Occupational per-patient radiation dose from a conservative protocol for veterinary (18) F-fluorodeoxyglucose positron emission tomography

The occupational external radiation dose to human medical personnel from positron emission tomography (PET) radiopharmaceuticals has been documented, but to date no corresponding veterinary staff dose data are available. Electronic personal dosimeters (EPDs) were used in this study to measure the per-patient external radiation doses to veterinary staff using a PET/CT (PET combined with computed tomography) protocol in which the patient radiopharmaceutical dose was injected after anesthetic induction. Radiation doses were recorded for the nuclear medicine technologists, the on-duty anesthesiology technologist, and an occasional observer from 19 veterinary (18) F-fluorodeoxyglucose PET/CT studies. Patient mass range was 2.8 to 61.0 kg (22.3 kg mean) and injected activity averaged 6 MBq kg(-1) . The dose range received by nuclear medicine technologists per procedure was 0-30 μSv (9.1 μSv mean), by anesthetists 1-22 μSv (8.2 μSv mean), and by the observer 0-2 μSv (0.5 μSv mean). In both feline and canine studies, placement of the EPD on staff was a significant predictor of radiation dose. Additional significant predictors of staff radiation dose from canine studies included job position and injected activity. The per-patient occupational radiation doses to veterinary PET/CT technologists were slightly greater than those reported for human nuclear medicine PET/CT technologists, but were comparable to estimated radiation doses for nurses caring for nonambulatory human PET/CT patients. Efforts toward maintaining staff radiation doses as low as reasonably achievable (ALARA) will be important as veterinary PET/CT caseload increases.     

Patterns of ionizing radiation exposure among women veterinarians

Radiation detection devices (film badges) were distributed to a random sample of 118 women in Ohio, Indiana, and Michigan, who had graduated from a US veterinary school between 1970 and 1980, inclusive. Ionizing radiation exposure exceeded 15 mrem/mo in 17% of the women monitored. The maximal recorded whole-body dose was 44.2 mrem/quarter-year, which was well below the maximal permissible doses of 1,250 mrem/quarter-year for nonpregnant women and 500 mrem/quarter-year for pregnant women. Associations between the women's safety beliefs or behaviors and recorded exposure were not observed; however, the school from which the women graduated was an important determinant of safety behavior.     

Preliminary study of plasma vascular endothelial growth factor (VEGF) during low- and high-dose radiation therapy of dogs with spontaneous tumors

High plasma vascular endothelial growth factor (VEGF) concentrations are associated with radiation resistance and poor prognosis. After an exposure to ionizing radiation in cell culture an early phase and a late phase of increased VEGF have been documented. The activation was dependent on the radiation dose. Therefore, the purpose of this study was to measure baseline plasma VEGF and changes in VEGF over the course of fractionated radiation therapy in dogs with spontaneous tumors. Dogs with tumors had a significantly higher pretreatment plasma VEGF than did dogs without tumors. Immediately after irradiation no increased plasma VEGF was observed. Over the course of radiation therapy there was an increased plasma VEGF in dogs treated with low doses per fraction/high total dose, whereas plasma VEGF remained stable in dogs irradiated with high doses per fraction/low total dose. The regulatory mechanisms are very complex, and therefore the value of plasma VEGF measurements as an indirect marker of angiogenesis induced by radiotherapy is limited.     

Estimation of the occupational radiation exposure during radiographic studies of horses]

Radiography of horses in veterinary practice is done normally with quite simple equipment. Thereby radiation protection is easily neglected. In this investigation sources of mistakes are demonstrated. The possible exposure of staff is evaluated by dose measuring over a long period of time. It can be stated that following the most simple radiation protection there will never be a significant exposure of staff.     

The toxicity of ochratoxin to ruminants.

Among the mold toxins the most toxic ochratoxin, ochratoxin A, commonly occurs in many grains, other feedstuffs, and in soil but in low concentrations. The amount required to produce acute toxicity in ruminants makes such occurrences unlikely. Toxic effects are more likely to occur in chronic low-level intoxication. The lethal single oral dose in cattle is high, probably being a few milligrams more than 13 mg/kg. The lethal level produced by repeated feeding to goats was 3 mg/kg. Ochratoxin A occurred in cows milk and urine but only when massive doses were ingested. Abortion or fetal death, though occurring in rodents, are unlikely to be induced in cattle.     

