Technical characterization of five x-ray detectors for paediatric radiography applications.

Physical image quality of five x-ray detectors used in the paediatric imaging department is characterized with the aim of establishing the range/scope of imaging performance provided by these detectors for neonatal imaging. Two computed radiography (CR) detectors (MD4.0 powder imaging plate (PIP) and HD5.0 needle imaging plate (NIP), Agfa HealthCare NV, B-2640 Mortsel, Belgium) and three flat panel detectors (FPD) (the Agfa DX-D35C and DX-D45C and the DRX-2530C (Carestream Health Inc., Rochester, NY 14608, USA)) were assessed. Physical image quality was characterized using the detector metrics given by the International Electrotechnical Commission (IEC 62220-1) to measure modulation transfer function (MTF), the noise power spectrum (NPS) and the detective quantum efficiency (DQE) using the IEC-specified beam qualities of RQA3 and RQA5. The DQE was evaluated at the normal operating detector air kerma (DAK) level, defined at 2.5 µGy for all detectors, and at factors of 1/3.2 and 3.2 times the normal level. MTF curves for the different detectors were similar at both RQA3 and RQA5 energies; the average spatial frequency for the 50% point (MTF0.5) at RQA3 was 1.26 mm-1, with a range from 1.20 mm-1 to 1.37 mm-1. The DQE of the NIP CR compared to the PIP CR was notably greater and similar to that for the FPD devices. At RQA3, average DQE for the FPD and NIP (at 0.5 mm-1; 2.5 µGy) was 0.57 compared to 0.26 for the PIP CR. At the RQA5 energy, the DRX-2530C and the DX-D45C had the highest DQE (~0.6 at 0.5 mm-1; 2.5 µGy). Noise separation analysis using the polynomial model showed higher electronic noise for the DX-D35C and DRX-2530C detectors; this explains the reduced DQE seen at 0.7 µGy/image. The NIP CR detector offers notably improved DQE performance compared to the PIP CR system and a value similar to the DQE for FPD devices at the RQA3 energy.

Dual-chamber pacemaker implantation via the cephalic vein in healthy equids.

The purpose of the present study was to develop a feasible and safe technique for dual-chamber pacemaker implantation in healthy horses. Implantation was performed in a standing, tranquilized horse and in ponies. Atrial and ventricular leads were transvenously inserted through the cephalic vein, and a subcutaneous pacemaker pocket was created between the lateral pectoral groove and the manubrium sterni in 6 equids. Positioning of each lead was guided by echocardiography and by measuring the electrical characteristics of the lead. The implantation procedure lasted about 4 hours in each animal and was well tolerated. In all animals, dual-chamber pacemaker function was obtained, and these results remained good throughout the follow-up period. At the time of implantation, atrial and ventricular sensing were between 2.1 and 7.2 mV and 7.8 and 16.8 mV, respectively, and atrial and ventricular pacing thresholds at 0.5 millisecond varied from 0.5 to 0.7 V and from 0.3 to 1.0 V, respectively. Six months after the implantation, sensing values varied from 2 to 10 mV for the atrial lead and from 2 to 16 mV for the ventricular lead, while pacing thresholds at 0.5 millisecond varied from less than 0.5 to 2.5 V for the right atrium and from less than 0.5 to 5.0 V for the right ventricle. Atrial lead dislodgment occurred in 2 animals, requiring insertion of a new lead. Ventricular lead dislodgment was not observed.

Radiographic, computed tomographic and arthroscopic findings in 23 dogs with osteochondrosis of the tarsocrural joint.

Twenty-three dogs with osteochondrosis of the tarsocrural joint were evaluated by radiography, computed tomography (CT) and arthroscopy. The radiographic examination included an extended and flexed mediolateral, a plantarodorsal, a flexed dorsoplantar skyline view, and a plantaromedial-dorsolateral and a plantarolateral-dorsomedial view (two oblique views). The CT examination was carried out in ventral recumbency and 1 mm slices were taken with a bone window setting; 31 lesions were identified in the 46 joints examined. The arthroscopic exploration used either a plantar or a dorsal puncture, depending on the site of the lesion. In six cases the lateral, and in 17 cases the medial trochlear ridge was involved. Although the survey radiographs were sufficient to make a diagnosis, the CT examination helped to determine the exact site, and the number and size of the fragments of bone. A four-stage classification system comparable to the one used in man was established. Arthroscopy provided information about synovial inflammation and damage to the joint cartilage, and made it possible to remove fragments of bone from one-third of the cases.

A comparison of the palmaroproximal-palmarodistal view of the isolated navicular bone to other views.

A collection of 69 isolated navicular bones, normal or affected with navicular disease, was examined radiographically using dorsopalmar, lateromedial and palmaroproximal-palmarodistal views. Radiographic findings on each view were recorded. A radiographic diagnosis of normality or navicular disease was made, first on each view separately and afterwards based on the combination of the 3 views. Forty-four navicular bones were considered radiographically normal and 25 navicular bones had distinct signs of radiographic navicular disease. The dorsopalmar and the lateromedial views of each navicular bone were assessed together and compared with the palmaroproximal-palmarodistal view. In not a single bone was the palmaroproximal-palmarodistal view considered indispensable to make the final diagnosis.