The purpose of this study was to assess the cytogenetic effects of the X ray irradiation used during a CT scan in order to estimate the mean absorbed dose in circulating lymphocytes. Chromosomal aberrations were scored in blood lymphocytes of ten patients undergoing CT scans, by applying fluorescence in situ hybridisation (FISH) to metaphase cells and premature chromosome condensation (PCC) with chromosomes 1, 3 and 4 painting probes immediately after exposure. This generated a dosimetric index that reflects the dose to the circulating lymphocytes. By using PCC a significant increase in the frequency of chromosomal fragment was observed immediately after a CT scan. However, no significant increase in chromosomal aberration was detected in metaphase cells. The mean dosimetric index immediately after exposure was 0.057 Gy (95% CI: 0.052-0.082 Gy). This dosimetric index depends essentially on the size of the examined and exposed blood volumes. This dose is in close agreement with the dose length product (DLP) (Gy cm) (R = 0.80). It should be kept in mind when justifying requests for diagnostic CT scan especially in young patients. The presence of chromosomal fragments after a CT scan indicated the cytogenetic effect of a low dose. PCC associated with chromosome painting is a method for detecting the cytogenetic effect of a low dose immediately after exposure.

Brachytherapy consists of sealed radioactive source implantation. The diversity in the nature of radioelements, in their energy and activity requires strict implantation and utilization rules. These rules include radioactive source physical parameters check, after-loading machine and treatment planning system quality assurance and safe and reproducible dosimetric systems. Patient and medical workers information guarantee radioprotection and prevention of accidental exposures.

La curiethérapie consiste en l’implantation de sources radioactives scellées. La diversité de la nature des radioéléments employés, de leur énergie et de leur activité, impose des règles d’implantation et d’utilisation très strictes. Ces règles incluent une vérification des caractéristiques physiques des sources radioactives, une assurance de qualité des projecteurs de source et des systèmes informatiques de planification et l’utilisation de systèmes dosimétriques fiables et reproductibles. L’information des patients et du personnel paramédical permet de garantir la radioprotection et de prévenir les accidents d’exposition.

UNLABELLEDThis study examines how scatter correction might affect lesion detection and quantitation of tumor-to-normal breast tissue activity ratio in planar scintimammography.METHODSForty-one phantom acquisitions were performed to mimic a wide variety of scintimammographic imaging conditions in which lesions would be close to the chest wall. For each acquisition, the images corresponding to a 10% energy window (110) and two scatter correction methods [the Jaszczak (JA) method and a factor analysis (FA)-based method] were obtained in addition to the conventional 20% image (120). A total of 368 images in which detection of the "tumor" was judged borderline were selected, and 10 independent observers were asked to detect lesions in these images. Receiver operating curve analyses were performed to assess detection performance. Tumor-to-normal tissue activity ratios were calculated for quantitative analysis.RESULTSDetection performance significantly improved for the I10, JA and FA images compared to the 120 images, with an increase in sensitivity up to 8% for FA images. Sensitivity was especially increased for small lesions (13- and 16-mm3 spheres) and true heart-to-normal tissue activity ratios of > 12. Scatter correction also increased the certainty with which the readers gave their judgment. The tumor-to-normal tissue activity ratio was approximately 8% larger on JA or FA images and 1% larger on the I10 images compared to the 120 images. For a given image, the variability with which this ratio was estimated was reduced by approximately 4% on JA and FA images.CONCLUSIONBased on these phantom results, scatter correction might be used with benefit in scintimammography.

Implementation of the principle of optimization (ALARA), an essential radiation protection regulations, remains very limited in the medical field, even though 80% of workers whose exposure exceeds 50 mSv are to be found in this domain. The doses measured by legal dosimetry sometimes underestimate the real exposure of workers. It is therefore necessary to optimize the protection of occupational exposure in the medical field. This paper reviews the steps of the optimization procedure with emphasis on specificity of its application in this domain. Operational dosimetry as well as information on the residual risk due to low exposures and a better estimation on the risk/benefit factor for the patient are needed for satisfactory implementation.

