Accuracy of three diagnostic tests to detect tooth resorption in unowned unsocialised cats in Denmark.

OBJECTIVES: To estimate the relative diagnostic sensitivity and specificity of oral clinical examination, full-mouth dental radiography, and cone-beam CT for the detection of tooth resorption in cats, and to estimate the prevalence of tooth resorption in unowned, unsocialised cats in Denmark. MATERIALS AND METHODS: Cadavers of 144 adult cats underwent an oral examination, full-mouth dental radiography, and cone-beam CT. Sensitivity and specificity of the three tests, along with the true prevalence, overall and stratified by sex and tooth location, were estimated using latent class methods. RESULTS: We found cone-beam CT to be the superior image modality, with a sensitivity of 99.5% and a specificity of 99.8%. Dental radiography had a sensitivity of 78.9% and a specificity of 100%, and oral clinical examination had a sensitivity of only 36.0% and specificity of 99.9%. We estimated the prevalence of tooth resorption among unowned unsocialised cats in Denmark to be 40% of adult individuals, and 6.1% of teeth. CLINICAL SIGNIFICANCE: When dealing with tooth resorption, cone-beam CT can help the operator to find and treat affected teeth that could otherwise go undiagnosed. The prevalence of tooth resorption among unowned, unsocialised cats in Denmark does not appear to differ from other populations of cats.

Comparison of cone-beam and fan-beam computed tomography and low-field magnetic resonance imaging for detection of proximal phalanx dorsoproximal osteochondral defects.

BACKGROUND: Dorsoproximal osteochondral defects commonly affect the proximal phalanx, but information about diagnosis on computed tomography (CT) and magnetic resonance imaging (MRI) is limited. OBJECTIVES: To assess CT and MRI diagnoses of osteochondral defects, describe the lesions and compare sensitivity and specificity of the modalities using macroscopic pathology as gold standard. STUDY DESIGN: Cross-sectional study. METHODS: Thirty-five equine cadaver limbs underwent standing cone-beam CT (CBCT), fan-beam CT (FBCT), low-field MRI and pathological examination. CT and MR images were examined for proximal phalanx dorsomedial and dorsolateral eminence osteochondral defects. Defect dimensions were measured. Imaging diagnoses and measurements were compared with macroscopic examination. RESULTS: Fifty-six defects were seen over 70 potential locations. On CBCT and FBCT, osteochondral defects appeared as subchondral irregularity/saucer-shaped defects. On MRI, osteochondral defects were a combination of articular cartilage defect on dorsal images and subchondral flattening/irregularity on sagittal images. Subchondral thickening and osseous short tau inversion recovery hyperintensity were found concurrent with osteochondral defects. Compared with pathological examination, the sensitivity and specificity of diagnosis were 86% (95% confidence interval [95% CI] 75%-93%) and 64% (95% CI 38%-85%) for FBCT; 64% (95% CI 51%-76%) and 71% (95% CI 46%-90%) for CBCT; and 52% (95% CI 39%-65%) and 71% (95% CI 46%-90%) for MRI. Sensitivity of all modalities increased with defect size. Macroscopic defect dimensions were strongly correlated with CBCT (r = 0.76, p < 0.001) and moderately correlated with FBCT and MRI (r = 0.65, p < 0.001). Macroscopic measurements were significantly greater than all imaging modality dimensions (p < 0.001), potentially because macroscopy included articular cartilage pathology. MAIN LIMITATIONS: Influence of motion artefact could not be assessed. CONCLUSIONS: Osteochondral defects could be visualised using both CT and MRI with sensitivity increasing with defect size. Diagnostic performance was best using FBCT, followed by CBCT then MRI, but CBCT-measured defect size best correlated with macroscopic examination. MRI provided useful information on fluid signal associated with defects, which could represent active pathology.

Surgical Treatment of Facial Abscesses and Jaw Osteomyelitis of Dental Origin Using Extraoral Tooth Extraction in the Domestic Rabbit: A Case Series.

