CLINICAL RELEVANCE OF ABNORMAL SCINTIGRAPHIC FINDINGS OF ADULT EQUINE RIBS

Horses with cranial rib abnormalities may exhibit severe acute lameness and may have unusual gait deficits characterized by forelimb abduction during protraction at the walk. Horses with caudal rib abnormalities may resent being saddled and ridden. In a retrospective evaluation of 20 horses with a documented rib lesion, 25 sites of increased radiopharmaceutical uptake were found in one or more ribs. Thirteen (52%) scintigraphic lesions involved the first rib; four were located immediately dorsal to the sternal articulation, eight were near the costochondral junction and one was at the costovertebral junction. Six (24%) scintigraphic rib lesions involved ribs 2–8; one was located immediately dorsal to the sternal articulation, three were at the costovertebral junction and two were near the costochondral junction. Six (24%) scintigraphic rib lesions involved the mid‐portion (five) or costovertebral junction (one) of ribs 9–18. The 20 horses were divided into three groups based on the clinical relevance of the scintigraphic findings. Group 1 (n=3) horses had clinical signs attributed to a rib abnormality; Group 2 (n=6) horses had a rib abnormality that was a plausible explanation for clinical signs; Group 3 (n=11) horses had clinical signs that could not be attributed to a rib abnormality. For horses with cranial rib abnormalities, a modified lateral scintigraphic image with the ipsilateral limb pulled caudally and a left (right) 45° caudal–right (left) radiograph facilitated the diagnosis.     

MAGNETIC RESONANCE IMAGING IN FOALS WITH INFECTIOUS ARTHRITIS

The magnetic resonance (MR) imaging findings of foals with infectious and noninfectious arthritis are described. Six foals with infectious arthritis and three foals with noninfectious arthritis were grouped based on synovial fluid analysis results and examined with radiography and MR imaging. Four out of six foals with infectious arthritis had osseous lesions in MR images indicative of osteomyelitis and only 4/19 lesions were detected on digital radiographs. The three foals with noninfectious arthritis had no osseous lesions in MR images or radiographically. Of the six joints that had osseous lesions detected with MR imaging, three had at least one lytic lesion detected radiographically. Osseous lesions in the epiphysis, metaphysis, and physis appeared in MR images as T2W, short tau inversion recovery, and proton density hyperintense foci with a hypointense halo. The same lesions appeared hyperintense in the 3D RSSG water excitation pulse sequence but lacked a surrounding hypointense halo. Most joints of foals with infectious arthritis had heterogenous signals within the synovial fluid whereas all of the nonseptic joints had homogenous synovial fluid signals. MR imaging appears to be better than radiography in the detection of osseous lesions in foals diagnosed with infectious arthritis and may be a valuable screening test for the presence of osteomyelitis.     

Arytenoid Lateralization for Treatment of Laryngeal Paralysis in 10 Cats

Objective— To describe the signalment, history, clinical signs, surgical technique, and outcome for cats with laryngeal paralysis that had arytenoid lateralization.
Study Design— Case series.
Animals— Cats with laryngeal paralysis (n=10).
Methods— Medical records (1996–2002) for cats with laryngeal paralysis that had arytenoid lateralization were reviewed for signalment, history, clinical signs, degree of paralysis, cause, concurrent medical conditions, surgical technique, and outcome. Follow-up information was obtained from owners or referring veterinarians.
Results— Of 10 cats, 9 had bilateral and 1 had unilateral laryngeal paralysis. Arytenoid lateralization were unilateral (n=7), bilateral (1), and staged bilateral procedures (2), 10 days and 3 years apart, respectively. Postoperatively, 1 cat had persistent inspiratory noise because of minimal enlargement of the rima glottidis and 2 cats required a temporary tracheostomy for management of laryngeal swelling. Three cats developed aspiration pneumonia and died 4, 7, and 150 days after surgery; all 3 had bilateral (simultaneous or staged) procedures. Of the 7 remaining cats, 4 were alive at follow-up and 3 had died of causes unrelated to arytenoid lateralization. The calculated mean survival time for all 10 cats was 406 days (median, 150 days; range, 4–1825 days).
Conclusions— Arytenoid lateralization was effective at enlarging the rima glottidis and reducing signs of airway obstruction in most cats.
Clinical Relevance— Unilateral arytenoid lateralization is a feasible option for the surgical management of cats with marked clinical signs; however, bilateral procedures should be avoided or at least performed with considerable caution because of the apparent risk for aspiration pneumonia.     

