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Biomedical subjects

G Storme

Publications and source records attributed to G Storme.

At least 19 recordsLinked to original sources
PubMed1998

Use of a simulator with CT option in radiotherapy of macular degeneration.

PURPOSE: To assess the accuracy of a conventional simulation procedure in radiotherapy of age-related macular degeneration. METHODS AND MATERIALS: A computed tomographic (CT) extension attached to the treatment simulator was used to acquire CT images immediately after conventional simulation in 18 patients referred for treatment of age-related macular degeneration. Analysis was performed on 16 one-sided treatment cases for whom images were obtained. Error was estimated by the displacement between the observed treatment isocenter and the intended isocenter based on reconstructed eye geometry. RESULTS: Based on single slice measurements, the mean error amplitude was 2.3 mm (range 0.2-5.6). Based on three-dimensional eye globe reconstruction, the mean error amplitude was 2.8 mm (range 0.8-5.3). An incidental finding previously unreported was the lower image quality at the center of the simulator-CT image acquisition field. CONCLUSIONS: Small but significant errors from conventional simulation were noted. The integrated simulation-CT procedure may help correct the errors to improve the accuracy of simulation setup. The lower image quality at the center of image acquisition field requires adaptation of the simulation-CT procedure.

Humans↗
PubMed1998

Electronic portal imaging with on-line correction of setup error in thoracic irradiation: clinical evaluation.

PURPOSE: To analyze setup errors and the feasibility of their on-line correction using electronic portal imaging in the irradiation of lung tumors. METHODS AND MATERIALS: Sixteen patients with lung cancer were irradiated through opposed anteroposterior fields. Localization images of anteroposterior fields were recorded with an electronic portal imaging device (EPID). Using an in-house developed algorithm for on-line comparison of portal images setup errors were measured and a correction of table position was performed with a remote couch control prior to treatment. In addition, residual errors were measured on the EPID verification image. Global and individual mean and standard deviation of setup errors were calculated and compared. The feasibility of the procedure was assessed measuring intra- and interobserver variability, influence of organ movement, reproducibility of error measurement, the extra time fraction needed for measuring and adjusting and the fraction of dose needed for imaging. RESULTS: In two setups the procedure could not be finished normally due to problems inherent to the procedure. The reproducibility, intraobserver variability, and influence of organ movements were each described by a distribution with a mean value less than or equal to 1 mm and a standard deviation (SD) of less than 1.5 mm. The interobserver variability showed to be a little bit larger (mean: 0.3 mm, SD: 1.7 mm). The mean time to perform the irradiation of the anteroposterior field was 4 +/- 1 min. The mean time for the measurement and correction procedure approximated 2.5 min. The mean extra time fraction was 65 +/- 24% (1 SD) with more than half of this coming from the error measurement. The dose needed for generation of EPID images was 5.9 +/- 1.4% of total treatment dose. The mean and SD of setup errors were, respectively, 0.1 and 4.5 mm for longitudinal and -2.0 and 5.7 mm for transversal errors. Of 196 measured translational errors 120 (61%) exceeded the adjustment criteria. For individual patients systematic and random setup errors can be as high as, respectively, 15.8 and 7.5 mm. Mean residual error and SD were for longitudinal direction 0.08 and 1.2 mm and for transversal direction -0.9 and 1.0 mm (pooled data). For individuals, the mean residual errors were smaller than 1 mm, with a typical SD per patient of less than 2 mm. CONCLUSION: Setup errors in thoracic radiation therapy are clinically important. On-line correction can be performed accurately with an objective measurement tool, although this prolongs the irradiation procedure for one field with 65%.

Algorithms↗
PubMed1998

Microprocessor controlled limitation system for a stand-alone freely movable treatment couch.

Because of the capability of free movement in the treatment room, we recently introduced a Hercules treatment couch on one of our linear accelerators. One of the advantages of this couch is that it allows for a more flexible way of patient setup and that it can be moved entirely out of the way to enable treatment with a hospital bed. A disadvantage, however, is that the couch can hit a wall or a cover of the accelerator accidentally. A limitation system has been developed to protect both the table and the accelerator against such collisions.

