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Abstract
OBJECTIVE
To perform qualitative and quantitative analysis of positron emission tomography (PET)/CT images using spontaneous ventilation (SV) and positive-pressure breath-hold (PPBH) techniques in order to demonstrate the feasibility of PPBH PET/CT to decrease respiration-induced artifacts.
ANIMALS
5 healthy female mixed-breed dogs.
PROCEDURES
2-([18F]fluoro)-2-deoxy-D-glucose (was administered to each anesthetized dog. An SV PET/CT scan was performed from the head to the femur using 8 bed positions (3 min/bed) followed by a PPBH scan centered over the diaphragm with a single bed position (1.5 min/bed). PET image quality, the misalignment of organs between PET and CT images, and standardized uptake values (SUVs) of liver adjacent to diaphragm were compared between SV and PPBH.
RESULTS
Overall image quality and conspicuity of anatomic structures were superior in PPBH than in SV PET images. PPBH induced significantly less misalignment of the liver and diaphragm in all planes compared to SV. For the gall bladder, PPBH showed significantly less misalignment than SV only in the transverse plane. The maximum SUV in all of the liver areas was significantly higher with PPBH compared to SV. PPBH exhibited significantly higher mean SUV in the liver adjacent to the left diaphragmatic dome and left lateral border and higher minimum SUV only in the liver adjacent to the left diaphragmatic dome.
CLINICAL RELEVANCE
PPBH was demonstrated to be a feasible PET/CT protocol with higher PET image quality, less organ misalignment on fused PET/CT, and more accurate SUVs of the liver compared to SV PET/CT in healthy dogs.
Abstract
OBJECTIVE
The objectives of this study were to investigate scattered radiation doses to the hands of equine workers holding the cassette and the x-ray tube by hand, for both limb and vertebral column studies, and to compare the scattered radiation attenuation of lead with radiation protection lead-free gloves. Radiation doses to the hands of the cassette holder in the primary beam were also investigated.
SAMPLE
A whole-body horse cadaver.
PROCEDURES
A portable x-ray unit was used to simulate 6 radiographic study types in the horse cadaver. Doses were measured with no shielding and, for cassette holders, with the ion chamber enclosed in a lead glove and a lead-free glove. Thirty exposures were performed for each study view and condition (n = 1,920).
RESULTS
Mean scattered doses to x-ray unit operators were higher than doses to cassette holders for ungula (hoof), thoracic vertebrae, and lumbar vertebrae studies, whereas doses to cassette holders were higher than doses to x-ray tube operators for studies of the metacarpophalangeal joint (fetlock) and tarsus (hock). Doses did not differ for the stifle joint. Mean percentage decrease in scattered radiation dose was 99.58% with lead gloves and 98.9% with lead-free gloves.
CLINICAL RELEVANCE
X-ray tube operators can be exposed to equal or higher scattered radiation doses to the hand as cassette holders. Lead-free hand shielding should only be considered as an alternative to lead gloves if their lighter weight increases frequency of use by workers.
Abstract
OBJECTIVE
To assess the usefulness of magnetic resonance urography (MRU) for the visualization of nondilated renal pelvises and ureters in dogs and to compare our findings for MRU versus CT urography (CTU).
ANIMALS
9 healthy Beagles.
PROCEDURES
Dogs underwent CTU, static-fluid MRU, and excretory MRU, with ≥ 7 days between procedures. Contrast medium was administered IV during CTU and excretory MRU, whereas urine in the urinary tract was an intrinsic contrast medium for static-fluid MRU. For each procedure, furosemide (1 mg/kg, IV) was administered, and reconstructed dorsal plane images were acquired 3 minutes (n = 2) and 7 minutes (2) later. Images were scored for visualization of those structures and for image quality, diameters of renal pelvises and ureters were measured, and results were compared across imaging techniques.
RESULTS
Excretory MRU and CTU allowed good visualization of the renal pelvises and ureters, whereas static-fluid MRU provided lower visualization of the ureters. Distention of the renal pelvises and ureters was good in excretory MRU and CTU. Distention of the ureters in static-fluid MRU was insufficient compared with that in CTU and excretory MRU. Distinct artifacts were not observed in CTU and excretory MRU images. Static-fluid MRU images had several mild motion artifacts.
CLINICAL RELEVANCE
Our findings indicated that excretory MRU with furosemide administration was useful for visualizing nondilated renal pelvises and ureters of dogs in the present study. When performing MRU for the evaluation of dogs without urinary tract dilation, excretory MRU may be more suitable than static-fluid MRU.
Abstract
OBJECTIVE
To evaluate the feasibility of CT lymphangiography via intrametatarsal pad injection in cats with chylothorax.
ANIMALS
7 client-owned cats.
PROCEDURES
This was a multicenter, retrospective, descriptive study. Medical records and imaging data from 4 veterinary hospitals were reviewed to identify cats with chylothorax that had undergone intrametatarsal pad injection via CT lymphangiography. In total, 7 client-owned cats were included in the study. Signalment, history, image findings, and follow-up data were recorded. Descriptive statistics were used to analyze the success rate of thoracic duct (TD) enhancement and describe relevant clinical findings.
