RFPID: development and 3D-printing of a female physical phantom for whole-body counter.

Whole-body counters (WBC) are used in internal dosimetry forin vivomonitoring in radiation protection. The calibration processes of a WBC set-up include the measurement of a physical phantom filled with a certificate radioactive source that usually is referred to a standard set of individuals determined by the International Commission on Radiological Protection (ICRP). The aim of this study was to develop an anthropomorphic and anthropometric female physical phantom for the calibration of the WBC systems. The reference female computational phantom of the ICRP, now called RFPID (Reference Female Phantom for Internal Dosimetry) was printed using PLA filament and with an empty interior. The goal is to use the RFPID to reduce the uncertainties associated within vivomonitoring system. The images which generated the phantom were manipulated using ImageJ®, Amide®, GIMP®and the 3D Slicer®software. RFPID was split into several parts and printed using a 3D printer in order to print the whole-body phantom. The newly printed physical phantom RFPID was successfully fabricated, and it is suitable to mimic human tissue, anatomically similar to a human body i.e., size, shape, material composition, and density.

DETERMINATION OF NEUTRON EFFECTIVE DOSES IN WHOLE BODY POINT SOURCE EXPOSURES.

The objective of this work is to obtain fluence to effective dose conversion coefficients for neutron point sources, using the GEANT4 toolkit. These calculations aim to investigate the aspects of neutron transport in the human body through Monte Carlo simulation using the International Commission on Radiological Protection (ICRP) voxel phantoms, described in its publication 110. A benchmarking of the code was made for the case of monoenergetic plane parallel neutron beam in the antero-posterior (AP) irradiation geometry and organ absorbed dose conversion coefficients were compared with those found in the ICRP publication 116. The results showed good agreement with ICRP results in the studied energy range. Conversion coefficients were presented for specific conditions with 241Am-Be and 252Cf point neutron sources 1 m away from the phantom in the AP geometry.

Improvement of the WBC calibration of the Internal Dosimetry Laboratory of the CDTN/CNEN using the physical phantom BOMAB and MCNPX code.

The Laboratory of Internal Dosimetry of the Center for Development of Nuclear Technology (LDI/CDTN) is responsible for routine internal monitoring of occupationally exposed individuals. The determination of photon emitting radionuclides in the human body requires calibration of the detector in specific counting geometries. The calibration process uses physical phantoms containing certified activities of the radionuclides of interest. The objective of this work was to obtain calibration efficiency curves of the Whole Body Counter in operation at the LDI/CDTN using a BOMAB physical phantom and Monte Carlo simulations.

Assessment of simulated high-dose partial-body irradiation by PCC-R assay.

The estimation of the dose and the irradiated fraction of the body is important information in the primary medical response in case of a radiological accident. The PCC-R assay has been developed for high-dose estimations, but little attention has been given to its applicability for partial-body irradiations. In the present work we estimated the doses and the percentage of the irradiated fraction in simulated partial-body radiation exposures at high doses using the PCC-R assay. Peripheral whole blood of three healthy donors was exposed to doses from 0-20 Gy, with 6°Co gamma radiation. To simulate partial body irradiations, irradiated and non-irradiated blood was mixed to obtain proportions of irradiated blood from 10-90%. Lymphocyte cultures were treated with Colcemid and Calyculin-A before harvest. Conventional and triage scores were performed for each dose, proportion of irradiated blood and donor. The Papworth's u test was used to evaluate the PCC-R distribution per cell. A dose-response relationship was fitted according to the maximum likelihood method using the frequencies of PCC-R obtained from 100% irradiated blood. The dose to the partially irradiated blood was estimated using the Contaminated Poisson method. A new D0 value of 10.9 Gy was calculated and used to estimate the initial fraction of irradiated cells. The results presented here indicate that by PCC-R it is possible to distinguish between simulated partial- and whole-body irradiations by the u-test, and to accurately estimate the dose from 10-20 Gy, and the initial fraction of irradiated cells in the interval from 10-90%.

