Canine hyperadrenocorticism (HAC) is one of the most common causes of general osteopenia. In this study, quantitative computed tomography (QCT) was used to compare the bone mineral densities (BMD) between 39 normal dogs and 8 dogs with HAC (6 pituitary-dependent hyperadrenocorticism [PDH]; pituitary dependent hyperadrenocorticism, 2 adrenal hyperadrenocorticism [ADH]; adrenal dependent hyperadrenocorticism) diagnosed through hormonal assay. A computed tomogaraphy scan of the 12th thoracic to 7th lumbar vertebra was performed and the region of interest was drawn in each trabecular and cortical bone. Mean Hounsfield unit values were converted to equivalent BMD with bone-density phantom by linear regression analysis. The converted mean trabecular BMDs were significantly lower than those of normal dogs. ADH dogs showed significantly lower BMDs at cortical bone than normal dogs. Mean trabecular BMDs of dogs with PDH using QCT were significantly lower than those of normal dogs, and both mean trabecular and cortical BMDs in dogs with ADH were significantly lower than those of normal dogs. Taken together, these findings indicate that QCT is useful to assess BMD in dogs with HAC.

. The aim of this study was to assess age-related changes and anatomic variation in trabecular bone mineral density (tBMD) using quantitative computed tomography (QCT) in normal cats. Seventeen normal cats were included in this study and divided into the following 3 age groups:<6 months (n=4), 2-5 years (n=10) and >6 years (n=3). A computed tomographic scan of each vertebra from the 12th thoracic to the 7th lumbar spine and the pelvis was performed with a bone-density phantom (50, 100 and 150 mg/cm 3 , calcium hydroxyapatite, CIRS phantom ® ). On the central transverse section, the elliptical region of interest (ROI) was drawn to measure the mean Hounsfield unit (HU) value. Those values were converted to equivalent tBMD (mg/cm 3 ) by use of the bone-density phantom and linear regression analysis (r 2 >0.95). The mean tBMD value of the thoracic vertebrae (369.4 ± 31.8 mg/cm 3 ) was significantly higher than that of the lumbar vertebrae (285 ± 58.1 mg/cm 3 ). The maximum tBMD occurred at the T12, T13 and L1 levels in all age groups. There was a statistically significant difference in the mean tBMD value among the 3 age groups at the T12 (P<0.001), T13 (P<0.001) and L4 levels (P=0.013), respectively. The present study suggests that age-related changes and anatomic variation in tBMD values should be considered when assessing tBMD using QCT in cats with bone disorders. KEY WORDS: bone mineral density, feline, quantitative computed tomography, trabecular bone. doi: 10.1292/jvms.11-0579; J. Vet. Med. Sci. 74(11): 1461-1467, 2012 Bone mineral density (BMD) decreases in accordance with normal aging and metabolic or systemic disease. The turnover rates for cancellous bone are 4 to 8 times greater than for cortical bone, so cancellous bone is more sensitive to disease-induced changes [25]. Therefore, in humans with osteoporosis, BMD has been primarily investigated in cancellous bone.On the basis of this relationship, several techniques have been developed to noninvasively measure bone mineralization at various skeletal sites. These include radioabsorptiometry (RA), single photon absorptiometry (SPA), dual photon absorptiometry (DPA), quantitative ultrasound (QUS), dual-energy x-ray absorptiometry (DEXA), quantitative computed tomography (QCT) and peripheral QCT (pQCT). Among these, DEXA, QCT and pQCT have become the established methods for evaluating skeletal status, assessing osteoporosis, determining fracture risk and monitoring metabolic diseases and therapies in humans [8,[10][11][12][13].Feline diseases affecting BMD include mucopolysaccharidosis, osteopetrosis, osteogenesis imperfect and osteopenia related to primary hyperparathyroidism and secondary to renal or nutritional hyperparathyroidism. Reports in cats have been limited to the studies for BMD evaluation using DEXA [17] and a few peer-reviewed studies that measured BMD in clinically normal cats and abnormal cats using DEXA [3,23]. DEXA has been accepted as the gold standard method of BMD measurement, and it requires less X-ray exposure for the patient...

Caudal pulmonary artery diameter (CPAD) to body surface area (BSA) ratios were measured in ventrodorsal thoracic radiographs to assess the correlation between CPAD to BSA ratios and systolic pulmonary arterial pressure (PAP) in dogs. Thoracic radiographs of 44 dogs with systolic pulmonary arterial hypertension (PAH) and 55 normal dogs were evaluated. Systolic PAP was estimated by Doppler echocardiography. CPADs were measured at their largest point at the level of tracheal bifurcation on ventrodorsal radiographs. Both right and left CPAD to BSA ratios were significantly higher in the PAH group than in the normal group (p < 0.0001). Linear regression analysis showed positive associations between PAP and right and left CPAD to BSA ratio (right, p = 0.0230; left, p = 0.0012). The receiver operating characteristic curve analysis revealed that the CPAD to BSA ratio had moderate diagnostic accuracy for detecting PAH. The operating point, sensitivity, specificity, and area under the curve were 28.35, 81.40%, 81.82%, and 0.870; respectively, for the right side and 26.92, 80.00%, 66.67%, and 0.822, respectively, for the left. The significant correlation of CPAD to BSA ratio with echocardiography-estimated systolic PAP supports its use in identifying PAH on survey thoracic radiographs in dogs.

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