RESULTS
Enhancement of TDs was successful in 6 of the 7 cats within 5 to 15 minutes after initiating intrametatarsal pad injection under general anesthesia. Successful migration of contrast medium into the lymphatic vessels cranial to the popliteal lymph nodes was observed in all cats within 5 minutes after injection. The recommended dose of contrast medium to achieve TD enhancement was 1 mL/kg (0.5 mL/kg/pad; concentration, 350 mg of iodine/kg). Only 1 cat had mild swelling of the paws after the procedure, and it recovered quickly without pain medication; no cats experienced lameness. Similar to dogs and unlike in previously published reports, 72% of TD branches were located in the right hemithorax.
CLINICAL RELEVANCE
CT lymphangiography via intrametatarsal pad injection is a feasible and safe procedure for cats with chylothorax. This technique provides detailed information regarding the unique TD anatomy and cisterna chyli location. It also contributes to surgical planning.
Abstract
OBJECTIVE
To characterize the anatomic location of the esophageal ostium relative to the rima glottidis in adult Labrador Retrievers with the use of CT.
ANIMALS
98 CT scans of 75 adult Labrador Retrievers.
PROCEDURES
A search of the medical records database identified records of Labrador Retrievers that underwent CT of the head and neck between January 1, 2015, and December 31, 2018. Evaluators, blinded to each other's results, reviewed CT images and measured esophageal area at the level of the rima glottidis. For each dog, the left esophageal percentage (LEP) was calculated as the esophageal area left of the rima glottidis midline divided by the overall esophageal area at that level. Variables (age, sex, patient position, intubation status, and maxillary support during CT) were evaluated for association with LEP. The CT images of dogs that had multiple scans were assessed for within-patient variance.
RESULTS
Mean LEP was 56.2 ± 18.1% for all dogs. Only right lateral recumbency was significantly associated with LEP, with a lower LEP for dogs positioned in right lateral recumbency (42.4 ± 12.7%), compared with left lateral (63.0 ± 7.4%) or sternal (57.3 ± 18.8%) recumbency. No association was detected between LEP and other variables assessed. Eleven dogs had multiple CT scans; within-patient variance for LEP was ± 26.6%.
CONCLUSIONS AND CLINICAL RELEVANCE
Results indicated that, although most dogs had an LEP > 50%, the esophageal ostium was fairly centrally located in most dogs and may be more mobile than previously thought. Additional research is warranted to assess this mobility and whether the esophageal ostium location, relative to the larynx, affects the incidence of aspiration pneumonia in dogs undergoing surgical treatment for geriatric-onset laryngeal paralysis and polyneuropathy.
Abstract
OBJECTIVE
To compare shear-wave velocities (SWVs) with shear-wave elastography of various peripheral lymph nodes (LNs).
ANIMALS
11 healthy Beagles.
PROCEDURES
For each dog, bilateral mandibular, medial retropharyngeal, superficial cervical, axillary, superficial inguinal, and popliteal LNs were evaluated with shear-wave elastography in sagittal and transverse scanning planes. Depth of each lymph node was recorded, and intra- and interobserver reliability was determined.
RESULTS
SWVs for all LNs were significantly higher in the sagittal scanning plane, compared with those in the transverse scanning plane. The SWV of the most superficial LN, the mandibular LN, was significantly higher, compared with that for the other LNs, except for the medial retropharyngeal LN. The SWV of the deepest LN, the medial retropharyngeal LN, was as high as that for the mandibular LN. Intra- and interobserver reliability was excellent.
CONCLUSIONS AND CLINICAL RELEVANCE
SWVs for normal peripheral LNs of Beagles may serve as a reference to compare with those for other breeds and diseased LNs. Scanning plane, LN depth, and interfering tissues between the LN and the transducer may affect SWV. Shear-wave elastography may not be operator dependent.
Abstract
OBJECTIVE
To assess the diagnostic value of the ultrasonographic description of a splenic mass or nodule as cavitated in dogs with nontraumatic hemoabdomen.
ANIMALS
106 dogs with a nontraumatic hemoabdomen that underwent abdominal ultrasonography and splenectomy with histologic examination of splenic lesions between 2005 and 2018.
PROCEDURES
Medical records were reviewed for abdominal ultrasonographic and histologic findings. Diagnostic performance of ultrasonographic description of a splenic mass or nodule as cavitated as evidence of hemangiosarcoma or any malignancy was evaluated.
RESULTS
Ultrasonographic description of splenic lesions as cavitated had poor diagnostic utility in predicting presence of hemangiosarcoma or malignancy. Sensitivity and specificity of this test were 41.9% (95% CI, 30.5% to 54.3%) and 51.2% (95% CI, 36.8% to 65.4%), respectively, for detecting hemangiosarcoma, with positive and negative predictive values of 55.3% (95% CI, 41.2% to 68.6%) and 37.9% (95% CI, 26.6% to 50.8%), respectively. Results were similar for detecting malignancy. Cavitated lesions outside of the spleen were too rare for statistical analysis to be of value.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that relying on ultrasonographic description of cavitation to diagnose splenic lesions as malignant in dogs with nontraumatic hemoabdomen is unfounded. Other preoperative diagnostic tests may be more valuable in determining short- and long-term prognoses.
