Preliminary experience with (68)Ga-DOTA-lanreotide positron emission tomography.

AIM: Positron emission tomography (PET) of (68)Ga-radiolabelled (SST) somatostatin receptor (R) binding peptides has recently been evaluated in SSTR positive tumor patients. First promising results in lung and thyroid tumor patients with (111)In-DOTA-Lanreotide (DOTA-LAN) scintigraphy have been described. We report our first experience with (68)Ga-labeled DOTA-LAN. METHODS: Eleven patients (3 non small cell lung cancer [NSCLC], 3 small cell lung cancer [SCLC], 3 radioiodine negative thyroid cancer, 2 medullary thyroid cancer [MTC]) were investigated. After intravenous injection of 75-150 MBq (68)Ga-DOTA-LAN dynamic studies were acquired over the tumor site for the first 40 min with a dedicated PET scanner in 3 patients, and 2 partial body scans were acquired at 20 and 50 min p.i. in 2 patients. Whole body acquisitions at 90 min after injection were acquired in all 11 patients. Image reconstruction was performed by iterative reconstruction utilizing additional transmission scans for attenuation correction. Vital parameters were recorded during the PET study and up to 24 h p.i. Blood and urinary sampling was done up to 4 hr after tracer injection in 8 patients. PET results were compared to conventional imaging techniques (CIT), i.e. computed tomography (CT) and/or magnetic resonance imaging (MRI). In 5 patients, (68)Ga-DOTA-LAN was compared with 2-[(18)F]fluoro-2-deoxy-D-glucose ((18)F-FDG). RESULTS: After intravenous (i.v.) injection of (68)Ga-DOTA-LAN the radioactivity in the blood rapidly decreased to less then 20% of the injected dose (ID) within the first 20 min and further decreased to less than 9% ID after 4 h. A cumulative urinary excretion of (68)Ga-DOTA-LAN up to 29.2 + or - 13.2% ID at 4 h was found. No acute side effects were observed. Tumor sites were visualized already during the first min after injection. Comparison of positron emission tomography (PET) and CIT showed concordant results in 3/8 patients and partial concordant results in 5/8 patients with matched results for the primary/recurrent tumor, mediastinal lymph nodes, or adrenal gland metastases. Partial concordant results were seen for the lung, bone, liver and cervical lymph node metastases. Micronodular metastases of the lung and the cerebrum were not visualized by (68)Ga-DOTA-LAN PET. The maximal standardized uptake values of the lung and bone tumor lesions ranged from 6 to 8 g/ml at 90 min p.i.. CONCLUSIONS: (68)Ga-DOTA-LAN visualized the majority of tumor lesions. Further studies are required to assess the clinical value, and to obtain the best imaging protocol of this new PET SSTR tracer.

FDG gamma camera PET equipped with one inch crystal and XCT. Assessment of myocardial viability.

UNLABELLED: Metabolic imaging with 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) is actually considered as the best method to detect and quantitatively assess myocardial tissue viability. The aim of this study was to investigate the accuracy of FDG gamma camera positron emission tomography (GCPET) imaging equipped with one inch NaI crystals in comparison to FDG dedicated PET (dPET) imaging as a "gold standard" in phantom and clinical studies. PATIENTS, METHODS: Nineteen patients with coronary artery disease (CAD) underwent both imaging modalities. Phantom and clinical GCPET imaging were performed with a dual-headed, coincidence based gamma camera equipped with 1 inch thick NaI crystals and an x-ray tube (XCT) for attenuation correction (AC), as well as with a dedicated PET scanner with AC. (99m)Tc tetrofosmin single-photon emission tomography (SPET) studies were performed for assessment of myocardial perfusion, with AC. RESULTS: Phantom studies showed a significant relation in segmental activity between FDG imaging with AC using GCPET and dPET (r = 0.91, p < 0.001). In clinical studies with AC correlation coefficients of mean segmental FDG uptake and regional defect size were r = 0.87 (p < 0.0001) and r = 0.83 (p < 0.0001), respectively. In regional analysis close agreement was even found in the most attenuated regions of the heart if AC was used in GCPET imaging. The overall agreement for detection of viable myocardium was 81% between FDG-dPET (AC) and FDG-GCPET (AC) and 74% between FDG-dPET (AC) and FDG-GCPET (NC). CONCLUSION: This study suggests that the assessment of myocardial metabolism by means of FDG is feasible with a coincidence based gamma camera equipped with 1 inch thick NaI crystals if AC is performed. The results reveal a close concordance and agreement between FDG-dPET (AC) and FDG-GCPET (AC) as compared to FDG-GCPET (NC).

