE syndrome than in PMR. J. Med. Invest. 70 : 145-149, February, 2023.

Sulfasalazine, a potent cystine-glutamate transporter inhibitor, enhances osteogenic differentiation of canine adipose-derived stem cells.

Cystine-glutamate transporter (xCT) is a plasma membrane transporter that imports cystine and indirectly contributes to the oxidative stress resistance associated with increased intracellular glutathione levels. Canine adipose-derived stem cells (CADSCs) include an xCT-positive subpopulation and show relatively low expression of osteogenic markers during in vitro osteogenic differentiation. Sulfasalazine (SSZ), a drug used to treat rheumatoid arthritis, suppresses xCT expression in cancer cells. In this study, we found that the SSZ treatment at 100 µM significantly suppressed xCT mRNA expression in CADSCs but did not significantly affect cell proliferation under the same conditions. Additionally, this treatment decreased the intracellular glutathione concentration. During in vitro osteogenic differentiation, the SSZ treatment at 50 µM and 100 µM significantly increased alizarin red staining and its quantification, as well as the concentration-dependent osteogenic differentiation markers (BMP1 and SPP) mRNA expression. Our results suggested that SSZ enhances the osteogenic differentiation potential of CADSCs and can potentially exhibit a superior therapeutic profile in canine bone regenerative medicine.

Comparison of surgical invasiveness between micro-endoscopic discectomy/microscopic discectomy and conventional hemilaminectomy in dogs.

Micro-endoscopic discectomy (MED) or microscopic discectomy (MD) have been performed for disc herniation in humans. The purpose of this study was to compare the invasiveness of the hemilaminectomy in dogs between the approach using a cylindrical retractor for the MED/MD and a conventional open surgical approaches in dogs. First, as preliminary studies, we analyzed the suitability of the cylindrical retractor for the vertebral body of small to medium-sized dogs on the X-ray computed tomographic images using the three-dimensional analysis software, and confirmed that it was possible to open a bone window of an approximate length of 1.72 clto the spinal canal with the cylindrical retractor with a diameter 17 mm using two medium-sized canine cadavers. Next, to determine difference in the invasiveness of hemilaminectomy, the magnitude of tissue damage, surgical stress and postoperative pain were compared between the conventional open approach (hemilaminectomy group: HL group, n=6) and the surgical approach using the cylindrical retractor (MD group, n=6) in 12 beagle dogs. The plasma creatine phosphokinase, C-reactive protein and cortisol concentrations, incision length and University of Melbourne Pain Scale scores after the hemilaminectomy were significantly lower in the MD group than in the HL group. There were no significant differences between the durations of surgery and the other evaluated indices. The approach using the MD can provide a less invasive hemilaminectomy than the conventional approach in dogs.

Osteosarcoma of the hyoid bone in a cat.

Case summary: A 10-year-old male neutered Abyssinian cat was presented with the chief complaint of a right pharyngeal mass. On palpation, the mass was easily palpable; it appeared well demarcated and mobile, and oval in shape. Radiographic examination showed a radiopaque pharyngeal mass, which was revealed to be a well-demarcated mass lesion with a radiopaque marginal area on CT examination. The inside of the mass was uniformly well enhanced on contrast CT examination. A three-dimensional image reconstructed from the CT images strongly suggested that the mass originated from the right stylohyoid bone. No abnormal lesions were observed in the thoracic and abdominal CT examinations. Surgical excision of the mass was scheduled 3 weeks after the first admission. The mass was bluntly separated from the surrounding musculature and resected together with the ipsilateral epihyoid bone adjacent to the mass. Histopathological examination of the resected mass showed neoplastic cells with osteoid formation, and the mass was histopathologically diagnosed as an osteosarcoma. The postoperative recovery from anaesthesia was uneventful, and the cat began feeding on its own from the third postoperative day. The 3-month postoperative CT evaluation revealed no local recurrence or distant metastasis. The cat showed no abnormal findings at the time of writing (6 months postoperatively). Relevance and novel information: Although osteosarcoma derived from the hyoid bone has rarely been reported in the veterinary field, this report suggests that such tumours may occur in cats. In addition, partial excision of the hyoid apparatus seems to be well tolerated in cats.

Feelings toward medicine in remote areas among medical students aiming to become generalists : A comparison with other specialists.

Geographic maldistribution of physicians is a serious problem in Japan, resulting in a few physicians in remote areas. We distributed questionnaires to 396 medical students at Tokushima University from 2013 to 2016. We examined the intensity of medical students toward medicine in remote areas by using a visual analog scale and investigated what medical specialty they chose after two years of clinical training. The intensity of interest in medicine and the intensity of willingness to contribute to it in remote areas were statistically higher among medical students who intended to choose general medicine. After graduation, only five participants chose to specialize in general medicine. Of the 14 medical students who originally chose general medicine, six chose internal medicine, three chose general medicine, and the others chose surgery, neurosurgery, anesthesiology, orthopedics, or emergency medicine. This study demonstrated that medical students who intend to choose general medicine have a higher intensity of willingness to contribute to medicine in remote areas, indicating that the support program for these students to become general practitioners after graduation increases the number of physicians in remote areas. J. Med. Invest. 70 : 129-134, February, 2023.

A Monte Carlo study on dose distribution of an orthovoltage radiation therapy system.

It is important to plan radiotherapy treatment and establish optimal dose distribution to reduce the chances of side effects and injury. Because there are no commercially available tools for calculating dose distribution in orthovoltage radiotherapy in companion animals, we developed an algorithm to accomplish this and verified its characteristics using tumor disease cases. First, we used the Monte Carlo method to develop an algorithm to calculate the dose distribution of orthovoltage radiotherapy (280 kVp; MBR-320, Hitachi Medical Corporation, Tokyo, Japan) using BEAMnrc at our clinic. Using development of Monte Carlo method, dose distribution for tumor and normal organs were evaluated in brain tumors, squamous cell carcinomas of the head, and feline nasal lymphomas. In all cases of brain tumors, the mean dose delivered to the GTV ranged from 36.2 to 76.1% of the prescribed dose due to the decrease through the skull. In the nasal lymphoma in cats, the eyes with covered a 2 mm-thick lead plate, the respective average dose to the eyes was 71.8% and 89.9% less than that to the uncovered eyes. The findings may be useful for informed decision making in orthovoltage radiotherapy with more effective and targeted irradiation and data collection allowing detailed informed consent.