Algorithms↗
PubMed1998

Target localization and treatment verification for intensity modulated conformal radiation therapy of the head and neck region. The AZ-VUB experience. Akademisch Ziekenhuis-Vrije Universiteit Brussel.

PURPOSE: Based on a previous evaluation of a conventional, non-invasive fixation technique in combination with a commercially available system for conformal radiation therapy by means of intensity modulation of the treatment beam some modifications have been proposed with respect to target localization and treatment verification. This paper reports on an on-going study of which some preliminary results are presented and discussed with respect to reproducibility of the treatment set-up and verification of the dose. METHODS AND MATERIALS: A slice-by-slice arc-rotation approach was used to deliver a conformal dose to the target and patient fixation was performed by means of a thermoplastic cast. In a previous study a procedure for target localization and verification of patient positioning suitable for this particular treatment technique had been developed and verified dosimetrically with an anthropomorphic phantom: both absolute dose measurements (alanine and thermoluminescent detectors) and relative dose distribution measurements (film dosimetry) have been applied. Two issues needed special attention, being: a) increased accuracy in patient set-up and b) deviations between measured and predicted dose values to organs at risk (OAR) in extreme situations. In a 2nd phase, fiducial markers fixed to customized ear moulds and a bite block have been introduced for target localization and verification of patient set-up on a day-to-day basis. A dosimetric verification by means of TLD and an anthropomorphic phantom has been performed to investigate the possible influence of leakage dose. RESULTS: The dose verification with the anthropomorphic phantom yielded a ratio between measured and predicted dose values of 1.0 for typical cases. However, large deviations (i.e. measured/calculated = 2.9) have been observed in cases with extreme dose constraints to the OAR due to a leakage dose of approximately 0.5%. Dosimetric verification showed good agreement with the dose calculation once the limitations of the system (10% of the target dose to the OAR) had been taken into consideration. Day-to-day variations in patient set-up of 0.3 cm (translations) and 2.0 degrees (rotations) were considered acceptable for this particular patient population in an initial phase, whereas variations of less than 0.1 cm can be achieved with the introduction of ear moulds and daily monitoring in a second phase. Preliminary results show a reproducibility of 0.08 cm in positioning of the fiducial landmarks with respect to anatomical landmarks. CONCLUSIONS: The non-invasive fixation technique in combination with fiducial markers fixed to individualized ear moulds and a bite block proved to be acceptable for IMRT of the head and neck region and allow for daily monitoring of patient set-up. The latter becomes mandatory if an accuracy of 0.1 cm and 1.0 degree is required. A clinical trial has been initiated recently to generate substantial data on the accuracy of the presented procedure for treatment set-up. Dose measurements confirmed the predicted dose values to the target and OAR, however, a physical limitation is represented by the 0.5% leakage through the leaves in that dose constraints to the OAR should be limited to 10% of the target dose.

Algorithms↗
PubMed1997

Initial experience with intensity-modulated conformal radiation therapy for treatment of the head and neck region.

PURPOSE: The efficacy of a conventional, noninvasive fixation technique in combination with a commercially available system for conformal radiotherapy by intensity modulation of the treatment beam has been studied. METHODS AND MATERIALS: A slice-by-slice arc-rotation approach was used to deliver a conformal dose to the target and patient fixation was performed by means of thermoplastic casts. Eleven patients have been treated, of which 9 were for tumors of the head and neck region and 2 were for intracranial lesions. A procedure for target localization and verification of patient positioning suitable for this particular treatment technique has been developed based on the superposition of digitized portals with plots generated from the treatment-planning system. A dosimetric verification of the treatment procedure was performed with an anthropomorphic phantom: both absolute dose measurements (alanine and thermoluminescent detectors) and relative dose distribution measurements (film dosimetry) have been applied. The dose delivered outside the target has also been investigated. RESULTS: The dose verification with the anthropomorphic phantom yielded a ratio between measured and predicted dose values of 1.0 for different treatment schedules and the calculated dose distribution agreed with the measured dose distribution. Day-to-day variations in patient setup of 0.3 cm (translations) and 2.0 degrees (rotations) were considered acceptable for this particular patient population, whereas the verification protocol allowed detection of 0.1 cm translational errors and 1.0 rotational errors. CONCLUSIONS: The noninvasive fixation technique in combination with an adapted verification protocol proved to be acceptable for conformal treatment of the head and neck region. Dose measurements, in turn, confirmed the predicted dose values to the target and organs at risk within uncertainty. Daily monitoring becomes mandatory if an accuracy superior to 0.1 cm and 1.0 degree is required for patient setup.

