Randomized Clinical Trial on Reduction of Radiotherapy Dose to the Elective Neck in Head and Neck Squamous Cell Carcinoma: Results on the Quality of Life.

PURPOSE: A randomized trial was initiated to investigate whether a reduction of the dose to the elective nodal sites would result in less toxicity and improvement in Quality of Life (QoL) without compromising tumor control. This paper aimed to compare QoL in both treatment arms. METHODS: Two-hundred head and neck cancer patients treated with radiotherapy (RT) or chemo-RT were randomized (all stages, mean age: 60 years, M/F: 82%/18%). The elective nodal volumes of patients randomized in the experimental arm were treated up to a 40 Gy equivalent dose. In the standard arm, the elective nodal volumes were treated up to a 50 Gy equivalent dose. The QoL data were collected using The European Organization for Research and Treatment of Cancer (EORTC) core questionnaire QLQ-C30 and the EORTC Head and Neck Cancer module (H&N35). RESULTS: A trend toward less decline in QoL during treatment was observed in the 40 Gy arm compared to the 50 Gy arm. Statistically significant differences for global health status, physical functioning, emotional functioning, speech problems, and trouble with social eating in favor of the 40 Gy arm were observed. A clinically relevant better outcome in the 40 Gy arm was found for physical functioning at the end of therapy. CONCLUSION: QoL during RT for head and neck cancer tends to be less impaired in the 40 Gy arm. However, reducing the dose only on the elective neck does not result in clinically relevant improvement of QoL. Therefore, additional treatment strategies must be examined to further improve the QoL of HNSCC patients.

Correlation of Patient- and Physician-Scored Dysphagia with Videofluoroscopies in Patients Treated with Radiotherapy for Head and Neck Cancer.

The aim of this study was to investigate the correlation between patient-scored dysphagia and physician-scored dysphagia in head and neck cancer patients treated with radiotherapy. Furthermore, we wanted to compare both patient- and physician-scored dysphagia with dysphagia evaluated on swallowing videofluoroscopies. Sixty-three patients from two different centers treated with radiotherapy for head and neck cancer were evaluated in the current study. Swallowing videofluoroscopies at baseline, 6, and 12 months following radiotherapy were evaluated by 2 observers using the Penetration Aspiration Scale (PAS) and Swallowing Performance Status Scale (SPS) and correlated with patient and physician scored dysphagia. We observed a significant association between physician and patient scored dysphagia (p < 0.01), pre-treatment and post-treatment. Furthermore, the risk of observing dysphagia on videofluoroscopies increased significantly with increasing scores of both physician as well as patient scored dysphagia, and this at all assessed time-points. Patient-scored dysphagia correlates better with dysphagia evaluated by the PAS. Physician-scored dysphagia, however, correlates better with dysphagia as evaluated using the SPS. Both physician- and patient-scored dysphagia correlate well with dysphagia evaluated on videofluoroscopies. Since patient-scored dysphagia correlates better with PAS and changes in the PAS score, and physician-scored dysphagia correlates better with SPS, we advocate to use both patient- and physician-scored dysphagia in future trials.

A patient immobilization device for prone breast radiotherapy: Dosimetric effects and inclusion in the treatment planning system.