Radiation therapy for the treatment of tumours in small companion animals

Radiation is becoming widely available to treat tumours in veterinary patients. Orthovoltage machines capable of delivering low energy external beam radiation are less versatile than linear accelerators and cobalt-60 machines that deliver megavoltage radiation. In addition, electron beam capabilities that are available with some linear accelerators allow more targeted treatment in smaller patients. Acute effects of radiation are to be expected, but in nearly all cases such side effects resolve without limiting protocols. In contrast, late effects of radiation are dose limiting and are more likely with higher doses per treatment fraction. Protocols that use smaller doses per fraction have a lower risk of late effects thereby allowing higher total doses to be delivered which leads to higher tumour control rates. It is possible to provide long-term tumour control in cats and dogs using radiation therapy, particularly for mast cell tumours, soft tissue sarcomas, oral tumours and brain tumours in dogs and soft tissue sarcomas and skin tumours in cats. Individualization of treatments for tumours based on tumour staging and proliferative fraction should be considered, rather than making blanket assumptions about the behaviour of histologically determined tumour types.     

Use of dopamine in acute renal failure

Objective: To review the current understanding of dopamine and its use in the prevention and treatment of acute renal failure (ARF). Data sources: Original research articles and scientific reviews. Human data synthesis: Low‐dose dopamine administration has been shown to increase natriuresis and urinary output in both healthy individuals and in a few small studies in human patients with renal insufficiency. However, in several large meta‐analyses, dopamine treatment did not change mortality or the need for dialysis. Due to the potential side effects, the use of dopamine for prevention and treatment of ARF is no longer recommended in human medicine. Veterinary data synthesis: Low‐dose dopamine increases urinary output in healthy animals and animal models of ARF if given before the insult. There are no available studies looking at the effect of low‐dose dopamine therapy in naturally occurring ARF in dogs or cats. Conclusion: Due to the potential side effects of low‐dose dopamine therapy, the results from large human trials, and the lack of information in veterinary medicine, the use of dopamine for treatment of ARF in veterinary patients should be further evaluated.     

Clinical outcome in dogs with nasal tumors treated with intensity-modulated radiation therapy

Intensity-modulated radiation therapy (IMRT) is a valuable tool in human radiation oncology, but information on its use in veterinary medicine is lacking. In this study, 12 dogs with nasal tumors were treated with IMRT at a median radiation dose of 54 Gy. Patient survival times and frequency and severity of side effects on ocular structures, oral mucosa, and skin were recorded. Eight dogs (67%) had resolution of clinical signs during radiation therapy. Median overall survival time was 446 d with a 50% 1-year and a 25% 2-year survival rate. Minimal grade 2 or 3 acute skin toxicity, no grade 2 or 3 late skin toxicity, and no grade 2 or 3 toxicity to oral mucosa or the eye opposite the tumor were identified in the dogs treated with IMRT in this study. The ipsilateral eye could not be routinely spared due to its proximity to the tumor.     

Prevalence of occupational exposures and protective practices in Australian female veterinarians

OBJECTIVE: To identify the prevalence of exposure to potentially harmful occupational hazards in Australian female veterinarians and to report factors associated with prevalence of occupational hazards in this profession. DESIGN: National cross-sectional survey of a cohort population. PROCEDURE: A self-administered questionnaire was mailed to 5748 veterinarians (males and females) graduating from Australian veterinary schools from 1960 to 2000. This paper reports the prevalence of occupational exposures in 1197 female veterinarians in their current job including radiation, anaesthetic gases, pesticides and long working hours. Comparisons were undertaken between respondents by practice type and decades of graduation. Multivariate logistic regression was undertaken to predict the risk for exposure to occupational hazards in female veterinarians by age, type of practice, graduation year and number of hours worked. RESULTS: The response rate for females was 59%. We found that age under 30 years, small and mixed animal practice, graduation year after 1990, and working more than 45 hours per week were all associated with greater exposure to putative risk factors. Mixed animal practitioners worked more than 45 hours per week (53%) and reported the highest exposure to anaesthetic gases (94%) and pesticides (54%). Twenty two percent of those who were exposed to anaesthetic gases did not have waste anaesthetic gas scavenging systems. Small animal practitioners reported they took more X-rays (90%). While taking X-rays, 56% of respondents reported physically restraining animals, and only one in five of respondents used film holders and lead screens. CONCLUSIONS: The high prevalence of potentially harmful exposures among female veterinarians and lack of use of protective equipment at work needs to be considered in developing and planning the safety of veterinary work.     