To determine the cytogenetic and genotoxic risk associated with therapeutic exposure to I-131 (3.7 GBq) in 50 patients with differentiated thyroid carcinoma, we estimated the dosimetric index that reflects,the dose to the circulating lymphocytes on Day 4 and al several time intervals after exposure over a period of 2 yr, Methods: Chromosomal aberrations were scored in peripheral lymphocytes obtained before and then 4 days, 3 mo, 6 mo, 1 yr and 2 yr after the first administration of 3.7 GBq I-131 according to two methods: conventional cytogenetics and chromosome 4 painting. Results: The dosimetric index was 0.52 Gy on Day 4, 0.49 Gy at 3 mo, 0.45 Gy at 6 mo, 0.44 Gy at 1 yr and 0.42 Gy at 2 yr by conventional cytogenetics and 0.47 Gy on Day 4, 0.45 Gy at 3 mo, 0.44 Gy at 6 mo, 0.43 Gy at 1 yr and 0.42 Gy at 2 yr by chromosome 4 painting, We found a decrease in the frequency of chromosomal aberrations between Day 4 and 3 mo after exposure. This may be due to the decrease of lymphocyte counts shortly after I-131 administration, which will recover later on, In contrast, the number of anomalies remained constant starting 3 mo after I-131 administration. Conclusion: These techniques permit retrospective biological dosimetry for up to 2 yr after therapeutic exposure to I-131.

Le personnel du milieu medical represente la majorite (70%) des travailleurs exposes aux rayonnement ionisants. Leur exposition est tres variable selon les pratiques et les domaines concernes. Nous nous sommes interesses dans ce travail a l'exposition externe en abordant successivement les concepts du passge de la dose a l'equivalent de dose, les principaux dosimetres (actifs et passifs) disponibles, l'origine de l'exposition et enfin, l'exposition individuelle au travers de la dosimetrie reglementaire et de quelques etudes de dosimetrie operationnelle. Actuellement les informations issues de la dosimetrie reglementaire sont rassurantes puisque 93% des travailleurs sont exposes a des niveaux inferieurs au niveau d'enregistrement des films dosimetres (0,2 mSv) et 98% a moins de 5 mSv/an. Cependant des etudes en medecine nucleaire et surtout en radiologie interventionnelle montrent la necessite d'un rappel constant des bonnes pratiques de radioprotection, le besoin de relais entre la personne competente et les services concernes et leur interet pour la mise en oeuvre d'une demarche d'optimisation.

UNLABELLED:Biological dosimetry was applied to 30 patients with differentiated thyroid carcinoma who were treated with 131I (3.7 GBq) to ablate thyroid remnants after surgery or in case of metastases.METHODS:Chromosomal aberrations were scored in peripheral blood samples obtained before and 4 days after the first administration of 3.7 GBq 131I according to two methods: conventional cytogenetics and chromosome 4 painting. This generated a dosimetric index that reflects the dose to the bone marrow.RESULTS:Results of both techniques were in close agreement. The mean dosimetric index at Day 4 was 0.54 Gy (95% CI: 0.45-0.62 Gy) by conventional cytogenetics and 0.48 Gy (95% CI: 0.42-0.61 Gy) by chromosome 4 painting. This dose is 2-4 times higher than that derived from the MIRD estimates. Since blood was drawn at Day 4, this technique underestimates the dose by at least a third. The high dose estimate may be related to the hypothyroid status of these patients at the time of 131I administration, a condition which decreases renal clearance of 131I and thus increases whole-body irradiation. This dose estimate was closely related to whole-body retention of 131I at Day 4.CONCLUSION:These data should be used to estimate the risk due to 131I exposure.