PURPOSE: To assess the dosimetric impact of a patient positioning device for prone breast radiotherapy and assess the accuracy of a treatment planning system (TPS) in predicting this impact. METHODS: Beam attenuation and build-up dose perturbations, quantified by ionization chamber and radiochromic film dosimetry, were evaluated for 3 components of the patient positioning device: the carbon fiber baseplate, the support cushions and the support wedge for the contralateral breast. Dose calculations were performed using the XVMC dose engine implemented in the Monaco TPS. All components were included during planning CT acquisition. RESULTS: Beam attenuation amounted to 7.57% (6MV) and 5.33% (15MV) for beams obliquely intersecting the couchtop-baseplate combination. Beams traversing large sections of the support wedge were attenuated by 12.28% (6MV) and 9.37% (15MV). For the support cushion foam, beam attenuation remained limited to 0.11% (6MV) and 0.08% (15MV) per centimeter thickness. A substantial loss of dose build-up was detected when irradiating through any of the investigated components. TPS dose calculations accurately predicted beam attenuation by the baseplate and support wedge. A manual density overwrite was needed to model attenuation by the support cushion foam. TPS dose calculations in build-up regions differed considerably from measurements for both open beams and beams traversing the device components. CONCLUSIONS: Irradiating through the components of the positioning device resulted in a considerable degradation of skin sparing. Inclusion of the device components in the treatment planning CT allowed to accurately model the most important attenuation effect, but failed to accurately predict build-up doses.

Prone left-sided whole-breast irradiation: significant heart dose reduction using end-inspiratory versus end-expiratory gating.

PURPOSE: To quantify the influence on heart dose metrics of prone left-sided whole-breast irradiation in an end-inspiratory phase (PrIN) versus an end-expiratory phase (PrEX). PATIENTS AND METHODS: Twenty patients underwent CT-simulation in PrIN and PrEX. Dynamic intensity-modulated radiotherapy was planned for whole-breast irradiation with a median prescription dose of 40.05Gy in 15 fractions and maximal sparing of the organs at risk. Dose-volume parameters were analyzed for heart, left anterior descending coronary artery, ipsilateral lung and both breasts. RESULTS: PrIN consistently reduced (P<0.001) heart and left anterior descending coronary artery dose metrics compared to PrEX. Population averages for maximum and mean heart dose were 6.2Gy and 1.3Gy for PrIN versus 21.4Gy and 2.5Gy for PrEX, respectively. Moreover, a maximum heart dose less than 10Gy was achieved in 80% of patients for PrIN. Target dose distribution, ipsilateral lung and contralateral breast sparing by radiation dose were similar for both procedures. CONCLUSIONS: Inspiratory gating consistently reduced heart dose metrics pointing to a possible benefit of breathing-adapted radiotherapy for prone left-sided whole-breast irradiation.

HPV-related oropharyngeal cancers in Flanders (Belgium): a multicenter study.

INTRODUCTION: Human papilloma virus (HPV) was recently reported to play a major role in oropharyngeal carcinoma. Large geographical differences in the disease prevalence have been described. Until now, no data have been reported for Flanders (Belgium). METHODS: A multicenter cooperative study was undertaken at the radiation-oncology departments of Flemish universities. Tumor blocks from patients diagnosed with oropharyngeal carcinoma between 2000 and 2010 were tested for HPV at a single center. Patients' characteristics, treatments, and follow-up data were recorded from medical files. Age standardized incidence rates of oropharyngeal carcinoma were collected from the Belgian Cancer Registry. RESULTS AND CONCLUSIONS: The incidence of oropharyngeal carcinoma has increased in males and females. Tissues were collected from 264 patients and the HPV status could be defined in 249 of them. The prevalence of HPV(+) oropharyngeal carcinoma was 24.78% (19.93-30.36%). In our cohort, HPV(+) tumors occurred in patients with more advanced tumor stages (p < 0.05), who smoked less (p < 0.05), consumed less alcohol (p < 0.05), had a tonsillar/base of tongue sublocalization (p < 0.05), and were older (p < 0.05). After radiotherapy, locoregional control and disease free survival were significantly better for patients with HPV(+) status (p < 0.05) in univariate analysis. HPV status remained a strong predictor of better locoregional control after multivariate analysis. We found that concurrent chemotherapy had an equal benefit for locoregional control in both HPV(+) and HPV(-) patients.

Serial comprehensive geriatric assessment in elderly head and neck cancer patients undergoing curative radiotherapy identifies evolution of multidimensional health problems and is indicative of quality of life.

