Intraoperative tumour detection using 111In-DTPA-D-Phe1-octreotide and a scintillation detector

Intraoperative tumour detection has been used in many applications. The examined tumour forms have varied and different detector systems and radiopharmaceuticals have also been used. The aim of this study was to evaluate and compare the ability of an NaI(Tl) scintillation detector to detect primary tumours and metastases in patients with different endocrine tumour types (e.g. carcinoid tumours, endocrine pancreatic tumours and thyroid tumours) and in patients with breast carcinoma or benign thyroid lesions, on the basis of their somatostatin receptor expression after i.v. injection of ¹¹¹In-DTPA-D-Phe¹-octreotide. Thirty patients were injected with ¹¹¹In-DTPA-D-Phe¹-octreotide intravenously. Scintigraphic images were taken 1 day after injection of the radiopharmaceutical, and surgery was performed 1-7 days post injection. An NaI(Tl) scintillation detector was used for intraoperative tumour detection. Tissue samples were collected during surgery for determination of ¹¹¹In activity concentration and histopathological examination. The scintigraphic images were positive in 29 out of 30 patients. Intraoperative tumour detection was successful in 43 of 66 collected biopsies: 10 out of 11 for carcinoid tumours, 7 out of 10 for medullary thyroid carcinoma (MTC) and 14 out of 22 for breast cancer. On the basis of our findings we conclude that intraoperative tumour detection with ¹¹¹In-DTPA-D-Phe¹-octreotide using this NaI(Tl) detector can be successful especially for carcinoid tumours and endocrine pancreatic tumours, due to the relatively high activity concentrations in these tumour types, but is less successful in other forms of thyroid cancer, including MTC, and breast cancer. For successful intraoperative detection, the detector characteristics are also very important, and further improvement of the detector systems is required to increase the sensitivity and specificity.     

111In-DTPA-D-Phe1-octreotide binding and somatostatin receptor subtypes in thyroid tumors.

The purpose of this study was to evaluate the potential for therapy of thyroid tumors using the radiolabeled somatostatin (SS) analog octreotide. METHODS: Concentrations of 111In activity in human thyroid tumors and normal thyroid tissue and blood samples were determined 1-15 d after intravenous injection of 111In-diethylenetriaminepentaacetic acid-Phe1-octreotide. The results were compared with SS receptor (sstr subtype profile (by Northern blot analysis) and the relative expression of the second subtype, sstr2 (by ribonuclease protection assay, RPA). The true tumor volumes in lymph node metastases from 1 patient were estimated. In total, tissues from 68 patients were included in the study. RESULTS: The highest tumor-to-blood ratio (T/B) for medullary thyroid carcinoma (MTC) was 360; for follicular adenoma (FA), 190; for Hurthle cell adenoma (HCA), 140; and for Hurthle cell carcinoma (HCC) and papillary carcinoma (PC), 70. The corresponding value was 7-18 for normal thyroid tissue, with higher values for colloid goiter (8-48) and thyroiditis (7-120). A high T/B was related to a large fraction of tumor cells in lymph node metastases. T/Bs were higher for the tumor samples with expression of sstr2 at Northern blot analysis than for those without. All thyroid tumor types regularly expressed sstr1, sstr3, sstr4, and sstr5. sstr2 was expressed in most MTC tumors but was not detected in FA or PC and was irregularly expressed in HCA and HCC. However, RPA analysis detected sstr2 in all tumors studied. CONCLUSION: Despite the lack of sstr2 at Northern blot analysis in most of the thyroid tumors studied, high T/Bs were in general found when compared with corresponding values for normal thyroid tissue. The sometimes extremely high ratios are promising and indicate a possibility of using radiolabeled octreotide for radiation therapy of sstr-positive tumors in the future.     

