COMPARATIVE RENAL DISPOSITION OF CREATINE, AND TECHNETIUM DIAGNOSTIC CONTRAST AGENTS IN THE PIGEON (COLUMBA LIVIA).

Clinical assessment of renal function in avian species often involves the measurement of plasma uric acid and blood urea nitrogen, relatively insensitive markers of renal dysfunction and dehydration. In mammals, endogenous creatinine is widely used as an indicator of renal glomerular dysfunction. However, avian species produce primarily creatine. Here, renal creatine, 99mTc99-DTPA (diethylenepentaacetic acid, DTPA) and 99mTc-MAG3 (mercaptoacetyl triglycine, MAG3) renal clearances are characterized in the pigeon avian model by infusing DTPA with inulin and creatine with each tracer and examining the slope of their blood disappearance curves. Clearance curves for inulin and DTPA were parallel, suggesting DTPA is cleared by renal filtration. MAG3 clearance (slope: -2.74 × 105, r2 = 0.97) had a slope almost 10-fold steeper than for DTPA (slope: -6.29 × 104, r2 = 0.90), and orders of magnitude steeper than for creatine (slope: -1.4, r2 = 1.0). These results suggest that DTPA is cleared by glomerular filtration like inulin, while MAG3 is filtered and actively excreted in a manner similar to mammals. In contrast, creatine is filtered and resorbed, has a larger volume of distribution (Vd), or exhibits a greater blood protein binding, making it more complex as a renal marker, when compared with creatinine handling in mammals. The two radiotracers can be readily adapted for use in birds, inviting both qualitative and semiquantitative functional evaluation of avian renal function for research and clinical purposes. The elimination of creatine appears to be more complex requiring further study.

Radiography, 99mTc-HDP, and 111In labeled vitamin B12 SPECT of canine osteosarcoma: a comparative study.

The objective of this article was to compare radiography, planar bone scintigraphy, and single-photon emission computed tomography (SPECT) to determine the size of osteosarcomas in long bones of dogs. Ten dogs with osteosarcoma in six radii, two humeri, one tibia, and one ulna were evaluated. Macroslides, mediolateral radiographs, planar scintigrams, and sagittal images from SPECT scans were used to obtain measurements. On the scintigraphic images, the edges of the tumor were established using the activity profile imaging tool. The radiographic magnification was factored. The mean percentage of tumor size overestimation was 9.29% on mediolateral radiographs, 5.35% on planar scintigrams, and 33.25% on SPECT images. The correlation coefficient adjusted for sample size was significantly higher (P<0.01) for technetium 99m ((99m)Tc) hydroxyethylene diphosphonate (HDP) (75.5%) and radiography (61.3%) compared with indium 111-vitamin B(12) (28.3%). The correlation coefficient for (99m)Tc-HDP was higher than that obtained for radiographs; however, statistical difference between the two variables was not demonstrated (P>0.05). (99m)Tc bone scan is a good estimator of intramedullary size of osteosarcoma in long bones when the activity profile tool to determine the margin of the tumor is used.

Design considerations for incorporating sodium iodide symporter reporter gene imaging into prostate cancer gene therapy trials.

This study was done to aid in the design of a phase I gene therapy trial in patients with prostate cancer. We determined the dosimetric characteristics of our reporter gene system when coupled with intravenous administration of radioactive sodium pertechnetate (Na(99m) TcO(4)) and determined the feasibility of using human sodium iodide symporter (hNIS) as a reporter gene to study the dynamics of adenoviral transgene expression in a large animal tumor. A replication-competent Ad5-yCD/mutTK(SR39) rep-hNIS adenovirus was injected into the prostate gland of dogs for dosimetry purposes, and into a canine soft tissue sarcoma (STS) for imaging purposes. After resection of the prostate, the amount of (99m)TcO(4)() sequestered in the prostate was determined, the radiation dose absorbed by the prostate and nontarget critical organs was calculated, and hNIS reporter gene expression was imaged in the STS by single-photon emission computed tomography (SPECT). On the basis of the findings from 25 dogs, the amount of (99m)TcO (4)() sequestered in the prostate ranged from 13 to 276 muCi. Using the highest value observed, absorbed radiation dose to critical organs was calculated and found to be below U.S. Food and Drug Administration limits for diagnostic imaging. Also, (99m)TcO (4)() uptake was readily detected by SPECT and found to persist in vivo for at least 4 days. On the basis of our dosimetry calculations, up to five imaging procedures can be safely performed in humans after intraprostatic injection of the Ad5-yCD/mutTK(SR39)rep-hNIS adenovirus and the hNIS reporter gene system can be used to study the dynamics of adenoviral gene therapy vectors in large animal tumors.

Use of scintigraphy for assessment of fracture healing and early diagnosis of osteomyelitis following fracture repair in rabbits.

