PRELIMINARY CLINICAL USE OF COMBINED BLOOD POOL AND BONE PHASE RADIONUCLIDE IMAGING IN DOGS

The case reports of three dogs, in which combined blood pool and bone phase radionuclide imaging was done, are presented. The procedure is accomplished by injecting ^99mTc-MDP and imaging at 3–5 min and 2 hours postinjection. These three cases suggest that a greater number of animals with varied etiologies should be scanned in this manner to determine the usefulness of the procedure.     

99mTc-MDP COMBINED BLOOD POOL AND BONE PHASE RADIONUCLIDE IMAGING IN PAPAIN-INJECTED CARPAL JOINTS

Scintigraphic changes, i.e. , increased activity, were induced by 1% papain, dissolved in phosphate-buffered physiologic saline (pH 7.4), injected into one antebrachiocarpal joint in each of eight dogs. Scintigraphic evaluation was by the use of combined blood pool and bone phase scintigraphy of affected and normal carpi over a 28-day period. The qualitative and quantitative scintigraphic appearance in injected carpal joints were very similar in both blood pool and bone phases. The clinical use of combined blood pool and bone phase scintigraphy to diagnose early inflammatory joint changes appears limited.     

UPTAKE OF 99mTCMDP IN MUSCLE ASSOCIATED WITH A PERIPHERAL NERVE BLOCK

A focal area of increased uptake of radioactivity was observed in muscle during bone imaging with ^99mTcMDP. The area was previously the site of a peripheral nerve block with mepivacaine hydrochloride. Additional experiments were done to document the action of the local anesthetic. The effect on uptake decreased over several days.     

UTILIZATION OF INSTANTANEOUS EJECTION VOLUME IMAGES TO PRODUCE VENTRICULAR VOLUME CURVES FROM AN EQUILIBRIUM RADIONUCLIDE VENTRICULOGRAM

Equilibrium radionuclide ventriculograms were performed in 6 normal dogs during resting and isoproterenol challenged states. A new method of analysis of the equilibrium radionuclide ventriculograms using a simple digital subtraction technique was compared to traditional methods of analysis and echocardiography. There was no significant difference between ejection fraction values from the three methods tested. The equilibrium radionuclide ventriculograms ejection fraction was significantly increased following isoproterenol administration using both the new and traditional methods of analysis but the pre versus post-isoproterenol increase ejection fraction derived from echocardiographic measurements of ejection fractions was not significantly different. The new digital subtraction method consistently produced reproducible, high quality ventricular volume curves for the left and right ventricle. Left and right ventricular maximum and average emptying and filing rates were determined from the slopes of the volume curve and the results were similar to those previously published for man and dog. The emptying and filling rates of both ventricles were significantly increased following isoproterenol administration. The time to peak emptying significantly decreased following isoproterenol. Time to peak filing decreased following isoproterenol but the difference was not significant.     

SCINTIGRAPHIC EVALUATION OF SKELETAL DISEASE AND ITS APPLICATION TO THE HORSE

Bone scintigraphy is a valuable aid in the evaluation of lameness in horses. This review describes the principles of bone radiolabeling, scanning, and scan interpretation. Examples are used to illustrate how bone imaging can contribute significantly to a diagnosis after equivocal physical examination or radiographic findings.     

LYMPH NODE UPTAKE OF 99MTc-MDP DURING BONE SCINTIGRAPHY IN DOGS

Localization of ^99mTc-MDP in lymph nodes was apparent on the three-hour bone-scan image in seven dogs. In six dogs injection or leakage of the radiopharmaceutical into the perivascular tissues was associated with subsequent uptake in an ipsilateral lymph node. In the remaining dog, ^99mTc-MDP localized in a lymph node infiltrated by metastatic osteosarcoma. This aided staging of the tumor. Possible mechanisms of ^99mTc-MDP localization in soft tissues are briefly reviewed.     

