A SURVEY OF VETERINARY RADIATION FACILITIES IN 2010

Radiotherapy in Equine Practice

Radiotherapy is a valuable treatment option for equine tumors that have a high rate of recurrence or where complete surgical resection may damage vital structures. Teletherapy, brachytherapy, and plesiotherapy have been used successfully for the treatment of a variety of tumors and locations in the horse. Radiobiology, treatment protocols, side effects, and patient management are reviewed, with a focus on linear accelerator-based teletherapy. There is evidence of good success rates for treatment of periocular sarcoids and squamous cell carcinoma but teletherapy treatment is often limited to tumors on the head and distal extremities.

Comparison of a new immobilization method using a reusable 3-point fixation cylinder system and bite-block type immobilization methods in veterinary radiotherapy

In veterinary radiotherapy, highly reproducible immobilization is important for accurate irradiation. Consequently, we developed a new reusable head-immobilization method for dogs using cylinders. This study aimed to compare the accuracy of our novel immobilization method using cylinders with that of bite-block type immobilization methods. Three immobilization methods were compared: bite-block only, bite-block combined with torso immobilization, and immobilization using cylinders. Five beagles with canine teeth underwent CT five times for each of the three immobilization methods. One beagle without canine teeth underwent CT 15 times using each method. Three maxillary landmarks (maxillary incisor, frontal sinus, and occipital bone) and one mandibular landmark (mandibular incisor) were established, and the errors in each immobilization method were measured. For all head landmarks, the error in the immobilization method using cylinders was the most reproducible, with the smallest errors. No significant differences were observed in the time required for immobilization. Although there were limitations (such as the use of dogs from a single breed, a single episode of anesthesia, no disassembly of the immobilization system between scans, and the same person performing the positioning on the same day), we found our new reusable immobilization method using cylinders was the most accurate among the three compared methods. This was a proof-of-principle study to evaluate head immobilization using cylinders, and further investigations are needed to confirm its clinical utility.

Automatic grading of intervertebral disc degeneration in lumbar dog spines

Background

Intervertebral disc degeneration is frequent in dogs and can be associated with symptoms and functional impairments. The degree of disc degeneration can be assessed on T2-weighted MRI scans using the Pfirrmann classification scheme, which was developed for the human spine. However, it could also be used to quantify the effectiveness of disc regeneration therapies. We developed and tested a deep learning tool able to automatically score the degree of disc degeneration in dog spines, starting from an existing model designed to process images of human patients.

Methods

MRI midsagittal scans of 5991 lumbar discs of dog patients were collected and manually evaluated with the Pfirrmann scheme and a modified scheme with transitional grades. A deep learning model was trained to classify the disc images based on the two schemes and tested by comparing its performance with the model processing human images.

Results

The determination of the Pfirrmann grade showed sensitivities higher than 83% for all degeneration grades, except for grade 5, which is rare in dog spines, and high specificities. In comparison, the correspondent human model had slightly higher sensitivities, on average 90% versus 85% for the canine model. The modified scheme with the fractional grades did not show significant advantages with respect to the original Pfirrmann grades.

Conclusions

The novel tool was able to accurately and reliably score the severity of disc degeneration in dogs, although with a performance inferior than that of the human model. The tool has potential in the clinical management of disc degeneration in canine patients as well as in longitudinal studies evaluating regenerative therapies in dogs used as animal models of human disorders.

AAPM WGVRTO report 390: A survey of veterinary radiation oncology equipment and infrastructure in 2022