A mobile bioassay laboratory for the assessment of internal doses based on in vivo and in vitro measurements.

Internal exposures may occur in nuclear power plants, radioisotope production, and in medicine and research laboratories. Such practices require quick response in case of accidents of a wide range of magnitudes. This work presents the design and calibration of a mobile laboratory for the assessment of accidents involving workers and the population as well as for routine monitoring. The system was set up in a truck with internal dimensions of 3.30 m × 1.60 m × 1.70 m and can identify photon emitters in the energy range of 100-3,000 keV in the whole body, organs, and in urine. A thyroid monitor consisting of a lead-collimated NaI(Tl)3" × 3" (7.62 × 7.62 cm) detector was calibrated with a neck-thyroid phantom developed at the IRD (Instituto de Radioproteção e Dosimetria). Whole body measurements were performed with a NaI(Tl)8" × 4" (20.32 × 10.16 cm) detector calibrated with a plastic-bottle phantom. Urine samples were measured with another NaI(Tl) 3" × 3" (7.62 × 7.62 cm) detector set up in a steel support. Standard solutions were provided by the National Laboratory for Metrology of Ionizing Radiation of the IRD. Urine measurements are based on a calibration of efficiency vs. energy for standard volumes. Detection limits were converted to minimum committed effective doses for the radionuclides of interest using standard biokinetic and dosimetric models in order to evaluate the applicability and limitations of the system. Sensitivities for high-energy activation and fission products show that the system is suitable for use in emergency and routine monitoring of individuals under risk of internal exposure by such radionuclides.

Thermal radiation absorbed by dairy cows in pasture.

The goal of the present paper was to assess a method for estimating the thermal radiation absorbed by dairy cows (0.875 Holstein-0.125 Guzerath) on pasture. A field test was conducted with 472 crossbred dairy cows in three locations of a tropical region. The following environmental data were collected: air temperature, partial vapour pressure, wind speed, black globe temperature, ground surface temperature and solar radiation. Average total radiation absorbed by animals was calculated as R(abs) = 640.0 +/- 3.1 W .m(-2). Absorbed short-wave radiation (solar direct, diffuse and reflected) averaged 297.9 +/- 2.7 W m(-2); long wave (from the sky and from terrestrial surfaces) averaged 342.1 +/- 1.5 W m(-2). It was suggested that a new environmental measurement, the effective radiant heat load (ERHL), could be used to assess the effective mean radiant temperature (T*(mr)). Average T*(mr) was 101.4 +/- 1.2 degrees C, in contrast to the usual mean radiant temperature, T(mr) = 65.1 +/- 0.5 degrees C. Estimates of T*(mr) were considered as more reliable than those of T (mr) in evaluating the thermal environment in the open field, because T (mr) is almost totally associated only with long wave radiation.

A methodology to evaluate occupational internal exposure to fluorine-18.

The objective of this work is to develop procedures for internal monitoring of (18)F to be applied in cases of possible incorporation of fluoride and (18)FDG, using in vivo and in vitro methods of measurements. The Na I (Tl) 8" x 4" scintillation detector installed at IRD-Whole Body Counter was calibrated for measurements with a whole body anthropomorphic phantom, simulating homogeneous distribution of (18)F in the body. The NaI(Tl) 3"x 3" scintillation detector installed at the IRD-Whole Body Counter was calibrated for in vivo measurements with a brain phantom inserted in an artificial skull, simulating (18)FDG incorporation. The HPGe detection system installed at the IRD-Bioassay Laboratory was calibrated for in vitro measurements of urine samples with 1 liter plastic bottles containing a standard liquid source. A methodology for bioassay data interpretation, based on standard ICRP models edited with the software AIDE-version 6, was established. It is concluded that in vivo measurements have sufficient sensitivity for monitoring (18)F in the forms of fluoride and (18)FDG. The use of both in vitro and in vivo bioassay data can provide useful information for the interpretation of bioassay data in cases of accidental incorporation in order to identify the chemical form of (18)F incorporated.

Biokinetics and dosimetry of 188Re-anti-CD20 in patients with non-Hodgkin's lymphoma: preliminary experience.

