A 200 CENTIMETER FOCAL SPOT-FILM DISTANCE (FFD) TECHNIQUE FOR EQUINE THORACIC RADIOGRAPHY

The construction of a variable kVp, variable mA radiographic technique chart for the equine thorax using linear regression analysis is described. The independent variables in the analysis were body weight (pounds) and thoracic girth (inches) and the dependent variables were the radiographic exposure techniques (mAs, kV.p). Four areas (lateral views only) of each horse's thorax were radiographed using a focal spot-film distance (FFD) of 200 cm with the animal standing. The four views were craniodorsal, cranioventral, caudodorsal and caudoventral. For comparison, an additional caudodorsal view was made at 100 cm FFD to quantitate the decrease in exposure, the increased magnification and the decreased area of the lung exposed on the x-ray tube side of the horse compared with 200 cm FFD technique. Body weight was a satisfactory means to determine radiographic technique factors for thoracic radiographs in the horse. Thoracic girth (inches) was also measured and used to determine radiographic technique factors but was less exacting and less convenient than body weight.     

Comparative evaluation of six different body regions of the dog using analog and digital radiography

In this study the quality of digital and analog radiography in dogs was compared. For this purpose, three conventional radiographs (varying in exposure) and three digital radiographs (varying in MUSI-contrast [MUSI = MUlti Scale Image Contrast], the main post-processing parameter) of six different body regions of the dog were evaluated (thorax, abdomen, skull, femur, hip joints, elbow). The quality of the radiographs was evaluated by eight veterinary specialists familiar with radiographic images using a questionnaire based on details of each body region significant in obtaining a radiographic diagnosis. In the first part of the study the overall quality of the radiographs was evaluated. Within one region, 89.5% (43/48) chose a digital radiograph as the best image. Divided into analog and digital groups, the digital image with the highest MUSI-contrast was most often considered the best, while the analog image considered the best varied between the one with the medium and the one with the longest exposure time. In the second part of the study, each image was rated for the visibility of specific, diagnostically important details. After summarisation of the scores for each criterion, divided into analog and digital imaging, the digital images were rated considerably superior to conventional images. The results of image comparison revealed that digital radiographs showed better image detail than radiographs taken with the analog technique in all six areas of the body.     

RADIOGRAPHY OF THE THORACO-ABDOMINAL CAVITY OF THE OSTRICH (Struthio Camelus)

A standard radiographic procedure was developed for the thoraco-abdominal cavity of female nonbreeding ostriches. Positioning, collimation, centering and a technique chart were defined to give reproducible and consistently good quality radiographs. Radiographs were obtained from one adult ostrich cadaver, two adult female ostriches as well as two growing ostriches at various stages. A 6-frame technique was established for lateral views taking the topographic tissue distribution into consideration and using easily palpable landmarks as centering points. Standing true right lateral radiographs are recommended for standard procedures. For dorsoventral exposures a 3-frame technique in the recumbent ostrich was found to be optimal. Birds should be fasted if possible. A technique chart for lateral exposures is provided.     

VALIDATION OF A NOVEL TECHNIQUE FOR CREATING SIMULATED RADIOGRAPHS USING COMPUTED TOMOGRAPHY DATASETS

Understanding radiographic anatomy and the effects of varying patient and radiographic tube positioning on image quality can be a challenge for students. The purposes of this study were to develop and validate a novel technique for creating simulated radiographs using computed tomography (CT) datasets. A DICOM viewer (ORS Visual) plug‐in was developed with the ability to move and deform cuboidal volumetric CT datasets, and to produce images simulating the effects of tube‐patient‐detector distance and angulation. Computed tomographic datasets were acquired from two dogs, one cat, and one horse. Simulated radiographs of different body parts (n = 9) were produced using different angles to mimic conventional projections, before actual digital radiographs were obtained using the same projections. These studies (n = 18) were then submitted to 10 board‐certified radiologists who were asked to score visualization of anatomical landmarks, depiction of patient positioning, realism of distortion/magnification, and image quality. No significant differences between simulated and actual radiographs were found for anatomic structure visualization and patient positioning in the majority of body parts. For the assessment of radiographic realism, no significant differences were found between simulated and digital radiographs for canine pelvis, equine tarsus, and feline abdomen body parts. Overall, image quality and contrast resolution of simulated radiographs were considered satisfactory. Findings from the current study indicated that radiographs simulated using this new technique are comparable to actual digital radiographs. Further studies are needed to apply this technique in developing interactive tools for teaching radiographic anatomy and the effects of varying patient and tube positioning.     