Since 2010, there has been little published data on the state of equipment and infrastructure in veterinary radiation oncology clinical practice. These data are important not only to identify the status and use of technology within the veterinary radiation oncology community but also to help identify the extent of medical physics support. The purpose of our study is to report findings from a survey of veterinary radiation oncologists in the USA, Canada, and select centers outside of North America in 2022. A 40-question survey covering topics such as type of radiotherapy equipment, techniques offered, treatment planning systems and dose calculation algorithms, special techniques, board-certified radiation oncologists and residents, and extent of medical physics support was distributed through an online survey tool. Results from 40 veterinary radiation oncology institutions, with equipment explicitly used for veterinary care, suggest that the current state of practice is not dissimilar to what currently exists in human radiation oncology facilities; techniques and technologies commonly employed include flattening filter-free mode megavoltage beams, volumetric arc therapy, daily cone-beam computed tomography, image-guided radiation therapy, and sophisticated dose calculation algorithms. These findings suggest the need for modern radiation oncology acceptance testing, commissioning, and quality assurance programs within the veterinary community. The increase in veterinary radiation oncology residency positions and increasing sophistication of equipment suggests that increased levels of standardized medical physics support would benefit the veterinary radiation oncology community.

Stereotactic radiotherapy outcomes for intraventricular brain tumours in 11 dogs

Published radiotherapy data for canine intraventricular tumours are limited. In this retrospective, longitudinal study (9/2011-2018), 11 dogs with intraventricular masses were treated with stereotactic radiotherapy (SRT). Pathologic diagnosis was available from surgery or necropsy in 6/11 cases, revealing choroid plexus papilloma (3) or carcinoma (2), and ependymoma (1). The remainder were magnetic resonance imaging (MRI)-diagnosed as suspected choroid tumours or ependymomas. Tumours were located in the third or lateral ventricle (8), fourth ventricle (2), and cerebellopontine angle (1). Surgery was performed in three dogs prior to radiotherapy, and all showed gross residual/recurrent disease at treatment. Dogs received 8 Gray × 3 fractions (7), or 15 Gray × 1 fraction (4). Ten dogs were deceased at analysis, and one was living. The estimated median overall survival time (OS) from first SRT treatment was 16.9 months (515 days, 95% CI 33-1593 days). The survival time for two pathology-diagnosed carcinoma dogs were 24 and 133 days, respectively, and survival time for dogs with moderate to marked ventriculomegaly (4/11) ranged from 24 to 113 days. A total of 10/11 showed clinical improvement per owner or clinician, but two had short-lived benefits and were euthanized within 6 weeks of SRT. Limited conclusions on radiation-specific complications are possible due to the small dataset and limited follow-up imaging. This study provides preliminary evidence that radiotherapy outcomes are variable with intraventricular tumours, and some long-term survivors are noted.

Automatic gross tumor segmentation of canine head and neck cancer using deep learning and cross-species transfer learning

Background

Radiotherapy (RT) is increasingly being used on dogs with spontaneous head and neck cancer (HNC), which account for a large percentage of veterinary patients treated with RT. Accurate definition of the gross tumor volume (GTV) is a vital part of RT planning, ensuring adequate dose coverage of the tumor while limiting the radiation dose to surrounding tissues. Currently the GTV is contoured manually in medical images, which is a time-consuming and challenging task.

Purpose

The purpose of this study was to evaluate the applicability of deep learning-based automatic segmentation of the GTV in canine patients with HNC.

Materials and methods

Contrast-enhanced computed tomography (CT) images and corresponding manual GTV contours of 36 canine HNC patients and 197 human HNC patients were included. A 3D U-Net convolutional neural network (CNN) was trained to automatically segment the GTV in canine patients using two main approaches: (i) training models from scratch based solely on canine CT images, and (ii) using cross-species transfer learning where models were pretrained on CT images of human patients and then fine-tuned on CT images of canine patients. For the canine patients, automatic segmentations were assessed using the Dice similarity coefficient (Dice), the positive predictive value, the true positive rate, and surface distance metrics, calculated from a four-fold cross-validation strategy where each fold was used as a validation set and test set once in independent model runs.

Results

CNN models trained from scratch on canine data or by using transfer learning obtained mean test set Dice scores of 0.55 and 0.52, respectively, indicating acceptable auto-segmentations, similar to the mean Dice performances reported for CT-based automatic segmentation in human HNC studies. Automatic segmentation of nasal cavity tumors appeared particularly promising, resulting in mean test set Dice scores of 0.69 for both approaches.