BACKGROUND: Radioimmunotherapy is a molecular targeting treatment for high-risk leukemia and lymphoma. Rhenium-188-labeled anti-CD66 monoclonal antibody has been used successfully in patients with high-risk acute myeloid leukemia or myelodysplastic syndrome. Our aim was to establish the biokinetics of (188)Re-anti-CD20 in patients and to evaluate its dosimetry as a target-specific radiopharmaceutical for non-Hodgkin's lymphoma (NHL) radioimmunotherapy. METHODS: Whole-body images were acquired at various times after administration of (188)Re-anti-CD20, obtained from instant freeze-dried kit formulations with radiochemical purity >95%. Regions of interest (ROIs) were drawn around source organs in each time frame. The cpm of each ROI was converted to activity using the conjugate view counting method. The image sequence was used to extrapolate time-activity curves in each organ to calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation dose estimates. RESULTS: Dosimetric studies indicated that after administration of 4.87-8.72 GBq of (188)Re-anti-CD20, the absorbed dose to total body would be 0.75 Gy, which corresponds with the recommended dose for NHL therapies. CONCLUSIONS: The calculated absorbed doses of (188)Re-anti-CD20 indicate that it may be used in radioimmunotherapy. Therefore, these preliminary data justify a full assessment of the safety, toxicity, and efficacy of (188)Re-anti-CD20 in a clinical study.

A protocol for the calibration of gamma cameras to estimate internal contamination in emergency situations.

The concern about accidents involving radioactive materials has led to the search of alternative methods to quickly identify and quantify radionuclides in workers and in the population. One of the options to face up an eventual demand for mass monitoring of internal contamination is the use of a nuclear medicine diagnostic equipment known as gamma camera, a device used to scan patients who have been administered specific amounts of radioactive materials for medical purposes. Although the gamma camera is used for image diagnosis, it can be calibrated with anthropomorphic phantoms or point sources for the quantification of radionuclide activities in the human body. This work presents a protocol for the calibration of gamma cameras for such application. In order to evaluate the suitability of this type of equipment, a gamma camera available in a public hospital located in Rio de Janeiro was calibrated for the in vivo measurement of 131I. The calibration includes the determination of detection efficiencies and minimum detectable activities for each radionuclide. The results show that the gamma camera presents enough sensitivity to detect activity levels corresponding to effective doses below 1 mSv. The protocol is the basis to establish a network of Nuclear Medicine Centres, located in public hospitals in eight countries of Latin America (Argentina, Brazil, Colombia, Cuba, Chile, Mexico, Peru and Uruguay) and in Spain that could be requested to collaborate in remediation actions in the event of an accident involving incorporation of radioactive materials. This protocol is one of the most significant outputs of the IAEA-ARCAL Project (RLA/9/049-LXXVIII) aimed to the Harmonization of Internal Dosimetry Procedures.

Calculation of absorbed fractions to human skeletal tissues due to alpha particles using the Monte Carlo and 3-D chord-based transport techniques.

Absorbed fraction (AF) calculations to the human skeletal tissues due to alpha particles are of interest to the internal dosimetry of occupationally exposed workers and members of the public. The transport of alpha particles through the skeletal tissue is complicated by the detailed and complex microscopic histology of the skeleton. In this study, both Monte Carlo and chord-based techniques were applied to the transport of alpha particles through 3-D microCT images of the skeletal microstructure of trabecular spongiosa. The Monte Carlo program used was 'Visual Monte Carlo--VMC'. VMC simulates the emission of the alpha particles and their subsequent energy deposition track. The second method applied to alpha transport is the chord-based technique, which randomly generates chord lengths across bone trabeculae and the marrow cavities via alternate and uniform sampling of their cumulative density functions. This paper compares the AF of energy to two radiosensitive skeletal tissues, active marrow and shallow active marrow, obtained with these two techniques.

In vivo measurements of 210Pb in skull and knee geometries as an indicator of cumulative 222Rn exposure in a underground coal mine in Brazil.

