Characterization of imaging performance of a novel helical kVCT for use in image-guided and adaptive radiotherapy.

ClearRT helical kVCT imaging for the Radixact helical tomotherapy system recently received FDA approval and is available for clinical use. The system is intended to enhance image fidelity in radiation therapy treatment planning and delivery compared to the prior MV-based onboard imaging approach. The purpose of this work was to characterize the imaging performance of this system and compare this performance with that of clinical systems used in image-guided and/or adaptive radiotherapy (ART) or computed tomography (CT) simulation, including Radixact MVCT, TomoTherapy MVCT, Varian TrueBeam kV OBI CBCT, and the Siemens SOMATOM Definition Edge kVCT. A CT image quality phantom was scanned across clinically relevant acquisition modes for each system to evaluate image quality metrics, including noise, uniformity, contrast, spatial resolution, and CT number linearity. Similar noise levels were observed for ClearRT and Siemens Edge, whereas noise for the other systems was ∼1.5-5 times higher. Uniformity was best for Siemens Edge, whereas most scans for ClearRT exhibited a slight "cupping" or "capping" artifact. The ClearRT and Siemens Edge performed best for contrast metrics, which included low-contrast visibility and contrast-to-noise ratio evaluations. Spatial resolution was best for TrueBeam and Siemens Edge, whereas the three kVCT systems exhibited similar CT number linearity. Overall, these results provide an initial indication that ClearRT image quality is adequate for image guidance in radiotherapy and sufficient for delineating anatomic structures, thus enabling its use for ART. ClearRT also showed significant improvement over MVCT, which was previously the only onboard imaging modality available on Radixact. Although the acquisition of these scans does come at the cost of additional patient dose, reported CTDI values indicate a similar or generally reduced machine output for ClearRT compared to the other systems while maintaining comparable or improved image quality overall.

First experimental measurement of the effect of cardio-synchronous brain motion on the dose distribution during microbeam radiation therapy.

PURPOSE: Microbeam radiation therapy (MRT) is an emerging radiation oncology modality ideal for treating inoperable brain tumors. MRT employs quasi-parallel beams of low-energy x rays produced from modern synchrotrons. A tungsten carbide multislit collimator (MSC) spatially fractionates the broad beam into rectangular beams. In this study, the MSC creates beams 50 µm wide ("peaks") separated by a center-to-center distance of 400 µm ("valleys"). The peak to valley dose ratio (PVDR) is of critical importance to the efficacy of MRT. The underlying radiobiological advantage of MRT relies on high peak dose for tumor control and low valley dose for healthy tissue sparing. Cardio synchronous brain motion of the order 100-200 µm is comparable to microbeam width and spacing. The motion can have a detrimental effect on the PVDR, full width at half maximum (FWHM) of the microbeams, and ultimately the dose distribution. We present the first experimental measurement of the effect of brain motion on MRT dose distribution. Dosimetry in MRT is difficult due to the high dose rate (up to 15-20 kGy/s) and small field sizes. METHODS: A real-time dosimetry system based on a single silicon strip detector (SSSD) has been developed with spatial resolution ~10 µm. The SSSD was placed in a water-equivalent phantom and scanned through the microbeam distribution. A monodirectional positioning stage reproduced brain motion during the acquisition. Microbeam profiles were reconstructed from the SSSD and compared with Geant4 simulation and radiochromic HD-V2 film. RESULTS: The SSSD is able to reconstruct dose profiles within 2 µm compared to film. When brain motion is applied the SSSD shows a two time increase in FWHM of profiles and 50% reduction in PVDR. This is confirmed by Geant4 and film data. CONCLUSIONS: Motion-induced misalignment and distortion of microbeams at treatment delivery will result in a reduced PVDR and increased irradiation of additional healthy tissue compromising the radiobiological effectiveness of MRT. The SSSD was able to reconstruct dose profiles under motion conditions and predict similar effects on FWHM and PVDR as by the simulation. The SSSD is a simple to setup, real-time detector which can provide time-resolved high spatial resolution dosimetry of microbeams in MRT.

