ANATOMY OF THE PORTAL AND HEPATIC VEINS OF THE DOG: A BASIS FOR SYSTEMATIC EVALUATION OF THE LIVER BY ULTRASONOGRAPHY

The objective of this study was to define, in detail, the anatomy of the portal and hepatic veins in the dog in order to establish a procedure for the systematic evaluation of the liver by ultrasonography. Anatomical details were obtained from the formalin fixed livers of ten dogs. The hepatic and portal veins were removed intact from these livers so that a detailed pattern of distribution could be established and the numbers of branches could be counted. Silastic casts were also made of the hepatic and portal veins of two livers, one in situ and one in which it had been removed. The former was to enable the relationship of the portal to the hepatic veins to be established as closely as possible within the animal and the other to provide a model of the distribution of each venous system within the liver. Contrast medium was infused into two other livers and radiographs taken to establish the relationship of each branch to each lobe. It was found that there was a consistent pattern of venous branching to each lobe of the liver in the dog with little variation between individual specimens. All liver lobes contained definite venous branches so that the left lateral and medial, quadrate, right medial and lateral, caudate and papillary veins could be distinguished in each venous system. We believe that an appreciation of this venous distribution will aid in the systematic evaluation of the liver during ultrasonography by enabling identification of each liver lobe. It should be of value for differentiating portal from hepatic veins and veins from dilated bile ducts.     

A REVIEW OF HIGH RESOLUTION COMPUTED TOMOGRAPHY AND A PROPOSED TECHNIQUE FOR REGIONAL EXAMINATION OF THE CANINE LUMBOSACRAL SPINE

High resolution computed tomography (CT) is a noninvasive imaging modality that has been used extensively in evaluating diseases of the human lumbosacral spine. Excellent spatial and contrast resolution, combined with multiplanar reformatting capability make high resolution CT scanners well-suited for similar applications in dogs. Consistently good quality images can be obtained when careful attention is given to factors affecting resolution. This paper reviews and illustrates some principles of high resolution CT, and proposes a technique for regional CT examination of the canine lumbosacral spine.     

COMPARISON OF SPIN ECHO, GRADIENT ECHO AND FAT SATURATION MAGNETIC RESONANCE IMAGING SEQUENCES FOR IMAGING THE CANINE ELBOW

Two comparison studies were performed. In the first conventional spin-echo (T1- and T2-weighted) sequences and a three-dimensional (3-D Fourier transform [3DFT]) echo gradient fast-imaging sequence were compared for imaging the canine normal elbow joint. In all three sequences, there was an isointense signal of the articular cartilage and a hyposignal of the subchondral bone, as compared with the muscles. The medial coronoid process of the ulna was clearly seen on the dorsal plane images, it appeared with a homogenous low-intensity signal. Its articulation with the radius was clearly outlined. In a second study, the 3DFT echo gradient fast-imaging sequence was compared to a fat saturation sequence on normal shoulder and elbow joints. Elbows were imaged with and without injection of saline, in an attmept to show the opposing cartilaginous articular surfaces. This distinction was possible in the shoulder joint but not in the elbow because of insufficient spatial resolution. On the three MRI sequences compared, gradient echo fast imaging with steady-state precession (GE FISP) sequence was found to be the most suitable for imaging the canine elbow joint.     

USE OF CONTRAST-ENHANCED COMPUTED TOMOGRAPHY TO ASSESS ANGIOGENESIS IN DEEP DIGITAL FLEXOR TENDONOPATHY IN A HORSE

We compared contrast-enhanced computed tomography (CT) and high field magnetic resonance (MR) imaging in a horse with deep digital flexor tendonopathy. Lesions in the distal extremity were documented grossly and histopathologically. In contrast-enhanced CT, the deep digital flexor tendon lesions were markedly contrast enhancing with evidence of angiogenesis in the core and dorsal border lesions. The lesion morphology was clearly delineated on MR imaging, but without contrast media angiogenesis cannot be identified. Gross examination, histopathologic examination, and CD31 immunohistochemistry confirmed the tendonopathy and an increased presence of small blood vessels. In this horse, deep digital flexor tendon lesions appeared similarly on contrast-enhanced CT and MR imaging. Contrast-enhanced CT may be an alternative to MR imaging for assessing tendon and ligament injury in the digit of the horse.     