Cumulative exposure to radon can be evaluated by measuring 210Pb in bone. The skull and knee are two convenient parts of the skeleton for in vivo measuring 210Pb because these regions of the body present a high concentration of bone, the detectors are easily positioned and the likelihood of cross contribution from other organs or tissues is low. A radiological survey of non-uranium mines in Brazil indicated that an underground coal mine in Paraná, located in the south of Brazil, exhibited a high radon concentration. In vivo measurements of 32 underground coal miners were performed in the IRD-CNEN Whole Body Counter shielded room using an array of four high-resolution germanium detectors. Estimations of 210Pb in the total skeleton were determined from direct in vivo measurements of 210Pb in the head and knees. In vivo measurements of 210Pb in 6 out of 32 underground coal miners ranged from 80 to 164 Bq, suggesting that these workers were significantly exposed to 222Rn.

131I effective half-life (Teff) for patients with thyroid cancer.

Nuclear medicine procedures that use I activity represent significant sources of potential absorbed dose to medical staff, volunteers, and the general public. The potential exposures are due principally from exposures to excreted and retained activities in the patients' bodies. In general, exposure rate decreases in a simple exponential manner. The average effective half-life found for all patients in the study reported here is 11.41 +/- 0.02 h; this information may be used in guidelines on the management of patients in thyroid cancer therapy and for general radioprotection practice.

Evaluation of the potential absorbed doses from patients based on whole-body 131I clearance in thyroid cancer therapy.

The evaluation of the absorbed dose from radioactive patients during the treatment of thyroid disease is an important factor in establishing precautions in these procedures, and the I retention/excretion by patients' bodies provides additional information to medical and radioprotection service. In 94 patients, the measurement of exposure rates was performed over 7 d following NaI administration, and the rates permitted the study of the dynamics of excretion and the potential dose evaluation. The administered activities ranged from 3.7 GBq (100 mCi) to 16.65 GBq (450 mCi), and the results proved that the majority of the activity is excreted by patients in the first 3 d after NaI administration. The average (131)I activity excreted at 24, 48, 72, 96, and 120 h after oral administration was (72 +/- 10), (91 +/- 6), (97 +/- 3), (98.9 +/- 1.5), and (99.6 +/- 0.7)%, respectively. According to the administered activity, the evaluation of the accumulated absorbed dose from patients ranged from 3.0 +/- 0.7 to 8.4 +/- 1.1 mSv at 1 m and 1.2 +/- 0.4 to 3.2 +/- 0.4 mSv at 2 m. The data reported here are important to radioprotection policy and to add to and improve on the guidelines reported in U.S. NRC Regulatory Guide 8.39.

Usefulness of recombinant human TSH aided radioiodine doses administered in patients with differentiated thyroid carcinoma.

The published studies confirming the safety and efficacy of rhTSH for diagnostic purposes have led to an increased interest in its use for preparation for radioiodine (RI) dose administration in patients with recurrent or persistent differentiated thyroid carcinoma (DTC). In order to establish the efficacy of RI therapy after rhTSH, we have reviewed 39 rhTSH-aided radioiodine treatment in a series of 28 DTC patients. Patients were divided into two groups: GI (n=17), with previous thyroid bed uptake and undetectable thyroglobulin (Tg) levels under levothyroxine treatment and GII (n=11), with proven metastatic local or distant disease. Median follow-up after the first rhTSH-aided radioiodine treatment was 32 +/- 13 months (range 8 to 54 months). Sixteen patients (94%) in GI were rendered disease free and one patient was shown to have persistent disease. In GII, the post therapy whole body scan showed pathological uptakes in all cases: in four patients in lungs, in four in mediastinum and in three in lateral neck. In two patients with mediastinum uptake, Tg levels were undetectable after rhTSH. In the follow-up, two patients with lateral neck uptake were rendered disease free, four patients died (three due to thyroid cancer) and five out of the remaining patients have persistent disease. In conclusion, rhTSH aided therapy was helpful to eliminate normal thyroid bed remnants in 16/17 (94%) patients (GI). rhTSH stimulated Tg was undetectable in two patients with mediastinal metastasis. We believe that rhTSH is a good alternative to levothyroxine withdrawal for the treatment of DTC with radioactive iodine, increasing the quality of life in these patients. Caution should be recommended in the follow-up of unselected DTC patients only with stimulated Tg levels.