Therapy using labelled somatostatin analogues: comparison of the absorbed doses with 111In-DTPA-D-Phe1-octreotide and yttrium-labelled DOTA-D-Phe1-Tyr3-octreotide

OBJECTIVE: We estimated the absorbed doses for (111)In-DTPA-D-Phe(1)-octreotide and (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide in the same patients in order to compare the potential effectiveness (tumour dose) and safety (kidney and red marrow dose) of these drugs for peptide-targeted radiotherapy of somatostatin receptor positive tumours. METHODS: Six patients with neuroendocrine tumours underwent quantitative (111)In-DTPA-D-Phe(1)-octreotide SPECT and (86)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide PET scan at intervals of 1 week. All studies were performed with a co-infusion of amino acids for renal protection. PET and SPECT were reconstructed using iterative algorithms, incorporating attenuation and scatter corrections. Tissue uptakes (IA%) were measured and used to calculate residence times. Absorbed doses to tissues were estimated and the maximal allowed activity, defined as either the activity delivering 23 Gy to the kidneys (MAA(K)) or 2 Gy to the red marrow (MAA(RM)), was calculated and the resulting tumour absorbed doses were computed. RESULTS: For the MAA(K) the mean absorbed dose to the red marrow was lower for (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide than for (111)In-DTPA-D-Phe(1)-octreotide (1.8+/-0.9 Gy vs. 6.4+/-1.6 Gy; P<0.001). The median absorbed dose to tumours for the MAA(K) was two-fold higher for (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide as compared to (111)In-DTPA-D-Phe(1)-octreotide (30.1 vs. 12.6 Gy; P<0.05). The median absorbed dose to tumours estimated for the MAA(RM) was 10-fold higher for (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide than for (111)In-DTPA-D-Phe(1)-octreotide (35.1 Gy vs. 3.9 Gy; P<0.05). CONCLUSIONS: This direct intra-patient comparison confirms that the use of (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide is more appropriate for therapy of somatostatin receptor bearing tumours. When using (111)In-DTPA-D-Phe(1)-octreotide, the red marrow represents the major critical organ; this can result in significant toxicity if high activities have to be administered to obtain efficient tumour irradiation.     

Detection of somatostatin receptor-positive tumours using the new 99mTc-tricine-HYNIC-D-Phe1-Tyr3-octreotide: first results in patients and comparison with 111In-DTPA-D-Phe1-octreotide

Indium- 111 labelled DTPA-D-Phe1-octreotide (DTPA-OC, OctreoScan) has been introduced into clinical routine for the detection of somatostatin receptor (SSTR)-positive tumours, which are predominantly of neuroendocrine origin. Potential further applications in other SSTR-positive cancers (e.g. small cell lung cancer, breast cancer, melanoma) have been limited mainly by the restricted availability and the high radionuclide costs. Previous attempts to introduce technetium-99m labelled analogues of octreotide have not been very successful in terms of the labelling procedure, in vivo biodistribution and/or tumour detection capabilities. The aim of this study was to assess the performance of the new 99mTc-labelled analogue HYNIC-D-Phe1-Tyr3-octreotide (HYNIC-TOC), using tricine as co-ligand, for the detection of SSTR-positive tumours in patients in comparison with 111In-DTPA-OC. Overall, 13 patients were examined using 99mTc-tricine-HYNIC-TOC. Twelve patients had proven SSTR-positive tumours, while one patient presented with an SSTR-negative tumour. In 9 of the 13 patients both tracers (99mTc-tricine-HYNIC-TOC and 111In-DTPA-OC) were used. Serial whole-body scans, spot views and/or single-photon emission tomography studies were performed. Images were qualitatively and semi-quantitatively (ROI analyses) evaluated. The biodistribution of 99mTc-tricine-HYNIC-TOC in patients showed high physiological uptake in kidneys, moderate uptake in liver and spleen and little uptake in the gut. The tracer showed predominantly renal and negligible hepatobiliary excretion. Known SSTR-positive tumour sites showed rapid and intense tracer accumulation. 99mTc-tricine-HYNIC-TOC demonstrated rapid tissue uptake within the first hour after injection and had basically no significant clearance (<20%) from normal or tumour tissue thereafter. In contrast, 111In-DTPA-OC showed continuous clearance from normal tissues as well as renal and very little hepatobiliary excretion. Nevertheless, the patterns of accumulation of 99mTc-tricine-HYNIC-TOC in tumours and normal organs were comparable to those of 111In-DTPA-OC. A lesion-by-lesion comparison showed comparable tumour detection capabilities in intrahepatic tumour sites and superior capabilities of 99mTc-tricine-HYNIC-TOC in respect of extrahepatic lesions. In conclusion, 99mTc-tricine-HYNIC-TOC shows promise as a tracer for SSTR imaging, given its favourable clinical characteristics (specific and high receptor affinity, good biodistribution, renal excretion, low radiation exposure, high imaging quality, on-demand availability) and cost-effectiveness. 99mTc-tricine-HYNIC-TOC allows earlier diagnosis (10 min-4 h) compared with 111In-DTPA-OC (4-24 h).     