OBJECTIVE: To evaluate use of technetium Tc 99m disodium hydroxymethylene diphosphonate (99m-Tc-HDP) for assessing fracture healing and 99m-Tc-HDP and technetium Tc 99m ciprofloxacin (99m-Tc-CIPRO) for early diagnosis of osteomyelitis in rabbits. ANIMALS: 32 skeletally mature New Zealand White rabbits. PROCEDURE: A femoral fracture defect stabilized with bone plates and cortical screws was used. Scintigraphy was performed 4, 8, 12, and 16 weeks after surgery. The 99m-Tc-CIPRO scan was performed 48 hours after the 99m-Tc-HDP scan. The uptake ratio of the experimental limb to the normal limb was calculated by use of multiple regions of interest. Results of radiography performed to determine external callus and lysis grade and percentage defect ossification at 16 weeks were compared with scintigraphy results. RESULTS: Infected fractures had a higher uptake ratio for 99m-Tc-HDP and 99m-Tc-CIPRO than noninfected fractures. Infected fractures could be differentiated from noninfected fractures late in healing by use of 99m-Tc-HDP. Although 99m-Tc-CIPRO was better than 99m-Tc-HDP for identifying infection, there was a high incidence of false positive and negative results with 99m-Tc-CIPRO. There was an association between 99m-Tc-HDP uptake ratio and callus formation and a good correlation between 99m-Tc-HDP uptake ratio and defect ossification after 4 weeks. CONCLUSIONS AND CLINICAL RELEVANCE: 99m-Tc-HDP and 99m-Tc-CIPRO may be useful for diagnosing osteomyelitis late in fracture healing; however, false positive and false negative results occur. Technetium Tc 99m disodium hydroxymethylene diphosphonate may be useful for evaluating fracture healing.

Use of positive contrast rhinography and intranasal sinography for diagnosis of a nasofacial sinus tract in a dog.

Twelve days after a dog fight, a 2-year-old sexually intact female Bulldog was evaluated because of subcutaneous emphysema of increasing severity throughout the dogs body. Thoracic radiography revealed severe pneumomediastinum from which free air had extended into the retroperitoneal space, resulting in pneumoperitoneum. Tracheoscopic examination did not reveal a discontinuity of the trachea, pharynx, or larynx. A breach between the nasal cavity and subcutaneous tissues of the nasal region was suspected. Further diagnostic investigations included positive contrast rhinography and intranasal sinography. Via an angiographic catheter inserted into the left naris, positive contrast intranasal sinography revealed a sinus tract extending between the left nasal cavity and the subcutaneous tissue of the dorsal aspect of the nasal planum. Resolution of subcutaneous emphysema, pneumomediastinum, and pneumoretroperitoneum began 1 day after surgical closure of the intranasal opening of the sinus tract. To the authors' knowledge, this radiographic technique has not been reported.

Evaluation and treatment of decreased libido associated with painful lumbar lesions in two bulls.

Painful lesions of the vertebral column may cause decreased libido in bulls. Radiographic evaluation of vertebral skeletal problems in mature bulls is limited because of high body mass. Two breeding bulls with signs of decreased libido and spermatozoa production were evaluated. Initial systemic medical treatment for the conditions had not focused on localized lesions and was unsuccessful. Nuclear scintigraphy was performed in both bulls to determine the location of vertebral column lesions and facilitate localized treatment. Localized medical treatment was successful and resulted in decreased signs of pain and increased spermatozoa production in both bulls.

The role of protective lead clothing in reducing radiation exposure rates to personnel during equine bone scintigraphy.

Bone scintigraphy is often used in horses because of its sensitivity and noninvasive nature. A 99mTc labeled radiopharmaceutical is injected at a dose of between 5.7 and 7.3GBq. Images are acquired immediately postinjection and 2-4h post. People are often in the room with the horse during the acquisition process. Objectives of this study were to (a) document the radiation exposure rates at different distances from various sites of the horse at varying times post injection and (b) study the usefulness of wearing lead aprons to reduce exposure rates to personnel. Radiation exposure rates were measured in at three distances (at skin surface and at 30 and 100 cm from the skin) from three sites (shoulder, thorax, and pelvis) in 19 horses. Exposure rates were measured with and without shielding by a 0.5-mm lead equivalent apron during both the pool and delayed phases. A 0.5mm equivalent lead apron significantly decreases radiation exposure (P<0.05) at these three distances from the three sites during both image acquisition phases. Mean dose reduction factors from the lead apron range from 3.6 to 5.7.

Indium-111 labeled vitamin B12 imaging of a ciliary adenoma with concurrent grade 2 soft tissue sarcoma of the leg in a Labrador Retriever.

An 11-year-old, male castrated, Labrador Retriever was evaluated for the presence of rapidly growing concurrent leg and intraocular masses. Metastasis was noted in the chest at time of initial presentation. Indium-111 labeled vitamin B12 imaging was performed, and there was significant uptake by both primary tumors and the lung metastases. Enucleation and amputation were performed for palliative relief. The leg mass was a grade 2 soft tissue sarcoma and the ocular mass a ciliary adenoma. The dog remained symptom-free for approximately 10 weeks before developing signs of respiratory distress. He was euthanized 12 weeks after initial presentation, and there was diffuse infiltration of the lungs with metastatic sarcoma. Indium-111 labeled vitamin B12 imaging identified a ciliary adenoma in this case and may provide a useful differentiation technique for evaluation of intraocular and retrobulbar masses if it can be demonstrated that there is differential uptake between inflammatory or infectious conditions and neoplasia.