Acquisition and interpretation of radiographs of the equine skull

The complex anatomy of the equine skull creates a radiographic challenge. However, radiographs are a commonly required tool in diagnosing dental and sinonasal disease, as well as other disorders of the equine skull. High quality, complete radiographic studies are essential for adequate evaluation. Radiographic technique and interpretation are reviewed in this paper.     

EVALUATION OF TWO OBJECTIVE METHODS TO OPTIMIZE KVP AND PERSONNEL EXPOSURE USING A DIGITAL INDIRECT FLAT PANEL DETECTOR AND SIMULATED VETERINARY PATIENTS

It is important to optimize digital radiographic technique settings for small animal imaging in order to maximize image quality while minimizing radiation exposure to personnel. The purpose of this study was to evaluate two objective methods for determining optimal kVp values for an indirect flat panel digital detector. One method considered both image quality and personnel exposure as endpoints and one considered only image quality. Phantoms simulated veterinary patients of varying thicknesses with lesions of varying sizes. Phantoms were exposed to a range of kVp values (60, 81, 100, and 121), using different mAs settings for each phantom. Additionally, all phantoms were exposed to a standard test exposure of 100 kVp/2.5 mAs. Scattered radiation was recorded and used as a measure of personnel exposure. When personnel exposure was considered, a figure of merit was calculated as an endpoint of optimization. The optimal kVp value for each phantom was determined based on the highest signal difference‐to‐noise ratio with or without inclusion of the figure of merit. When personnel exposure was not considered, increasing kVp resulted in higher signal difference‐to‐noise ratios and personnel exposure increased when both patient thickness and kVp increased. Findings indicated that a single standard technique of 100 kVp/2.5 mAs was only optimal for most medium‐sized patients. Images of thinner patients should be made with a lower kVp. Very large patients require a higher kVp than 100 regardless of the optimization method used. Personnel exposure from optimized techniques was low and not expected to exceed annual occupational dose limits.     

Diagnostic imaging of the canine and feline ear.

Radiographic evaluation of the tympanic bulla is limited. Improper obliquity or angulation of the skull for radiographs or malpositioning of the tongue can result in an inadequate study [4]. Additionally, because of the complex anatomy of the canine and feline skull, with superimposition of multiple osseous structures, radiography can result in false-negative examinations or understimation of the disease present [2]. When compared with surgical findings of 19 clinical cases of presumptive middle ear disease, false-negative radiographic findings were found in 25% of the surgically confirmed cases of otitis media [4]. Therefore, radiographs are not considered to be a highly sensitive mode of diagnosing otitis media. Radiographs may be helpful in determining lysis associated with neoplasia; however, the extent of involvement is still underestimated. In a study comparing CT and radiographic evaluation of otitis media, CT was determined to be more sensitive but less specific than radiography [11]. CT is the preferred modality for the evaluation of the tympanic bulla at our institution. This opinion may be biased by the fact that most cases are presented for recurrent or chronic otitis. Although radiography is more accessible, the availability of CT in local referral settings is increasing as opposed to being limited to university settings. After the cost (i.e., anesthesia, radiographs) and amount of time necessary to make optimum radiographic studies are taken into account, a CT study may actually be faster and more informative. Given our preference for the CT examination, the cost of the examination has been adjusted to make it more appealing to the owner and clinician. For example, a bulla CT study is only 1.3 times the cost of a radiographic bulla study. In conclusion, imaging of the ear canal can provide important information about ear disease, including unilateral or bilateral ear disease, the degree of middle or inner ear involvement, peripheral versus central vestibular disease, an infectious or inflammatory versus neoplastic process, the chronicity of the disease process, involvement of adjacent structures, and postsurgical complications.     

