Biomedical subjects

J Gouriou

Publications and source records attributed to J Gouriou.

10 recordsLinked to original sources

PubMed2006

Comparison of PENELOPE Monte Carlo dose calculations with Fricke dosimeter and ionization chamber measurements in heterogeneous phantoms (18 MeV electron and 12 MV photon beams).

Different measurements of depth-dose curves and dose profiles were performed in heterogeneous phantoms and compared to dose distributions calculated by a Monte Carlo code. These heterogeneous phantoms consisted of lung and/or bone heterogeneities. Irradiations and simulations were carried out for an 18 MeV electron beam and a 12 MV photon beam. Depth-dose curves were measured with Fricke dosimeters and with plane and cylindrical ionization chambers. Dose profiles were measured with a small cylindrical ionization chamber at different depths. The LINAC was modelled using the PENELOPE code and phase space files were used as input data for the calculations of the dose distributions in every simulation. The detectors (Fricke dosimeters and ionization chambers) were not modelled in the geometry. There is generally a good agreement between the measurements and PENELOPE. Some discrepancies exist, near interfaces, between the ionization chamber and PENELOPE due to the attenuation of the lower energy electrons by the wall of the ionization chamber.

Body Burden↗

PubMed2001

Calculation of perturbation correction factors for some reference dosimeters in high-energy photon beams with the Monte Carlo code PENELOPE.

The BNM-LNHB (formerly BNM-LPRI, the French national standard laboratory for ionizing radiation) is equipped with a SATURNE 43 linear accelerator (GE Medical Systems) dedicated to establishing national references of absorbed dose to water for high-energy photon and electron beams. These standards are derived from a dose measurement with a graphite calorimeter and a transfer procedure to water using Fricke dosimeters. This method has already been used to obtain the reference of absorbed dose to water for cobalt-60 beams. The correction factors rising from the perturbations generated by the dosimeters were determined by Monte Carlo calculations. To meet these applications, the Monte Carlo code PENELOPE was used and user codes were specially developed. The first step consisted of simulating the electron and photon showers produced by primary electrons within the accelerator head to determine the characteristics of the resulting photon beams and absorbed dose distributions in a water phantom. These preliminary computations were described in a previous paper. The second step, described in this paper, deals with the calculation of the perturbation correction factors of the graphite calorimeter and of Fricke dosimeters. To point out possible systematic biases, these correction factors were calculated with another Monte Carlo code, EGS4, widely used for years in the field of dose metrology applications. Comparison of the results showed no significant bias. When they were possible, experimental verifications confirmed the calculated values.

Computer Simulation↗

PubMed1999

DOSE3D: EGS4 Monte Carlo code-based software for internal radionuclide dosimetry.

UNLABELLED: MIRDOSE3 software is currently the main tool available in clinical practice to evaluate absorbed dose in nuclear medicine. Because MIRDOSE3 provides dosimetric parameters for specific anatomic models that cannot be modified by the user, it cannot be used to obtain information concerning metastases or to consider patients whose anatomy differs significantly from that of the standard models. METHODS: To address some of these inconveniences, we developed an original program based on the EGS4 Monte Carlo code, DOSE3D, which calculates dosimetric parameters for anthropomorphic phantoms defined with combinatorial geometry. DOSE3D allows the user to add spheres within the phantom for simulating tumors, to change the shape of one or more organs and, for organs defined by pair, to calculate individual dosimetric parameters for each organ. The program was validated for 131I and 99mTc by calculating S values for the Medical Internal Radiation Dose (MIRD) adult male phantom and comparing these results with data provided by MIRDOSE3. Moreover, two studies were performed to illustrate DOSE3D features. The first one concerned the evaluation of the individual influence of two bone metastases (located in the pelvis and in the lower spine and containing 131I) on testes in terms of S values compared with the influence on testes of other source organs (kidneys, liver, lungs, spleen, thyroid gland and urinary bladder contents). The second study determined the differences of S values between right and left lungs and right and left kidneys when 131I is contained in the liver. RESULTS: The DOSE3D S values were on average within 20% of the MIRDOSE3 results for both radionuclides. Regarding the bone metastases study, S(testes<--metastases) and S(testes<--any source organs) were of the same order of magnitude. In the second study, the S values ratio between right and left organs was 7.7 for the lungs and 5.2 for the kidneys. CONCLUSION: The agreement between DOSE3D and MIRDOSE3 results for most organs shows the validity of DOSE3D. The presented examples of calculation show that DOSE3D could provide additional data to dosimetric parameters given by MIRDOSE3 for a more patient-specific dosimetric approach.

Adult↗

PubMed1987