Conclusion

In conclusion, deep learning-based automatic segmentation of the GTV using CNN models based on canine data only or a cross-species transfer learning approach shows promise for future application in RT of canine HNC patients.

ICRP PUBLICATION 153 Approved by the Commission in September 2022

Veterinary use of radiation in the diagnosis, management, and treatment of disease has expanded and diversified, as have the corresponding radiological protection concerns. Radiological exposure of personnel involved in veterinary procedures and, where applicable, members of the public providing assistance (e.g. owners or handlers) has always been included within the system of radiological protection. Veterinary practice is now addressed explicitly as the modern complexities associated with this practice warrant dedicated consideration, and there is a need to clarify and strengthen the application of radiological protection principles in this area. The Commission recommends that the system of radiological protection should be applied in veterinary practice principally for the protection of humans, but with explicit attention to the protection of exposed animals. Additionally, consideration should be given to the risk of potential contamination of the environment associated with applications of nuclear medicine in veterinary practice. This publication focuses primarily on justification and optimisation in veterinary practice, and sets the scene for more detailed guidance to follow in future Recommendations. It is intended for a wide-ranging audience, including radiological protection professionals, veterinary staff, students, education and training providers, and members of the public, as an introduction to radiological protection in veterinary practice.© 2022 ICRP. Published by SAGE.

Deep-Learning-Based Automatic Segmentation of Head and Neck Organs for Radiation Therapy in Dogs

Purpose: This study was conducted to develop a deep learning-based automatic segmentation (DLBAS) model of head and neck organs for radiotherapy (RT) in dogs, and to evaluate the feasibility for delineating the RT planning.

Materials and Methods: The segmentation indicated that there were potentially 15 organs at risk (OARs) in the head and neck of dogs. Post-contrast computed tomography (CT) was performed in 90 dogs. The training and validation sets comprised 80 CT data sets, including 20 test sets. The accuracy of the segmentation was assessed using both the Dice similarity coefficient (DSC) and the Hausdorff distance (HD), and by referencing the expert contours as the ground truth. An additional 10 clinical test sets with relatively large displacement or deformation of organs were selected for verification in cancer patients. To evaluate the applicability in cancer patients, and the impact of expert intervention, three methods–HA, DLBAS, and the readjustment of the predicted data obtained via the DLBAS of the clinical test sets (HA_DLBAS)–were compared.

Results: The DLBAS model (in the 20 test sets) showed reliable DSC and HD values; it also had a short contouring time of ~3 s. The average (mean ± standard deviation) DSC (0.83 ± 0.04) and HD (2.71 ± 1.01 mm) values were similar to those of previous human studies. The DLBAS was highly accurate and had no large displacement of head and neck organs. However, the DLBAS in the 10 clinical test sets showed lower DSC (0.78 ± 0.11) and higher HD (4.30 ± 3.69 mm) values than those of the test sets. The HA_DLBAS was comparable to both the HA (DSC: 0.85 ± 0.06 and HD: 2.74 ± 1.18 mm) and DLBAS presented better comparison metrics and decreased statistical deviations (DSC: 0.94 ± 0.03 and HD: 2.30 ± 0.41 mm). In addition, the contouring time of HA_DLBAS (30 min) was less than that of HA (80 min).

Conclusion: In conclusion, HA_DLBAS method and the proposed DLBAS was highly consistent and robust in its performance. Thus, DLBAS has great potential as a single or supportive tool to the key process in RT planning.