Head and neck (H&N) cancer is mainly a cancer of the elderly; however, the implementation of comprehensive geriatric assessment (CGA) to quantify functional age in these patients has not yet been studied. We evaluated the diagnostic performance of screening tools [Vulnerable Elders Survey-13 (VES-13), G8 and the Combined Screening Tool 'VES-13 + (17-G8)' or CST], the feasibility of serial CGA, and correlations with health-related quality of life evolution [HRQOL; European Organisation for Research and Treatment of Cancer Quality of Life Questionnaires (EORTC QLQ)-C30 and -HN35] during therapy in hundred patients, aged ≥65 years, with primary H&N cancer undergoing curative radio(chemo)therapy. Respectively 36.8%, 69.0%, 62.1% and 71.3% were defined vulnerable according to VES-13, G8, CST and CGA at week 0, mostly due to presence of severe grade co-morbidities, difficulties in community functioning and nutritional problems. At week 4, significantly more patients were identified vulnerable due to nutritional, functional and emotional deterioration. The CST did not achieve the predefined proportion necessary for validation. Vulnerable patients reported lower function and higher symptom HRQOL scores as compared with fit patients. A comparable deterioration in HRQOL was observed in both groups through therapy. In conclusion, G8 remains the screening tool of choice. Serial CGA identifies the evolution of multidimensional health problems and HRQOL conditions during therapy with potential to guide individualised supportive care.

Improved cone-beam computed tomography in supine and prone breast radiotherapy. Surface reconstruction, radiation exposure, and clinical workflow.

BACKGROUND AND PURPOSE: Cone-beam computerized tomography (CBCT) enables three-dimensional information of the scanned region and provides soft tissue images with good spatial resolution. Our aim was to optimize image acquisition settings for prone and supine breast radiotherapy with respect to contour accuracy, clinical practicalities, and radiation dose. PATIENTS AND METHODS: CBCT images were acquired for both prone and supine anthropomorphic phantoms and a female cadaver in supine and prone set-up. CBCT protocols were investigated by altering the tube current, exposure time, range of projection views, field of view (FOV), and starting angle. For clinical practicalities, the frequency of the use of an offset CBCT isocenter was evaluated at 558 205°-CBCTs (37 patients; 13 prone and 24 supine) and 1272 360°-CBCTs (102 patients; 13 prone and 89 supine). RESULTS: Prone and supine breast CBCT images acquired with a bowtie filter, a small FOV, a range of projection views equaling 180°, a tube current of 20 mA and an exposure time of 32 ms, demonstrated adequate contour accuracy and an elimination of the offset CBCT isocenter procedure, while this occurred in 40.7 % for the old full-rotation protocol. Furthermore a 4.3-fold dose reduction was observed for the Computed Tomography Dose Index (CTDIw) compared to the preset Chest M20 protocol. CONCLUSION: The established 180° protocol demonstrated acceptable contour accuracy, eliminated the CBCT isocenter offset procedure and reduced patient radiation exposure.

Comparison of measured with calculated dose distribution from a 120-MeV electron beam from a laser-plasma accelerator.

PURPOSE: To evaluate the dose distribution of a 120-MeV laser-plasma accelerated electron beam which may be of potential interest for high-energy electron radiation therapy. METHODS: In the interaction between an intense laser pulse and a helium gas jet, a well collimated electron beam with very high energy is produced. A secondary laser beam is used to optically control and to tune the electron beam energy and charge. The potential use of this beam for radiation treatment is evaluated experimentally by measurements of dose deposition in a polystyrene phantom. The results are compared to Monte Carlo simulations using the geant4 code. RESULTS: It has been shown that the laser-plasma accelerated electron beam can deliver a peak dose of more than 1 Gy at the entrance of the phantom in a single laser shot by direct irradiation, without the use of intermediate magnetic transport or focusing. The dose distribution is peaked on axis, with narrow lateral penumbra. Monte Carlo simulations of electron beam propagation and dose deposition indicate that the propagation of the intense electron beam (with large self-fields) can be described by standard models that exclude collective effects in the response of the material. CONCLUSIONS: The measurements show that the high-energy electron beams produced by an optically injected laser-plasma accelerator can deliver high enough dose at penetration depths of interest for electron beam radiotherapy of deep-seated tumors. Many engineering issues must be resolved before laser-accelerated electrons can be used for cancer therapy, but they also represent exciting challenges for future research.

