ABSTRACT
A MCNP model was developed for the efficiency calibration of an in situ gamma ray spectrometry system based on a high purity germanium (HPGe) detector. The detector active crystal volume was adjusted semi-empirically against experimental measurements. Calculated full energy peak efficiency curves, over the photon energy range between 50 keV and 5 MeV, are presented for surface and slab source configurations. The effect of different collimator apertures and the contribution of different HPGe crystal regions in the detector response are also shown.
ABSTRACT
PURPOSE: The aim of this study is to evaluate the effectiveness of (111)In-DTPA-Phe(1)-octreotide infusions after selective catheterization of the hepatic artery in inoperable metastasised liver, sst(2) receptor-positive neuroendocrine tumours due to the effect of (111)In Auger electron emission, minimising in parallel the toxicity of non-target tissue. METHODS: The average dose per session administered monthly to each patient (17 cases in total) was 6.3+/-2.3 GBq. Repetitions did not exceed 12-fold, except in one case (15 sessions). Response assessment was classified according to the Response Evaluating Criteria in Solid Tumours. CT/MRI scans were performed as baseline before, during and after the end of treatment, and monthly ultrasound images for follow-up measurements. Toxicity (World Health Organization criteria) was measured using blood and urine tests of renal, hepatic and bone marrow function. RESULTS: Complete response was achieved in one (5.9%) patient and partial in eight (47.0%), and disease stabilization in 3 (17.7%) patients; five (29.4%) did not respond. A 32-month median survival time was estimated in 12 (70.5%). Nine of these 12 surviving had a mean target diameter shrinkage from 144+/-81 to 60+/-59 mm. Grade 1 erythro-, leuko- and thrombo-cytopenia occurred in three (17.6%) cases. CONCLUSION: In unresectable metastatic liver lesions positive for somatostatin receptors repeated, transhepatic high doses of (111)In-DTPA-Phe(1)-octreotide show an effective therapeutic outcome. Given the locoregional modality character of the administration technique plus the extremely short range of (111)In Auger and internal conversion electrons emission, no nephro-, liver- or myelo-toxicity has so far been observed.
Subject(s)
Hepatic Artery , Liver Neoplasms/radiotherapy , Liver Neoplasms/secondary , Neuroendocrine Tumors/radiotherapy , Neuroendocrine Tumors/secondary , Adult , Aged , Female , Humans , Infusions, Intra-Arterial , Liver Neoplasms/diagnostic imaging , Male , Middle Aged , Neuroendocrine Tumors/diagnostic imaging , Radionuclide Imaging , Treatment OutcomeABSTRACT
UNLABELLED: 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.
Subject(s)
Image Interpretation, Computer-Assisted/methods , Models, Biological , Neuroendocrine Tumors/diagnostic imaging , Neuroendocrine Tumors/radiotherapy , Radiometry/methods , Radiotherapy Planning, Computer-Assisted/methods , Somatostatin/analogs & derivatives , Adult , Aged , Body Burden , Body Size , Computer Simulation , Female , Hepatic Artery/diagnostic imaging , Hepatic Artery/metabolism , Humans , Infusions, Intra-Arterial , Male , Middle Aged , Radionuclide Imaging , Radiopharmaceuticals/administration & dosage , Radiopharmaceuticals/therapeutic use , Radiotherapy Dosage , Relative Biological Effectiveness , Reproducibility of Results , Sensitivity and Specificity , Somatostatin/administration & dosage , Somatostatin/therapeutic useABSTRACT
Thirteen (13) patients with liver neuroendocrine carcinomas metastases, positive for somatostatin receptors, confirmed by scintigraphy were infused with 4070-7030 MBq per session of In-111-octreotide after selective hepatic catheterization, exploiting the catastrophic activity of Indium Auger and Internal Conversion electron emission on cell DNA. Evaluation of the treatment was assessed by ultrasonography (US) as well as by computed tomography and/or magnetic resonance imaging scans. US appears to be the imaging procedure of choice because the examination is sensitive for evaluating lesions' edema and cystic components, provides precise measurement of tumor size, and is inexpensive. Degeneration US signs were classified in stage I (an echolucent rim in the periphery of the lesion), stage IIa (lesion with large cystic spaces), stage IIb (tiny cystic spaces) and stage III (absorption of the cystic component or stable cystic remnants).