NORMAL THORACIC AND ABDOMINAL DISTRIBUTION OF 2-DEOXY-2-[18F]FLUORO-d-GLUCOSE (18FDG) IN ADULT CATS

Positron emission tomography (PET) with 2-deoxy-2-[¹⁸F]fluoro- d -glucose (¹⁸FDG) is an important imaging modality for diagnosis and staging of human neoplastic disease. The purpose of this study is to describe the normal ¹⁸FDG uptake in adult cats. Six adult healthy female cats were used. Cats were sedated and then injected intravenously with 74.0±13.0 (mean±SD) MBq of ¹⁸FDG. General anesthesia was induced and cats were placed in ventral recumbancy on the PET scanner's bed. Static images using multiple bed positions were acquired approximately 60–90 min after injection. A transmission scan was acquired at each bed position utilizing a ⁵⁷Co point source to perform attenuation and scatter correction. Regions of interest (ROIs) were drawn over the liver, right and left renal cortices, left ventricular wall, and wall of ascending and descending colonic segments. Standardized uptake values (SUV) were calculated using an established formula. Kidneys and intestinal tract had relatively intense uptake of ¹⁸FDG; liver activity was intermediate; the spleen was not identified in any of the cats. Cardiac activity was variable but intense activity was noted in the left ventricular myocardium in most cats. No appreciable lung uptake was noted. Mean±SD SUV values were calculated. This study established the normal pattern of uptake of ¹⁸FDG in adult cats and provided baseline data for comparison with future studies evaluating a variety of neoplastic and nonneoplastic diseases.     

SCINTIGRAPHIC DETECTION OF SUBCUTANEOUS METASTASIS IN A DOG WITH APPENDICULAR OSTEOSARCOMA

This report describes the detection of subclinical soft tissue metastasis of an appendicular osteosarcoma in a dog using bone scintigraphy. A 7-year-old spayed female Rottweiler was presented with a biopsy confirmed diagnosis of osteosarcoma. Initial radiographs revealed an aggressive bone lesion of the left distal radius. At presentation, there was no clinical or radiographic evidence of metastasis; however, a nuclear bone scan showed the primary bone lesion of the distal left radius and numerous soft tissue lesions consistent with diffuse soft tissue metastases. A left foreleg amputation was performed and cisplatin chemotherapy was given post-operatively. A second bone scan performed one month following initial presentation showed progression in size and number of soft tissue masses. Many of the lesions had become apparent on physical exam and survey radiographs. Excisional biopsy was performed on one of the soft tissue masses and a diagnosis of metastatic osteosarcoma was made. The dog was euthanized 2 months after initial presentation at the owners request due to deterioration of the animals physical condition.     

Imaging features of orbital myxosarcoma in dogs

Myxomas and myxosarcomas are infiltrative connective tissue tumors of fibroblastic origin that can be distinguished by the presence of abundant mucinous stroma. This paper describes the clinical and imaging features of orbital myxosarcoma in five dogs and suggests a predilection for the orbit. The main clinical signs were slowly progressive exophthalmos with soft swelling of the pterygopalatine fossa, and in two dogs, of the periorbital area. No pain was associated with the eye or orbit but one dog had pain on opening the mouth. The dogs were imaged using combinations of ultrasonography, radiography, and magnetic resonance imaging. In four dogs, extensive fluid-filled cavities in the orbit and fascial planes were seen and in the fifth dog, the tumor appeared more solid with small, peripheral cystic areas. In all dogs, the lesion extended along fascial planes to involve the temporomandibular joint, with osteolysis demonstrable in two dogs. Fluid aspirated from the cystic areas was viscous and sticky, mimicking that from a salivary mucocoele. Myxomas and myxosarcomas are known to be infiltrative and not readily amenable to surgical removal but their clinical course seems to be slow, with a reasonable survival time with palliative treatment. In humans, a juxta-articular form is recognized in which a prominent feature is the presence of dilated, cyst-like spaces filled with mucinous material. It is postulated that orbital myxosarcoma in dogs may be similar to the juxta-articular form in man, and may arise from the temporomandibular joint.     

Imaging diagnosis--cervical spine chondroma in a dog

An extradural chondroma originating in the cervical spine was diagnosed in an 8-year-old, intact male Chow-Chow that presented acute cervical pain and chronic right thoracic limb lameness. Myelographic images were within normal limits. With magnetic resonance (MR) imaging, an extradural mass was identified at the level of the C4-C5 vertebrae. This mass was excised, and the histologic diagnosis was chondroma. Fifteen months after surgery, the dog was clinically normal, and no regrowth of the mass was identified on follow-up MR images. Spinal chondromas are rare tumors in the dog, but should be considered as a rule out for contrast-enhancing extradural vertebral masses.     

Initial Experience Using Contrast Magnetic Resonance Imaging in Laminitic Horses: 18 Studies

Plain radiographic imaging inadequately identifies soft-tissue pathology and only distinguishes chronic laminitis after the development of notable displacement of the distal phalanx. The window of opportunity for maximum response to treatment occurs before biomechanical failure of the lamellar attachment. Radiographic and magnetic resonance venograms allow vascular assessment of patients affected with acute laminitis. When vascular findings are interpreted with additional magnetic resonance information, the degree of damage to the foot in patients affected with laminitis is understood more thoroughly. This article describes the technique, findings, and outcome in a group of laminitic horses that underwent contrast magnetic resonance imaging.     