A simple test phantom in the form of a staircase for running control of the image in veterinary roentgenology

Quality control in veterinary radiology seems to be neglected. For the correct estimation of the radiographic quality, there is no adequate phantom available. Although measurements have shown that the exposure to radiation is far under the admissible limits, the quantity of repeated examination has to be reduced. So it was necessary to create a phantom, which allows the objective judgement of the x-ray photograph taken immediately from the patient. The phantom shows the following characteristics: 1) It is small-sized, so that it can be represented on the radiograph together with the object, but without remarkable enlargement of the beam and additional exposure to radiation. 2) It consists of tissue-similar material, which absorbs and scatters x-rays similar to the body region. According to the fact that the indications for radiographs in veterinary medicine are mostly problems in skeleton regions, this region is represented first of all. 3) Therefore the phantom shows variable thickness, so that it can simulate different skeleton parts. 4) The represented parameters are: 4.1 the different radiographic densities; 4.2 the latitude; 4.3 the radiographic contrast; 4.4 the radiographic detail visibility (film-far, film-close) in the relevant parts of the x-ray picture 5) The phantom is universally applicable. By a way of "calibration" it is multipurpose for certain kinds and sizes of animals.     

Radiographic techniques for medical-dental research with minipigs

Techniques were developed to obtain standardised intra- and extra-oral radiographs in minipigs for use in medical-dental research. Twelve male minipigs (BR-1 Minipigs) were chosen at random. Two animals each at 3, 5, 7, 9, 12 and 15 months of age were anaesthetised and subjected to radiographic examinations to assess six techniques. Three intra-oral and three extra-oral techniques, standardised for humans, were used with variations of the angle of incidence of the X-ray beams, focus-film distance and exposure time. Two film positioners were developed for the intra-oral techniques. Two examiners then chose the radiographs with the least image distortion, greatest clarity and least superimposition of images. For each technique, the suitable angle of incidence of the X-ray beams, the focus-film distance and exposure time that produced the highest quality radiographs were standardised.     

Radiographic Calibration for Analysis of Bone Mineral Density of the Equine Third Metacarpal Bone

Digital radiography represents the primary diagnostic tool the veterinarian uses to diagnose skeletal injuries in the horse. Advances in digital radiography have provided the veterinarian with opportunities to make simple radiographic assessments from calibrated digital radiographs such as dimensional analyses; however, more complex variables such as radiographic opacity have yet to be standardized. Therefore, we investigated the quantification of bone mineral density (BMD) via computed radiographic absorptiometry at various radiographic exposure intensities (kV), times (sec), and milliamps (mA) in the third metacarpal in the horse. By developing a brightness/darkness index (BDI), the grayscale of radiographs, calibrated with an aluminum (Al) marker of various known thicknesses and uniform densities, can be compared to the average BMD of a region of interest at various radiographic exposures. Al BDI was a significant predictor of bone BDI (r² = 0.960, P < .001) and BMD (r² = 0.971, P < .001). This method of calibration can be used for quantitative noninvasive bone mineral analysis and allows direct comparison of radiographs taken under different exposure settings.     

Radiographic interpretation of normal skeletal variations and pseudolesions in the equine foot.

Effective radiographic interpretation requires a veterinarian who is knowledgeable of equine limb anatomy and the various principles that affect the resulting image. The normal and its variations must be recognized and understood before the abnormal can be confidently identified as pathologic. Proper patient positioning and sound radiographic technique are mandatory if reliable diagnostic radiographs are to be produced. This review emphasizes equine foot radiographic variations of normal and pseudolesions that occur with commonly used radiographic views performed in equine practice.     

MULTISCALE IMAGE PROCESSING AND ANTISCATTER GRIDS IN DIGITAL RADIOGRAPHY

Scatter radiation is a source of noise and results in decreased signal-to-noise ratio and thus decreased image quality in digital radiography. We determined subjectively whether a digitally processed image made without a grid would be of similar quality to an image made with a grid but without image processing. Additionally the effects of exposure dose and of a using a grid with digital radiography on overall image quality were studied. Thoracic and abdominal radiographs of five dogs of various sizes were made. Four acquisition techniques were included (1) with a grid, standard exposure dose, digital image processing; (2) without a grid, standard exposure dose, digital image processing; (3) without a grid, half the exposure dose, digital image processing; and (4) with a grid, standard exposure dose, no digital image processing (to mimic a film-screen radiograph). Full-size radiographs as well as magnified images of specific anatomic regions were generated. Nine reviewers rated the overall image quality subjectively using a five-point scale. All digitally processed radiographs had higher overall scores than nondigitally processed radiographs regardless of patient size, exposure dose, or use of a grid. The images made at half the exposure dose had a slightly lower quality than those made at full dose, but this was only statistically significant in magnified images. Using a grid with digital image processing led to a slight but statistically significant increase in overall quality when compared with digitally processed images made without a grid but whether this increase in quality is clinically significant is unknown.     