Cone beam computed tomography and intraoral radiography for diagnosis of dental abnormalities in dogs and cats

The development of veterinary dentistry has substantially improved the ability to diagnose canine and feline dental abnormalities. Consequently, examinations previously performed only on humans are now available for small animals, thus improving the diagnostic quality. This has increased the need for technical qualification of veterinary professionals and increased technological investments. This study evaluated the use of cone beam computed tomography and intraoral radiography as complementary exams for diagnosing dental abnormalities in dogs and cats. Cone beam computed tomography was provided faster image acquisition with high image quality, was associated with low ionizing radiation levels, enabled image editing, and reduced the exam duration. Our results showed that radiography was an effective method for dental radiographic examination with low cost and fast execution times, and can be performed during surgical procedures.     

Triggers for prophylactic use of platelet transfusions and optimal platelet dosing in thrombocytopenic dogs and cats.

Prophylactic platelet transfusions are frequently given to human patients with hypoproliferative thrombocytopenia. For several decades, the most common transfusion trigger was 20,000/microL, but the trend is now to use 10,000/microL in the absence of other risk factors for bleeding. This trigger seems to reduce the number of transfusions without increasing the risk of severe bleeding. Most studies involved in establishing platelet transfusion policies have involved patients with acute leukemia, with fewer studies involving patients undergoing hematopoietic stem cell transplantation or aggressive chemotherapy for other cancers and patients with aplastic anemia. In the presence of other risk factors for spontaneous bleeding, 20,000/microL is still considered an appropriate trigger. The trigger for prophylactic transfusion before surgery has not undergone the same recent scrutiny as has the trigger for spontaneous bleeding. The recommendation remains to raise the platelet count to 50,000 to 100,000/microL if possible, although it is recognized that surgery and other invasive procedures have been performed at lower platelet counts without major bleeding. Prophylactic transfusion is not used in disorders of platelet consumption and destruction to prevent spontaneous bleeding but is used before surgery. Because of the comparative lack of experience with platelet transfusion in veterinary medicine, it is difficult to make generalizations for dogs and cats. Using the guidelines established for therapeutic and prophylactic transfusion of human patients is a reasonable starting point, however. A therapeutic transfusion policy is suggested in the veterinary setting provided that the patient can be closely observed for critical bleeding and a prompt transfusion can be given. This policy should ultimately reduce the overall number of platelet transfusions given to hospital patients. If an animal cannot be closely observed or the ability to transfuse on demand is limited, prophylactic transfusion is recommended. The triggers for initiating a platelet transfusion in dogs are extrapolated from human data; these values are lower by 50% for cats. Because of the imprecision of platelet counting at low values, platelet counts must always be interpreted in conjunction with clinical signs of hemorrhage. If platelet-rich plasma or platelet concentrate is available, a dose of 1 platelet unit per 10 kg is recommended, although resources may dictate a smaller dose. This will raise the recipient platelet count by a maximum of about 40,000/microL. Assuming a trigger of 10,000/microL, a transfusion will probably be required approximately every 3 days. It must be remembered that the frequency of platelet transfusions may be greater in the presence of factors accelerating platelet loss or destruction. If fresh whole blood is used, a rule of thumb is to transfuse 10 mL/kg, which will raise the recipient platelet count by a maximum of approximately 10,000/microL. Daily transfusions or transfusions every other day will probably be required.     

Higher sensitivity of LEC strain rat in radiation-induced acute intestinal death.