Radiation-induced oesophagitis in lung cancer patients. Is susceptibility for neutropenia a risk factor?

BACKGROUND: Radiation-induced oesophagitis is a major side effect of concurrent chemotherapy and radiotherapy. A strong association between neutropenia and oesophagitis was previously shown, but external validation and further elucidation of the possible mechanisms are lacking. METHODS AND PATIENTS: A total of 119 patients were included at two institutions. The concurrent group comprised 34 SCLC patients treated with concurrent carboplatin and etoposide, and concurrent chest irradiation, and 36 NSCLC patients with concurrent cisplatin and etoposide, and concurrent radiotherapy, while the sequential group comprised 49 NSCLC patients received sequential cisplatin and gemcitabine, and radiotherapy. RESULTS: Severe neutropenia was very frequent during concurrent chemoradiation (grade: 4 41.4%) and during induction chemotherapy in sequentially treated patients (grade 4: 30.6%), but not during radiotherapy (only 4% grade 1). In the concurrent group, the odds ratios of grade 3 oesophagitis vs. neutropenia were the following: grade 2 vs. grade 0/1: 5.60 (95% CI 1.55-20.26), p = 0.009; grade 3 vs. grade 0/1: 10.40 (95% CI 3.19-33.95); p = 0.0001; grade 4 vs. grade 0/1: 12.60 (95% CI 4.36-36.43); p < 0.00001. There was no correlation between the occurrence of neutropenia during induction chemotherapy and acute oesophagitis during or after radiotherapy alone. In the univariate analysis, total radiation dose (p < 0.001), overall treatment time of radiotherapy (p < 0.001), mean oesophageal dose (p = 0.038) and neutropenia (p < 0.001) were significantly associated with the development of oesophagitis. In a multivariate analysis, only neutropenia remained significant (p = 0.023). CONCLUSION: We confirm that neutropenia is independently correlated with oesophagitis in concurrent chemoradiation, but that the susceptibility for chemotherapy-induced neutropenia is not associated with radiation-induced oesophagitis. Further studies focusing on the underlying mechanisms are thus warranted.

Evaluation of a glassless photographic film scanner for high-gradient radiochromic film dosimetry.

This study evaluates the performance of the Nikon Coolscan 9000 ED film scanner for high-gradient radiochromic film dosimetry. As a reference for comparison, analogue experiments were performed on the Epson Expression 10000XL flatbed scanner. Based on these results, a dosimetric protocol was established for the Nikon scanner and its overall performance for high-gradient dosimetry was evaluated. The Nikon scanner demonstrated a high sensitivity for radiochromic film dosimetry, resulting in more contrast in the digitized image. The scanner's optics also demonstrated excellent stability and did not necessitate warm-up scans prior to data acquisition. Moreover, negative effects of temperature changes of the film inside the scanner were shown to be limited. None of the digitized images showed significant disturbances by moiré-patterns, by virtue of the absence of a glass plate for film positioning. However, scanner response was found to vary considerably across the reading area, requiring an optical density-dependent correction procedure to be incorporated into the scanning protocol. The main limitation of the Nikon Coolscan 9000 ED transmission scanner remains its film size restriction to 6.2 × 20 cm2. Nevertheless, its excellent characteristics render it the preferential tool for high-gradient radiochromic film dosimetry in applications limited to small film sizes, such as dosimetry in the build-up region.