THE USE OF SMALL FIELD‐OF‐VIEW 3 TESLA MAGNETIC RESONANCE IMAGING FOR IDENTIFICATION OF ARTICULAR CARTILAGE DEFECTS IN THE CANINE STIFLE: AN EX VIVO CADAVERIC STUDY

Noninvasive identification of canine articular cartilage injuries is challenging. The objective of this prospective, cadaveric, diagnostic accuracy study was to determine if small field‐of‐view, three tesla magnetic resonance imaging (MRI) was an accurate method for identifying experimentally induced cartilage defects in canine stifle joints. Forty‐two canine cadaveric stifles (n = 6/group) were treated with sham control, 0.5, 1.0, or 3.0 mm deep defects in the medial or lateral femoral condyle. Proton density‐weighted, T1‐weighted, fast‐low angle shot, and T2 maps were generated in dorsal and sagittal planes. Defect location and size were independently determined by two evaluators and compared to histologic measurements. Accuracy of MRI was determined using concordance correlation coefficients. Defects were identified correctly in 98.8% (Evaluator 1) and 98.2% (Evaluator 2) of joints. Concordance correlation coefficients between MRI and histopathology were greater for defect depth (Evaluator 1: 0.68–0.84; Evaluator 2: 0.76–0.83) compared to width (Evaluator 1: 0.30–0.54; Evaluator 2: 0.48–0.68). However, MRI overestimated defect depth (histopathology: 1.65 ± 0.94 mm; Evaluator 1, range of means: 2.07–2.38 mm; Evaluator 2, range of means: 2–2.2 mm) and width (histopathology: 6.98 ± 1.32 mm; Evaluator 1, range of means: 8.33–8.8 mm; Evaluator 2, range of means: 6.64–7.16 mm). Using the paired t‐test, the mean T2 relaxation time of cartilage defects was significantly greater than the mean T2 relaxation time of adjacent normal cartilage for both evaluators (P < 0.0001). Findings indicated that MRI is an accurate method for identifying cartilage defects in the cadaveric canine stifle. Additional studies are needed to determine the in vivo accuracy of this method.     

COMPARISON OF THE IMAGE QUALITY OF A HIGH‐RESOLUTION SCREEN–FILM SYSTEM AND A DIGITAL FLAT PANEL DETECTOR SYSTEM IN AVIAN RADIOGRAPHY

A conventional high‐resolution screen–film system was compared with a digital detector system. A total of 20 birds (14 pigeons and six psittacine birds) with an average body mass of 533 g were examined in dorsoventral as well as lateral projections. Digital radiographs were acquired with the same mAs as well as half the mAs used for the conventional radiographs. Three criteria and one overall assessment were defined for each of four anatomic regions and assessed by five veterinarians using a score system. Comparison of the ratings was done by visual grading analysis. For the majority of criteria, there was no significant difference regarding image quality between the digital and screen–film projections. However, for certain criteria the quality of the digital images was significantly superior. Using the same mAs as for the conventional radiographs, the humeral joint surfaces and the honeycomb structure of the lung were assessed as superior with the digital imaging system. The tracheal rings and the delineation of the trachea from the surrounding tissue were also superior with the digital system. Assessment of the trabecular structure of the humerus was superior when the full mAs was used compared with the reduced mAs. In conclusion the digital technique is equal or superior to the conventional screen–film high‐resolution system for pet birds of a medium size. With some limitations, a dose reduction is possible with the digital system.     

IOHEXOL AND IOPAMIDOL MYELOGRAPHY IN THE DOG: A CLINICAL TRIAL COMPARING ADVERSE EFFECTS AND MYELOGRAPHIC QUALITY

In a blind clinical trial, adverse effects after iohexol and iopamidol myelography were evaluated in 151 dogs. Eighty-one dogs were given iohexol (240 mgI/ml) and 70 dogs were given iopamidol (200 mgI/ml) by pre-determined assignment. Each dog was evaluated postmyelographically for seizures, hyperthermia, prolonged recovery from anesthesia and intensification of pre-existing neural signs. Myelographic quality was evaluated with a subjective scoring method. In comparing iohexol and iopamidol groups, there was not a statistically significant difference in the incidence of adverse effects or in myelographic quality. Iopamidol and iohexol appeared to be equally efficacious for routine canine myelography.     