LEC strain rats (LEC rats), which have been known to develop hereditarily spontaneous fulminant hepatitis 4-5 months after birth, were highly sensitive to whole-body X-irradiation as compared to WKAH strain rats (WKAH rats). Radiation-induced acute intestinal death occurred at doses higher than 6.5 Gy in LEC rats, and at doses higher than 12.8 Gy in WKAH rats, respectively. By the probit analysis of survival data, it was shown that the LD50/7 value of LEC rats was estimated to be 7.03 Gy which was significantly lower than that (12.99 Gy) of WKAH rats. Histopathological examinations of small intestines from LEC rats 2 days after irradiation at the dose of 8.5 Gy showed severe epithelial death together with edema, whereas little or no significant changes were noted in intestinal epithelium of 8.5 Gy-irradiated WKAH rats. These results suggest that the radiosensitivity of LEC rats to ionizing radiation appears to be higher than that of other strains of rats.     

TECHNIQUES OF AFTERLOADING IRIDIUM-192 INTERSTITIAL BRACHYTHERAPY IN VETERINARY MEDICINE

Continuous low-dose-rate irradiation of animal tumors has become feasible through the implantation of iridium-192 by an afterloading technique. ¹⁹²Ir is an ideal radioisotope for interstitial brachytherapy in veterinary medicine because of its 74.2-day half-life, medium-energy gamma radiation (0.35 MeV), moderate shielding requirements, low cost, and adaptability to most tumor configurations. The afterloading technique can easily be applied to veterinary patients. The effectiveness of interstitial brachytherapy may be enhanced by combination with surgery and/or hyperthermia. Computer-assisted dose calculations make afterloaded ¹⁹²Ir implantation an accurate, precise method of interstitial brachytherapy.     

Stratospheric ozone depletion and animal health.

There is an increasing concern over ozone depletion and its effects on the environment and human health. However, the increase in ultraviolet-B radiation (UV-B) that would result from significant losses of ozone is also potentially harmful to animals. Any increase in disease in domestic species would not only have serious animal welfare implications but may also be economically important. The diseases which are likely to increase if ozone depletion continues include the squamous cell carcinomas of the exposed, non-pigmented areas of cats, cattle, sheep and horses. Uberreiter's syndrome in dogs is also associated with exposure to UV-B and may be expected to increase, as may the severity of conditions such as infectious keratoconjunctivitis (New Forest eye) in cattle. Aquaculture systems in which fish often have little or no protection by shading may also be at risk. Cataracts and skin lesions have been associated with the exposure of farmed fish to ultraviolet radiation and have resulted in significant losses.     

Ultraviolet Radiation Dose to be Applied in Recipient Zebrafish Embryos for Germ‐line Chimaerism is Strain Dependent

Germ‐line chimaerism is a powerful technique that has proved to be useful to produce viable gametes when transplanted blastomeres colonize the germinal ridges in recipient embryos and obtaining offspring from such transplanted cells. In fish, ionizing radiations were commonly used for embryo penalization to cancelling the cell participation of recipient embryos in development and in gamete production. The ultraviolet (UV) radiation when compared with other radiation types is cheaper, easier and no special installations are required for its use. So, the aim of this work was to establish the optimal UV radiation dose to be applied in zebrafish embryos at mid‐blastula transition stage of development, in order to use them as penalized recipient embryos in futures chimaerism assays. A UV germicide lamp was used as radiation source (0.529 mW/cm²). Four exposure levels and three exposure times of UV radiation were tested. The survival rates obtained with the non‐dechorionated embryos without lid group suggested that it could be the optimal exposure level to achieve the objective proposed. With the obtained results, we concluded that this UV radiation dose for 60 and 30 s are optimal parameters to penalize recipient wild and gold strain zebrafish embryos, respectively in chimaerism assays, but without involving their survival and apparently normal development.     

