Sentinel node detection in an animal study: evaluation of a new portable gamma camera.

We tested the capacity of a newly developed portable gamma camera to precisely locate sentinel nodes by injecting a radiotracer. Two sets of experiments were performed on eight pigs under general anesthesia. 99mTc-Nanocolloid and dye complex was injected in the submuscular layer of the small bowel in the first set and subcutaneously in the knee region in the second set of experiments. Image acquisition of the sentinel nodes was performed with the Camera placed at various angles. A mosaic of images was obtained encompassing the injection sites, lymphatic pathways, and sentinel lymph nodes. Three-dimensional visualizations were obtained, allowing the precise location and complete excision of these nodes. The use of the portable gamma camera allowed the rapid visualization of the lymphatic pathways leading from the injection sites to the sentinel nodes and precise location of these nodes. The Camera was also useful to verify the complete removal of the labeled target tissues.

A newly developed intra-operative gamma camera: performance characteristics in a laboratory phantom study.

PURPOSE: Radioguided surgery depends on the intra-operative detection of radiolabelled tissues. This is currently accomplished with hand tools capable of providing a tone signal, depending on the proximity and direction of a radioactive source in relation to the probe. The advantages of visual images of radiolabelled tissues are well recognised, but satisfactory means of acquiring such images intra-operatively are not yet available. The goal of this study was to examine the performance of a newly developed intra-operative gamma camera, compact enough to be a hand tool and capable of yielding a visual image of the source field. METHODS: The study was performed in the laboratory with a phantom consisting of a water bath and small hollow spheres (1-2 cm in internal diameter) filled with 99mTc (1-5 microCi/cc), placed in different configurations within the bath. For comparison, studies were also performed using a standard intra-operative gamma probe, and others using a standard single-head high-resolution gamma camera. RESULTS: Compared with the gamma probe, the intra-operative camera was found to possess a superior ability to distinguish small, deep and weakly localised radioactivity sources from background. By acquiring images from different angles, it allowed a 3D understanding of multiple radioactive sources. It detected "cold" defects within a "hot" radiolabelled sphere. It discriminated a weak source located near a much "hotter" radioactivity source, similar to discrimination with the standard gamma camera, and discerned localised sources against a background of radioactivity. CONCLUSION: It is anticipated that the high imaging potential of the camera tested in this study will offer clinical advantages.

Assessment of osteoporosis by quantitative ultrasound versus dual energy X-ray absorptiometry in children with chronic rheumatic diseases.

OBJECTIVE: To evaluate the validity of quantitative ultrasound bone sonometry (QUBS) as a screening tool for the diagnosis of osteoporosis in children with chronic rheumatic diseases (CRD), compared to the conventional dual energy x-ray absorptiometry (DEXA). METHODS: Forty children with CRD [32 with juvenile idiopathic arthritis (JIA), 6 with systemic lupus erythematosus, and 2 with dermatomyositis] aged 9.9 +/- 4.3 years, were evaluated by QUBS of radius and tibia and DEXA of the lumbar spine. Twenty-five (62.5%) patients were treated with corticosteroids. Measurements of the velocity of the ultrasound wave, expressed as speed of sound (SOS) in m/s, and the results of the bone mineral density (BMD) assessed by DEXA were compared to reference data from healthy age and sex matched Israeli children. RESULTS: Compared to controls, patients with CRD had significantly lower values by QUBS and DEXA alike. BMD and SOS z scores < -1 SD were found in 45% and 38% of the patients, respectively. Reduced BMD and SOS values correlated with age at disease onset and corticosteroid treatment. BMD alone correlated negatively with disease duration and methotrexate therapy. BMD was significantly lower in patients with polyarticular JIA compared to patients with oligoarticular disease (p < 0.03). SOS values did not differ between subtypes of JIA. A significant positive correlation was found between the lumbar DEXA and radius SOS. CONCLUSION: QUBS evaluation of radius and tibia yielded results comparable to DEXA and may therefore be used for screening patients with CRD for osteoporosis. QUBS might represent a promising means of evaluating bone quality in at-risk children.