The treatment of facial abscesses of dental origin is difficult as jaw osteomyelitis in rabbits is mainly associated with a thick caseous pus that is particularly difficult to drain. Precise identification of the teeth involved in the infected site with the use of cone beam computed tomography (CBCT) was expected to ensure a favorable surgical treatment plan without a long-term local antibiotic strategy or local marsupialization. The first part of the study compared multi-planar reconstruction (MPR) and 3D reconstruction complemented by a maximum intensity projection filter (MIP). The surgical part of the study included rabbits with documentation of the treatment outcome for a period greater than one month after surgery and having had at least one post-operative CBCT demonstrating the achievement of surgical extraction. MPR is significantly more efficient than MIP techniques for alveolar bone (P < 10-7), spongious bone (P < 10-10) and apical elongation (P < 10-5) parameters. Nineteen of 20 surgical sites gave radiological confirmation of the success of the surgical plan. Eighteen of 20 of the abscess sites were clinically healed within one month. Seven out of 20 of the abscess sites presented evidence of one dental structure regrowth following the CBCT recheck. Two out of these seven cases presented with a concomitant persistent chronic facial fistula. Both cases healed after second-stage surgery to extract the tooth structure. The mean number of teeth extracted was 2.85, and seven of the 20 procedures included one incisor.

Evaluation of Dental Enamel Thickness in Maxillary Teeth of Alouatta guariba clamitans, Alouatta caraya, and Sapajus nigritus by Cone Beam Computed Tomography.

Tooth enamel thickness is widely studied in primates and is important in differentiating taxa and in interpreting diet and feeding behavior. The objective of this study was to measure enamel thickness and discuss whether the results can be associated with different feeding patterns. Thirty-four syncraniums of Alouatta guariba clamitans, Alouatta caraya, and Sapajus nigritus were subjected to cone beam computed tomographic (CBCT) scans, and the dental enamel was measured in different regions of the crown using the multiplanar reconstruction tool. The differences observed indicate that for many variables and teeth, A. guariba clamitans showed significantly higher values compared to the other 2 species, with the exception of the cuspid region. Although the A. guariba clamitans is a folivorous species, it showed thicker enamel for most of the variables. CBCT was efficient in performing the measurements, allowing analysis of the syncraniums.

Cone-beam computed tomography produces images of numerically comparable diagnostic quality for bone and inferior quality for soft tissues compared with fan-beam computed tomography in cadaveric equine metacarpophalangeal joints.

Cone-beam computed tomography (CBCT) is an emerging modality for imaging of the equine patient. The objective of this prospective, descriptive, exploratory study was to assess visualization tasks using CBCT compared with conventional fan-beam CT (FBCT) for imaging of the metacarpophalangeal joint in equine cadavers. Satisfaction scores were numerically excellent with both CBCT and FBCT for bone evaluation, and FBCT was numerically superior for soft tissue evaluation. Preference tests indicated FBCT was numerically superior for soft tissue evaluation, while preference test scoring for bone was observer-dependent. Findings from this study can be used as background for future studies evaluating CBCT image quality in live horses.

Interobserver agreement of lateral and oblique radiography and standing cone beam CT of the caudal cervical articular process joints of horses.

Caudal cervical articular process joint osteoarthritis (CAPJ OA) leads to career-altering clinical signs in the horse. Oblique radiographs and standing cone beam computed tomography (CBCT) facilitate the assessment of this area, however, the variability of interpretation of these images is currently unknown. This retrospective, secondary analysis, methods comparison study investigated interobserver agreement between clinicians and modality in grades of CAPJ OA on lateral and oblique radiographs and CBCT. We hypothesized that agreement between clinicians' grades of CAPJ OA would be lowest for oblique radiographs and highest for CBCT, and agreement between grades of CAPJ OA would be low for all pairs of modalities. Horses underwent lateral and oblique radiography and CBCT of the CAPJs of C5-C6 and C6-C7. Radiographs and CBCT images were graded retrospectively by four blinded clinicians using 3-point scales. Cohen's kappa analysis was used to evaluate interobserver agreement between grades of CAPJ OA, and agreement between grades of CAPJ OA between different modalities was explored using kappa-weighted analysis. Agreement between clinicians' grades of CAPJ OA was moderate for lateral radiographs (0.49), and fair for oblique radiographs (0.23) and CBCT (0.36). For all modalities, agreement was slight to fair between clinicians for CAPJs with grade 1 (normal, 0.21-0.32) or 2 (mild, 0.13-0.36) CAPJ OA, and moderate to substantial for grade 3 (moderate to severe, 0.45-0.77) CAPJ OA. Agreement between grades of CAPJ OA was fair for all pairs of modalities. This study provides important information regarding the inconsistency of interpretation of mild CAPJ OA on radiographs and CBCT amongst clinicians.