Volumetric tumor response assessment is inefficient without overt clinical benefit compared to conventional, manual veterinary response assessment in canine nasal tumors

Accurate assessment of tumor response to therapy is critical in guiding management of veterinary oncology patients and is most commonly performed using response evaluation criteria in solid tumors criteria. This process can be time consuming and have high intra- and interobserver variability. The primary aim of this serial measurements, secondary analysis study was to compare manual linear tumor response assessment to semi-automated, contoured response assessment in canine nasal tumors. The secondary objective was to determine if tumor measurements or clinical characteristics, such as stage, would correlate to progression-free interval. Three investigators evaluated paired CT scans of skulls of 22 dogs with nasal tumors obtained prior to and following radiation therapy. The automatically generated tumor volumes were not useful for canine nasal tumors in this study, characterized by poor intraobserver agreement between automatically generated contours and hand-adjusted contours. The radiologist's manual linear method of determining response evaluation criteria in solid tumors categorization and tumor volume is significantly faster (P < .0001) but significantly underestimates nasal tumor volume (P < .05) when compared to a contour-based method. Interobserver agreement was greater for volume determination using the contour-based method when compared to response evaluation criteria in solid tumors categorization utilizing the same method. However, response evaluation criteria in solid tumors categorization and percentage volume change were strongly correlated, providing validity to response evaluation criteria in solid tumors as a rapid method of tumor response assessment for canine nasal tumors. No clinical characteristics or tumor measurements were significantly associated with progression-free interval.

Emerging Translational Opportunities in Comparative Oncology With Companion Canine Cancers: Radiation Oncology

It is estimated that more than 6 million pet dogs are diagnosed with cancer annually in the USA. Both primary care and specialist veterinarians are frequently called upon to provide clinical care that improves the quality and/or quantity of life for affected animals. Because these cancers develop spontaneously in animals that often share the same environment as their owners, have intact immune systems and are of similar size to humans, and because the diagnostic tests and treatments for these cancers are similar to those used for management of human cancers, canine cancer provides an opportunity for research that simultaneously helps improve both canine and human health care. This is especially true in the field of radiation oncology, for which there is a rich and continually evolving history of learning from the careful study of pet dogs undergoing various forms of radiotherapy. The purpose of this review article is to inform readers of the potential utility and limitations of using dogs in that manner; the peer-reviewed literature will be critically reviewed, and current research efforts will be discussed. The article concludes with a look toward promising future directions and applications of this pet dog “model.”

A retrospective analysis of radiation oncology related scientific articles in the journal Veterinary Radiology and Ultrasound: Trends over 40 years (1976-2015)

The journal Veterinary Radiology & Ultrasound is a veterinary specialty journal devoted to the fields of veterinary diagnostic imaging and radiation oncology. The purpose of this retrospective, observational study is to evaluate progressive trends in radiation oncology articles published in Veterinary Radiology & Ultrasound during the 40-year period (1976-2015) and describe a shift of trends through several viewpoints. This 40-year period was divided into four subperiods: Period 1 (1976-1985), Period 2 (1986-1995), Period 3 (1996-2005), and Period 4 (2006-2015). These articles were divided into six categories based on the nature of the study: 1) studies related to teletherapy with endpoints being patient outcome, 2) radiation therapy dosimetry/planning, 3) patient setup, 4) reviews, 5) case reports, and 6) others. The number of radiation oncology articles in Veterinary Radiology & Ultrasound has increased over the 40-year period. The number of authors per article has increased between Periods 1 and 3. The number of articles related to linear accelerator has increased between Periods 3 and 4. The median number of treated patients per clinical article related to teletherapy ranged from 15 to 21, which has not changed significantly over the 40-year period. The most commonly used radiation therapy protocols during Periods 2 and 3 were fine-fractionated protocols (defined as 10 or more fractions), whereas coarse-fractionated protocols were more common during Periods 1 and 4. Findings from this study highlight the notable changes of trends in veterinary radiation oncology articles published in Veterinary Radiology & Ultrasound, which clearly reflect changes in the field of veterinary radiation oncology during the past 40 years.

