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.

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.

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.

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.

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.