Morphometry and Morphology of the Articular Surfaces of the Medial Region of the Temporomandibular Joint in the Felis Catus (Domestic cat) - A Cone Beam Computed Tomography Study.

The articular surfaces of the temporomandibular joint (TMJ) in the cat consist of the articular head of the condylar process of the ramus of the mandible and the mandibular fossa of the petrous part of the temporal bone. Anatomic conformation of the TMJ articular surfaces can vary; however, this has not been studied in the cat. Thus, the aim of this study was to characterize the conformation of the medial region of the TMJ in mesocephalic adult cats as well as to determine the articular relationship by measurement of the degree of coverage of the mandibular fossa over the articular head. This was accomplished by assessing 60 TMJs from 30 mesocephalic adult cats by means of cone-beam computed tomography (CBCT). The width and depth of the mandibular fossa, and the degree of coverage of the mandibular fossa were evaluated using parasagittal reconstructions of the medial aspect of the TMJ by two observers. No statistically significant difference was observed during the intra and interobserver evaluation of the mandibular fossa width and depth and the degree of coverage of the mandibular fossa over the articular head. P-values for the studied variables were greater than 0.05. The resulting measurements demonstrated a concave mandibular fossa with a prominent retroarticular process and a poorly developed articular eminence; a well-defined rounded articular surface, and a high degree of coverage (171°) of the mandibular fossa over the articular head. In conclusion, the articular surfaces at the medial aspect of the TMJ displayed elevated geometric similarity, with an articular head of the condylar process deeply seated in the mandibular fossa.

Semi-Automatic Segmentation of Cone Beam Computed Tomography Datasets for Volume Measurements of Equine Cheek Teeth.

The volumes of equine teeth may change considerably over time for several reasons including domestication, routine dental floating, and the hypsodont and anelodont nature of the teeth. Cone beam computed tomography (CBCT) of the head is routinely performed in standing horses and, in this proof of concept study, the feasibility of measuring tooth volume from CBCT datasets was determined. The CBCT images of 5 equine cadaver cheek teeth were segmented with a software 3-dimensional (3D) Slicer using a predefined protocol, corrected manually, and re-assembled into a 3D model. Individual tooth volume (VS) was calculated from the model. After extraction, the volumes were also measured using the "gold-standard" water displacement method (VW) for comparison. The VS of 77 teeth ranged from 7114 to 42,300 mm3 which strongly correlated with VW (r = 0.99), and on average VS was 6.1% less than VW. There was no significant difference in VS between the right and left arcades in individual animals. Maxillary cheek tooth volume was on average 40% larger than it was for mandibular counterparts. Semi-automatic image segmentation of equine cheek teeth from CBCT data is feasible and accurate but requires some manual intervention. This preliminary study provides initial data on the volume of equine cheek teeth and creates new possibilities for future in vivo studies.

Diagnostic Imaging of Oral and Maxillofacial Anatomy and Pathology.

This article describes the technical principles and indications for the most often encountered diagnostic imaging modalities in veterinary dentistry and oral surgery; with extensive coverage of intraoral (and extraoral) dental radiographic imaging and interpretation through detailed example figures of common dental and maxillofacial diseases in the dog and cat. Multidetector/multislice computed tomography (MDCT/MSCT) and emergent technologies such as cone-beam computed tomography (CBCT) are presented here in detail. Magnetic resonance imaging (MRI) and diagnostic ultrasound, which are used less frequently, are briefly discussed.

Radiographic Assessment of the Feline Temporomandibular Joint with Oblique Projections: A Preliminary Ex Vivo Study.

