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Biomedical subjects

O Caselles

Publications and source records attributed to O Caselles.

7 recordsLinked to original sources
PubMed2006

Iodine-131 pharmacokinetics in patients on hemodialysis for end stage renal disease: clinical implications.

AIM: Curative treatment of thyroid cancer is a major issue for patients with end stage renal disease (ESRD) undergoing dialysis because they might not be included in a renal transplant protocol once they have overcome this disease. Since 131I is mostly eliminated by the kidneys, there is concern regarding the toxicity, efficacy and feasibility of 131I-therapy of anuric dialyzed patients. METHODS: This paper reports on 131I uptake and elimination from remnant thyroid tissue (T), salivary glands (SG), stomach (S) and blood, after administration of 3.7 GBq of 131I for 2 patients on twice weekly dialysis for ESRD. RESULTS: Compared to normal renal function patients, radio-iodine recirculation is observed, and SG and blood irradiation is about 6 times higher, but the dose delivered to the thyroid is not significantly enhanced. Dialysis removes more 131I from SG, S and blood than from T. Anticipated dialysis will reduce irradiation by 38% for the blood, 45% for SG and 34% for T. CONCLUSIONS: Therefore, a higher 131I amount could then be used, providing that accurate personalized dosimetry is previously performed using 131I pharmacokinetic models. Concerning radiation protection issues, no significant dialysis equipment contamination is noted, and nurses and medical staff exposure remains below 0.2 mSv.

Adult↗
PubMed2005

[The impact of 18F-fluorodeoxyglucose positron emission tomography on the 3D conformal radiotherapy planning in patients with non-small cell lung cancer].

Traditional radiation treatment planning relies on density imaging such as Computed Tomography for anatomic information of various structures of interest including target and normal tissues. However, the difficulties to distinguish malignant from normal tissue on CT slides often leads to inaccurate outlining of the GTV and/or to geographic misses. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) has shown an increase in both sensitivity and specificity over CT in locoregional staging of patients with non-small cell lung cancer (NSCLC). The co registration of FDG-PET images to the data of the CT planning offers the radiation oncologist the possibility to include functional information into the target outlining. For the treatment of patients with NSCLC, it has been shown that the use of FDG-PET images: 1) modified the shape and volume of radiation fields in 22-62% of cases, mainly due to a better nodal staging and distinction of atelectasis from tumor and; 2) significatively reduced the interobserver and intraobserver variability. This paper reviews the results reported in the literature. Challenges and proposed solutions are discussed.

Carcinoma, Non-Small-Cell Lung↗
PubMed1998

Improvement of the Cockcroft-Gault equation for predicting glomerular filtration in cancer patients.

In order to determine the morphological and biological covariables which better predict the glomerular filtration rate in cancer patients, we performed the present study in a population of 123 patients (78 men, 45 women) with various tumor types; 55 of these patients had previously received cisplatin, and 12 had undergone unilateral nephrectomy. The 51Cr-EDTA plasma concentration versus time data of 80 patients were analysed according to a population pharmacokinetic approach by using the Nonlinear Mixed Effects Model (Nonmem) program. The best fit for 51Cr-EDTA clearance estimation was given by the following formula: [formula: see text] (with ABW for actual body weight in kg, age in years, sex = 0 if male and sex = 1 if female, and Scr for serum creatinine in mumol/l). Actual body weight was the most predictive morphologic parameter, and the adjustment was not improved by taking into account the ideal body weight. The GFR of patients previously treated with cisplatin was 18% lower than that of untreated patients age for age. However, this covariable was not present in the final model because it was redundant with other covariables, likely Scr. The formula was then prospectively evaluated with the data of 43 other patients. The mean (+/- SD) ratio between GFR predicted according the Nonmem formula and the observed GFR was 0.95 +/- 0.23 which did not differ significantly from unity. Conversely, the mean ratio between creatinine clearance calculated according to the Cockcroft-Gault equation and the observed GFR (0.86 +/- 0.21) differed significantly from unity. This study shows that in cancer patients the formula to calculate GFR drawn from Nonmem analysis is more accurate than the Cockcroft-Gault equation. However, an accurate determination of GFR requires specific techniques as 51Cr-EDTA clearance investigation.

Adult↗
PubMed1997

Validation of reconstructed bremsstrahlung spectra between 6 MV and 25 MV from measured transmission data.

We have previously investigated a method of high-energy x-ray spectral reconstruction from transmission data by direct resolution of a matrix system. This technique uses the spectral vectorial algebra formalism. The resolution has previously been tested on a 12 MV photon beam. To extend and to test the validity of the results to the entire radiotherapy energy range, we have performed the method on photon beams with nominal energies of 6, 12, 15, and 25 MV. The influence on the 6 MV spectrum of a 60 degrees built-in wedge has also been investigated to test the sensitivity of the method and the results are reported. To validate our reconstructed spectra, dosimetric quantities such as tissue phantom ratios (TPR), water-to-air stopping power ratios (S/p) air water, and quality indexes TPR 10 (20) have been calculated. The results show good agreement between the measured and calculated data. Mean mass energy absorption coefficient ratios for different materials have also been computed and compared to data published recently and the results are very close (within +/- 0.5%). Primary depth dose functions in water have also been computed to deduce primary dose attenuation coefficients.

Evaluation Studies as Topic↗
PubMed1995

[Contribution of a new technique of digital enhancement for the control of radiation fields].

To increase geometric treatment accuracy in radiation therapy, we used a novel digitized method and original image processing. The radiographic films that are conventionally used for verifying each beam during the treatment were digitized by a Kodak digital system and then an original image enhancement was applied. For the evaluation of our technique, a clinical trial with two tests was used. The trial involved four readers doing 80 reading. The enhanced films were judged to be of higher quality than the non enhanced films (p = 0.001) and were read more accurately (p < or = 0.001). This automatic enhancement of digitized captured portal images can be easily integrated into the busy routine of a radiotherapy department.

Brain Neoplasms↗