Usefulness of recombinant human TSH aided radioiodine doses administered in patients with differentiated thyroid carcinoma

The published studies confirming the safety and efficacy of rhTSH for diagnostic purposes have ledto an increased interest in its use for preparation for radioiodine (RI) dose administration in patientswith recurrent or persistent differentiated thyroid carcinoma (DTC). In order to establish the efficacy of RItherapy after rhTSH, we have reviewed 39 rhTSH-aided radioiodine treatment in a series of 28 DTC patients.Patients were divided into two groups: GI (n=17), with previous thyroid bed uptake and undetectable thyroglobulin(Tg) levels under levothyroxine treatment and GII (n=11), with proven metastatic local or distant disease.Median follow-up after the first rhTSH-aided radioiodine treatment was 32 ± 13 months (range 8 to 54 months).Sixteen patients (94%) in GI were rendered disease free and one patient was shown to have persistent disease.In GII, the post therapy whole body scan showed pathological uptakes in all cases: in four patients in lungs, infour in mediastinum and in three in lateral neck. In two patients with mediastinum uptake, Tg levels wereundetectable after rhTSH. In the follow-up, two patients with lateral neck uptake were rendered disease free,four patients died (three due to thyroid cancer) and five out of the remaining patients have persistent disease. Inconclusion, rhTSH aided therapy was helpful to eliminate normal thyroid bed remnants in 16/17 (94%) patients(GI). rhTSH stimulated Tg was undetectable in two patients with mediastinal metastasis. We believe that rhTSHis a good alternative to levothyroxine withdrawal for the treatment of DTC with radioactive iodine, increasing thequality of life in these patients. Caution should be recommended in the follow-up of unselected DTC patientsonly with stimulated Tg levels.

Los estudios publicados que confirman la seguridad yeficacia de la TSH recombinante (rhTSH) llevaron a un incremento en el interés para su uso como adyuvanteterapéutico en el CDT (ablación o tratamiento de enfermedad metastática). Para evaluar la efectividad de laadministración de dosis terapéuticas de RI luego de la administración de rhTSH, realizamos un análisisretrospectivo en 28 pacientes con CDT que recibieron 39 dosis de RI. Los pacientes se dividieron en 2 grupos:GI (n=17) pacientes con captación en el lecho tiroideo y niveles indetectables de tiroglobulina (Tg) bajo tratamientosupresivo con levotiroxina y GII (n=11), pacientes con enfermedad metastática local o a distancia, previamentecomprobada. El seguimiento promedio luego de la primera dosis de RI fue de 32 ± 13 meses (rango 8 a 54meses). Dieciseis pacientes (94%) del GI fueron considerados libres de enfermedad y un paciente presentó unapersistencia local. En el GII, las captaciones patológicas fueron: en 4 pacientes en pulmones; en 4 en mediastinoy en 3 a nivel lateral cervical. Dos pacientes con captaciones mediastinales presentaron niveles indetectablesde Tg. En el seguimiento, dos pacientes con captaciones latero-cervicales se consideraron libres de enfermedad,cuatro pacientes murieron (tres debido al CDT avanzado) y cinco de los restantes tienen enfermedad persistente.En conclusión, la terapia con RI luego de rhTSH fue útil para ablacionar remanentes normales en el GI. Losniveles de Tg estimulados con rhTSH fueron indetectables en dos pacientes con metástasis mediastinales. Eluso de rhTSH parece ser una alternativa válida frente a la suspensión de la terapia hormonal en el tratamientode pacientes con CDT, incrementando la calidad de vida de estos pacientes.