Biokinetics of 111In-DTPA-D-Phe(1)-octreotide in nude mice transplanted with a human carcinoid tumor

The long time biokinetics of the radiolabeled somatostatin analogues 111In-DTPA-D-Phe(1)-octreotide was studied in nude mice transplanted with the human carcinoid tumor, GOT1. The results were compared with those from the patient with the original tumor. This patient has been diagnosed and later treated with 111In-DTPA-D-Phe(1)-octreotide. The animals received about 2 MBq 111In-DTPA-D-Phe(1)-octreotide (0.1 microg) by injection into a tail vein. The animals were killed 0.5 h-14 d after injection of the radiopharmaceutical. Tumor tissue and normal tissues were collected and weighed and measured for 111In activity. The 111In uptake in the tumor was higher than in all normal tissues except the kidneys. The tumor-to-normal-tissue activity concentration, TNC, increased with time for all normal tissues studied. These data were similar to those observed for the original tumor in the patient. The similar biokinetics for 111In-DTPA-D-Phe(1)-octreotide in the tumor-bearing mice and the patient makes this animal model suitable as a model for evaluation of therapy of somatostatin receptor (sstr) expressing tumors with radiolabeled somatostatin analogues. Furthermore, the increase with time of TNC both in mice and the patient indicates that long-lived radionuclides are preferred for therapy with radiolabeled somatostatin analogues.     

Nuclear localization of 111In after intravenous injection of [111In-DTPA-D-Phe1]-octreotide in patients with neuroendocrine tumors.

Treatment with tumor-targeting substances is currently being evaluated in clinical trials. For patients with neuroendocrine tumors expressing somatostatin receptors, the 111In-labeled somatostatin analog [diethylenetriaminepentaacetic acid (DTPA)-DPhe1]-octreotide has been used with promising results. To further investigate the clinical effect of the injected conjugate, we analyzed the cellular distribution of 111In by ultrastructural autoradiography. METHODS: Seven patients with somatostatin receptor-expressing midgut carcinoid tumors scheduled for abdominal surgery were investigated by somatostatin receptor scintigraphy. During operation, tumor tissue samples and samples of normal intestine were collected, fixed, and processed for electron microscopy. A thin layer of film emulsion was applied on sections and after the exposure film was developed. The cellular distribution of silver precipitations indicating the presence of isotope was evaluated. RESULTS: Cell surface receptor binding and internalization of [111In-DTPA-D-Phe1]-octreotide in the tumor cells was easily revealed by silver precipitations in the film. Multiple silver grains were seen at the plasma membrane, in the cytoplasmic area among secretory granules and vesicular compartments, and in the perinuclear area. Silver grains were also regularly located in the nucleus. For all patients, the silver precipitation patterns from 111In decay were identical in all examined cells from removed tumors, and in most cells 111In could be seen in the nucleus. The specificity of the silver reaction products is supported by the observation that enterocytes in intestinal tissue specimens from near the tumor did not show any silver grains and no background labeling was seen in the plastic. CONCLUSION: After internalization through the somatostatin receptor system, 111In is translocated to the perinuclear area and into the nucleus. Whether the nuclide is still conjugated to the intact somatostatin analog or to part of it cannot be evaluated in this study. Despite the short irradiation range of 111In, the nuclear localization can explain its clinical effectiveness. The results from this study suggest that [111In-DTPA-D-Phe1]-octreotide may act as a powerful tumor cell-targeting substance.     

Patient-specific dosimetry calculations using mathematic models of different anatomic sizes during therapy with 111In-DTPA-D-Phe1-octreotide infusions after catheterization of the hepatic artery.