The diagnosis of lameness associated with distal limbpathology in a horse: A comparison of radiography, computed tomography and magnetic resonance imaging

A cadaver limb from an eight-year-old horse with right forelimb lameness that was relieved with an intra-articular distal interphalangeal joint block was imaged with radiographs, spiral computed tomography (CT) and magnetic resonance imaging (MRI). Spiral CT demonstrated several lucencies within the deep digital flexor tendon immediately proximal to the navicular bone. On MRI these areas had increased signal and there was enlargement of the tendon at this site. Effusion in the proximal interphalangeal joint and navicular bursa and thinning of the fibrocartilage of the navicular bone were also observed on MRI images. These changes were not detected on radiographs. Histopathology confirmed that there were focal areas of collagen necrosis within the deep digital flexor tendon with thinning and degenerative changes in the fibrocartilage of the navicular bone.     

建立人工草地是维护陕北黄土高原生态平衡和发展畜牧业的战略措施

本文通过陕北草地资源的遥感调查,并结合该地区的生态变迁及畜牧业发展的历史与现状的资料分析研究认为,各种优良牧草具有分蘖力强,地面郁闭度大;根量大,在土层内能积聚大量有机物质;产量高,质量好等特点。因而在这里建立人工草地是保持水土,恢复生态平衡和发展畜牧业的战略措施。与此同时,还要处理好保护资源与开发利用、经济效益与生态效益和农牧林业之间的三个关系。     

A COMPARISON OF PULMONARY ANGIOGRAPHY, DIGITAL SUBTRACTION ANGIOGRAPHY, AND 99mTc-DTPA/MAA VENTILATION-PERFUSION SCINTIGRAPHY FOR DETECTION OF EXPERIMENTAL PULMONARY EMBOLI IN THE DOG

The abilities of pulmonary angiography, digital subtraction angiography and ventilation-perfusion scintigraphy (V/Q) to detect experimental acute pulmonary emboli were evaluated in a group of 18 research dogs. Emboli were produced by forceful intravenous injection of clotted blood. In five dogs, emboli were labeled with thallium-201 prior to reinjection so that embolus position could be confirmed on scintigraphic studies.
Studies were independently reviewed by three observers. Results were combined so that the relative sensitivity, specificity, and accuracy of each imaging technique could be compared using chi-square and receiver-operating characteristic curve analysis. Digital subtraction angiography and V/Q studies proved to be significantly more specific and accurate than conventional pulmonary angiography. V/Q studies were uniformly of good to excellent quality while the quality of digital subtraction angiography studies was variable depending on the adverse effects of respiratory motion. It was concluded that ventilation-perfusion scintigraphy is the best available method to screen dogs suspected of having pulmonary thromboembolism.     

IRIDIUM-192: A LITERATURE REVIEW FOR FURTHER REFERENCING THE ISOTOPE, ITS ACTIVITY UNITS, AND DOSIMETRY TECHNIQUES

The individual embarking on an iridium-192 brachytherapy program is faced with an abundance of concepts, terms and dosimetry techniques. This article introduces the beginning brachytherapist to the basic physical parameters of iridium-192, to the potential units for source strength and to the general concepts of the various dosimetry techniques. Multiple literature references are listed for more in-depth study.     

A NEW DEVICE FOR STEREOTACTIC CT-GUIDED BIOPSY OF THE CANINE BRAIN: DESIGN, CONSTRUCTION, AND NEEDLE PLACEMENT ACCURACY

An inexpensive device was created for computed tomographic (CT)-guided stereotactic biopsy of the canine brain. The accuracy of the device was tested using 16, formalin-perfused, canine head specimens. For each dog, a 6-inch biopsy needle was guided into pituitary gland and caudate nucleus targets. Needle tracks were measured using the CT computer and infused with tissue staining solution. Hit success and actual needle track lengths were determined from sliced brain specimens. The device enabled accurate orientation and placement of the canine head in the slice plane, such that progressive penetration of the biopsy needle could be monitored. The caudate nucleus was hit 12/16 times (75% accuracy) and the pituitary gland 15.5/16 times (98.6% accuracy). Hit proportions for the two targets did not differ (P < 0.05). A significant difference was found between CT and actual track length for both targets (P < 0.01). This was attributed to incomplete staining of the bevel portion of the needle track.     

