IMAGE MAGNIFICATION IN DIGITAL FLUOROSCOPY

Image magnification is inherent in radiography. In digital fluoroscopy, the three components of magnification are geometric, electronic and photographic. In this study, the total magnification factor of a digital imaging system was determined by two methods, 1) comparison of measurements of a known object to its image and 2) calculation of geometric, electronic and photographic magnification from the imaging system specifications. Both methods were employed for various focal-film distances, image intensifier tube modes and laser printer formats. Results of these two methods were different due to the detrimental effect of penumbra on image quality with increasing magnification. If a radiographic image is to be used to approximate object size, then a technique should be used that will minimize magnification. In digital fluoroscopy this is achieved with the shortest object-film distance (assuming a fixed focal-object distance), largest image intensifler mode and greatest number of images per sheet of film.     

Assessment of changes in blood volume in response to resuscitative fluid administration in dogs

Objective: To determine the continuous changes in blood volume in response to fluid administration using an in‐line hematocrit monitor. Design: Prospective study. Setting: Research laboratory. Animals: Four healthy dogs. Interventions: Each dog received intravenous boluses of 80 mL/kg of 0.9% saline (S), 4 mL/kg of 7.5% saline (HS), 20 mL/kg of dextran 70 (D), 20 mL/kg of hetastarch (HES), or no fluids (control, C) on separate occasions. Fluids were administered at 150 mL/min in the S, D, and HES groups, and at 1 mL/kg/min in the HS group. Measurements and main results: Blood volume changes were measured every 20 seconds for 240 minutes using an in‐line hematocrit monitor. There was a rapid rise in blood volume during all infusions. Immediately after the administration of crystalloid fluids, the rapid rise in blood volume ceased. Subsequently, there was a steep decline in blood volume for 10 minutes, and a slower decline thereafter. In contrast, the rise in blood volume continued for at least 10 minutes after the infusion of the colloids was complete, and a plateau was observed for the remainder of the experiment. The blood volume effect, as measured by area under the curve, was significantly greater in the saline group than the other groups during the infusion time and for the 0–240 minutes time period. The areas under the curve for the two colloid solutions were not significantly different from each other during any time periods. The percent increase in blood volume immediately following the infusions was 76.4±10.0 in the S group, 17.1±3.2 in the HS group, 23.0±10.5 in the D group, and 27.2±6.4 in the HES group. At 30 minutes from the start of the infusion, the mean percent increases in blood volumes were 35.2±9.3 in the S group, 12.3±0.9 in the HS group, 35.9±7.3 in the D group, and 36.8±6.5 in the HES group. At 240 h post‐infusion, the mean percent increases in blood volume were 18.0±9.7 in the S group, 2.9±6.1 in the HS group, 25.6±16.1 in the D group, and 26.6±8.6 in the HES group. The C group had a mean percent change in blood volume of ?3.7±3.4 at the end of the experiment. Conclusions: This study indicates that the rapid administration of saline at clinically relevant doses leads to the largest immediate increase in blood volume, although this change is transient because of rapid redistribution of the fluid. Despite a brief increase in blood volume that was almost 3 times the volume administered, hypertonic saline led to the smallest increase in blood volume post‐infusion. The synthetic colloid solutions increased the blood volume by an amount greater than that infused and the effect was sustained for a longer period of time than seen following crystalloid administration, but the maximum increase in blood volume was significantly less than saline. The measurement of continuous changes in blood volume, using an in‐line hematocrit monitor, was a useful means of assessing the dynamic effects of fluid administration in dogs in a research setting.     

SUBTRACTION PORTAL VENOGRAPHY

Photographic subtraction was made of 38 canine portal venograms to remove the images of the overlying abdominal structures and enhance the radiographic contrast of portal veins. The improved visual quality of the subtracted portogram aided in the detection of portosystemic shunts and intrahepatic portal veins. The subtraction studies revealed portosystemic shunts not detected on the initial portal venogram.     