Usefulness of recombinant human TSH aided radioiodine doses administered in patients with differentiated thyroid carcinoma

The published studies confirming the safety and efficacy of rhTSH for diagnostic purposes have ledto an increased interest in its use for preparation for radioiodine (RI) dose administration in patientswith recurrent or persistent differentiated thyroid carcinoma (DTC). In order to establish the efficacy of RItherapy after rhTSH, we have reviewed 39 rhTSH-aided radioiodine treatment in a series of 28 DTC patients.Patients were divided into two groups: GI (n=17), with previous thyroid bed uptake and undetectable thyroglobulin(Tg) levels under levothyroxine treatment and GII (n=11), with proven metastatic local or distant disease.Median follow-up after the first rhTSH-aided radioiodine treatment was 32 ± 13 months (range 8 to 54 months).Sixteen patients (94%) in GI were rendered disease free and one patient was shown to have persistent disease.In GII, the post therapy whole body scan showed pathological uptakes in all cases: in four patients in lungs, infour in mediastinum and in three in lateral neck. In two patients with mediastinum uptake, Tg levels wereundetectable after rhTSH. In the follow-up, two patients with lateral neck uptake were rendered disease free,four patients died (three due to thyroid cancer) and five out of the remaining patients have persistent disease. Inconclusion, rhTSH aided therapy was helpful to eliminate normal thyroid bed remnants in 16/17 (94%) patients(GI). rhTSH stimulated Tg was undetectable in two patients with mediastinal metastasis. We believe that rhTSHis a good alternative to levothyroxine withdrawal for the treatment of DTC with radioactive iodine, increasing thequality of life in these patients. Caution should be recommended in the follow-up of unselected DTC patientsonly with stimulated Tg levels. (AU)

Los estudios publicados que confirman la seguridad yeficacia de la TSH recombinante (rhTSH) llevaron a un incremento en el interés para su uso como adyuvanteterapéutico en el CDT (ablación o tratamiento de enfermedad metastática). Para evaluar la efectividad de laadministración de dosis terapéuticas de RI luego de la administración de rhTSH, realizamos un análisisretrospectivo en 28 pacientes con CDT que recibieron 39 dosis de RI. Los pacientes se dividieron en 2 grupos:GI (n=17) pacientes con captación en el lecho tiroideo y niveles indetectables de tiroglobulina (Tg) bajo tratamientosupresivo con levotiroxina y GII (n=11), pacientes con enfermedad metastática local o a distancia, previamentecomprobada. El seguimiento promedio luego de la primera dosis de RI fue de 32 ± 13 meses (rango 8 a 54meses). Dieciseis pacientes (94%) del GI fueron considerados libres de enfermedad y un paciente presentó unapersistencia local. En el GII, las captaciones patológicas fueron: en 4 pacientes en pulmones; en 4 en mediastinoy en 3 a nivel lateral cervical. Dos pacientes con captaciones mediastinales presentaron niveles indetectablesde Tg. En el seguimiento, dos pacientes con captaciones latero-cervicales se consideraron libres de enfermedad,cuatro pacientes murieron (tres debido al CDT avanzado) y cinco de los restantes tienen enfermedad persistente.En conclusión, la terapia con RI luego de rhTSH fue útil para ablacionar remanentes normales en el GI. Losniveles de Tg estimulados con rhTSH fueron indetectables en dos pacientes con metástasis mediastinales. Eluso de rhTSH parece ser una alternativa válida frente a la suspensión de la terapia hormonal en el tratamientode pacientes con CDT, incrementando la calidad de vida de estos pacientes. (AU)

Usefulness of recombinant human TSH aided radioiodine doses administered in patients with differentiated thyroid carcinoma

