Biomedical subjects

Stefano Gianolini

Publications and source records attributed to Stefano Gianolini.

5 recordsLinked to original sources

PubMed2006

Evaluating the relationship between erectile dysfunction and dose received by the penile bulb: using data from a randomised controlled trial of conformal radiotherapy in prostate cancer (MRC RT01, ISRCTN47772397).

AIM: To evaluate the relationship between erectile function and the radiation dose to the penile bulb and other proximal penile structures in men receiving conformal radiotherapy (CFRT) for prostate cancer (PCa). METHODS: The Medical Research Council (MRC) RT01 trial randomised 843 men who had localised PCa to receive either 64 or 74 Gy after 3 - 6 months neoadjuvant hormonal treatment. Fifty-one men were selected who were potent prior to hormonal treatment, having completed both pre-hormone and 2-year post-CFRT Quality of Life assessments, and on whom dose volume data were available for analysis. The men were divided into three groups according to 2-year follow-up: potent, reduced potency, and impotent. The bulb of the penis together with the crura, were outlined on restored treatment plans. Dose - volume histograms were generated and compared between the three groups. An ordered logistic regression model was used to calculate the odds ratio of a range of dose - volume parameters to the penile bulb and effect on erectile dysfunction. The dose to the penile bulb was correlated to the dose received by the crura. RESULTS: Of the 51 patients, 12 remained potent, 22 had reduced potency, and 17 were impotent at 2 years. No differences were seen in mean dose to the penile bulb by allocated treatment (t test = 1.61, p = 0.11). The mean doses to the penile bulb received by the potent, reduced potency, and impotent groups were 45.5 Gy (SD 17.1), 48 Gy (SD 16.1), and 59.2 Gy (SD 13.8), respectively. There was a strong correlation between the mean dose received by the penile bulb and dose to the crura (r = 0.82, p < 0.0001). 83.3% of impotent patients received a D90 > or = 50 Gy to the penile bulb compared with 29.4% of patients who maintained potency at 2 years (p = 0.006). CONCLUSION: There is evidence from this study to suggest a dose volume effect on the penile bulb and erectile dysfunction. A D90 > or = 50 Gy is associated with a significant risk of erectile dysfunction and this should form a basis for selecting dose constraints in future dose escalation studies.

Adenocarcinoma↗

PubMed2006

[Application of normoxic polymer gels in 3D-dosimetry for radiosurgery].

The aim of this study was to describe the manufacture of normoxic polymer gels, to characterize their dose response relationship, to optimize MR imaging parameters in order to minimize the standard deviation in the measured dose and to use the gel in a dose verification experiment in radiosurgery. The normoxic polymer gel used is simple to manufacture under normal atmospheric conditions and is characterized by a linear dose relationship up to 40 Gy. MR imaging was performed using 2-dimensional (20) single spin echo pulse sequences with two different echo times. The imaging parameters were optimized in order to minimize the standard deviation of the measured transversal relaxation rate R2 and to achieve a geometrical resolution of 1.5 mm. Comparisons of calculated and measured relative 3D dose distributions using a multi isocentric irradiation with Gamma Knife B showed a good overall agreement of both the isodose levels and the differential and cumulative dose volume histograms. The standard deviation in the measured dose was approximately 9% at 30 Gy. The evaluation according to the gamma criterion showed that 96% of the dose voxels remained within a spatial uncertainty of 1.5 mm and a dose uncertainty of 8%.

Gels↗

PubMed2003

A cylindrical model of the rectum: comparing dose-volume, dose-surface and dose-wall histograms in the radiotherapy of prostate cancer.