Evaluation of Internal Obturator Muscle Transposition in Treatment of Perineal Hernia in Dogs

A technique that utilizes transposition of the internal obturator muscle for repair of perineal hernias was evaluated. Forty-two male dogs were followed for at least one year after surgery. The repair failed in only one animal, a dog with previously operated bilateral hernias. Microangiography demonstrated an adequate blood supply to the transposed internal obturator muscles of two dogs examined at three weeks and three months after surgery.     

Arthroscopic Treatment of Osteochondritis Dissecans in the Canine Shoulder

Twenty-three shoulders of 21 dogs were treated arthroscopically for osteochondritis dissecans (OCD). Thirteen dogs had bilateral lesions detectable radiographically; however, only two dogs had arthroscopic surgery on both shoulders. Arthroscopic procedures included removal of the osteochondral flap, curettage of the subchondral defect, and partial synovectomy. Fourteen dogs were using the treated limb within 1 day and eight dogs within 2 days, although some lameness may have persisted for several weeks. Force plate evaluation was effective for comparison of preoperative and postoperative mean peak force/body weight (PF/BW) values. Improvement was detected objectively in 9 of the 10 dogs returned for postoperative force plate analysis. All owners were satisfied with the cosmetic results and the rapid return to function.     

Pancreatic Polypeptide and Insulin-Secreting Tumor in a Dog With Duodenal Ulcers and Hypertrophic Gastritis

A 7-year-old spayed female Cocker Spaniel was hospitalized with a history of chronic vomiting, anorexia, and weight loss. Laboratory abnormalities included leukocytosis, metabolic alkalosis, hypoglycemia, hypoproteinemia, and hyperinsulinemia. Gastroscopy and ultrasonography revealed multiple gastric masses and a possible pancreatic mass, respectively. Examination of tissues obtained at necropsy showed a pancreatic adenocarcinoma with hepatic metastasis, gastric hypertrophy, and multiple duodenal ulcers. Immunocytochemical staining of the neoplasia was positive for pancreatic polypeptide (PP) and insulin and negative for gastrin, calcitonin, adrenocorticotropic hormone (ACTH), serotonin, L-enkephalin, chromagranin, glucagon, and somatostatin. Subsequent serum gastrin and PP assays showed a fasting hypergastrinemia with a normal response of gastrin to provocative testing and extremely increased PP values. The high PP values may have resulted in the vomiting and gastrointestinal ulceration. A PP-secreting tumor has not previously been reported in the dog.     

Distribution of Topical Agents in the Frontal Sinuses and Nasal Cavity of Dogs: Comparison Between Current Protocols for Treatment of Nasal Aspergillosis and a New Noninvasive Technique

To document and compare patterns of distribution of topically applied antifungal medication, heads from 42 canine cadavers were assigned to seven treatment groups which included two current surgical treatment protocols for nasal aspergillosis, and a new, noninvasive method. Catheters (8 Fr) were placed through trephine holes into the frontal sinuses and nasal cavity. Dilute dye was injected through the catheters and the heads were sectioned sagittally. The administration of 5 mL of dye into the lateral frontal sinus and nasal cavity (group IA, 10 mL total) was compared with 25 mL injected through catheters placed bilaterally in the lateral frontal sinus and nasal cavity (group II, 100 mL total). Both were compared with the administration of 50 mL of dye through a catheter placed in the dorsal nasal meatus via each nostril (group III). The heads in group III had significantly ( P <.05) better dye distribution to all cavities than group IA and better distribution to the rostral frontal sinus than group II. Groups IV to VI were designed to show the pattern of distribution of dye to the contralateral nasal cavity and frontal sinuses. In all groups, dye injected into the lateral frontal sinus did not cross into the ipsilateral rostral frontal sinus or vice versa unless the transverse septum dividing the compartments had been penetrated during trephination.     

SONOGRAPHY OF THE EQUINE PALMAR METACARPAL SOFT TISSUES

It was hypothesized that ultrasonography may be a sensitive method for identifying pathologic changes in the tendons and ligaments of the palmar metacarpus of the horse. The palmar meta-carpi of equine cadavers and live horses were examined sonographically. The advantages and disadvantages of various ultrasound scanning techniques and the normal appearance of longitudinal and transverse palmar metacarpal sonograms are described.