Brain Neoplasms↗
PubMed1997

Improved survival in patients with locally advanced prostate cancer treated with radiotherapy and goserelin.

BACKGROUND: We conducted a randomized, prospective trial comparing external irradiation with external irradiation plus goserelin (an agonist analogue of gonadotropin-releasing hormone that reduces testosterone secretion) in patients with locally advanced prostate cancer. METHODS: From 1987 to 1995, 415 patients with locally advanced prostate cancer were randomly assigned to receive radiotherapy alone or radiotherapy plus immediate treatment with goserelin. The patients had a median age of 71 years (range, 51 to 80). Patients in both groups received 50 Gy of radiation to the pelvis over a period of five weeks and an additional 20 Gy over an additional two weeks as a prostatic boost. Patients in the combined-treatment group received 3.6 mg of goserelin (Zoladex) subcutaneously every four weeks starting on the first day of irradiation and continuing for three years; those patients also received cyproterone acetate (150 mg orally per day) during the first month of treatment to inhibit the transient rise in testosterone associated with the administration of goserelin. RESULTS: Data were available for analysis on 401 patients. The median follow-up was 45 months. Kaplan-Meier estimates of overall survival at five years were 79 percent (95 percent confidence interval, 72 to 86 percent) in the combined-treatment group and 62 percent (95 percent confidence interval, 52 to 72 percent) in the radiotherapy group (P=0.001). The proportion of surviving patients who were free of disease at five years was 85 percent (95 percent confidence interval, 78 to 92 percent) in the combined-treatment group and 48 percent (95 percent confidence interval, 38 to 58 percent) in the radiotherapy group (P<0.001). CONCLUSIONS: Adjuvant treatment with goserelin, when started simultaneously with external irradiation, improves local control and survival in patients with locally advanced prostate cancer.

Adenocarcinoma↗
PubMed1997

A feasibility study of high dose rate brachytherapy in solitary urinary bladder cancer.

PURPOSE: To determine the feasibility of high dose rate brachytherapy in the treatment of T1-T3 solitary bladder cancer and to compare results and side-effects to those obtained by others using conventional, i.e., low dose rate regimens. METHODS AND MATERIALS: Between July 1992 and 1995, 16 patients entered the study. Median age at diagnosis was 64 years (range: 45-79 years). Diagnostic transurethral resection showed four T1, five T2, and seven T3 lesions, all proven solitary by random biopsies. Radiotherapy consisted of low-dose preoperative external beam irradiation (3 x 3.5 Gy on the 3 consecutive days prior to implantation), followed by high dose rate brachytherapy (15 x 3 Gy during the 8 consecutive days thereafter). Median follow-up from the date of implantation was 23 months (range: 6-43 months). In 15 patients, cystoscopy was systematically performed during follow-up, whereas the 16th patient was followed on a clinical basis only. RESULTS: Recurrences have occurred in 2 of 15 evaluable patients (both stage T3): metastasis in 1 and combined local plus distant failure in the other patient. Cystoscopic evaluation showed persisting alterations of the implanted portion of the bladder mucosa in 11 of 15 evaluable patients (ulceration, calcifications, and/or punctiform bleedings). Symptomatic radiation cystitis was mild and transient in 14 but persisting and severe in 2 patients. CONCLUSION: This study documents the feasibility of high dose rate brachytherapy in a selected group of bladder cancer patients. Both patient outcome and side-effects are comparable to the best results obtained with low dose rate schedules. Additional follow-up is still needed to enforce the comparison.

