Impact of machines on plan quality: volumetric modulated arc therapy and intensity modulated radiation therapy.

PURPOSE: To evaluate the impact of different machines on plan quality using both intensity modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques. MATERIALS AND METHODS: Eight patients with squamous cell carcinoma of the oropharynx were selected at random. Plans were computed for IMRT and VMAT Smart Arc, using Pinnacle TPS for an Elekta (IMRT-E, VMAT-E) and Varian linac (IMRT-V, VMAT-V). A three-dose level prescription was used to deliver 70, 63 and 58.1 Gy to regions of macroscopic, microscopic high- and low-risk disease, respectively. All doses were given in 35 fractions. Comparisons were performed on dose-volume histogram data, monitor units (MU), and delivery time. RESULTS: VMAT-E plans resulted slightly MU efficient (-24 % p < 0.05) compared to VMAT-V while IMRT-V shortened delivery time (-19 % p < 0.05) compared to IMRT-E. All the delivery techniques resulted in equivalent target coverage in terms of D(98) % and D(2) %. For VMAT technique, a significant improvement of 7 % in homogeneity index (HI) for PTV58.1 was observed for Varian machine. A slight improvement in OARs sparing was observed with Elekta machine both for IMRT and VMAT techniques. CONCLUSION: Similar plan quality was observed for Elekta and Varian linacs, significant differences were observed in delivery efficiency, as MU number and delivery times, in favor of Elekta and Varian, respectively.

To evaluate the accuracy of dynamic versus static IMRT delivery using portal dosimetry.

INTRODUCTION: To evaluate the delivery accuracy of dynamic (DMLC) and static (SMLC) intensity modulated radiation therapy (IMRT) techniques using portal dosimetry (PD) in Varian Eclipse Treatment Planning System. MATERIALS AND METHODS: Seven DMLC IMRT Head and Neck plans were retrospectively generated for the study using SMLC mode at 20, 10 and 5 levels of intensity (SMLC20, SMLC10, SMLC5). Dosimetric verifications performed by PD on a total of 107 fields were evaluated using the gamma index (maximum (γmax), average (γavg), percentage of points with (γ%) ≤ 1). The images were acquired at a source-detector distance of 100 cm at gantry zero degree and also at clinically planned gantry angles. RESULTS: For both modes, measurements are within acceptable criteria. (γ%) ≤ 1 improves by increasing SMLC levels (+3.4 % from SMLC5 to SMLC20, p < 0.001) and using DMLC (+3.9 % and +0.6 % compared to SMLC5 and SMLC20, respectively, p < 0.001). Also (γmax) parameter improves significantly by increasing SMLC levels (+22 % from SMLC5 to SMLC20) and using DMLC (+34 % and +16 % compared to SMLC5 and SMLC20, respectively). The effect of the gantry rotation influences the delivery accuracy by up to -7 % (p < 0.05). The effect of leaves travelling direction was almost negligible (1 %). CONCLUSIONS: A good agreement between calculated and measured fluences was obtained for DMLC and SMLC techniques at higher intensity levels; however, DMLC delivery ensures the best reproduction of computed fluence maps. The gantry rotation influences the delivery accuracy in particular for SMLC modes at lower intensity levels.

The impact of computed tomography slice thickness on the assessment of stereotactic, 3D conformal and intensity-modulated radiotherapy of brain tumors.

