Eva González Pérez

Mast cell tumors (MTCs) are a common splenic neoplasia in cats, although their ultrasonographic characteristics have been reported to be nonspecific and overlap with those of other proliferative diseases. The objective of this study was to describe ultrasonographic findings of the spleen and metastatic sites in a large cohort of cats with cytologically or histopathologically confirmed primary or disseminated splenic involvement by MCTs with high-frequency transducers, and to determine whether specific ultrasonographic characteristics could be identified. Cats with available ultrasonographic images and cytological or histological confirmation of splenic involvement by MCTs were retrospectively included in a multicenter study. Forty-one cats met the inclusion criteria. A linear transducer was used for the majority of cats (80%). Splenic abnormalities were identified in 85% of cats. The most common finding was diffuse splenomegaly (63%) with irregular margins (46%) and homogeneously hypoechoic parenchyma (24%). Specific patterns were uncommon, with a reticulonodular pattern present in 27% and a marbled appearance in 12% of cats. Discrete nodular lesions or masses were present in 44%. The liver was sampled in 66% of cats, and hepatic disseminated disease was confirmed in 59%; however, the liver was ultrasonographically normal in the majority of those cases. For the cats with hepatic MCTs and ultrasonographic abnormalities, diffuse hepatomegaly with abnormal echogenicity or echotexture was observed. Lymph node metastasis was confirmed in 20% of cats. Only one cat had confirmed gastrointestinal involvement by MCTs, and gastrointestinal ulceration was ultrasonographically noted in 7% of cats. In conclusion, to the authors’ knowledge, this is the largest study describing findings in splenic MCTs in which images were acquired predominantly using a high-frequency linear transducer. Nonspecific ultrasonographic splenic changes were associated with this disease. A normal ultrasonographic spleen or liver did not exclude mast cell tumor (MCT) involvement. Cytology or histopathology remains warranted when an MCT is suspected, particularly in the presence of splenomegaly in combination with suspicion of disseminated disease and a cutaneous MCT. Lymph node metastasis, gastrointestinal involvement by MCTs, and gastrointestinal ulceration were uncommon findings.

This study evaluated three computed tomography (CT)‐based automatic fat segmentation methods and identified the optimal regression model for predicting whole‐body fat in rabbits. CT scans were performed on 21 postmortem companion rabbits to estimate fat percentage (Fat%‐CT) and fat volume (FV‐CT, mm ³ ). Two techniques were used to determine CT number (Hounsfield units [HU]) ranges for fat (HU Ranges 1 and 2). These were applied to four body regions using three voxel counting techniques (one‐, two‐, and three‐dimensional techniques) to quantify Fat%‐CT and FV‐CT. Data from whole‐body chemical carcass analysis (whole‐body Fat% and whole‐body fat in grams) were used as gold standard values. The relationship between the extracted CT data and carcass fat estimates was determined using a Spearman rank correlation. Simple linear regression and assumption tests were performed to identify the best model for predicting whole‐body Fat%, and whole‐body fat (g). There was a high correlation between measured fat estimated by CT and by chemical carcass analysis ( r _s > 0.7, p < 0.001) for all but one body region—counting combination. The best model predicting whole‐body Fat% used CT data from left kidney region, HU Range 2, and three‐dimensional counting technique. The optimal model predicting whole‐body fat (g) used CT data from the entire abdominal region, HU Range 1, and a one‐dimensional counting technique. The CT‐based models for estimating whole‐body fat in rabbits are feasible. Model optimization requires appropriate selection of the body region, CT number ranges, and counting techniques.