PURPOSETo optimize use of iodized oil for diagnostic computed tomography (CT) enhanced with iodized oil and for interstitial radiation therapy with iodine-131-labeled iodized oil, the authors quantified the distribution of iodized oil after injection of different formulations of iodized oil into the hepatic artery.MATERIALS AND METHODSI-125-labeled iodinated ethyl ester of poppyseed oil in two viscosities (iodized oil ultrafluid [viscosity, 0.04 Pa/sec] and iodized oil fluid [viscosity, 0.17 Pa/sec]) was injected (pure forms and three different emulsions of each) into the hepatic artery of rabbits bearing VX2 tumors in the liver. All rabbits received a radiation dose of 4 MBq per kilogram of body weight in 0.1 mL/kg iodized oil. Animals were killed 4 days later, and iodized oil uptake was evaluated in the tumor, nontumorous liver, and lung.RESULTSThere were no statistically significant differences in uptake between pure iodized oil ultrafluid or fluid or between the same type of emulsions made with each type of iodized oil. Lung uptake was significantly higher with pure iodized oil ultrafluid and fluid (19.75 kBq/g +/- 3.25 [standard error of the mean] vs 19.48 kBq/g +/- 6.15, respectively) than with any emulsions (range, 3.72-8.14 kBq/g; mean, 5.68 kBq/g) except the small-droplet oil-in-water emulsion (10.51 kBq/g +/- 1.18). The ratio of tumor to nontumorous liver uptake of iodized oil was significantly higher with large-droplet water-in-oil emulsions made of iodized oil ultrafluid or fluid (10.26 +/- 2.88 and 9.53 +/- 0.64, respectively) than with any other product (range, 4.07-5.38; mean, 4.49).CONCLUSIONUse of large-droplet water-in-oil emulsions limited lung uptake and increased tumor uptake of iodized oil after intraarterial hepatic injection in rabbits bearing VX2 tumors in the liver.

A non-destructive, automatic and quantitative method was developed in order to characterize the structure of the gamma camera collimators because they remain the weakest part of the system. As the quality of a collimator depends on the regularity of the hole shape, the authors developed software implemented on a microcomputer using the macro programming language provided by the image processing program NIH Image 1.52. A radiograph is first obtained by means of a home made rectilinear scanner and digitized with a film scanner. These data are then analyzed. The hole dimension and septal thickness are determined by applying a matched mask on the digitized image made binary. The hole inclination is estimated by the shift of the center of gravity determined from the gray level image. For foil collimators the results show a big spread; e.g. S.D. are equal to 0.98 and 0.24 mm for 2.3 mm diameter and 0.15 mm septal thickness (manufacturers data) respectively. A cast collimator with the same characteristics has S.D. equal to 0.16 and 0.08 mm. In terms of hole inclination, a value of up to 1.3 degrees was found with foil technology. This method allows to detect automatically the manufacturing defaults of a collimator. Any geometry (parallel, fan beam) may be evaluated with minor changes in the technique

En 1993, plus de 10 000 travailleurs, soit pres du quart des travailleurs exposes de facon significative, travaillent dans les domaines medical, de la recherche et des industries non electronucleaires en France. La dose moyenne annuelle par travailleur significativement expose est de 2 mSv pour les veterinaires, 3 mSv pour les travailleurs du secteur medical, 5,5 mSv pour les travailleurs de l'industrie non electronucleaire. Dans le secteur industriel, plus de 8 % des travailleurs exposes ont une exposition annuelle superieure a 15 mSv. Ces expositions ne sont ni negligeables, ni veritablement plus faibles que celles observees dans l'electronucleaire ou l'optimisation de la radioprotection est couramment appliquee. A ce jour, aucune publication ne fait etat d'experiences en matiere d'optimisation dans les autres secteurs. La realisation d'etudes d'optimisation dans des centres de reference, pour des examens radiologiques ou des pratiques industrielles specifiques, en particulier pour toutes les nouvelles pratiques telles que la radiologie interventionnelle, permettrait de fournir aux autres entreprises, services ou cabinets, des informations sur ce que pourrait etre une pratique optimisee, dans des conditions de reference, en matiere de radioprotection. Les vraies difficultes pour la mise en œuvre de l'optimisation dans les secteurs industriel et medical ne sont pas celles le plus souvent mises en avant (faibles niveaux d'exposition, ressources insuffisantes, complexite...), mais plutot un manque de donnees appropriees et surtout une absence de culture du risque residuel.