Owner perceptions of radiotherapy treatment for veterinary patients with cancer

Veterinary clients may have trepidation about treating their pet with radiotherapy because of concerns about radiation side effects or repeated anaesthetics. The purpose of this study is to assess whether owners' attitudes towards veterinary radiotherapy, including concerns over side effects, change during the course of treatment, and whether radiotherapy was perceived to affect pets' quality of life (QOL). A prospective cohort study of clients from 2012 to 2015 was performed. Pets received palliative or definitive radiotherapy for various tumours. Clients completed questionnaires before, during and after radiotherapy. Questions assessed owner preconceptions before treatment, including side effect expectations, actual side effects experienced and overall satisfaction with the process. In addition, at each time point, the owners assessed their pet's QOL using a simple numerical scale. Forty-nine patients were included. After completing treatment, owners were significantly less concerned about potential side effects of radiotherapy (P < 0.001), side effects associated with repeat anaesthetics (P < 0.001), and about radiotherapy in general (P < 0.001). QOL did not show a significant change at any point during or after treatment. Following treatment, 94% reported that the experience was better than expected and 100% supported the use of radiotherapy in pets. This is the first prospective study evaluating client attitudes and satisfaction before and after radiotherapy treatment in pets. The results indicate that radiotherapy is well tolerated, and the anxiety associated with radiotherapy is significantly alleviated after experiencing the process. These results will help veterinarians allay client concerns, and will hopefully lead to an increase in clients pursuing radiotherapy in pets.

Long-term survival with stereotactic radiotherapy for imaging-diagnosed pituitary tumors in dogs

Published studies on the use of stereotactic radiotherapy for dogs with pituitary tumors are limited. This retrospective observational study describes results of stereotactic radiotherapy for 45 dogs with imaging-diagnosed pituitary tumors. All dogs were treated at a single hospital during the period of December 2009-2015. The stereotactic radiotherapy was delivered in one 15 Gray (Gy) fraction or in three 8 Gy fractions. At the time of analysis, 41 dogs were deceased. Four were alive and censored from all survival analyses; one dog received 8 Gy every other day and was removed from protocol analyses. The median overall survival from first treatment was 311 days (95% confidence interval 226-410 days [range 1-2134 days]). Thirty-two dogs received 15 Gy (median overall survival 311 days; 95% confidence interval [range 221-427 days]), and 12 received 24 Gy on three consecutive days (median overall survival 245 days, 95% confidence interval [range 2-626 days]). Twenty-nine dogs had hyperadrenocorticism (median overall survival 245 days), while 16 had nonfunctional masses (median overall survival 626 days). Clinical improvement was reported in 37/45 cases. Presumptive signs of acute adverse effects within 4 months of stereotactic radiotherapy were noted in 10/45, and most had improvement spontaneously or with steroids. Late effects versus tumor progression were not discernable, but posttreatment blindness (2), hypernatremia (2), and progressive neurological signs (31) were reported. There was no statistical difference in median overall survival for different protocols. Patients with nonfunctional masses had longer median overall survival than those with hyperadrenocorticism (P = 0.0003). Survival outcomes with stereotactic radiotherapy were shorter than those previously reported with definitive radiation, especially for dogs with hyperadrenocorticism.

A survey of stereotactic radiation therapy in veterinary medicine

Radiotherapy plays an important role in curative and palliative cancer treatment. As a novel radiation delivery technique, stereotactic radiotherapy utilizes three-dimensional-conformal treatment planning, high-precision beam delivery technology, and patient specific position verification to target tumors, often in one to five high-dose fractions. Currently, there is no consensus about best stereotactic radiotherapy practices in veterinary radiotherapy. The objective of this study was to document the breadth of perspectives, techniques, and applications of stereotactic radiotherapy in veterinary medicine. We conducted an online survey of American College of Veterinary Radiology members specializing in radiation oncology to assess how, when, and why stereotactic radiotherapy is being used. Both stereotactic radiotherapy users and nonusers completed the survey. The overall response and survey completion rates were 54% (67/123) and 87% (58/67), respectively. Overall, 55% of respondents reported providing stereotactic radiotherapy at their facility, with a median of 4.5 canine cases and one feline case per month. Delivery methods included C-arm linear accelerator with multi-leaf collimator, helical tomotherapy, and CyberKnife. Nonpituitary intracranial tumors, pituitary tumors, and sinonasal tumors were the most common cancers treated using stereotactic radiotherapy in both species. The most common fractionation scheme was three fractions of 10 Gy/fraction. The results of this survey suggest common availability of stereotactic radiotherapy in veterinary radiation facilities. These results provide valuable information regarding current stereotactic radiotherapy practices in veterinary medicine, and may provide an initial step toward standardizing methods and establishing consensus guidelines.