The aim of the study was to provide dosimetric data on intrahepatic (111)In-diethylenetriaminepentaacetic acid (DTPA)-D-Phe(1)-octreotide therapy for neuroendocrine tumors with overexpression of somatostatin receptors. METHODS: A dosimetric protocol was designed to estimate the absorbed dose to the tumor and healthy tissue in a course of 48 treatments for 12 patients, who received a mean activity of 5.4 +/- 1.7 GBq per session. The patient-specific dosimetry calculations, based on quantitative biplanar whole-body scintigrams, were performed using a Monte Carlo simulation program for 3 male and 3 female mathematic models of different anatomic sizes. Thirty minutes and 2, 6, 24, and 48 h after the radionuclide infusion, blood-sample data were collected for estimation of the red marrow radiation burden. RESULTS: The mean absorbed doses per administered activity (mGy/MBq) by the critical organs liver, spleen, kidneys, bladder wall, and bone marrow were 0.14 +/- 0.04, 1.4 +/- 0.6, 0.41 +/- 0.08, 0.094 +/- 0.013, and (3.5 +/- 0.8) x 10(-3), respectively; the tumor absorbed dose ranged from 2.2 to 19.6 mGy/MBq, strongly depending on the lesion size and tissue type. CONCLUSION: The results of the present study quantitatively confirm the therapeutic efficacy of transhepatic administration; the tumor-to-healthy-tissue uptake ratio was enhanced, compared with the results after antecubital infusions. Planning of treatment was also optimized by use of the patient-specific dosimetric protocol.     

L-3-[123I]Iodo-alpha-methyltyrosine scintigraphy in carcinoid tumors: correlation with biochemical activity and comparison with [111In-DTPA-D-Phe1]-octreotide imaging.

Carcinoid tumors can produce serotonin (5-hydroxytryptamine) and catecholamines from the precursors tryptophan and tyrosine. Our aim was to evaluate the tyrosine analog L-3-[123I]iodo-alpha-methyltyrosine (IMT) in the detection and the determination of biochemical activity of these tumors in comparison with 111In-labeled [diethylenetriaminepentaacetic acid (DTPA)-D-Phe1]-octreotide (111In-octreotide) scintigraphy. METHODS: SPECT and planar whole-body imaging were performed 15 min after administration of 300 MBq IMT in 22 patients with metastatic carcinoid tumors. The number of lesions detected was compared with the number detected by 111In-octreotide scintigraphy. The size and intensity of uptake of all lesions were graded using a simple scoring system, yielding a total body uptake score for both tracers. These scores were compared (nonparametric correlation) with biochemical markers of serotonin and catecholamine metabolism. RESULTS: IMT SPECT detected only 63 of 145 lesions detected by 111In-octreotide imaging (43%). IMT SPECT performance was best in the liver (60% detection rate). Both IMT uptake and 111In-octreotide uptake scores correlated with markers of serotonin metabolism (respective values for urinary 5-hydroxyindoleacetic acid: r = 0.67 and 0.48, P < 0.001 and 0.05; for urinary serotonin: r = 0.56 and 0.40, P = 0.002 and 0.05; and for platelet serotonin: r = 0.57 and 0.45, P < 0.01 and 0.05). No correlation with adrenaline or noradrenaline metabolites was found. However, IMT uptake, but not 111In-octreotide uptake, correlated with dopamine metabolite excretion (homovanillic acid: r = 0.60, P < 0.05; and dopamine relative sum: r = 0.61, P < 0.05). IMT uptake was higher in patients with increased dopamine metabolite excretion (P = 0.05). CONCLUSION: IMT uptake can be demonstrated in carcinoid lesions, but the method detected only 43% of carcinoid lesions that were positive on 111In-octreotide scintigraphy. Uptake of both tracers is related to the serotonin secretory activity. However, IMT uptake, but not 111In-octreotide uptake, was related to tumor dopamine metabolism. These findings may be of interest in the metabolic targeting of carcinoids.     

Biodistribution of [111In-DTPA-D-Phe1]-octreotide in dogs: uptake in the stomach and intestines but not in the spleen points towards interspecies differences

The purpose of the present study was to establish the tissue distribution in abdominal organs and the excretion of radioactivity after intravenous administration of [(111)In-DTPA-D-Phe(1)]-octreotide in healthy dogs. In five Beagle dogs computed tomography and single photon emission computed tomography (SPECT) at 24 h after injection of [(111)In-DTPA-D-Phe(1)]-octreotide revealed accumulation of radioactivity in the kidneys, gall bladder, gastric fundus and cardia, intestinal tract, but not in the spleen. These findings were confirmed by in vitro scintigraphy of single abdominal organs. This also demonstrated accumulation of radioactivity in the pancreas and located the radioactivity in the gastrointestinal tract primarily in the wall itself. In vitro autoradiography with (125)I-[Tyr(3)]-octreotide on tissue samples in two dogs revealed sst receptors in the medullary part of the kidney, the basal two-thirds of the gastric mucosa of the cardia and fundus, Peyer's patches and neural plexus of the gastrointestinal tract. No sst receptors were demonstrated in the liver, spleen, and pancreas. These results differ to findings in man, where there is uptake in the spleen but not in the stomach, most likely caused by interspecies variations in sst receptor subtype expression.     