Deterministic model for the transport of energetic particles: Application in the electron radiotherapy.

A new deterministic method for calculating the dose distribution in the electron radiotherapy field is presented. The aim of this work was to validate our model by comparing it with the Monte Carlo simulation toolkit, GEANT4. A comparison of the longitudinal and transverse dose deposition profiles and electron distributions in homogeneous water phantoms showed a good accuracy of our model for electron transport, while reducing the calculation time by a factor of 50. Although the Bremsstrahlung effect is not yet implemented in our model, we propose here a method that solves the Boltzmann kinetic equation and provides a viable and efficient alternative to the expensive Monte Carlo modeling.

Technology for Innovation in Radiation Oncology.

Radiation therapy is an effective, personalized cancer treatment that has benefited from technological advances associated with the growing ability to identify and target tumors with accuracy and precision. Given that these advances have played a central role in the success of radiation therapy as a major component of comprehensive cancer care, the American Society for Radiation Oncology (ASTRO), the American Association of Physicists in Medicine (AAPM), and the National Cancer Institute (NCI) sponsored a workshop entitled "Technology for Innovation in Radiation Oncology," which took place at the National Institutes of Health (NIH) in Bethesda, Maryland, on June 13 and 14, 2013. The purpose of this workshop was to discuss emerging technology for the field and to recognize areas for greater research investment. Expert clinicians and scientists discussed innovative technology in radiation oncology, in particular as to how these technologies are being developed and translated to clinical practice in the face of current and future challenges and opportunities. Technologies encompassed topics in functional imaging, treatment devices, nanotechnology, and information technology. The technical, quality, and safety performance of these technologies were also considered. A major theme of the workshop was the growing importance of innovation in the domain of process automation and oncology informatics. The technologically advanced nature of radiation therapy treatments predisposes radiation oncology research teams to take on informatics research initiatives. In addition, the discussion on technology development was balanced with a parallel conversation regarding the need for evidence of efficacy and effectiveness. The linkage between the need for evidence and the efforts in informatics research was clearly identified as synergistic.

Characterization of a microDiamond detector in high-dose-per-pulse electron beams for intra operative radiation therapy.

PURPOSE: To characterize a synthetic diamond dosimeter (PTW Freiburg microDiamond 60019) in high dose-per-pulse electron beams produced by an Intra Operative Radiation Therapy (IORT) dedicated accelerator. METHODS: The dosimetric properties of the microDiamond were assessed under 6, 8 and 9 MeV electron beams by a NOVAC11 mobile accelerator (Sordina IORT Technologies S.p.A.). The characterization was carried out with dose-per-pulse ranging from 26 to 105 mGy per pulse. The microDiamond performance was compared with an Advanced Markus ionization chamber and a PTW silicon diode E in terms of dose linearity, percentage depth dose (PDD) curves, beam profiles and output factors. RESULTS: A good linearity of the microDiamond response was verified in the dose range from 0.2 Gy to 28 Gy. A sensitivity of 1.29 nC/Gy was measured under IORT electron beams, resulting within 1% with respect to the one obtained in reference condition under (60)Co gamma irradiation. PDD measurements were found in agreement with the ones by the reference dosimeters, with differences in R50 values below 0.3 mm. Profile measurements evidenced a high spatial resolution of the microDiamond, slightly worse than the one of the silicon diode. The penumbra widths measured by the microDiamond resulted approximately 0.5 mm larger than the ones by the Silicon diode. Output factors measured by the microDiamond were found within 2% with those obtained by the Advanced Markus down to 3 cm diameter field sizes. CONCLUSIONS: The microDiamond dosimeter was demonstrated to be suitable for precise dosimetry in IORT applications under high dose-per-pulse conditions.