The published studies confirming the safety and efficacy of rhTSH for diagnostic purposes have ledto an increased interest in its use for preparation for radioiodine (RI) dose administration in patientswith recurrent or persistent differentiated thyroid carcinoma (DTC). In order to establish the efficacy of RItherapy after rhTSH, we have reviewed 39 rhTSH-aided radioiodine treatment in a series of 28 DTC patients.Patients were divided into two groups: GI (n=17), with previous thyroid bed uptake and undetectable thyroglobulin(Tg) levels under levothyroxine treatment and GII (n=11), with proven metastatic local or distant disease.Median follow-up after the first rhTSH-aided radioiodine treatment was 32 ± 13 months (range 8 to 54 months).Sixteen patients (94%) in GI were rendered disease free and one patient was shown to have persistent disease.In GII, the post therapy whole body scan showed pathological uptakes in all cases: in four patients in lungs, infour in mediastinum and in three in lateral neck. In two patients with mediastinum uptake, Tg levels wereundetectable after rhTSH. In the follow-up, two patients with lateral neck uptake were rendered disease free,four patients died (three due to thyroid cancer) and five out of the remaining patients have persistent disease. Inconclusion, rhTSH aided therapy was helpful to eliminate normal thyroid bed remnants in 16/17 (94%) patients(GI). rhTSH stimulated Tg was undetectable in two patients with mediastinal metastasis. We believe that rhTSHis a good alternative to levothyroxine withdrawal for the treatment of DTC with radioactive iodine, increasing thequality of life in these patients. Caution should be recommended in the follow-up of unselected DTC patientsonly with stimulated Tg levels. (AU)

Los estudios publicados que confirman la seguridad yeficacia de la TSH recombinante (rhTSH) llevaron a un incremento en el interés para su uso como adyuvanteterapéutico en el CDT (ablación o tratamiento de enfermedad metastática). Para evaluar la efectividad de laadministración de dosis terapéuticas de RI luego de la administración de rhTSH, realizamos un análisisretrospectivo en 28 pacientes con CDT que recibieron 39 dosis de RI. Los pacientes se dividieron en 2 grupos:GI (n=17) pacientes con captación en el lecho tiroideo y niveles indetectables de tiroglobulina (Tg) bajo tratamientosupresivo con levotiroxina y GII (n=11), pacientes con enfermedad metastática local o a distancia, previamentecomprobada. El seguimiento promedio luego de la primera dosis de RI fue de 32 ± 13 meses (rango 8 a 54meses). Dieciseis pacientes (94%) del GI fueron considerados libres de enfermedad y un paciente presentó unapersistencia local. En el GII, las captaciones patológicas fueron: en 4 pacientes en pulmones; en 4 en mediastinoy en 3 a nivel lateral cervical. Dos pacientes con captaciones mediastinales presentaron niveles indetectablesde Tg. En el seguimiento, dos pacientes con captaciones latero-cervicales se consideraron libres de enfermedad,cuatro pacientes murieron (tres debido al CDT avanzado) y cinco de los restantes tienen enfermedad persistente.En conclusión, la terapia con RI luego de rhTSH fue útil para ablacionar remanentes normales en el GI. Losniveles de Tg estimulados con rhTSH fueron indetectables en dos pacientes con metástasis mediastinales. Eluso de rhTSH parece ser una alternativa válida frente a la suspensión de la terapia hormonal en el tratamientode pacientes con CDT, incrementando la calidad de vida de estos pacientes. (AU)

Phase I/II clinical trial of the humanized anti-EGF-r monoclonal antibody h-R3 labelled with 99mTc in patients with tumour of epithelial origin.

AIM: To evaluate the biodistribution, internal radiation dosimetry and toxicity of the humanized MAb h-R3 labelled with Tc in humans. METHODS: Twenty-five patients with suspected epithelial-derived tumours were included in this study and divided into two groups: group I consisted of 10 patients who received 3 mg/1110 MBq (3 mg/30 mCi); and group II consisted of 15 patients who received 6 mg/2220 MBq (6 mg/60 mCi). Single photon emission computed tomography (SPECT) and planar images, and multiple blood and urine samples were collected up to 24 h after injection. Haematological parameters and adverse effects were classified according to the WHO criteria. Biodistribution, human anti-mouse antibody (HAMA) response and absorbed doses were estimated and reported. RESULTS: Liver, spleen, kidneys and heart were identified as source organs. Their higher uptakes were 53.3+/-6.4%ID, 2.0+/-1.4%ID, 9.8+/-4.3%ID and 2.8+/-0.9%ID, respectively. The urinary bladder and large intestine also had a significant uptake. The mean urinary excretion was around 22%ID. The liver received the highest absorbed doses followed by the kidneys and the urinary bladder wall. There were no haematological or biochemical abnormalities with clinical significance related to the product. No patient developed HAMA response. Preliminary analysis of clinical results showed a sensitivity of 76.5% and a specificity of 100%. CONCLUSIONS: The results of this study suggest that Tc-h-R3 could be used in patients in a safe and effective way, for the diagnosis of epithelial-derived tumours at the two evaluated dose levels.