Radiographic assessment of the temporomandibular joint in the domestic cat using conventional radiographic views can be challenging due to superimposition of overlying structures and the complex anatomy of the skull. The use of computed tomography, magnetic resonance imaging, and cone beam computed tomography to assess the temporomandibular joint in the cat has increased, but these modalities are not always available in general veterinary practices. Conventional radiography is still commonly used for first line assessment of the temporomandibular joint. The aim of this preliminary study was to determine optimal angle of obliquity of lateroventral-laterodorsal and laterorostral-laterocaudal (nose up lateral oblique) oblique radiographic views in the assessment of the temporomandibular joints in five feline mesaticephalic dry skulls. Visibility of the mandibular head, mandibular fossa, retroarticular process, and temporomandibular joint space were evaluated and scored by two veterinary radiologists. The results of this study identified that the dependent temporomandibular joint anatomy was best seen on the latero-10°-ventral-laterodorsal, latero-15°-ventral-laterodorsal, and latero-20°-ventral-laterodorsal, oblique views, and opposite lateral oblique views at these angulations may be helpful in characterization of this anatomy in clinical patients. The results also indicate that the laterorostral-laterocaudal (nose up lateral oblique) oblique view did not allow adequate discrimination of all TMJ anatomy at any angle, and is not recommended.

Use of cone-beam computed tomography for advanced imaging of the equine patient.

Access to volumetric imaging modalities, such as magnetic resonance imaging (MRI) and computed tomography (CT), has increased over the past decade and has revolutionised the way clinicians evaluate equine anatomy. More recent advancements have resulted in the development of multiple commercially available cone-beam CT (CBCT) scanners for equine use. CBCT scanners modify the traditional fan-shaped beam of ionising radiation into a three-dimensional pyramidal- or cone-shaped beam of radiation. This modification enables the scanner to acquire sufficient data to create diagnostic images of a region of interest after a single rotation of the gantry. The rapid acquisition of data and divergent X-ray beam causes some artifacts to be more prominent on CBCT images-as well as the unique cone-beam artifact-resulting in decreased contrast resolution. While the use of CT for evaluation of the equine musculoskeletal anatomy is not new, there is a paucity of literature and scientific studies on the capabilities of CBCT for equine imaging. CBCT units do not require a specialised table for imaging and in some cases are portable for imaging in the standing or anaesthetised patient. This review article summarises the basic physics of CT technology, including how CBCT imaging differs, and provides objective information about the strengths and limitations of this modality. Finally, potential future applications and techniques for imaging with CT which will need to be explored in order to fully consider the capabilities of CT imaging in the horse are discussed.

Multidetector CT and cone-beam CT have substantial agreement in detecting dental and sinus abnormalities in equine cadaver heads.

The performance of cone-beam CT (CBCT) systems compared to conventional helical multidetector CT (MDCT) imaging of the equine head is unknown. The aim of this prospective, method-comparison study was to compare the ability of CBCT and MDCT to detect abnormalities in equine cadaver heads. Eleven equine cadaver heads were scanned using a CBCT scanner and a 64-slice MDCT scanner. Consensus evaluations for CBCT and MDCT scans were performed by three observers. Identified abnormalities were grouped into subcategories with a focus on dental abnormalities. Kappa agreement values between detected abnormalities for CBCT and MDCT methods were calculated. Of 468 teeth evaluated, 122 (26.1%) were found to have abnormalities (including in 58 infundibula and 7 pulps) using MDCT and 105 (22.4%) were found to have abnormalities (including in 52 infundibula and 2 pulps) using CBCT. The agreement between CBCT and MDCT was almost perfect for overall detection of dental abnormalities (k = 0.90) with k = 1 for diastema k = 0.95 for clinical crown abnormalities, and k = 0.93 for infundibular abnormalities. However, the detection of pulp changes by CBCT was only moderate k = 0.44. Increased scatter radiation, non-calibrated Hounsfield Unit and artefacts in CBCT images made accurate identification of the pulp density difficult. In conclusion, CBCT results were similar to conventional MDCT for the majority of dental abnormalities, however, pulp abnormalities were not reliably identified using CBCT, potentially limiting its clinical use for detecting endodontic disease in its current form. Further comparison with more cases with confirmed dental disease and studies in clinical cases are warranted.

Estimation of planning organ at risk volumes for ocular structures in dogs undergoing three-dimensional image-guided periocular radiotherapy with rigid bite block immobilization.