Increased dose near the skin due to electromagnetic surface beacon transponder.

The purpose of this study was to evaluate the increased dose near the skin from an electromagnetic surface beacon transponder, which is used for localization and tracking organ motion. The bolus effect due to the copper coil surface beacon was evaluated with radiographic film measurements and Monte Carlo simulations. Various beam incidence angles were evaluated for both 6 MV and 18 MV experimentally. We performed simulations using a general-purpose Monte Carlo code MCNPX (Monte Carlo N-Particle) to supplement the experimental data. We modeled the surface beacon geometry using the actual mass of the glass vial and copper coil placed in its L-shaped polyethylene terephthalate tubing casing. Film dosimetry measured factors of 2.2 and 3.0 enhancement in the surface dose for normally incident 6 MV and 18 MV beams, respectively. Although surface dose further increased with incidence angle, the relative contribution from the bolus effect was reduced at the oblique incidence. The enhancement factors were 1.5 and 1.8 for 6 MV and 18 MV, respectively, at an incidence angle of 60°. Monte Carlo simulation confirmed the experimental results and indicated that the epidermal skin dose can reach approximately 50% of the dose at dmax at normal incidence. The overall effect could be acceptable considering the skin dose enhancement is confined to a small area (~ 1 cm2), and can be further reduced by using an opposite beam technique. Further clinical studies are justified in order to study the dosimetric benefit versus possible cosmetic effects of the surface beacon. One such clinical situation would be intact breast radiation therapy, especially large-breasted women.

Atrioventricular node ablation in Langendorff-perfused porcine hearts using carbon ion particle therapy: methods and an in vivo feasibility investigation for catheter-free ablation of cardiac arrhythmias.

BACKGROUND: Particle therapy, with heavy ions such as carbon-12 ((12)C), delivered to arrhythmogenic locations of the heart could be a promising new means for catheter-free ablation. As a first investigation, we tested the feasibility of in vivo atrioventricular node ablation, in Langendorff-perfused porcine hearts, using a scanned 12C beam. METHODS AND RESULTS: Intact hearts were explanted from 4 (30-40 kg) pigs and were perfused in a Langendorff organ bath. Computed tomographic scans (1 mm voxel and slice spacing) were acquired and (12)C ion beam treatment planning (optimal accelerator energies, beam positions, and particle numbers) for atrioventricular node ablation was conducted. Orthogonal x-rays with matching of 4 implanted clips were used for positioning. Ten Gray treatment plans were repeatedly administered, using pencil beam scanning. After delivery, positron emission tomography-computed tomographic scans for detection of ß(+) ((11)C) activity were obtained. A (12)C beam with a full width at half maximum of 10 mm was delivered to the atrioventricular node. Delivery of 130 Gy caused disturbance of atrioventricular conduction with transition into complete heart block after 160 Gy. Positron emission computed tomography demonstrated dose delivery into the intended area. Application did not induce arrhythmias. Macroscopic inspection did not reveal damage to myocardium. Immunostaining revealed strong γH2AX signals in the target region, whereas no γH2AX signals were detected in the unirradiated control heart. CONCLUSIONS: This is the first report of the application of a (12)C beam for ablation of cardiac tissue to treat arrhythmias. Catheter-free ablation using 12C beams is feasible and merits exploration in intact animal studies as an energy source for arrhythmia elimination.

Exploring the influence of Traditional Chinese Medicine on self-care among Chinese cancer patients.