Investigating the in vitro interactive effects of ionizing radiation and pamidronate in a canine osteosarcoma cell line

Introduction: Dogs with osteosarcoma suffer intense bone pain. Conventional palliative treatment options include ionizing radiation with or without systemic chemotherapy. Intravenous pamidronate is a first‐line therapeutic agent in people with painful skeletal metastases and is currently being evaluated for the management of osteolytic pain associated with canine osteosarcoma. The theoretical combination of radiation and pamidronate for managing bone pain appears to be a rational treatment option, however, in vitro experiments demonstrating additive or supraadditve cytotoxic effects of these two modalities would further support the clinical institution of this novel combination therapy. The purpose of this study was to evaluate the in vitro cytotoxicity of ionizing radiation and pamidronate in a canine OSA cell line and to characterize the interaction between these two therapeutic modalities when used in combination. Methods: The canine osteosarcoma cell line, HMPOS, was subjected independently to varying doses of ionizing radiation (100 cGy, 300 cGy, 400 cGy, 600 cGy, 800 cGy, or 1000 cGy) or different concentrations of pamidronate (10, 25, 50, 66, 75, 100, 150, 200, and 250 μM). Cells were harvested following 48 hours of incubation and cell viability was assessed by flow cytometric analysis. Dose‐response curves were generated, and a theoretical ED₅₀ for each treatment modality calculated. An ED₅₀ isobologram was created to determine if different combinations of ionizing radiation and pamidronate (isoboles) would demonstrate subadditive, additive, or supraadditve cytotoxic effects. Results: The ED₅₀ of ionizing radiation and pamidronate were 614 cGy and 65.3 μM, respectively. Of the six different isobole combinations evaluated, three produced supraadditve effects, one produced a subadditive effect, and two produced additive effects. Conclusions: Both ionizing radiation and pamidronate independently exert in vitro cytotoxic effects. Positive interactive effects can be generated, but only with specific isobole combinations. The results from this in vitro study support the use of specific combinations of ionizing radiation and pamidronate in order to maximize the cytotoxic properties of both treatment modalities.     

ESTIMATED OPERATOR EXPOSURE FOR HAND HOLDING PORTABLE X‐RAY UNITS DURING IMAGING OF THE EQUINE DISTAL EXTREMITY

Hand holding of portable X‐ray units is common in large animal ambulatory veterinary practice. Portable X‐ray equipment manuals, veterinary teaching institutions, and state regulations discourage, or prohibit, hand holding of portable X‐ray units. Our goal was to quantify surface radiation leakage of a typical portable X‐ray unit and to measure operator exposure at simulated hand and collar positions during imaging of the equine distal extremity. Each exposure for the study was performed at 80 kVp and 7.5 mAs and repeated 10 times. Measurement of tube radiation leakage was performed along each surface of the portable X‐ray unit. To determine the operator exposure more accurately, an equine cadaver limb was used to generate scatter radiation for the following views: lateral carpus, lateral foot, palmaroproximal–palmarodistal, and dorsal 60° proximal–palmarodistal obliques of the navicular region. A Pancake Ion Chamber was placed at the handle and at simulated collar position to record estimated occupational exposure. To estimate the effect of lead shielding, exposure measurements were performed within the primary beam and behind a 0.5 mm lead equivalent apron and within an >0.5 mm lead equivalent glove. The average hand and collar dose was 0.471 and 0.327 mR/exposure, respectively. The lead apron and glove attenuated the primary beam 96.9 and 99.2%, respectively. This reduced average hand and collar exposures to 0.0038 and 0.0101 mR/exposure, respectively. Theoretical occupational limits are reached for the collar (whole body) before the hand (extremity).     

Epidemiology of mammary gland disorders in multiparous Finnish Ayrshire cows

Logistic regression was used to investigate the effects of host characteristics, milk production and 23 veterinary diagnoses on the odds of contracting acute and chronic mastitis, and teat injury among 41 989 multiparous Finnish Ayrshire cows that calved during 1983.

Cows which had higher previous-lactation milk yields were at increased risk of acute and chronic mastitis, and teat injury. All of the mammary gland disorders were directly interrelated. Abomasal disorder, indoor hypomagnesemia, prolapsed uterus and vagina, and abortion were not risk factors for any of the three mammary gland disorders; however, retained placenta, udder edema, ketosis, non-parturient paresis, rumen acidosis, traumatic reticuloperitonitis, silent heat, ovarian cyst and other types of infertility were all direct risk factors for at least two mammary gland disorders.