Value of combined XCT/SPECT technology for avoiding false positive planar (123)I-MIBG scintigraphy.

AIM: The clinical value of combined XCT/SPECT technology in a single device in patients undergoing (123)I-MIBG scintigraphy was analyzed. METHODS: 31 patients (19 men, 12 women; mean age 55 years, range: 31-79 years) demonstrating focal accumulation in planar (123)I-MIBG scan were further investigated with a double headed gamma camera with an X-ray tomograph mounted on the same gantry (GE Medical Systems, Millennium VG with Hawkeye, Milwaukee, USA) for anatomical definition of the focal (123)I-MIBG uptake. The patients were referred to (123)I-MIBG scintigraphy because of biochemically (81%) and/or clinically (19%) suspected pheochromocytoma. RESULTS: In 23 out of 31 patients (74%) the fused images demonstrated physiological accumulation (i. e. intestinal, renal) of (123)I-MIBG. In two patients (6%) suspected adrenal MIBG-accumulation was caused by inhomogeneous liver uptake. In two patients (6%) focal abdominal accumulation was correctly localised in the adrenal glands. Furthermore, the differentiation of bone metastasis from a local recurrence for phaeochromocytoma was accurately possible for two patients (6%). Adrenal lesions mimicking liver foci were correctly localised in the remaining two patients (6%). CONCLUSION: Our study demonstrates the clinical value of XCT/SPECT in a single device in patients demonstrating focal (123)I-MIBG uptake in planar scintigraphy. The combined XCT/SPECT technology provides a higher diagnostic accuracy.

Combined transmission and (99m)Tc-sestamibi emission tomography for localization of mediastinal parathyroid glands.

AIM: Although parathyroid scintigraphy using (99m) Tc-sestamibi is considered the best preoperative localization method for hyperfunctioning parathyroid tissue it lacks the anatomical details required for successful, minimal invasive surgery of ectopic parathyroid lesions. This study presents the role of combined SPECT/X-ray-CT imaging in a single device for localization of mediastinal parathyroid glands. METHODS: (99m) Tc-sestamibi SPECT/X-ray-CT was performed by gamma camera-mounted anatomical X-ray tomography (GMAXT; GE Medical systems, Millenium VG with Hawkeye) in four patients with ectopic parathyroid glands (two patients with primary, two with persistent secondary hyperparathyroidism). The device contains an X-ray tube and a set of detectors that rotate around the patient combined with a gamma camera. For comparison with GMAXT addition-ally high resolution computed tomography images of the neck and mediastinum were performed. RESULTS: Correct preoperative localization was achieved. The parathyroid glands were located in the anterior mediastinum. High resolution computed tomography could not provide further details. Three patients were operated by a minimal invasive open and one patient by a transsternal approach because of concomitant aortic valve replacement. CONCLUSION: (99m)Tc-sestamibi/X-ray-CT fusion imaging in a single device can accurately localise ectopic or supernumerary mediastinal parathyroid tumours in primary and secondary hyperparathyroidism. Morbidity,radiation exposure, time, and costs are reduced by avoiding multiple diagnostic examinations and minimal invasive parathyroid surgery becomes possible.