PURPOSE: The aim of this study was to explore the influence of traditional Chinese medicine (TCM) on self-care among Chinese cancer patients. METHODS: This was an exploratory qualitative study. A purposive sample of thirty cancer patients who were currently undergoing either chemotherapy or radiotherapy was interviewed. Qualitative content analysis was conducted for data analysis. RESULTS: Two core categories were emerged from their accounts of experiences with practising TCM-supported self-care activities: perceived beneficial effects and concerns about undesirable effects. The perceived beneficial effects of these self-care activities were mainly stemmed from the traditional beliefs in TCM, which included: strengthening the "origin", removing toxins, and mind-soothing. Concerns about undesirable effects of these self-care activities were raised due to lack of knowledge and unpleasant experience with these self-care activities. CONCLUSION: The findings revealed that the philosophy of TCM had been deeply integrated by Chinese cancer patients into their self-care. While Western medicine is the mainstream cancer treatment, Chinese cancer patients also practised various TCM-supported self-care activities. However, they were perplexed about the effects of these self-care activities. They could not ascertain whether the perceived benefits were just due to their own belief in the TCM philosophy, and their lack of knowledge in this aspect and unpleasant experience further confused them. Nurses have to be proactive in identifying the unique health-deviation self-care requisites of their clients in a culturally sensitive manner, explore how their self-care experience affects their wellbeing and treatment compliance, and be prepared to clarify misconceptions about their conditions and progress.

[Radiotherapy of soft tissue sarcomas of the extremities and superficial trunk]. / A végtag és a törzsfelszín lágyrészszarkómáinak sugárkezelése.

Soft tissue sarcomas represent a histopathologically and clinically heterogeneous group of tumors that make up around 1% of malignancies, in which soft tissue sarcomas of the extremities and superficial trunk (STSET) are treated with more or less the same strategy. Over the past 30 years, there has been a migration away from amputation and radical ablative surgical procedures for localized STSET toward more conservative, function-preserving surgery combined with radiotherapy +/- chemotherapy. The latter complex treatment ensures equal local control to radical surgery. This multidisciplinary management includes organ sparing surgery as the main procedure but also radiotherapy of different types applied before, during or after the surgery, chemotherapy depending of the stadium of the tumor and plastic, reconstructive surgery, and last but not least rehabilitation of the patient after treatment. In this publication we overview the practical guidelines for the treatment of STSET based on the available literature from the last decades. Indication and timing of radiotherapy of STSET as well as available external beam and brachytherapy techniques are summarized. The prescribed radiation dose, the role of alternative fractionations, the combination of radiotherapy and systemic chemotherapy, hyperthermia or limb perfusion regards to STSET are also discussed. Practical considerations of radiotherapy, the target volumes and the role of newer radiotherapy technology in STSET treatment are overviewed.

African American women share 'real talk' stories about fatigue related to breast cancer treatment.

Fatigue is the most common side effect experienced by women undergoing treatment for breast cancer. The fatigue experience of African American (AA) women who undergo breast cancer treatment has been understudied. The purpose of this qualitative exploratory study is to share stories of 10 AA women who experienced fatigue related to breast cancer treatment. AA women provided real talk descriptors of fatigue. Women expressed how physicians were supportive of their exercising to manage their fatigue. However, many women describe the medications prescribed for fatigue as not very helpful or even making them feel worse. Women shared use of complementary treatment approaches and that their physicians approved of such complementary treatment use. All the participants described how they relied on prayer for their spiritual strength to deal with the overwhelming effects of fatigue on their daily lives. An understanding by health care practitioners of the fatigue and coping experiences related to breast cancer among AA women can provide better ways for health care practitioners to treat and help their AA patients address fatigue symptoms.

Monte Carlo simulation and measurement of radiation leakage from applicators used in external electron radiotherapy.