Adenocarcinoma↗
PubMed1996

Dynamic radiotherapy: interactive movement of patient couch for treatment of craniospinal axis.

PURPOSE: The various techniques that have been described for treatment of the craniospinal axis show the common challenge of edge matching between adjacent orthogonal and parallel photon beams. Such edge matching is needed because the maximum field length provided by modern treatment machines is generally insufficient to treat adults with less than three matching fields. Using the common techniques, field edge matching becomes difficult, if for medical reasons, the patient cannot be treated in the prone position. METHODS AND MATERIALS: A scanning couch technique is proposed, with the patient lying in supine position. After treating the cerebral and upper neck regions by two lateral opposed half beam fields defined by asymmetric collimators (split beam), the patient is being moved along the spinal axis through an 8.0 cm wide by 15.0 cm long posterior split beam (allowing edge matching with the lateral fields at the neck region) by means of remote controlled couch movement. Stopping and starting of the scanning field resulted in a linear decrease of dose on both sides of the scan. Two ways of resolving this problem were investigated. RESULTS: The administered dose varied less than 8.5% through the craniospinal axis. Flatness of the rectangular scanned field was 0.76%. Apart from dose homogeneity, patient comfort and decreased simulation time are major advantages. CONCLUSIONS: The proposed technique represents a suitable alternative using a common linear accelerator, requiring a remote couch controller as an additional component.

Adult↗
PubMed1995

Clinical implementation of an objective computer-aided protocol for intervention in intra-treatment correction using electronic portal imaging.

In order to test the feasibility of a protocol for intra-fractional adjustment of the patient position, during radiation therapy treatment in the pelvic region, a two-fold study is carried out. The protocol involves an objective quantitative measurement of the error in positioning starting from the comparison of a portal image with a reference image. The first part of the study applies the protocol to determine the efficacy of adjustment using subjective determination of the positioning errors by a clinician by measuring the residual errors after adjustment. A group of 13 patients was followed extensively throughout their treatment, analyzing 240 fields. In the second part the measurement itself determines the extent of readjustment of the position. Throughout the procedure elapsed time is measured to determine the extra time involved in using this procedure. For this part a group of 21 patients was followed yielding statistics on 218 fields. Using this computer aided protocol it is shown that systematic as well as random errors can be reduced to standard deviations of the order of 1 mm. The price to pay however is additional treatment time up to 58% of the treatment time without the protocol. Time analysis shows that the largest part of the added time is spent on the readjustment of the patients' position adding a mean of 37% of time to the treatment of one field. This is despite the fact that the readjustment was performed using a remote couch controller. Finally a statistical analysis shows that it is possible to select patients benefiting from the use of such a protocol after a limited number of fractions.

Feasibility Studies↗
PubMed1995

Prognostic factors in locoregional non-small cell lung cancer treated with radiotherapy.

By means of a retrospective study an evaluation was made of prognostic factors on survival in patients with inoperable locoregional non-small cell lung cancer. The study was performed on a group of 239 patients with a median age of 69 years, 225 men, and 14 women. Patients were treated with external radiotherapy without (184) or with (55) chemotherapy. They received either continuous-course radiotherapy (5,500 cGy in 27-28 fractions and 5.5 weeks) or split-course radiotherapy (1 series of 3,000 cGy, 2 series of respectively 3,000 cGy and 2,500 cGy, or 3 series of, respectively 3,000 cGy, 2,500 cGy, and 2,000 cGy; each series in 10 fractions and 2 weeks, separated by a 4-week interval). Univariate analysis was done by life-table analysis and log-rank test, multivariate analysis by the Cox Proportional Hazards model. The overall survival at 1, 2, and 3 years was 36%, 11%, and 4%. Survival was not significantly influenced by localization of the tumor, grading, distance to the carina, growth pattern, diameter, partial or total atelectasis, lymph node invasion or stage. No significant difference in survival was found between patients who received only radiotherapy and those treated with a combination of radiotherapy and chemotherapy. Univariate analysis showed significant better survival in patients with squamous cell epithelioma, patients without pleural effusion, patients younger than 75 years and patients receiving higher radiation doses. Multivariate analysis showed dose of radiation (P < .001) and pleural effusion (P = .03) to be independent prognostic factors.