Management of Radiation Side Effects to the Skin

Radiation therapy (RT) is an essential component for management of many cancers. Veterinary health care professionals must counsel owners about the potential side effects of RT, the anticipated management plan, and associated costs. For most veterinary patients treated with RT, acute radiation side effects are mild; however, careful radiation treatment planning and appropriate management of acute side effects are essential to try to prevent chronic sequelae and the need for ongoing wound care. This article reviews acute and late side effects to the skin and their management.

Principles and Applications of Radiation Therapy in Exotic Animals

Radiation therapy is a treatment modality for cancer that is widely used in veterinary medicine, although its use in exotic animal practice has remained limited. However, there are case reports and case series of treating birds, small mammals, and reptiles for a variety of cancers with radiotherapy with varied outcomes. In this article the basic principles of radiation therapy are reviewed and the literature regarding its use in exotic animal practice is summarized. Side effects of radiotherapy are also discussed.

2016 AAHA Oncology Guidelines for Dogs and Cats*

All companion animal practices will be presented with oncology cases on a regular basis, making diagnosis and treatment of cancer an essential part of comprehensive primary care. Because each oncology case is medically unique, these guidelines recommend a patient-specific approach consisting of the following components: diagnosis, staging, therapeutic intervention, provisions for patient and personnel safety in handling chemotherapy agents, referral to an oncology specialty practice when appropriate, and a strong emphasis on client support. Determination of tumor type by histologic examination of a biopsy sample should be the basis for all subsequent steps in oncology case management. Diagnostic staging determines the extent of local disease and presence or absence of regional or distant metastasis. The choice of therapeutic modalities is based on tumor type, histologic grade, and stage, and may include surgery, radiation therapy, chemotherapy, immunotherapy, and adjunctive therapies, such as nutritional support and pain management. These guidelines discuss the strict safety precautions that should be observed in handling chemotherapy agents, which are now commonly used in veterinary oncology. Because cancer is often a disease of older pets, the time of life when the pet–owner relationship is usually strongest, a satisfying outcome for all parties involved is highly dependent on good communication between the entire healthcare team and the client, particularly when death or euthanasia of the patient is being considered. These guidelines include comprehensive tables of common canine and feline cancers as a resource for case management and a sample case history.

Treatment of MRI-Diagnosed Trigeminal Peripheral Nerve Sheath Tumors by Stereotactic Radiotherapy in Dogs

Background

Stereotactic radiotherapy (SRT) is an emerging technique for treating tumors in animals.

Objectives

To assess the outcome of dogs with suspected intracranial trigeminal nerve peripheral nerve sheath tumors (PNST) treated with SRT.

Animals

Eight dogs with presumptive PNST.

Methods

This was a retrospective study of dogs identified by searching UC Davis Veterinary Medical Teaching Hospital medical records for dogs treated with SRT for a presumed PNST. Presumptive diagnosis was based on magnetic resonance imaging. SRT was delivered in 3 dose fractions of 8 Gray (Gy) on consecutive days or every other day to a total dose of 24 Gy.

Results

Median disease‐specific survival was 745 days (range: 99–1375 days, n = 6). No signs of acute adverse effects of radiation treatment were recorded. Late radiation effects versus tumor progression could not be confirmed histopathologically because of few animals undergoing necropsy.

Conclusions and Clinical Importance

This study provides preliminary evidence that dogs with PNST benefit from SRT in terms of long‐term survival. The treatment appears to be well tolerated and requires fewer anesthetic events for animals compared to full‐course radiation.