External electron radiotherapy is performed using a cone or applicator to collimate the beam. However, because of a trade-off between collimation and scattering/bremsstrahlung X-ray production, applicators generate a small amount of secondary radiation (leakage). We investigate the peripheral dose outside the radiation field of a Varian-type applicator. The dose and fluence outside the radiation field were analyzed in a detailed Monte Carlo simulation. The differences between the calculation results and data measured in a water phantom in an ionization chamber were less than ±1% in regions more than 3 mm below the surface of the phantom and at the depth of dose maximum. The calculated fluence was analyzed inside and outside the radiation field on a plane just above the water phantom surface. Changing the electron energy affected the off-axis fluence distribution outside the radiation field; however, the size of the applicator had little effect on this distribution. For each energy, the distributions outside the radiation field were similar to the dose distribution at shallow depths in the water phantom. The effect of secondary electrons generation by photon transmission through the alloy making up the lowest scraper was largest in the region from the field edge to directly below the cutout and at higher beam energies. The results of the Monte Carlo simulation confirm that the peripheral dose outside the field is significantly affected by radiation scattered or transmitted from the applicator, and the effect increases with the electron energy.

Re-irradiation plus regional hyperthermia for recurrent non-small cell lung cancer: a potential modality for inducing long-term survival in selected patients.

PURPOSE: The purpose of this study was to assess the toxicity and efficacy of re-irradiation plus regional hyperthermia for recurrent NSCLC and to identify the predictors of long-term survival. METHODS AND MATERIALS: A total of 33 patients with recurrent NSCLC treated with re-irradiation plus regional hyperthermia were retrospectively analyzed. The median total dose of initial radiotherapy and re-irradiation were 70 Gy and 50 Gy, respectively. A median of 5 hyperthermia treatments using an 8-MHz radiofrequency-capacitive device were applied during re-irradiation in all patients. RESULTS: Toxicity of Grade 3 was seen in 3 (9%) patients, and no Grade 4 or 5 toxicity was observed. The median overall survival, local control, and disease progression-free survival times after re-irradiation were 18.1, 12.1, and 6.7 months, respectively. Eight patients achieved a long-term survival (more than 3 years after re-irradiation), and 4 of them underwent a third round of irradiation for re-recurrent tumors. Univariate analyses showed that a smaller tumor size (<4 cm) and the absence of distant metastases were significant predictors for a better overall survival. The absence of distant metastases was also found to be a significant predictor for better disease progression-free survival in the univariate analyses. In the subset analyses of 23 patients treated with hyperthermia using electrodes of 30 cm in diameter, the use of a higher radiofrequency-output power tended to be associated with a better prognosis in terms of the local control rate. CONCLUSIONS: Re-irradiation plus regional hyperthermia for recurrent NSCLC appears feasible, with acceptable toxicity, and may be a promising treatment that can result in the long-term survival of patients without distant metastasis and larger recurrent tumors.

Neoadjuvant therapy and mini-invasive total mesorectal excision for rectal cancer: feasibility and outcome analysis from a single institution prospectively collected data base.

AIM AND BACKGROUND: Neoadjuvant treatment for rectal adenocarcinoma improves local control and represents the standard for locally advanced disease. Laparoscopic and robotic total mesorectal excision has been increasingly adopted. It provides magnified visualization of the pelvic cavity, thereby facilitating the mesorectal dissection. METHODS: Consecutive patients with locally advanced/ultralow rectal adenocarcinoma received neoadjuvant treatment and mini-invasive total mesorectal excision at our center. We retrospectively reviewed the clinical records by using a prospectively collected data base and focusing on feasibility, tumor response and treatment outcomes. RESULTS: In a 13-year period, 117 rectal adenocarcinoma patients (80 males and 37 females) received neoadjuvant treatment and mini-invasive total mesorectal excision. Median age at diagnosis was 67 years; pre-treatment stage was I in 10 (9%); IIA in 58 (50%); IIC in 5 (4%); IIIA in 10 (9%); IIIB in 31 (26%) and IV in 3 (2%) patients. All patients received external beam radiation therapy, 79 (67%) combined with fluorouracil-based chemotherapy. One-hundred and three patients underwent laparoscopic surgery and 14 robotic surgery. Overall, 90 patients (77%) had anterior resection and 27 (23%) had abdominoperineal resection. Down-staging was obtained in 70 patients (66%). No major intraoperative nor delayed surgical complications were observed. At a median follow up of 52 months, 8 patients (7%) had a local relapse, 7 of them along with distant relapse, and 16 (14%) had distant relapse. The 5-year relapse-free survival was 76.5%. CONCLUSIONS: Our data suggest that in a community hospital mini-invasive surgery after neoadjuvant treatment is feasible in real clinical practice and achieves consistent results in term of disease control rate.