Adult↗
PubMed1995

Patterns of axillary lymph node metastasis in breast cancer.

The pattern of axillary lymph node involvement was analyzed in a review of 377 cases of T1-4 breast cancers. Clinical judgment of the axillary status proved to be wrong in approximately one-third of the cases. In univariate analysis, a strong correlation (P < .01) between the number of involved nodes, tumor size, and blood vessel invasion was found. Other features of the primary tumor (lymphatic invasion, degree of differentiation, presence of necrotic areas) were related to a lesser degree (P < .05). While others (age, site) were not at all significant. However, the number of nodes resected proved to be the most important determinant of all (P = .003). Also, the simple distinction between node-negative and node-positive cases is strongly dependent on the extent of axillary dissection (P = .009). In multivariate analysis, only the number of resected nodes and T stage showed a good relationship with the number of positive nodes. Skip metastases above levels 1 and 2 were seen in only 2% of the cases. A clear influence of the number of invaded nodes on survival could be demonstrated. These findings are discussed, especially as concerns the technique, prognostic significance, and therapeutic usefulness of axillary dissection.

Adult↗
PubMed1994

On the determination of the effective transmission factor for stainless steel ovoid shielding segments and estimation of their shielding efficacy for the clinical situation.

Commercially available ovoid tubes for gynecological applications used in conjunction with the microSelectron-HDR (Nucletron International B.V., Waardegelder 1, 3905 TH Veenendaal, The Netherlands) for 192Ir sources, allow for shielding. Publications concerning the transmission properties of these 4.5-mm thick stainless steel (AISI number 303/304) shielding segments are scarce and not compatible for implementation in treatment planning. Therefore the effect of shielding on dose distribution is unknown. The effective transmission factor has been measured and implemented in the planning computations. Screening efficacy was evaluated on 20 actual treatment plans, analyzing dose reduction to critical tissue and comparing dose distribution in planes relevant for this particular application. Due to high transmission (effective transmission factor = 0.85), stainless steel screening segments only provide low, local dose reductions of maximum 15%. A new approach with regard to optimization and source configuration is needed to reduce dose to vulnerable tissue, exploiting the screening segments to a maximum extent. Better shielding, especially at the midline (plane bisecting the ovoids) could be expected by using shielding segments with other geometrical characteristics.

Biophysical Phenomena↗
PubMed1994

Computers create new perspectives in radiotherapy.

In diagnostic radiology a revolution has taken place over the last decade with the development of computer-based imaging (CT, MR). Such technologies are now available routinely even in medium-sized radiology departments. In radiotherapy departments, however, computer applications have often been limited to calculation of dose distributions on CT images and administrative tasks. The last few years applications are emerging and utilize the full power of modern computer technology and promise to revolutionize treatment planning and execution in everyday radiotherapy. The authors present their view on some of these applications and the way they may push ahead frontiers in clinical radiotherapy.

Humans↗
PubMed1993

On-line portal imaging: image quality defining parameters for pelvic fields--a clinical evaluation.