Planning organ at risk volume (PRV) estimates have been reported as methods for sparing organs at risk (OARs) during radiation therapy, especially for hypofractioned and/or dose-escalated protocols. The objectives of this retrospective, analytical, observational study were to evaluate peri-ocular OAR shifts and derive PRVs in a sample of dogs undergoing radiation therapy for periocular tumors. Inclusion criteria were as follows: dogs irradiated for periocular tumors, with 3D-image-guidance and at least four cone-beam CTs (CBCTs) used for position verification, and positioning in a rigid bite block immobilization device. Peri-ocular OARs were contoured on each CBCT and the systematic and random error of the shifts in relation to the planning CT position computed. The formula 1.3×Σ+0.5xσ was used to generate a PRV of each OAR in the dorsoventral, mediolateral, and craniocaudal axis. A total of 30 dogs were sampled, with 450 OARs contoured, and 2145 shifts assessed. The PRV expansion was qualitatively different for each organ (1-4 mm for the dorsoventral and 1-2 mm for the mediolateral and craniocaudal axes). Maximal PRV expansion was ≤4 mm and directional for the majority; most pronounced for corneas and retinas. Findings from the current study may help improve awareness of and minimization of radiation dose in peri-ocular OARs for future canine patients. Because some OARs were difficult to visualize on CBCTs and/ or to delineate on the planning CT, authors recommend that PRV estimates be institution-specific and applied with caution.

Feasibility, indications, and radiographically confirmed diagnoses of standing extremity cone beam computed tomography in the horse.

OBJECTIVE: To report on the feasibility, indications, and diagnostic yield of cone beam computed tomography (CBCT) of horses' extremities performed under standing sedation. STUDY DESIGN: Retrospective clinical case series. SAMPLE POPULATION: Fifty-nine CBCT examinations in 58 horses. METHODS: Examinations were categorized for indications for CBCT dependent on a suspicion, presence, or absence of a diagnosis prior to CBCT. The number of acquisitions per examination, total time for the examination, diagnostic score of each acquisition (diagnostic, diagnostic-compromised, nondiagnostic), and additional diagnostic information regarding preexisting diagnostic information were recorded. RESULTS: Three (median) acquisitions were performed per examination in a median study time of 14 minutes. In 24 of 33 cases with a suspected diagnosis, this diagnosis was confirmed or definitively refuted; in seven of 33 cases, the suspected diagnosis was refuted without a new diagnosis; and, in two of 33 cases, the suspected diagnosis could not be confirmed nor could a new diagnosis be made. In five of nine cases without a preexisting diagnosis, a diagnosis was established. In 16 cases with a diagnosis prior to CBCT, additional information was recorded, or a surgical plan was prepared. In 14 of 18 cases in which additional contrast techniques were used, additional information was gained. CONCLUSION: Standing CBCT of the horses' extremities is feasible and can produce diagnostic information in a timely fashion. CLINICAL SIGNIFICANCE: The results provide evidence of the practicality and diagnostic potential of standing CBCT of horses' extremities.

Validation of standing cone beam computed tomography for diagnosing subchondral fetlock pathology in the Thoroughbred racehorse.

BACKGROUND: Subchondral bone pathology is common in Thoroughbred racehorses and believed to precede more serious injury. Early identification of pathology is critical to allow for intervention. OBJECTIVES: To determine interobserver variability of fetlock subchondral bone lesions using cone beam and fan beam computed tomography (CBCT, FBCT) and to validate a robotics-controlled CBCT to identify fetlock subchondral bone pathology in the Thoroughbred racehorse. STUDY DESIGN: Prospective cohort study. METHODS: FBCT and CBCT images were acquired of 25 metacarpo-/metatarsophalangeal joints of Thoroughbred racehorses. Images were analysed for subchondral bone lesions commonly identified in Thoroughbred fetlocks by an imaging specialist and surgery specialist. Interobserver and intermodality equivalence were determined with a Pearson correlation analysis and Bland-Altman equivalence test. RESULTS: Interobserver FBCT correlation was significant (P < .05) for 19 of 25 variables (Pearson R mean 0.77). Concordance was significant for all 25 variables (Bland Altman average difference 0.28 ± 0.21 mm). Interobserver CBCT correlation was significant for 21 of 25 variables (Pearson R mean 0.73). Concordance was significant for all variables (Bland Altman average difference 0.07 ± 1.90 mm). Intermodality (FBCT vs CBCT) correlation and concordance was significant for all variables as interpreted by the radiologist (Pearson R mean of 0.72, Bland Altman average difference 0.21 ± 0.47 mm). Intermodality correlation was significant for 19 of 25 variables as interpreted by the surgeon (Pearson R mean of 0.72). Concordance was significant for all variables (Bland Altman average difference 0.49 ± 0.52 mm). MAIN LIMITATIONS: Neither FBCT nor CBCT images were compared with other imaging modalities/histopathology; limited number of cases included; inconsistent agreement of small lesions in specific categories. CONCLUSIONS: Standing CBCT is a valid diagnostic modality to identify subchondral bone lesions in Thoroughbred fetlocks. This technology may provide valuable information regarding the development and progression of fetlock pathology and yield insight into predisposing factors leading to more severe pathology.