Metabolic tumour volume. Prognostic value in locally advanced squamous cell carcinoma of the head and neck.

PURPOSE: Evaluate the predictive and prognostic value of semi-quantitative FDG-PET variables derived from pretreatment FDG-PET images in patients suffering from locally advanced squamous cell carcinoma of the head and neck (SCCHN), treated by means of concomitant radiochemotherapy. PATIENTS, METHODS: 40 patients with newly diagnosed SCCHN that were treated with concomitant radiochemotherapy underwent FDG-PET/CT for treatment planning; 18 patients had neck dissection prior to their baseline scan and to receiving radiochemotherapy. FDG-PET images were used to calculate metabolic tumour volumes using region growing and a threshold of 50% (MTV50) of primary lesions and involved lymph nodes as well as the mean and maximum standard uptake value (SUVmean and SUVmax) of the primary tumours. RESULTS: Neither SUVmean nor SUVmax values of the primary tumour were significantly different between responders and non-responders whereas MTV50 values of the primary tumour proved significantly higher in non-responders. SUVmean, SUVmax and MTV50 of the primary tumour were not predictive for overall or disease free survival. Contrariwise, dichotomized summed MTV50 values (cut-off≥31 cm3) of the primary tumour and involved lymph nodes in patients that didn't have neck dissection prior to radiochemotherapy were predictive for disease free and overall survival in both univariate and multivariate analysis (p≤0.05). CONCLUSION: Summed MTV50 values of both the primary tumour and involved lymph nodes provided independent prognostic information on disease free and overall survival.

A comparison of the acute toxicity profile between two-dimensional and three-dimensional image-guided radiotherapy for postoperative prostate cancer.

AIMS: To compare acute gastrointestinal and genitourinary toxicity for patients positioned with an electronic portal imaging device (EPID) and patients positioned with kilovoltage cone beam computed tomography (CBCT) during postoperative prostate radiotherapy. MATERIALS AND METHODS: Between 1999 and April 2010, 196 prostate cancer patients were referred for postoperative salvage radiotherapy. Patient position was corrected using EPID (1999 to December 2006, n=116) or CBCT (January 2007 to present, n=80). The treatment technique, number of beams, dose prescription, dose computation algorithm and planning target volume margins were not altered over time. Grade 1-3 acute gastrointestinal and genitourinary toxicity were compared between the EPID group and the CBCT group. RESULTS: The incidence of grade 1 and 2 genitourinary toxicity was significantly reduced by 17 and 14%, respectively, in the CBCT group compared with the EPID group (P<0.05). This was mainly attributed to a decrease in the following grade 1 symptoms: frequency (P<0.05), nocturia (P=0.06) and urgency (P=0.07). Grade 2 incontinence (P=0.06) and frequency (P=0.06) were lower in the CBCT group. Grade 3 genitourinary toxicity was comparably low (EPID 3% versus CBCT 1%). There was no significant difference in gastrointestinal grade 1-2 toxicity between both groups. No grade 3 gastrointestinal toxicity was observed. CONCLUSIONS: Patient positioning with CBCT significantly reduces acute genitourinary toxicity compared with positioning with EPID.

A randomized phase II study comparing induction or consolidation chemotherapy with cisplatin-docetaxel, plus radical concurrent chemoradiotherapy with cisplatin-docetaxel, in patients with unresectable locally advanced non-small-cell lung cancer.