PURPOSE: To evaluate radiotherapy treatment planning accuracy by varying computed tomography (CT) slice thickness and tumor size. METHODS: CT datasets from patients with primary brain disease and metastatic brain disease were selected. Tumor volumes ranging from about 2.5 to 100 cc and CT scan at different slice thicknesses (1, 2, 4, 6 and 10 mm) were used to perform treatment planning (1-, 2-, 4-, 6- and 10-CT, respectively). For any slice thickness, a conformity index (CI) referring to 100, 98, 95 and 90 % isodoses and tumor size was computed. All the CI and volumes obtained were compared to evaluate the impact of CT slice thickness on treatment plans. RESULTS: The smallest volumes reduce significantly if defined on 1-CT with respect to 4- and 6-CT, while the CT slice thickness does not affect target definition for the largest volumes. The mean CI for all the considered isodoses and CT slice thickness shows no statistical differences when 1-CT is compared to 2-CT. Comparing the mean CI of 1- with 4-CT and 1- with 6-CT, statistical differences appear only for the smallest volumes with respect to 100, 98 and 95 % isodoses-the CI for 90 % isodose being not statistically significant for all the considered PTVs. CONCLUSIONS: The accuracy of radiotherapy tumor volume definition depends on CT slice thickness. To achieve a better tumor definition and dose coverage, 1- and 2-CT would be suitable for small targets, while 4- and 6-CT are suitable for the other volumes.

Intimal-medial thickness and carotid arteries lumen in irradiated patients for head and neck cancer: preliminary data of an observational study.

OBJECTIVES: To investigate the effect of external beam radiotherapy (EBRT) for head and neck cancer (HNC) the intimal-medial thickness (IMT) and the lumen of the carotid artery. METHODS: Patients with HNC and an indication for EBRT were enrolled. A carotid artery color Doppler examination was performed before and 6 and 12 months after EBRT. RESULTS: From 2008 to 2011, 50 patients were enrolled. The mean carotid IMT was 0.9 vs. 1.02 mm before and 6 months after EBRT, respectively (p = 0.0001). The common carotid artery lumen was narrowed without statistical significance, 6 months after EBRT (p = 0.3). 1 year from EBRT, the IMT increase and the lumen reduction were statistically significant (p = 0.001, p = 0.01, respectively). Neurological events (stroke or TIA) were not observed. CONCLUSIONS: Our data showed a significant IMT increase 6 months from EBRT without a corresponding narrowing of the common carotid lumen while a significant increase 12 months after EBRT.

Do comorbidity influences acute toxicity and outcome in elderly patients with endometrial cancer treated by adjuvant radiotherapy plus brachytherapy?

PURPOSE: To correlate comorbidity and acute radiation toxicity in elderly patients treated with adjuvant external beam radiotherapy (EBRT) plus brachytherapy-high dose rate (HDR-BRT) for endometrial cancer (EC). METHODS: Endometrial cancer patients over 65 were treated and evaluated for comorbidity assessment with ACE-27 and Charlson comorbidity index (CCI). EBRT total dose was 45-50.4 Gy (1.8 Gy/day). The vault vagina boost of dose was performed by HDR-BRT with 2/3 fractions with a total dose of 10-15 Gy. RESULTS: From 2008 to 2011, 35 patients were analyzed. Eighteen patients (51.43 %) had not ACE-27 comorbidity; while 27 patients (77.14 %) had CCI lower than three. During treatment, acute toxicity was mild and not influenced by the comorbidity score. Two-year Progression Free and Overall Survival were 69 and 80 %. ACE-27 and CCI did not affect progression-free survival (p = 0.51, p = 0.3) and OS (p = 0.26, p = 0.5). CONCLUSION: External beam radiotherapy plus BRT-HDR are well tolerated in EC elderly with good performance status and low comorbidity profile.

Clinical target volume definition for glioblastoma radiotherapy planning: magnetic resonance imaging and computed tomography.