Comparative morphometry of the temporomandibular joint in brachycephalic and mesocephalic cats using multislice CT and cone beam CT.

OBJECTIVES: The purpose of this study was to analyse and compare morphometric measurements of the temporomandibular joint (TMJ) in two groups of cats with brachycephalic and mesocephalic craniofacial skull conformations using multislice CT and cone beam CT. METHODS: CT records of 20 cats without TMJ pathology were included in the study, and were divided into two groups according to those with mesocephalic or brachycephalic skull conformation. Width and depth of the mandibular fossa, width and height of the head of the mandible, and two different angles were measured in 40 TMJs. RESULTS: TMJ conformation differed between groups: 3/6 parameters were statistically different. Brachycephalic cats had a significantly narrower mandibular fossa, a shorter head of the mandible and a wider angle of congruence (angle 2). CONCLUSIONS AND RELEVANCE: The results provide morphometric measurements that can serve as a reference tool for the veterinary radiologist and surgeon when TMJ evaluation is necessary. Moreover, the study identified significant differences between the two craniofacial skull conformations.

Inflammatory cytokines in horses with cervical articular process joint osteoarthritis on standing cone beam computed tomography.

BACKGROUND: Standing cone beam computed tomography (CT) provides cross-sectional imaging of the caudal cervical articular process joints (CAPJs) in the sedated horse, though the clinical implications of osteoarthritis (OA) identified on CT in this location are unknown. Increases in concentrations of intra-synovial cytokines could lend support to the clinical significance of CAPJ OA identified on this imaging modality. OBJECTIVES: Investigate the presence and concentration of intra-synovial inflammatory cytokines in CAPJs with and without standing cone beam CT evidence of OA using an equine specific multiplex assay. STUDY DESIGN: Prospective clinical study. METHODS: Standing cone beam CT of C5-6 and C6-7 was performed on horses with CAPJ OA and control horses. Synovial fluid samples of the CAPJs of C5-6 and C6-7 were obtained bilaterally using ultrasound guidance and analysed for concentrations of IFN-γ, IL-1ß, IL-6, IL-10, IL-17 and TNFα with the Milliplex® multi-analyte profiling kit. CT Images were retrospectively graded using a novel grading scheme. Significant differences between concentrations of inflammatory cytokines between joints with different categories of osteoarthritis severity were explored using a Wilcoxon rank-sum test or Kruskal-Wallis test. RESULTS: Concentrations of intra-synovial cytokines were higher in joints with moderate to severe OA when compared to joints with no or mild OA, with differences in concentrations of IL-17 reaching statistical significance (P = .007). MAIN LIMITATIONS: Limitations include discrepancy in number, age, and breed between control and OA populations, use of a novel grading scheme, and lack of a histologic gold-standard to confirm the presence and severity of CAPJ OA. CONCLUSIONS: Differences in inflammatory cytokines between caudal CAPJs with and without evidence of moderate to severe osteoarthritis on standing cone beam CT exist. This finding lends support to the clinical relevance of a diagnosis of moderate to severe CAPJ OA in the caudal cervical vertebral column as identified with this imaging modality.

A three-dimensional computed tomographic volume rendering methodology to measure the tibial torsion angle in dogs.