Abstract
OBJECTIVE
To describe the technique and assess the diagnostic potential and limitations of tomosynthesis for imaging of the metacarpophalangeal joint (MCPJ) of equine cadavers; compare the tomosynthesis appearance of pathological lesions with their conventional radiographic, CT, and MRI appearances; and evaluate all imaging findings with gross lesions of a given MCPJ.
SAMPLE
Distal portions of 4 forelimbs from 4 equine cadavers.
PROCEDURES
The MCPJs underwent radiography, tomosynthesis (with a purpose-built benchtop unit), CT, and MRI; thereafter, MCPJs were disarticulated and evaluated for the presence of gross lesions. The ability to identify pathological lesions on all images was assessed, followed by semiobjective scoring for quality of the overall image and appearance of the subchondral bone, articular cartilage, periarticular margins, and adjacent trabecular bone of the third metacarpal bone, proximal phalanx, and proximal sesamoid bones of each MCPJ.
RESULTS
Some pathological lesions in the subchondral bone of the third metacarpal bone were detectable with tomosynthesis but not with radiography. Overall, tomosynthesis was comparable to radiography, but volumetric imaging modalities were superior to tomosynthesis and radiography for imaging of subchondral bone, articular cartilage, periarticular margins, and adjacent bone.
CONCLUSIONS AND CLINICAL RELEVANCE
With regard to the diagnostic characterization of equine MCPJs, tomosynthesis may be more accurate than radiography for identification of lesions within subchondral bone because, in part, of its ability to reduce superimposition of regional anatomic features. Tomosynthesis may be useful as an adjunctive imaging technique, highlighting subtle lesions within bone, compared with standard radiographic findings.
Abstract
OBJECTIVE
To assess the feasibility of blood oxygen level–dependent (BOLD) MRI for measurement of the renal T2* relaxation rate (R2*; proxy for renal oxygenation) before and after furosemide administration and to evaluate the reliability and repeatability of those measurements in healthy dogs.
ANIMALS
8 healthy adult Beagles (4 males and 4 females).
PROCEDURES
Each dog was anesthetized and underwent BOLD MRI before (baseline) and 3 minutes after administration of furosemide (1 mg/kg, IV) twice, with a 1-week interval between scanning sessions. Mapping software was used to process MRI images and measure R2* and the difference in R2* (∆R2*) before and after furosemide administration. The intraclass correlation coefficient was calculated to assess measurement reliability, and the coefficient of variation and Bland-Altman method were used to assess measurement repeatability.
RESULTS
Mean ± SD baseline R2* in the renal medulla (24.5 ± 3.8 seconds−1) was significantly greater than that in the renal cortex (20.6 ± 2.7 seconds−1). Mean R2* in the renal cortex (18.6 ± 2.6 seconds−1) and medulla (17.8 ± 1.5 seconds−1) decreased significantly after furosemide administration. Mean ∆R2* in the medulla (6.7 ± 2.4 seconds−1) was significantly greater than that in the renal cortex (2.1 ± 0.7 seconds−1). All R2* and ∆R2* values had good or excellent reliability and repeatability, except the cortical ∆R2*, which had poor repeatability.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that BOLD MRI, when performed before and after furosemide administration, was noninvasive and highly reliable and repeatable for dynamic evaluation of renal oxygenation in healthy dogs.
Abstract
OBJECTIVE
To investigate the efficacy of a phospholipid-stabilized sulfur hexafluoride microsphere (SHM) contrast agent and water for hydrosonography of the upper portion of the gastrointestinal tract of dogs.
ANIMALS
12 healthy adult Beagles.
PROCEDURES
In a crossover study, each dog was anesthetized and underwent noncontrast ultrasonography then hydrosonography following administration of tap water (30 mL/kg) without (water method) or with SHM (0.1 mL; SHM method) via an orogastric tube. There were at least 3 days between hydro-sonographic procedures. Wall thickness, wall layer definition, conspicuity of the mucosal-luminal interface, and image quality were evaluated separately in the near and far fields for the gastric cardia, body, and pylorus and descending duodenum and compared among the 3 scanning methods.
RESULTS
Mean wall thickness measurements did not differ significantly between the water and SHM methods at any location except the far-field gastric cardia where the mean wall thickness for the SHM method was less than that for the water method. In general, the SHM method improved wall layer definition and conspicuity of the mucosal-luminal interface of structures in the near field, compared with noncontrast method. The water and SHM methods both resulted in superior image quality relative to the noncontrast method for the near-field gastric cardia, far-field gastric cardia, and far-field duodenum.
CONCLUSIONS AND CLINICAL RELEVANCE
Results indicated that, for dogs, gastrointestinal hydrosonography by use of the SHM method improved wall layer definition and mucosal conspicuity, particularly in near-field images of the upper portion of the gastrointestinal tract. (Am J Vet Res 2021;82:712–721)