BACKGROUND: In stage III non-small-cell lung cancer (NSCLC), the role of systemic chemotherapy preceding or following concurrent chemo-radiotherapy (CT-RT) is unclear. We carried out a randomized phase II study to study the toxicity involved-field CT-RT with either induction or consolidation cisplatin-docetaxel (Taxotere). PATIENTS AND METHODS: Patients were randomly assigned to receive two cycles of docetaxel (D) 75 mg/m(2) on day 1 and cisplatin (C) 40 mg/m(2) on days 1 and 2, either preceding (IND arm) or following (CON arm) concurrent CT-RT, where 66 Gy was delivered using involved-fields concurrent with weekly D 20 mg/m(2) and C 20 mg/m(2). Patients at higher risk for lung toxicity (V(20) > 35%) crossed over to IND arm. Seventy patients were needed to exclude grade (G)3-4 esophagitis in >25%. RESULTS: Of the 70 eligible patients, 26 were treated in IND and 34 CON; five with V(20) >35% switched from CON to IND. The differences in G3-4 esophagitis observed (32/2% IND versus 21/3% CON) were not significantly different from the hypothesized 25% rate. Rates of G≥2 pneumonitis were similar, but IND arm had less G3-4 neutropenia. One-year survival was 63.2% [95% confidence interval (CI) 48.4% to 78.0%] and 65.5% (95% CI 48.2% to 82.8%) for the IND and CON arms, respectively. CONCLUSION: Both study arms merit further testing in patients with limited volume stage III NSCLC.

Comparison of Bayesian network and support vector machine models for two-year survival prediction in lung cancer patients treated with radiotherapy.

PURPOSE: Classic statistical and machine learning models such as support vector machines (SVMs) can be used to predict cancer outcome, but often only perform well if all the input variables are known, which is unlikely in the medical domain. Bayesian network (BN) models have a natural ability to reason under uncertainty and might handle missing data better. In this study, the authors hypothesize that a BN model can predict two-year survival in non-small cell lung cancer (NSCLC) patients as accurately as SVM, but will predict survival more accurately when data are missing. METHODS: A BN and SVM model were trained on 322 inoperable NSCLC patients treated with radiotherapy from Maastricht and validated in three independent data sets of 35, 47, and 33 patients from Ghent, Leuven, and Toronto. Missing variables occurred in the data set with only 37, 28, and 24 patients having a complete data set. RESULTS: The BN model structure and parameter learning identified gross tumor volume size, performance status, and number of positive lymph nodes on a PET as prognostic factors for two-year survival. When validated in the full validation set of Ghent, Leuven, and Toronto, the BN model had an AUC of 0.77, 0.72, and 0.70, respectively. A SVM model based on the same variables had an overall worse performance (AUC 0.71, 0.68, and 0.69) especially in the Ghent set, which had the highest percentage of missing the important GTV size data. When only patients with complete data sets were considered, the BN and SVM model performed more alike. CONCLUSIONS: Within the limitations of this study, the hypothesis is supported that BN models are better at handling missing data than SVM models and are therefore more suitable for the medical domain. Future works have to focus on improving the BN performance by including more patients, more variables, and more diversity.

Microstructural analysis of foam by use of NMR R2 dispersion.

The spin-spin relaxation rate R2 (=1/T2) in hydrogel foams measured by use of a multiple spin echo sequence is found to be dependent on the echo time spacing. This property, referred to as R2-dispersion, originates to a large extent from molecular self-diffusion of water within internal field gradients that result from magnetic susceptibility differences between the gel and air phase. Another contribution to the R2 relaxation rate is surface relaxation. Numerical simulations are performed to investigate the relation between the foam microstructure (the mean air bubble radius and standard deviation of the air bubble radius) and foam composition properties (such as magnetic susceptibilities, diffusion coefficient and surface relaxivity) at one hand and the R2-dispersion at the other hand. The simulated R2-dispersions of gel foam are in agreement with the measured R2-dispersions. By correlating the R2-dispersion parameters and simulated microstructure properties a semi-empirical relationship is obtained that enables the mean air bubble size to be derived from measured R2-dispersion curves. The R2-derived mean air bubble size of a hydrogel foam is in agreement with the bubble size measured with X-ray micro-CT. This illustrates the feasibility of using 1H R2-dispersion measurements to determine the size of air bubbles in hydrogel foams and of alveoli in lung tissue.