OBJECTIVE: To describe a three-dimensional (3D) computed tomographic (CT) methodology to measure the tibial torsion angle (TTa) and to evaluate intrarater and interrater agreements and accuracy through comparison with anatomic measurements. STUDY DESIGN: Ex vivo cadaveric study. SAMPLE POPULATION: Thirty-six tibiae from 18 dogs. METHODS: Tibial torsion angle of each tibia was measured by using two CT techniques (axial and 3D volume rendering) by three raters who blindly measured TTa in duplicate. A semitransparent bone filter was used to enhance the visibility of the target anatomical landmarks for the 3D volume rendering CT technique. Tibial torsion angle was also quantitated in tibial specimens. Intrarater and interrater agreements were analyzed by using intraclass coefficients (ICC). Accuracy was evaluated by using adjusted R2 coefficients (R2 > 80% was considered acceptable). RESULTS: The 3D volume rendering CT technique had excellent intrarater and interrater agreements (ICC > 0.94) and an R2 value of 97%. The axial CT technique had good to excellent intrarater and interrater agreements (0.8 < ICC < 0.95) and an R2 of 86%. No difference was found between axial and 3D CT techniques. A mean internal TT angle of approximately -6° was found with CT and anatomic measurements. CONCLUSION: The 3D volume rendering and axial CT techniques were precise and accurate for measuring TTa in dogs unaffected by patellar luxation. CLINICAL RELEVANCE: Combining 3D bone manipulation with application of a semitransparent filter allows simultaneous visualization of anatomic landmarks, which may facilitate the evaluation of complex bone deformations. Internal tibial torsion may be present in nonchondrodystrophic dogs without patella luxation.

Clinical use of computer-assisted orthopedic surgery in horses.

OBJECTIVE: To describe clinical applications of computer-assisted orthopedic surgery (CAOS) in horses with a navigation system coupled with a cone beam computed tomography unit. STUDY DESIGN: Retrospective clinical case series. ANIMALS: Thirteen adult horses surgically treated with CAOS. METHODS: Medical records were searched for horses that underwent CAOS between 2016 and 2019. Data retrieved included signalment, diagnosis, lameness grade prior to surgery, surgical technique and complications, anesthesia and surgery time, and information pertaining to the perioperative case management and outcome. RESULTS: In 10 cases, surgical implants were placed in the proximal phalanx, third metatarsal bone, ulna, or medial femoral condyle. In one case, navigated transarticular drilling was performed to promote ankylosis of the distal tarsal joints. In another case, an articular fragment of the middle phalanx was removed with the help of CAOS guidance. In the final case, a focal osteolytic lesion of the calcaneal tuber was curetted with the aid of CAOS. In seven cases, a purpose-built frame was used for the surgical procedure. All surgeries were performed successfully and according to the preoperative plan. CONCLUSION: Computer-assisted orthopedic surgery can be an integral part of the clinical case management in equine surgery. To optimize workflow and time-efficiency, the authors recommend designating one team for operative planning and another for the execution of the surgical plan. Specialized equipment, such as the purpose-built frame, will further improve CAOS applications in equine surgery. CLINICAL SIGNIFICANCE: After they have become familiar with the operational principles, equine surgeons can readily apply CAOS for a broad spectrum of indications.

Setup error with and without image guidance using two canine intracranial positioning systems for radiation therapy.

Daily image guidance reduces inter-fractional variation in patient position for intracranial radiation therapy. However, the ability to detect and correct positioning errors is limited below a certain level. Because of these limitations, the accuracy achieved with a positioning system prior to image guidance may affect the error remaining after image guidance (the residual setup error). The objective of this study was to compare the setup accuracy achieved before and after megavoltage (MV) and cone-beam computed tomography (CBCT) guidance between two intracranial positioning systems. Equipment included a four degrees-of-freedom couch capable of 1 mm translational moves. Six dog cadavers were positioned 24 times as for clinical treatment in a head re-positioner (HPS), and the coordinates of five fiducial markers were measured before and after image-guided correction. The values obtained for the HPS were compared with those previously reported for the standard positioning system (SPS) used at this facility. The mean three-dimensional distance vector (3DDV) was lower for the HPS than for the SPS when no image guidance was used (P = .019). The mean 3DDV after MV guidance was lower for the HPS than for the SPS (P = .027), but not different after CBCT guidance (P = .231). The 95th percentiles of the 3DDV after MV and CBCT guidance were 2.1 and 2.9 mm, respectively, for the HPS, and 2.8 and 3.6 mm for the SPS. The setup error after MV guidance was lower for the positioning system that achieved a more accurate patient position before image guidance.