ULTRASONOGRAPHIC EVALUATION OF EQUINE TENDONS: A QUANTITATIVE IN VITRO STUDY OF THE EFFECTS OF AMPLIFIER GAIN LEVEL, TRANSDUCER-TILT, AND TRANSDUCER-DISPLACEMENT

The objective of the in vitro experiments described in this paper was to quantify the effects of some instrumental variables on the quantitative evaluation, by means of first-order gray-level statistics, of ultrasonographic images of equine tendons. The experiments were done on three isolated equine superficial digital flexor tendons that were mounted in a frame and submerged in a waterbath. Sections with either normal tendon tissue, an acute lesion, or a chronic scar, were selected. In these sections, the following experiments were done: 1) a gradual increase of total amplifier gain output subdivided in 12 equal steps; 2) a transducer tilt plus or minus 3 degrees from perpendicular, with steps of 1 degree; and 3) a transducer displacement along, and perpendicular to, the tendon long axis, with 16 steps of 0.25 mm each. Transverse ultrasonographic images were collected, and in the regions of interest (ROI) first-order gray-level statistics were calculated to quantify the effects of each experiment. Some important observations were: 1) the total amplifier gain output has a substantial influence on the ultrasonographic image; for example, in the case of an acute lesion, a low gain setting results in an almost completely black image; whereas, with higher gain settings, a marked "filling in" effect on the lesion can be observed; 2) the relative effects of the tilting of the transducer are substantial in normal tendon tissue (18%) and chronic scar (12%); whereas, in the event of an acute lesion, the effects on the mean gray level are dramatic (40%); and 3) the relative effects of displacement of the transducer are small in normal tendon tissue, but on the other hand, the mean gray-level changes 7% in chronic scar, and even 20% in an acute lesion. In general, slight variations in scanner settings and transducer handling can have considerable effects on the gray levels of the ultrasonographic image. Furthermore, there is a strong indication that this quantitative method, as far as based exclusively on the first-order gray-level statistics, may be not discriminative enough to accurately assess the integrity of the tendon. Therefore, the value of a quantitative evaluation of the first-order gray-level statistics for the assessment of the integrity of the equine tendon is questionable.     

A NOVEL,REMOVABLE, CERROBEND,BEAM‐BLOCKING DEVICE FOR RADIATION THERAPY OF THE CANINE HEAD AND NECK: PILOT STUDY

Radiation therapy of the head and neck can result in mucositis and other acute affects in the oral cavity. This prospective pilot study evaluated a novel, intraoral, beam‐blocking device for use during imaging and therapeutic procedures. The beam‐blocking device was made from a metal alloy inserted into a coated frozen dessert mold (Popsicle® Mold, Cost Plus World Market, Oakland, CA). The device was designed so that it could be inserted into an outer shell, which in turn allowed it to be placed or removed depending on the need due to beam configuration. A Farmer type ionization chamber and virtual water phantom were used to assess effects of field size on transmission. Six large breed cadaver dogs, donated by the owner after death, were recruited for the study. Delivered dose at the dorsal and ventral surfaces of the device, with and without the alloy block in place, were measured using radiochromic film. It was determined that transmission was field size dependent with larger field sizes leading to decreased attenuation of the beam, likely secondary to scatter. The mean and median transmission on the ventral surface without the beam‐blocking device was 0.94 [range 0.94–0.96]. The mean and median transmission with the beam‐blocking device was 0.52 [range 0.50–0.57]. The mean and median increase in dose due to backscatter on the dorsal surface of the beam‐blocking device was 0.04 [range 0.02–0.04]. Findings indicated that this novel device can help attenuate radiation dose ventral to the block in dogs, with minimal backscatter.