USE OF 3'-DEOXY-3'-[18F]FLUOROTHYMIDINE PET/CT FOR EVALUATING RESPONSE TO CYTOTOXIC CHEMOTHERAPY IN DOGS WITH NON-HODGKIN'S LYMPHOMA

Imaging and measurement of proliferation with computed tomography (CT) and positron emission tomography (PET) provide a noninvasive method for improved staging and monitoring of response to cancer treatment. We evaluated prospectively the proliferation marker 3'-deoxy-3'[¹⁸F] fluorothymidine (FLT) in the context of FLT-PET/CT for detection of early response, confirmation of posttreatment response, and prediction of relapse in dogs with non-Hodgkin's lymphoma. Nine dogs with non-Hodgkin's lymphoma who were scheduled to receive five cycles of an investigational cytotoxic chemotherapy agent were included. All dogs received baseline FLT-PET/CT imaging immediately before chemotherapy. Intent was to repeat imaging with FLT-PET/CT at various time points: group 1 ( n =4), 5 days after initiation of chemotherapy and 3 weeks following the last chemotherapy administration; group 2 ( n =5), before the fourth cycle of chemotherapy and 3 weeks following the last administration. Two dogs in group 2 did not undergo repeat PET/CT. Body mass standardized uptake values (SUV) for FLT were calculated for each dog. Eight dogs had initially increased FLT uptake (mean SUV_max=9.8 [2.6–22.3]). Mean SUV decreased significantly for the seven dogs that underwent follow-up PET/CT following chemotherapy (mean SUV_max=3.5 [1.1–7.9], P <0.016). Increased uptake preceded clinical and cytological evidence of relapse in two dogs. Ki-67 immunohistochemistry confirmed decreased proliferation corresponding to decreased SUV in three canine lymph node samples. FLT-PET/CT functional and anatomical imaging shows promise for the evaluation of response to cytotoxic chemotherapy in dogs with non-Hodgkin's lymphoma and for predicting relapse before standard clinical and clinicopathologic confirmation.     

PROOF OF PRINCIPLE OF OCULAR SPARING IN DOGS WITH SINONASAL TUMORS TREATED WITH INTENSITY‐MODULATED RADIATION THERAPY

Intensity‐modulated radiation therapy (IMRT) allows optimization of radiation dose delivery to complex tumor volumes with rapid dose drop‐off to surrounding normal tissues. A prospective study was performed to evaluate the concept of conformal avoidance using IMRT in canine sinonasal cancer. The potential of IMRT to improve clinical outcome with respect to acute and late ocular toxicity was evaluated. Thirty‐one dogs with sinonasal cancer were treated definitively with IMRT using helical tomotherapy and/or dynamic multileaf collimator (DMLC) delivery. Ocular toxicity was evaluated prospectively and compared with a comparable group of historical controls treated with conventional two‐dimensional radiotherapy (2D‐RT) techniques. Treatment plans were devised for each dog using helical tomotherapy and DMLC that achieved the target dose to the planning treatment volume and limited critical normal tissues to the prescribed dose–volume constraints. Overall acute and late toxicities were limited and minor, detectable by an experienced observer. This was in contrast to the profound ocular morbidity observed in the historical control group treated with 2D‐RT. Overall median survival for IMRT‐treated and 2D‐treated dogs was 420 and 411 days, respectively. Compared with conventional techniques, IMRT reduced dose delivered to eyes and resulted in bilateral ocular sparing in the dogs reported herein. These data provide proof‐of‐principle that conformal avoidance radiotherapy can be delivered through high conformity IMRT, resulting in decreased normal tissue toxicity as compared with historical controls treated with 2D‐RT.     

USE OF CONE‐BEAM COMPUTED TOMOGRAPHY TO CHARACTERIZE DAILY URINARY BLADDER VARIATIONS DURING FRACTIONATED RADIOTHERAPY FOR CANINE BLADDER CANCER

Urinary bladder cancer is difficult to treat accurately with fractionated radiation therapy (RT) due to daily positional changes of the bladder and surrounding soft‐tissue structures. We quantified the daily motion experienced by the canine bladder with patients in dorsal vs. sternal vs. lateral recumbency. We also described the dose distribution for three different planning target volume expansions (5, 10, and 15 mm) for each of the three positions to ensure adequate bladder dose and minimize irradiation of nearby healthy tissues. Analysis was based on data from retrospective daily cone‐beam computed tomography (CT) (CBCT) images obtained for positioning of canine patients undergoing routine RT. Organs of interest were contoured on each CBCT data set and the images, along with the contours, were registered to the original planning CT. All measurements were made relative to the planning CT and dosimetric data for the organs of interest was determined using a dose volume histogram generated from sample parallel‐opposed beam configuration. There was a wide range in bladder position throughout treatment. The least amount of bladder variation and the lowest rectal dose was with dogs in lateral recumbency. It was also determined that a margin of 10 mm would allow for sufficient dose to be delivered to the bladder while minimizing rectal dose.