The calculation of the percentage cumulative histogram of the rectal wall (DWH) in prostate cancer radiotherapy may be subject to large uncertainties due to the difficulty of assessing the wall thickness on CT images. For this reason often only the external contour is used to define the rectum and then the percentage cumulative dose-volume histogram (DVH) of the rectum including any filling is calculated as a 'surrogate' for the DWH. More recently, other approaches using only the external contour have been proposed to estimate the DWH such as the percentage normalized dose-surface histograms (NDSH). A similar concept can be used when considering the solid rectum (the percentage normalized DVH, NDVH). The purpose of this investigation was to assess the relationships between rectal DVH, NDVH, DSH, NDSH and DWH in the common case of three- and four-field techniques in prostate cancer irradiation. Analytical relationships between the above parameters have been derived for a cylindrical rectum model in the case of three- and four-field techniques. The model is applied to the case of an empty rectum, a full rectum and to the more realistic mixed full/empty rectum situation for a four-field technique delivering 76 Gy (ICRU dose) with 18 MV x-rays. Different positions of the lateral beam with respect to the rectum axis were simulated. In the case of no lumen variation along the z-axis, the DWH is found to be very close to the DVH and to the DSH for empty and full rectum, respectively. The largest differences (up to 15%) between DVH and DSH were seen in the high-dose region (>70 Gy). In the more realistic case of lumen variation along the z-axis, the DWH always lies between NDVH and NDSH and, excluding the full-rectum situation, the DWH differs from the DVH by less than 7% in the 50-75 Gy range. In the case of significant portions of rectum being completely shielded, the DVH may differ from the NDVH/NDSH/DWH by up to 10-15%. In most clinical situations NDVH is within a few per cent of DWH, whilst NDSH may differ from DWH by up to 15-20%, especially in the high-dose region (V70). In conclusion, for most situations, the DVH is highly correlated with NDVH and DWH. A high degree of consistency between NDVH and DWH was found in most clinical cases whilst largest deviations between NDSH and DWH were evident in the high-dose region (70-75 Gy). In the less common case of a very full rectum a poorer correlation between DVH/NDVH and DWH was found whilst NDSH mimicked the DWH very well. In summary, except for the case of a 'very full' rectum, NDVH may be used as a robust surrogate for DWH. The DVH seems to be sufficiently robust if the rectum is prevalently empty.

Algorithms↗

PubMed2002

Precision dosimetry for narrow photon beams used in radiosurgery-determination of Gamma Knife output factors.

Treatment units for radiosurgery, like Leksell Gamma Knife and adapted, or dedicated, linear accelerators use small circular beams of ionizing radiation down to 4 mm in diameter at the isocenter. By cross-firing, these beams generate a high dose region at the isocenter together with steep dose gradients of up to 30% per mm. These units are used to treat small complex shaped lesions, often located close to critical structures within the brain, by superimposing several single high dose regions. In order to commission such treatment units for stereotactic irradiations, to carry out quality assurance and to simulate treatment conditions, as well as to collect input data for treatment planning, a precise dosimetric system is necessary. Commercially available radiation dosimeters only partially meet the requirements for narrow photon beams and small field sizes as used in stereotactic treatment modalities. The aim of this study was the experimental determination of the output factors for the field defining collimators used in Gamma Knife radiosurgery, in particular for the smallest, the 4 mm collimator helmet. For output factor measurements a pin point air ionization chamber, a liquid ionization chamber, a diode detector, a diamond detector, TLD microcubes and microrods, alanine pellets, and radiochromic films were used. In total, more than 1000 measurements were performed with these different detection systems, at the sites in Munich and Zurich. Our results show a resultant output factor for the 4 mm collimator helmet of 0.8741 +/- 0.0202, which is in good agreement with recently published results and demonstrates the feasibility of such measurements. The measured output factors for the 8 mm and 14 mm collimator helmets are 0.9578 +/- 0.0057 and 0.9870 +/- 0.0086, respectively.

Equipment Failure Analysis↗

PubMed2002

Radiosurgery for residual or recurrent nonfunctioning pituitary adenoma.

OBJECT: Nonfunctioning pituitary adenomas comprise approximately 30% of all pituitary tumors. The purpose of this retrospective study is to evaluate the efficacy and role of gamma knife radiosurgery (GKS) in the management of residual or recurrent nonfunctioning pituitary adenomas. METHODS: A review was conducted of the data obtained in 42 patients who underwent adjuvant GKS at the University of Pittsburgh between 1987 and 2001. Prior treatments included transsphenoidal resection, craniotomy and resection, or conventional radiotherapy. Endocrinological, ophthalmological, and radiological responses were evaluated. The duration of follow-up review varied from 6 to 102 months (mean 31.2 months). Fifteen patients were observed for more than 40 months. The mean radiation dose to the tumor margin was 16 Gy. Conformal radiosurgery planning was used to restrict the dose to the optic nerve and chiasm. Tumor control after GKS was achieved in 100% of patients with microadenomas and 97% of patients with macroadenomas. Gamma knife radiosurgery was equally effective in controlling adenomas with cavernous sinus invasion and suprasellar extension. No patient developed a new endocrinological deficiency following GKS. One patient's tumor enlarged with an associated decline in visual function. Another patient experienced a deterioration of visual fields despite a decrease in tumor size. CONCLUSIONS: Gamma knife radiosurgery can achieve tumor control in virtually all residual or recurrent nonfunctioning pituitary adenomas. Dose sparing facilitates tumor management even when the adenoma is close to the optic apparatus or invades the cavernous sinus.

Adenoma↗