A COMPARISON OF NORMAL FELINE THORACIC RADIOGRAPHS MADE IN DORSAL VERSUS VENTRAL RECUMBENCY

Thoracic radiographs of 11 normal cats were made in dorsal (VD) and ventral (DV) recumbency with a vertically directed x-ray beam. These radiographs were compared subjectively and objectively with each other and with an additional pair of radiographs made with the cats in dorsal and ventral recumbency using a horizontally directed x-ray beam. Differences were found between VD and DV thoracic radiographs but they were minimal. In VD radiographs the caudal mediastinum and accessory lobe regïon of the lung were more clearly seen but cardiac shape varied somewhat. In DV radiographs, the appearance of the heart was more constant and caudal lobar pulmonary arteries more clearly seen. The results of this study indicated that both VD and DV radiographs are satisfactory for radiographic examination of the feline thorax     

RADIOGRAPHIC AND ECHOCARDIOGRAPHIC MEASUREMENT OF THE HEART IN OBESE CATS

A prospective study was undertaken to reconcile radiographic cardiomegaly and normal echocardiography in obese cats and to test a radiographic technique for better distinguishing between pericardial fat and the heart. Ten obese, but otherwise normal cats and 10 non-obese normal cats were used. A body condition scoring system was used to objectively group obese and non-obese normal cats. Two-dimensional echocardiograms were made to verify that all cats had a normal heart. Thoracic radiographs then were made using standard and altered exposure techniques. The hearts were measured on these radiographs using the metric and a vertebral scale system. Obese cats consistently had excessive fat around the heart especially if they also had a large amount of falciform fat. Altering exposure technique by increasing mAs and decreasing kVp sometimes enhanced the radiographic contrast between fat and myocardium. Enhanced radiographic contrast accentuated the double silhouette identifying the true cardiac silhouette within the fat expanded silhouette. Pericardial fat usually was distinguished more readily in lateral than in VD radiographs. In two cats, pericardial fat had a characteristic prominent square corner to the right cranial margin of the cardiac silhouette in VD radiographs. Obesity caused increased width and depth of the thoracic cage. 2D echocardiograms revealed normal cardiac dimensions in both groups of cats and increased precordial distance in the obese group.     

INTEROBSERVER AGREEMENT ON THE ASSESSABILITY OF STANDARD VENTRODORSAL HIP-EXTENDED RADIOGRAPHS AND ITS EFFECT ON AGREEMENT IN THE DIAGNOSIS OF CANINE HIP DYSPLASIA AND ON ROUTINE FCI SCORING

Insufficient agreement on scoring hip quality might be caused by differences in the assessability of a radiograph (exposure, contrast, positioning, and diagnostic quality). We studied the agreement in assessability of standard ventrodorsal hip-extended radiographs by experienced (nine) and inexperienced (21) observers, using the standard subjective method of quality control, currently applied in screening programs. The effect of assessability on the agreement of scoring hip quality [dysplastic vs. nondysplastic and the final Federation Cinologique International (FCI) score] was also investigated. There was a significant difference ( P <0.0001) in agreement on assessability between the experienced and inexperienced observers. In 68% of evaluations, experienced observers stated that the radiograph was assessable. Inexperienced observers evaluated the radiographs as being assessable in only 46.5% of evaluations. Increased interobserver agreement on assessability of a radiograph did not increase the overall interobserver agreement in the diagnosis of hip dysplasia, nor did it result in consistent scoring of the hip status from that radiograph, despite a significant ( P <0.05) increase in agreement of FCI scoring with an increasing agreement on assessability at a one to five ratio in the experienced group. The inconsistent evaluation of radiographic quality, as well as the inconsistent evaluation of the hip quality, caused differences in diagnosing hip dysplasia and FCI scoring in the same dog ranging from excellent hips to moderate hip dysplasia. Therefore, the credibility of the FCI screening method for canine hip dysplasia, using the standard hip-extended radiographic view, as currently applied in most European countries, is questionable.     