Comparison between effective doses for voxel-based and stylized exposure models from photon and electron irradiation.

For the last two decades, the organ and tissue equivalent dose as well as effective dose conversion coefficients recommended by the International Commission on Radiological Protection (ICRP) have been determined with exposure models based on stylized MIRD5-type phantoms representing the human body with its radiosensitive organs and tissues according to the ICRP Reference Man released in Publication No. 23, on Monte Carlo codes sometimes simulating rather simplified radiation physics and on tissue compositions from different sources. Meanwhile the International Commission on Radiation Units and Measurements (ICRU) has published reference data for human tissue compositions in Publication No. 44, and the ICRP has released a new report on anatomical reference data in Publication No. 89. As a consequence many of the components of the traditional stylized exposure models used to determine the effective dose in the past have to be replaced: Monte Carlo codes, human phantoms and tissue compositions. This paper presents results of comprehensive investigations on the dosimetric consequences to be expected from the replacement of the traditional stylized exposure models by the voxel-based exposure models. Calculations have been performed with the EGS4 Monte Carlo code for external and internal exposures to photons and electrons with the stylized, gender-specific MIRD5-type phantoms ADAM and EVA on the one hand and with the recently developed tomographic or voxel-based phantoms MAX and FAX on the other hand for a variety of exposure conditions. Ratios of effective doses for the voxel-based and the stylized exposure models will be presented for external and internal exposures to photons and electrons as a function of the energy and the geometry of the radiation field. The data indicate that for the exposure conditions considered in these investigations the effective dose may change between +60% and -50% after the replacement of the traditional exposure models by the voxel-based exposure models.

[Investigating patients with differentiated thyroid carcinoma and elevated serum thyroglobulin but negative whole-body scan]. / Abordagem dos pacientes com carcinoma diferenciado de tireóide com tireoglobulina sérica elevada e pesquisa de corpo inteiro negativa.

Findings of elevated thyroglobulin (Tg) and a negative whole-body scan (WBS) are not uncommon during the follow-up of differentiated thyroid carcinoma. In 12% of our patients submitted to thyroidectomy and radioiodine with Tg >10 ng/ml during hypothyroidism had a negative diagnostic WBS. This finding generally corresponds to a false-negative WBS. Inadequate preparation in terms of iodine exposure and insufficient elevation of TSH should be excluded. Micrometastases which do not accumulate sufficient iodine to be detected by low radioiodine activity and the loss of the capacity to express the sodium/iodine symporter explain many cases. In patients with elevated Tg, metastases can be identified after the administration of a therapeutic radioiodine dose, with this procedure being indicated in cases with Tg >10 ng/ml during hypothyroidism or >5 ng/ml after recombinant TSH, after exclusion of lung and cervical macrometastases. In the present study, 5 of 7 patients with these criteria showed ectopic uptake on post-therapy WBS. If the post-therapy scan is negative or reveals discrete uptake in the thyroid bed, other methods (e.g. FDG PET) can be performed, and the physician should not insist on radioiodine therapy. If WBS detect lymph node metastases, surgery is indicated, while in cases of diffuse lung metastases radioiodine is indicated until the occurrence of a negative WBS or normalization of stimulated Tg levels. Patients with a positive post-therapy scan may show a significant reduction in Tg, with even complete remission in some cases after radioiodine, but the impact of this treatment on mortality remains controversial.