PURPOSE: To assess the differences between the target delineation using computed tomography (CT) and imaging fusion CT/magnetic resonance imaging (MRI) for the radiotherapy planning of glioblastoma. METHODS: One hundred-twenty gross tumor volume and clinical target volume on CT and MRI (GTVCT/CTVCT, GTVMRI/CTVMRI, respectively) were contoured and evaluated. The treatments planning (total dose 60 Gy) based on CTVCT were analysed in terms of percentage of CTVCT and CTVMRI receiving 95 % of the prescribed dose (V95-CTVCT, V95-CTVMRI). RESULTS: GTVs and CTVs contoured on MRI were significantly larger than those delineated on CT (p = 0.0003, p = 0.0006, respectively). Nighty-two percent of CTVCT was coincident with the CTVMRI and 8 % was normal tissue; 20 % of CTVMRI, considered as tumor volume, was not included on CTVCT. The V95-CTVMRI was significantly lower than the V95-CTVCT (p = 0.0005). CONCLUSIONS: In the delineation of glioblastoma target volume, fusion CT/MRI was preferred. The CT only is insufficient for the CTV dose coverage.

Planning target volume assessment in lung tumors during 3D conformal radiotherapy by means of an aSi electronic portal imaging device in cine mode.

PURPOSE: The major uncertainties in treating lung cancer are the repositioning errors and respiratory lung tumor motion. Typically, margins are added to the clinical target volume (CTV) to obtain a planning target volume (PTV) allowing the accommodation of such uncertainties. We want to test a new technique to assess the adequacy of the chosen PTV using an aSi electronic portal imaging device (EPID). METHODS: Four patients affected by lung cancer and treated by radical 3D conformal radiotherapy (3DRT) were studied. During treatment the EPID was used in cine mode acquisition: acquired images were used to the aim. RESULTS AND CONCLUSIONS: Treatment monitoring with an EPID in cine mode is shown to be a clinically feasible and useful tool.

Cone-beam computed tomography dose monitoring during intensity-modulated radiotherapy in head and neck cancer: parotid glands.

PURPOSE: To evaluate the dosimetric changes of parotid glands (PG) during a course of intensity-modulated radiotherapy (IMRT) in head and neck (H&N) cancer patients. METHODS: Ten patients with H&N cancer treated by IMRT were analyzed. The original treatment plan (CT(plan)) was transferred to cone-beam computed tomography (CBCT) acquired at the 15th and 20th treatment day (CBCT(plan) I and II, respectively). The PG mean dose (D(mean)), the dose to 50 % of the volume, and the percent of volume receiving 30 and 50 Gy were measured by the dose volume histogram. RESULTS: 30 IMRT plans were evaluated (3 plans/patient). All dosimetric end points increased significantly for both PG only when CT(plan) was compared to CBCT(plan) I. The D(mean) increased significantly only for ipsilateral PG (p = 0.02) at week 3. CONCLUSION: During a course of IMRT, CBCT is a feasible method to check the PG dosimetric variations. Perhaps, the 3rd week of radiotherapy could be considered as the time-check-point.

Multidisciplinary approach to chronic pain from myofascial pain dysfunction syndrome: a four-year experience at a Brazilian center.

Chronic pain is the major complaint of myofascial pain dysfunction syndrome (MPDS) and is a complex problem which involves physical, psychological and social aspects. The etiology of MPDS is multifactorial and the multidisciplinary approach is essential for differential diagnosis and for comprehensive treatment planning. In 1993, the Dental School of Piracicaba-UNICAMP, Brazil, opened a Center for Pain Studies (CPS), staffed by health care providers including, dentists, psychologists, physicians, physiotherapists and phonoaudiologists. The major aims of the CPS are to provide clinical care and to develop basic and applied research. Sixty-two MPDS patients had been admitted to the CPS by 1997. There were 60 females and 2 males, mean age-32.5 years. The mean duration of chronic pain was 48 months. Pain intensity and unpleasantness were measured employing the Visual Analogue Scale. The tendency to develop stress-related diseases was assessed by the Social Readjustment Scale. There was a mean reduction of chronic pain of 69.89% and 71.78% relative to intensity and unpleasantness, respectively. The experience of clinical attendance at a multidisciplinary center showed the relevance of a team consisting of health care providers from different specialties with well-established aims, completely integrated and sensitive enough to understand the painful complaints of MPDS patients.