For more than a decade radioiodinated meta-iodobenzylguanidine (mIBG) has been commonly used for neuroblastoma imaging. The accuracy of this scintigraphic method in detecting both primary and secondary tumour sites is crucial when evaluating the extent of disease. The aim of our study was to assess the impact of high-activity mIBG scintigraphy on neuroblastoma staging. Eighteen scans (TS) were obtained in 15 children after a therapeutic dose of iodine-131 mIBG and compared to diagnostic mIBG scans (DS) (in eight cases with131I-mIBG and in ten cases with123I-mIBG). The superiority of TS over DS was confirmed by the overall results: a total of 220 lesions were disclosed with TS and 171 with DS. However, in only one case did the TS findings, namely skeletal involvement not evidenced on corresponding DS, have an impact on clinical staging. In contrast, neither TS nor DS detected proven bone involvement in four patients. The dose-related sensitivity of mIBG scintigraphy in detecting neuroblastoma tumour sites was confirmed. The ultimate impact of high-dose scans on neuroblastoma management, however, seems limited.

Although the Imatron is based on a technology different from that of conventional CT scanners, its physical principle is comparable. For this reason dosimetric studies were carried out in the same manner that is by employing small thermoluminescent dosimeters. The results obtained with this technique for the four specific protocols of the Imatron indicated surface doses between 0.7 and 15.7 cGy and between 0.1 and 7.2 cGy at surface of the slice. The weakest doses were recorded during cardiac exams for which this type of CT scanner was designed and developed. This highest doses were delivered for scans of the head region.

Patient tailored dosimetry is important in some diagnostic and most of therapeutic applications in Nuclear Medicine. The most widely used tool to compute internal doses is the absorbed fraction method from which S factor tables and the MIRD formalism are derived. Nevertheless, for organs or phantoms for which absorbed fractions do not exist, other methods, such as the build up factor method or the geometric factor method, can be applied. We have developed an interactive program which integrates all these methods. It can be used for the whole range of nuclear medicine applications and takes into account individual characteristics of each patient. Our program considers several cases: a patient without and with metastases and with characteristics close or very different from those of one of the phantoms described by Cristy. Depending on the case, the dosimetric evaluation is performed either with the data of the MIRD pamphlets or with the aid of an equivalent patient phantom computed to obtain the gravity center of various organs. Then the dosimetry can be established by using one of the methods previously mentioned. When metastases are present, they are located with the help of an interactive process based on digitized anatomical representations showing anteriormore » and lateral views of organs or skeleton which guide the operator to locate metastases with respect to organs. Our results have been compared with those obtained by MIRDOSE 2. For example, where the thyroid is the source organ and iodine 131 the radionuclide, the doses for the target organs differ by less than 8%. At present oar method is being validated by measurements obtained from a RANDO phantom. This program offers a dosimetric tool well suited to the patient morphology and to any radionuclide distribution to determine the dose to healthy tissue and lesions. Its application should be helpful in the field of metabolic radiotherapy, especially in radioimmunotherapy and treatment with mIBG.« less

Dans les applications diagnostiques des radionucléides, la méthode habituellement utilisée pour les évaluations dosimétriques est celle développée par le “Medical internal radiation dose committee”. Cette méthode présente, cependant, des limitations car elle s'adresse à des modèles donnés et à des organes bien définis. Aussi, afin de satisfaire tous les besoins en dosimétrie interne pour les applications diagnostiques et thérapeutiques, nous avons développé un programme permettant de tenir compte non seulement des caractéristiques propres à chaque patient (âge, taille, poids et sexe) mais également de celles des sites radioactifs (tumeur, métastases, lésions) de position, de forme et de dimension quelconques. Ce programme permet de calculer la dose délivrée à des organes “cibles” par des “sources” soit préalablement choisies, soit localisées sur un écran à partir de la représentation d'un squelette et de planches anatomiques. Ainsi, ce programme, qui offre une approche de dosimétrie personnalisée, répond à la fois aux besoins diagnostiques pour la quasi totalité des radionucléides disponibles et aux besoins thérapeutiques pour l'évaluation de doses à des organes particulièrement critiques telles que la moelle et les gonades.