PURPOSE: A test of several image enhancement techniques, performed on on-line portal images in real clinical circumstances, is presented. In addition a score system enabling us to evaluate image quality on pelvic fields is proposed and validated. METHODS AND MATERIALS: Localization images (n = 546) generated by an on-line portal imaging system during the treatment of 13 patients on pelvic fields were obtained by delivering a radiation dose of 6-8 cGy by an 18 MV photon beam, and recorded with a silicon intensified target video camera with adjustable gain, kV- and black level. Set-up errors were corrected before continuing irradiation. A scoring system based on the number of visible bone-soft tissue edges and transformed to a scale 0 to 5 was developed to judge image quality. A validation of this classification of images was performed with the use of transsectional bone-densities (bone-density*radiological path length) specified at the score defining landmarks. A high pass filter was used on all images, additional on-line open field subtraction was performed on 242 fields. Off-line study was performed in which a panel consisting of two groups (one composed of three radiation oncologists, the other of three radiotherapy technologists), scored 470 pelvic fields without further enhancement, and the same images with Contrast Limited Adaptive Histogram Equalization (CLAHE) (Pizer et al.). Two different clipping levels (3.0 and 5.0) were studied. RESULTS: Gender and transsectional bone-densities were the most defining patient-related factors influencing image quality. Camera settings, gantry angle, and image post-processing were important non-patient-related factors. All investigators judged CLAHE to ameliorate low contrast images and to deteriorate good quality images (p < 0.001).

Humans↗
PubMed1993

Interactive use of on-line portal imaging in pelvic radiation.

We have evaluated a fluoroscopic on-line portal imaging system in routine clinical radiotherapy, involving the treatment of 566 pelvic fields on 13 patients. The image was typically generated by delivering a radiation dose of 6-8 cGy. Comparison between portal image and simulator film was done by eye and all visible errors were corrected before continuing irradiation. If possible, these corrections were performed from outside the treatment room by moving the patient couch by remote control or by changing collimator parameters. Adjustments were performed on 289/530 (54.5%) evaluable fields or 229/278 (82.4%) evaluable patient set-ups. The lateral couch position was most frequently adjusted (n = 254). The absolute values of the adjustments were 6.8 mm mean (SD 6.6 mm) with a maximum of 40 mm. All absolute values of adjustments exceeding 25 mm were recorded in one patient and those exceeding 15 mm were observed in two patients. Both patients were obese females. Adjustments exceeding 5 mm were observed in all 13 patients. Related to the use of on-line portal imaging, treatment time was increased by a median of 36.5% (mean 45.8%; SD 42.1%). The range was 7.7 to 442%. The fraction of the total treatment time to perform corrections was 22.7% median (mean: 26.0; SD: 11.8%). Statistically significant systematic in-plane errors were found in 7/13 patients. A systematic error was detected on the lateral position of the field in five patients. In one patient a systematic error of the longitudinal field position and in one patient a rotational error was detected. For adjustments in the lateral direction the present method does not allow to detect lateral shifts of less than 2 mm. For adjustments in the longitudinal direction the sensitivity could not be estimated but the available data suggest that 80% of errors < or = 5 mm were not adjusted. In obese patients, random errors may be surprisingly large.

Evaluation Studies as Topic↗
PubMed1993

Adjuvant radiation after conservative surgery for early breast cancer. Local control and cosmetic outcome.

Between 1980 and 1987, 115 patients with early breast cancer underwent conservative surgery and radiation therapy. Median follow-up from the date of surgery was 48 months. There was local recurrence in 5 of the 115 patients. Of this group, 67 patients were evaluable for cosmetic outcome. The overall cosmetic result was judged by a panel to be excellent or good in 61%, fair in 27%, and poor in 12%. Patients themselves found the cosmetic result to be excellent or good in 94%. Retraction of the inferior border of the breast, surface difference between both breasts, breast induration, scar retraction and telangiectasia correlated with the cosmetic score. Type of surgery, axillary irradiation, use of bolus, and length of follow-up all influenced the cosmetic outcome in a univariate analysis.

Breast Neoplasms↗
PubMed1993

Experience with high dose chemotherapy and autologous bone marrow transplantation in testicular cancer.

Carboplatin based HDCT followed by ABMT produces reasonable response rates (40-60%) and some durable remissions in patients with advanced and cisplatin resistant testicular cancer. Patients eligible for such an approach are those with primary refractory or recurrent disease and low probability for salvage by conventional dose regimens. The use of recombinant human growth factors and peripheral stem cell transplantation will probably reduce the toxicity and mortality of HDCT.

Antineoplastic Combined Chemotherapy Protocols↗