DIURETIC RENAL SCINTIGRAPHY IN NORMAL DOGS

Diuretic renal scintigraphy is commonly used in human medicine to differentiate obstructive from nonobstructive pyelectasia. In order to determine normal parameters, 99mTc-DTPA renal scintigraphy was performed twice in 20 healthy adult Mongrel dogs. Each dog was injected with either 3.0 mg/kg furosemide or an equivalent volume of saline 4.5 min following injection of the radiopharmaceutical. The following parameters were evaluated: (1) global and individual glomerular filtration rate (GFR); (2) time of peak (TOP) of the time-activity curve (TAC); (3) shape of the TAC; (4) individual kidney excretion half-time (T1/2); (5) proportion of maximum activity measured at end of study (8 min); (6) time of onset; and (7) duration of the effect of the diuretic. Most TAC in the diuretic renography group showed a steep drop in the curve following administration of the diuretic compared with a gradual slope in the saline control group. There was a statistically significant difference in T1/2 between the control renograms (median 10.25 min, range 4.41-18.07 min) and the diuretic renograms (median 4.16 min, range 3.62-5.90 min). There was a statistically significant difference in percentage maximum activity between the control renograms (median 65.25%, range 48.27-93.68%) and the diuretic renograms (median 48.54%, range 35.64-58.76%). Median time of onset of the diuretic effect was 1.10 min (0.20-2.40 min), and median duration was 0.83 min (0.30-2.35 min).     

Nuclear Medical Bone Imaging and Targeted Radiography for Evaluation of Skeletal Neoplasms in 23 Dogs

Nuclear medical bone imaging was used in combination with targeted radiography to detect metastatic or multicentric lesions in 23 dogs with skeletal neoplasms. Each dog with a radio-graphically diagnosed skeletal neoplasm was injected with Technetium-99m labeled methylene diphosphonate (^99mTc-MDP) (15.0 mCi intravenously) for whole body imaging. All areas with increased uptake of ^99mTc-MDP were radiographed. In 19 dogs, the amount of bone shaft involvement in primary sites indicated by bone imaging was larger than the amount indicated by radiography. Eighteen dogs had secondary areas of increased ^99mTc-MDP uptake, six of which had secondary areas that were suspected radiographically to be neoplastic. Four dogs had lesions characterized histologically as neoplasia, one as bone infarction and one as normal cortical bone. Positive predictive value for this strategy was 66.7%. Results of this study suggest that nuclear medical bone imaging with targeted radiography is a quick, noninvasive technique with a good positive predictive value for evaluation of the skeleton for metastatic or multicentric sites of neoplasia.     

Quantitative Evaluation of Equine Deep Digital Flexor Tendon Morphology using Magnetic Resonance Imaging

Injury of the distal aspect of the deep digital flexor tendon (DDFT) is a recognized cause of lameness, but diagnosis is difficult. This study aimed to improve understanding of DDFT morphology and pathology using retrospective evaluation of magnetic resonance (MR) images. We hypothesized that: (1) The distal aspect of the DDFT in normal horses would have a repeatable proximal/distal pattern and symmetry between limbs and between lobes; (2) DDFT dimensions would be related to bodyweight, navicular bone dimensions and hoof size; (3) this symmetry and pattern would be lost in DDFT injury; and (4) DDFT size would increase with injury. MR images of 64 live horse limbs, 26 with no identified DDFT lesion and 38 with identified DDFT abnormalities, and 19 normal cadaver limbs were analyzed. Using standardized transverse images, measurements of DDFT cross-sectional area, medial-lateral (ML) width and dorsal-palmar depth were obtained at six preselected sites. A uniform distal to proximal shape pattern was identified in all horses. The flattened crescent shape at the insertion changed to a deeper bilobed shape more proximally, with the mid-navicular area having the greatest cross-sectional area. Strong ML (P < 0.0006) and left/right symmetry (P < 0.02) were observed. In addition, there was a strong association between DDFT cross-sectional area and horse weight (P = 0.005) and between DDFT and navicular bone ML width (P = 0.004). Symmetry between sides or between lobes was lost at sites with a unilateral lesion and correlation between horse weight and DDFT cross-sectional area was lost in the presence of lesions. DDFTs with core lesions had a consistent increase in cross-sectional area overall, but other lesion types had no significant increase in size. The shape and symmetry seen in normal tendons could be related to the mechanical demands placed upon individual lobes. The limited increase in cross-sectional area with injury may be explained by the restrictive structures of the hoof, possibly explaining the ongoing pain seen in such lesions.