Iodine-131 is uniquely able to demonstrate iodine uptake of differentiated thyroid carcinoma (DTC), but precise localization may be difficult, especially in the thorax, due to the quality of image resolution with 1311 and the lack of anatomical landmarks. When bone metastases do not show radioiodine uptake, bone scintigraphy can be used to detect them. We studied two groups of patients. In group 1, 15 patients with known bone metastases of DTC were treated with 3.7 GBq 131I. After 4 or 5 days, technetium-99m hydroxymethylene diphosphonate (HMDP; 740 MBq) was injected and a whole-body scan with simultaneous acquisition of 131I and 99mTc-HMDP images was carried out using a large field of view gamma camera fitted with a high-energy collimator. Technetium uptake was abnormal in 47 of 63 localizations, being increased in 29 foci, decreased in 7 and heterogeneous in 11. The superimposition of 131I and 99mTc-HMDP scans permitted an accurate localization in 80% of spine metastases and in 46% of osseous thoracic localizations, even in the presence of lung metastases. In group 2, 9 patients, who had bone pain, neurological signs or elevated serum thyroglobulin, had DTC bone metastases without iodine uptake. They received a diagnostic dose of 99mTc-HMDP 3h prior to scintigraphy with a large field of view gamma camera fitted with a low-energy collimator. Technetium uptake was abnormal in 37 of 38 localizations, being increased in 34 foci and decreased in 3. One false-negative was found in a skull metastasis. In both groups of patients, 99mTc-HMDP scans were useful. The procedure allows accurate localization of bone metastases and can be used as a guide for subsequent radiological investigations.

Twenty patients, 16 males and 4 females, aged 11–76 yr, were treated for a metastatic pheochromocytoma at our institution between 1985 and 1990. A neurofibromatosis was associated in 4. Thirteen patients had a unilateral adrenal tumor, 3 had an extraadrenal retroperitoneal tumor, 2 had a bilateral adrenal pheochromocytoma, one had a unilateral tumor with a contralateral medullary hyperplasia and one an adrenal and an extraadrenal pheochromocytoma. Metastases occurred in all patients, at presentation in 11,10 to 30 months later in 7, and 9 and 28 yr later, respectively in two. Histology did not afford conclusive evidence for malignancy. Catecholamine hyperproduction was present in all, predominantly affecting norepinephrine. Neuron Specific Enolase level was elevated in 11, Neuropeptide Y level in 9 and procalcitonin level in 11/18. High dopamine, methoxytyramine and homovanilic acid excretion levels seemed to correlate with large tumors or terminal stage. MIBG uptake was found in 16 after a diagnostic dose and in 1 only after a therapeutic dose. Surgery was performed on primary tumor in 18 and on distant métastase in 10. lodine-131 MIBG therapy was performed in 11, among whom 9 were évaluable. Cumulative activity ranged from 100 to 711 mCi, in 1 to 6 courses. Symptomatic improvement occurred in 5 patients, stabilization was observed in 3 and tumor partial response in two, which lasted for 28 and 9 months, respectively terminating in a rapidly progressing disease with bone marrow involvement. Moderate myelosuppression occurred in 4 patients. Chemotherapy gave no response in 7 evaluable patients. Fourteen patients died with a median survival of 16 months from diagnosis of metastases (range 3–60). Response to therapy was poor and warrants further cooperative trials.

The purpose of this study was to evaluate the feasibility of a method that would use 59Fe quantitative sequential scintigrams together with a few blood samples in place of conventional ferrokinetic studies. To quantitate the efficiency of erythropoiesis or iron deposition sites, the radio-iron blood activity was subtracted by means of a whole body scanning with 99mTc-labelled erythrocytes. The study was performed on 31 patients (36 examinations) and regions of interest were drawn by three physicians on the sacral bone, the liver, the spleen and the femoral bone. To assess the physical feasibility of the scintigraphic method, correlation coefficients were computed between the number of counts of the 59Fe and 99mTc images and the corresponding 99mTc and 59Fe activities. To assess the clinical feasibility, the consistency of the data resulting from the drawing of the ROIs was verified and those of conventional ferrokinetics were introduced and their consistency verified. These assessments suggest that the scintigraphic method can be used in place of the conventional external counting method.