Development and feasibility of new cardiac measurement method using vertebral heart area ratio in dogs.

The vertebral heart scale (VHS) is the most common method used for the objective evaluation of heart size, however, VHS cannot evaluate the entire heart area. This retrospective study aimed to evaluate the development and feasibility of vertebral heart area ratio (VHAR=heart area/the fourth thoracic vertebra [T4] body area) as a new cardiac measurement method. A total of 125 dogs considered without clinical heart abnormalities in the pre-anesthetic examination, measurements of the VHS and VHAR using thoracic radiography were compared with computed tomography measurements of the vertebral cardiac volume ratio (VCVR=cardiac volume/T4 body volume) and investigate whether the VHAR values differed between observers. The mean cardiac and T4 body volumes were 116.99 ± 108.07 cm3 and 0.92 ± 0.91 cm3, respectively. The mean values of observers 1 and 2 were 9.9 ± 0.7 v (VHS), 42.64 ± 27.94 cm2 (heart area), and 1.37 ± 0.96 cm2 (T4 body area). Intraclass coefficients were the highest for the heart area, followed by the T4 body area and VHS. The VHAR showed a moderate correlation with VHS in observers 1 (r=0.671) and 2 (r=0.633). The VCVR showed a more positive correlation with VHAR (r=0.573) than with VHS (r=0.426). These results indicated that VHAR could be used as a complement to VHS for heart size measurement, and the high degree of observer agreement for the measurements indicated the measurement reproducibility of VHAR.

Single-slab 3D double inversion recovery for magnetic resonance brain imaging in clinically healthy dogs.

Introduction: In veterinary medicine, magnetic resonance imaging (MRI) is widely utilized for brain imaging. But the complex structures of brain tissues can give rise to artifacts such as partial volume averaging in conventional sequences. To address this issue, several studies about double inversion recovery (DIR) sequences have been conducted in human medicine. However, published clinical studies about brain MRI using DIR sequences in dogs are currently lacking. The purpose of this study was to evaluate the magnetic resonance features of single-slab 3D DIR sequences in the normal canine brain. Methods: Five healthy Beagle dogs were examined and the following pulse sequences were acquired for each: (1) spin-echo T2-weighted (T2W), (2) fluid attenuated inversion recovery (FLAIR), (3) gray matter (GM) selective, and (4) white matter (WM) selective single-slab 3D DIR sequence. For qualitative analysis, the distinction between gray and white matter of the cerebral cortex, presence and severity of the image artifacts were assessed for each pulse sequence. In addition, reconstructed images of single-slab 3D DIR sequences were qualitatively evaluated. For quantitative analysis, contrast ratios (CRs), signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs) of the GM, WM and cerebrospinal fluid (CSF) were measured for each pulse sequence. Results and Discussion: GM selective 3D DIR was superior to T2W and FLAIR in delineating the boundaries between GM and WM in the overall brain area. Whereas WM selective 3D DIR provided better gray-white matter distinction of the cerebral cortex than T2W and FLAIR at the level of the medulla oblongata, where T2W and FLAIR images exhibited severe partial volume averaging artifacts. In general, the 3D DIR images demonstrated fewer artifacts compared to other sequences, and the reconstructed sagittal and dorsal images of these sequences maintained same spatial resolution as the original transverse images without any image degradation. Both gray and white matter selective 3D DIR sequences effectively suppressed unwanted signals, thereby providing high contrast between gray and white matter. Findings from this study could serve as a foundation for further studies on DIR sequences for the evaluation of brain diseases in dogs.

Shoulder magnetic resonance arthrography in dogs: Comparison of craniolateral and caudolateral approach for ultrasound-guided contrast injection.

Shoulder joint disease is a common cause of forelimb lameness in dogs. To diagnose this condition, shoulder magnetic resonance arthrography (MRA) is performed, which involves the injection of contrast agents into the shoulder joint space under ultrasound (US)-guidance. The objective of this study was to compare the craniolateral and caudolateral approaches for shoulder MRA using US-guided injection techniques, and investigate their clinical feasibility in dogs. Forty shoulder joints from 10 adult beagles were studied in two repetitions. The craniolateral (n = 20) and caudolateral (n = 20) injection techniques were applied randomly under US-guidance. The shoulder MRA was conducted immediately after the contrast agents was injected. The procedure time (scan and injection time), number of attempts, joint distension and degree of extraarticular extravasation were recorded and compared between the two groups. The results showed that the caudolateral approach had significantly more contrast agents extravasation compared to the craniolateral approach (p < 0.05). However, there were no significant differences between the two groups in terms of procedure time (scan time p = 0.80, injection time p = 0.74), number of attempts (p = 0.70) and joint distension (p = 0.23). The craniolateral approach of US-guided contrast injection techniques for shoulder MRA minimizes damage to the juxta-articular structures and reduces extraarticular extravasation, resulting in good-quality images. This study demonstrates the feasibility and advantages of the craniolateral approach under US-guidance for shoulder MRA in dogs.

Respiratory phase can affect pulmonary vein-to-pulmonary artery ratio measured with CT.

OBJECTIVE: To evaluate pulmonary vein (PV)-to-pulmonary artery (PA) ratios obtained in healthy dogs by means of various CT protocols, accounting for the effects of the respiratory phase and contrast agent used. ANIMALS: 10 healthy Beagles. PROCEDURES: Before and after contrast medium (600 mg iodine/kg) was injected IV, thoracic CT was performed with a positive-pressure breath-hold (inspiratory phase) and at the end of expiration (expiratory phase). After CT scanning, echocardiography was performed, and an optimized right parasternal long-axis view was obtained for measurement of PV and PA diameters. The PV and PA diameters were measured subsequently for each CT protocol. RESULTS: Mean ± SD PV:PA values obtained from pre- and postcontrast inspiratory CT were 1.058 ± 0.072 and 1.020 ± 0.053, respectively, which were comparable to the echocardiographic value (P > .05). Mean PV:PA values obtained with pre- and postcontrast expiratory CT were 1.259 ± 0.094 and 1.239 ± 0.066, respectively, which were significantly (P = .005) greater than inspiratory CT measurements. There was a significant (r > 0.5, P < .05) linear relationship between PV:PA values obtained with pre- and postcontrast inspiratory CT and echocardiography. CLINICAL RELEVANCE: PV:PA could be measured with thoracic CT in a manner similar to that for echocardiography. However, PV:PA values measured with expiratory CT were different from previously reported values. Therefore, the respiratory phase should be considered when evaluating pulmonary vascular size through CT, and measurements with the inspiratory CT protocol would be more accurate.