Chromosomal radiosensitivity in head and neck cancer patients: evidence for genetic predisposition?

The association between chromosomal radiosensitivity and genetic predisposition to head and neck cancer was investigated in this study. In all, 101 head and neck cancer patients and 75 healthy control individuals were included in the study. The G(2) assay was used to measure chromosomal radiosensitivity. The results demonstrated that head and neck cancer patients had a statistically higher number of radiation-induced chromatid breaks than controls, with mean values of 1.23 and 1.10 breaks per cell, respectively (P<0.001). Using the 90th percentile of the G(2) scores of the healthy individuals as a cutoff value for chromosomal radiosensitivity, 26% of the cancer patients were radiosensitive compared with 9% of the healthy controls (P=0.008). The mean number of radiation-induced chromatid breaks and the proportion of radiosensitive individuals were highest for oral cavity cancer patients (1.26 breaks per cell, 38%) and pharynx cancer patients (1.27 breaks per cell, 35%). The difference between patients and controls was most pronounced in the lower age group (

Monte Carlo modeling of the ModuLeaf miniature MLC for small field dosimetry and quality assurance of the clinical treatment planning system.

The purpose of this investigation was the verification of both the measured data and quality of the implementation of the add-on ModuLeaf miniature multileaf collimator (ML mMLC) into the clinical treatment planning system for conformal stereotactic radiosurgery treatment. To this end the treatment head with ML mMLC was modeled in the BEAMnrc Monte Carlo (MC) code. The 6 MV photon beams used in the setup were first benchmarked with a set of measurements. A total ML mMLC transmission of 1.13% of the 10 x 10 cm2 open field dose was measured and reproduced with the BEAMnrc/DOSXYZnrc code. Correspondence between calculated and measured output factors (OFs) was within 2%. Correspondence between MC and measured profiles was within 2% dose and 2 mm distance, only for the smallest 0.5 x 0.5 cm2 field the results were within 3% dose. In the next step, the MC model was compared with Gafchromic film measurements and Pinnacle(3) 7.4 f (convolution superposition algorithm) calculated dose distributions, using a gamma evaluation comparison, for a multi-beam patient setup delivered to a Lucytrade mark phantom. The gamma evaluation of the MC versus Gafchromic film resulted in 3.4% of points not fulfilling gamma

Precautions and strategies in using a commercial flatbed scanner for radiochromic film dosimetry.

The purpose of this study was to investigate the value of a commercially available flatbed scanner for film dosimetry with radiochromic film for external radiotherapy. The EPSON Pro 1680 Expression scanner was examined as a densitometer for two-dimensional film dosimetry with Gafchromic EBT film. An accurate and efficient scanning procedure was established. Possible drift and warm-up effects of the scanner were studied and the direct physical influence of the scanner light on the radiochromic film was assessed. Next, we investigated the scan field uniformity. Also, we examined if the accuracy of radiochromic film was improved by subtracting the optical density of the unirradiated blank film from the optical density of the irradiated film. To assess the accuracy of Gafchromic EBT film when the EPSON scanner was used as a densitometer, the depth dose of a 2 x 15 cm(2) field and the in-plane and cross-plane profiles of a 15 x 15 cm(2) field were measured and compared with diamond detector measurements. When taking consecutive scans, we found that the optical density taken from the first scan was about 1% higher than the optical density taken from subsequent scans. We attribute this to the warming up of the lamp of the scanner. Longer-term drift of the scanner was found to be absent. We found that the use of a correction matrix was necessary to correct for the non-uniform scanner response over the scan field. Subtracting the optical density of the unirradiated blank film from the irradiated film improves the precision of the Gafchromic EBT film. Depth dose and profile measurements with Gafchromic EBT film and the diamond detector are in agreement within 2.5%. The EPSON Pro 1680 Expression scanner is an excellent tool for accurate two-dimensional film dosimetry with Gafchromic EBT film provided that some precautions and corrections are taken into account.