How to obtain and interpret periodontal radiographs in dogs

Oral radiography plays an important role in the diagnosis of periodontal disease. The diagnostic yield of radiographs is high, and they should be obtained in all cases presenting for periodontal treatment and to assess the long-term success of therapy. Diagnostic-quality radiographs for evaluating the periodontium are best obtained with a dental x-ray unit and with the patient under general anesthesia. The standard full-mouth radiographic survey contains a minimum of 6 views, and with practice, can be obtained with minimal effort and time. Interpretation of dental radiographs, however, requires a keen understanding of the normal radiographic anatomy of a tooth and its supporting structures. The radiographic diagnosis of periodontal disease is characterized by rounding of the alveolar crest with loss in continuity of the lamina dura, widening of the periodontal ligament space, and loss of alveolar crest height.     

Microfocal radiography as an aid to the diagnosis of canine elbow osteochondrosis

One normal cadaver specimen and six labrador retrievers with suspected elbow osteochondrosis were examined using a microfocal radiographic technique as an aid to diagnosis. This allowed the production of a magnified image (macro-radiograph) with high spatial resolution. The macroradiographs were compared with radiographs obtained using a standard technique to see if they facilitated decision making with respect to case management. The lesions that were suspected from radiographic examination were correlated with the gross lesions found at elbow arthrotomy. Microfocal radiography gave additional information about the changes within the joints but it still remained difficult to image the lesion satisfactorily in some cases.     

Comparison of digitized and conventional radiographic images for assessment of hip joint conformation in dogs

OBJECTIVE: To determine agreement between assessments of canine hip joint conformation provided by board-certified radiologists after evaluation of digitized and conventional radiographic images. SAMPLE POPULATION: 200 pelvic radiographs previously evaluated by radiologists using the Orthopedic Foundation for Animals standard grading system for canine hip joint conformation. PROCEDURES: Each of 20 board-certified radiologists evaluated conventional and digitized pelvic radiographs from each of 200 dogs for hip joint conformation. A weighted kappa coefficient and intraclass correlation were used to determine agreement between assessments derived from digitized radiographic images and conventional radiographs and between the original Orthopedic Foundation for Animals conformation ratings and assessments derived from each image format. RESULTS: Overall, agreement between assessments derived from the digitized images and conventional radiographs was good, with all but 1 radiologist attaining a weighted kappa coefficient > 0.61. Intraclass correlation for each radiologist ranged from 0.75 to 0.98 (95% confidence interval, 0.67 to 0.984). On comparison of conformation assessments, 95.7% of those derived from conventional radiographs and digitized images were within 1 grade. On comparison of digitized radiographic conformation assessments and conformation ratings, 94.2% were within 1 grade. On comparison of conventional radiographic conformation assessments and conformation ratings, 92.3% were within 1 grade. CONCLUSIONS AND CLINICAL RELEVANCE: The use of digitized radiographic images does not appear to impact the radiographic assessments of canine hip joint conformation made by consultant radiologists. Compared with conventional radiographs, the use of digitized radiographic images decreases storage space requirements and enables more rapid reporting of assessment results for individual dogs.     

RADIOGRAPHIC DIAGNOSIS OF LAMENESS IN AFRICAN ELEPHANTS (LOXODONTA AFRICANA)

Lameness in captive elephants is most commonly caused by pododermatitis or degenerative joint disease. Hard surfaces such as concrete, which produce a damp and cold environment, wet and muddy conditions, as well as restricted movement are the major causes of these problems. Radiography was performed in two African elephants at the Schoenbrunn Zoo in Vienna to determine the cause and extent of lameness. Various radiographic techniques are described for use in trained elephants. Low time settings were used to avoid loss of detail through movement and to minimize exposure while observing radiation safety. A 37-year-old elephant had front limb lameness due to an interdigital abscess. In radiographs of the foot an inhomogenous soft-tissue swelling without involvement of the phalanges was seen. Ultrasonography was helpful in visualizing the fluid-filled abscess. In additional joint radiographs severe degenerative joint disease was identified. A 13-year-old elephant had lameness of the hind limb. Radiographs of the hind limb from the foot to the stifle were made. Open physes and early signs of degenerative joint disease were identified on the radiographs.