Data acquisition using a scintillation detector interfaced to a personal microcomputer

A method is described for interfacing a cadmium telluride semiconductor nonimaging detector to a personal microcomputer in order to store and display nuclear medicine data. There was virtual identity between the count rates stored in the computer and those recorded from the detector's display, demonstrating that the computer accurately acquired data from the probe without erroneous loss or addition of data. Interfacing a nonimaging detector to a microcomputer may provide an extremely versatile method of acquiring, storing, and displaying nuclear medicine data.     

Radiation doses deriving from patients undergoing 111In-DTPA-d-Phe-1-octreotide scintigraphy

The purpose of this study was to estimate the radiation doses to nursing staff, other patients, accompanying persons and family members deriving from patients undergoing ¹¹¹In-DTPA-d-Phe-1-octreotide (¹¹¹In-OCT) scintigraphy. Dose rates were measured from 16 patients who had received an intravenous injection of 140±40 MBq ¹¹¹In-OCT. The measurements were performed at three different distances (0.5, 1 and 2 m) at 10–20 min, 5–7 h and 24 h (and in some cases, up to 48 h) after administration of ¹¹¹In-OCT. The effective half-lives of the biexponential decrease of the dose rates were estimated to be 2.94±0.27 h (T ₁) and 65.17±0.58 h (T ₂). The calculated maximum dose to other persons in the waiting area was 27.2 μSv, to family members 61.5 μSv, to nursing staff in a ward 24.1 μSv and to neighbouring patients in the ward 69.5 μSv. Our results clearly demonstrate that the calculated maximum radiation exposure to accompanying persons, personnel, family members and other patients is well below the maximum annual dose limit for non-professionally exposed persons. Received 20 May and in revised form 9 July 1997     

A new radiolabelled somatostatin analogue [111In-DTPA-D-Phe1]RC-160: preparation,biological activity,receptor scintigraphy in rats and comparison with [111In-DTPA-D-Phe1]octreotide

We have evaluated the potential usefulness of indium-111 labelled [DTPA-D-Phe¹]RC-160, derived from the octapeptide somatostatin analogue RC-160, as a radiopharmaceutical for the in vivo detection of somatostatin receptor-positive tumours. For this purpose ¹¹¹In-and ¹¹¹In-labelled [DTPA-D-Phe¹]RC-160 was tested for its biological activity, and applied for somatostatin receptor scintigraphy in vivo to rats bearing the transplantable rat pancreatic tumour CA20948, which expresses somatostatin receptors. We previously described the development of the ¹¹¹In-labelled somatostatin analogue [DTPA-D-Phe¹]octreotide and its use in the in vivo visualization of somatostatin receptor-positive tumours in rats and in humans. Like [¹¹¹In-DTPA-D-Phe¹]octreotide, [¹¹¹In-DTPA-D-Phe¹]RC-160 showed uptake in and specific binding in vivo to somatostatin receptor-positive organs and tumours, and the tumours were clearly visualized by gamma camera scintigraphy. However, as compared to [¹¹¹In-DTPA-D-Phe¹]octreotide, blood radioactivity (background) was higher, resulting in a lower tumour to blood (background) ratio. Using this animal model we therefore conclude that [¹¹¹In-DTPA-DPhe¹]RC-160 has no advantage over [¹¹¹In-DTPA-DPhe¹]octreotide as a radiopharmaceutical in the visualization of somatostatin receptors which bind both analogues. However, recent reports suggest the existence of different somatostatin receptor subtypes on some human cancers, which differentially bind RC-160 and not octreotide. These tumours include cancers of the breast, ovary, exocrine pancreas, prostate and colon. [¹¹¹In-DTPA-D-Phe¹]RC-160 might be of interest for future use in such cancer patients as a radiopharmaceutical for imaging somatostatin receptor-positive tumours, which do not bind octreotide.     

Somatostatin receptor scintigraphy with indium-111-DTPA-D-Phe-1-octreotide in man: metabolism, dosimetry and comparison with iodine-123-Tyr-3-octreotide.

Scintigraphy with 123I-Tyr-3-octreotide has several major drawbacks as regards its metabolic behavior, its cumbersome preparation and the short physical half-life of the radionuclide. The use of another radiolabeled analog of somatostatin, 111In-DTPA-D-Phe-1-octreotide, has consequently been proposed. DTPA-D-Phe-1-octreotide can be radiolabeled with 111In in an easy single-step procedure. DTPA-D-Phe-1-octreotide is cleared predominantly via the kidneys. Fecal excretion of radioactivity amounts to only a few percent of the administered radioactivity. For the radiation dose to normal tissues, the most important organs are the kidneys, the spleen, the urinary bladder, the liver and the remainder of the body. The calculated effective dose equivalent is 0.08 mSv/MBq. Optimal 111In-DTPA-D-Phe-1-octreotide scintigraphic imaging of various somatostatin receptor-positive tumors was obtained 24 hr after injection. In the six patients studied, tumor localization with 123I-Tyr-3-octreotide and with 111In-DTPA-D-Phe-1-octreotide were found to be similar. However, the normal pituitary is more frequently visualized with the latter radiopharmaceutical. In conclusion, 111In-DTPA-D-Phe-1-octreotide appears to be a sensitive somatostatin receptor-positive tissue-seeking radiopharmaceutical with some remarkable advantages: easy preparation, general availability, appropriate half-life and absence of major interference in the upper abdominal region, because of its renal clearance. Therefore, 111In-DTPA-D-Phe-1-octreotide may be suitable for use in SPECT of the abdomen, which is important in the localization of small endocrine gastroenteropancreatic tumors.     

Comparison of 111In-DOTA-DPhe1-Tyr3-octreotide and 111In-DOTA-lanreotide scintigraphy and dosimetry in patients with neuroendocrine tumours

Purpose Somatostatin receptor scintigraphy with ¹¹¹In-DOTA-DPhe¹-Tyr³-octreotide (¹¹¹In-DOTA-TOC) and ¹¹¹In-DOTA-lanreotide (¹¹¹In-DOTA-LAN) has been used for staging of neuroendocrine tumours (NETs). However, the comparative diagnostic value of these radioligands on a lesion basis has not yet been established. The aim of this study was to compare the diagnostic capacity of ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN scintigraphy in patients with NETs, evaluating whether significant differences exist in lesion imaging with these radioligands. Furthermore, dosimetric data were compared. Methods Forty-five patients with NETs were investigated with ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN scintigraphy. Scintigraphic results were compared with those of conventional imaging and/or surgery in each patient, and also ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) in 20 patients. Results ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN scintigraphy were true positive in 42/45 (93%) and 39/45 (87%) patients, and imaged 74/91 (81%) and 73/91 (80%) tumour lesions, respectively. ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN detected liver metastases in 21 and 14 patients, mediastinal metastases in seven and 11 patients, and bone metastases in two and seven patients, respectively. These radioligands revealed lesions not seen by conventional imaging in seven and eight patients, respectively, or by ¹⁸F-FDG-PET in eight and seven patients, respectively. The estimated tumour absorbed doses for ⁹⁰Y-DOTA-TOC were higher than those for ⁹⁰Y-DOTA-LAN in 14 patients, whereas the opposite was true in 12 patients. Conclusion Both ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN are suitable for imaging tumour lesions in patients with NETs and can detect lesions that may not be seen by conventional imaging and ¹⁸F-FDG-PET. Compared with ¹¹¹In-DOTA-LAN, ¹¹¹In-DOTA-TOC has a superior diagnostic capacity for liver metastases, but a lower diagnostic capacity for metastatic lesions in mediastinum and bone.     

Investigation of the PGNAA using the LaBr3 scintillation detector

The Joint Research Centre of the European Commission develops instrumentation for detection of hazardous materials. In relation to this a new experimental facility was constructed for research into methods applying the detection of characteristic gamma rays subsequent to neutron irradiation. This includes the detection of prompt gamma rays from neutron inelastic scattering and neutron capture. For this purpose the device employs LaBr₃ scintillation detectors. The paper investigates the applicability of the LaBr₃ scintillation detector to PGNAA.     

Monte Carlo simulation of the standardization of 22Na using scintillation detector arrays

In order to calibrate PET devices by a sealed point source, we contrived an absolute activity measurement method for the sealed point source using scintillation detector arrays. This new method was verified by EGS5 Monte Carlo simulation.