Endocervical ultrasound applicator for integrated hyperthermia and HDR brachytherapy in the treatment of locally advanced cervical carcinoma.

PURPOSE: The clinical success of hyperthermia adjunct to radiotherapy depends on adequate temperature elevation in the tumor with minimal temperature rise in organs at risk. Existing technologies for thermal treatment of the cervix have limited spatial control or rapid energy falloff. The objective of this work is to develop an endocervical applicator using a linear array of multisectored tubular ultrasound transducers to provide 3-D conformal, locally targeted hyperthermia concomitant to radiotherapy in the uterine cervix. The catheter-based device is integrated within a HDR brachytherapy applicator to facilitate sequential and potentially simultaneous heat and radiation delivery. METHODS: Treatment planning images from 35 patients who underwent HDR brachytherapy for locally advanced cervical cancer were inspected to assess the dimensions of radiation clinical target volumes (CTVs) and gross tumor volumes (GTVs) surrounding the cervix and the proximity of organs at risk. Biothermal simulation was used to identify applicator and catheter material parameters to adequately heat the cervix with minimal thermal dose accumulation in nontargeted structures. A family of ultrasound applicators was fabricated with two to three tubular transducers operating at 6.6-7.4 MHz that are unsectored (360 degrees), bisectored (2 x 180 degrees), or trisectored (3 x 120 degrees) for control of energy deposition in angle and along the device length in order to satisfy anatomical constraints. The device is housed in a 6 mm diameter PET catheter with cooling water flow for endocervical implantation. Devices were characterized by measuring acoustic efficiencies, rotational acoustic intensity distributions, and rotational temperature distributions in phantom. RESULTS: The CTV in HDR brachytherapy plans extends 20.5 +/- 5.0 mm from the endocervical tandem with the rectum and bladder typically <8 mm from the target boundary. The GTV extends 19.4 +/- 7.3 mm from the tandem. Simulations indicate that for 60 min treatments the applicator can heat to 41 degrees C and deliver > 5EM(43 degrees C) over 4-5 cm diameter with Tmax < 45 degrees C and 1 kg m(-3) s(-1) blood perfusion. The 41 degrees C contour diameter is reduced to 3-4 cm at 3 kg m(-3) s(-1) perfusion. Differential power control to transducer elements and sectors demonstrates tailoring of heating along the device length and in angle. Sector cuts are associated with a 14-47 degrees acoustic dead zone, depending on cut width, resulting in a approximately 2-4 degrees C temperature reduction within the dead zone below Tmax. Dead zones can be oriented for thermal protection of the rectum and bladder. Fabricated devices have acoustic efficiencies of 33.4%-51.8% with acoustic output that is well collimated in length, reflects the sectoring strategy, and is strongly correlated with temperature distributions. CONCLUSIONS: A catheter-based ultrasound applicator was developed for endocervical implantation with locally targeted, 3-D conformal thermal delivery to the uterine cervix. Feasibility of heating clinically relevant target volumes was demonstrated with power control along the device length and in angle to treat the cervix with minimal thermal dose delivery to the rectum and bladder.

High-dose (80 Gy) intensity-modulated radiation therapy with daily image-guidance as primary treatment for localized prostate cancer.

PURPOSE: to report acute and late toxicity in prostate cancer patients treated by high-dose intensity-modulated radiation therapy (IMRT) with daily image-guidance. PATIENTS AND METHODS: from 06/2004-03/2008, 102 men were treated with 80 Gy IMRT with daily image-guidance. The risk groups were as follows: low, intermediate, and high risk in 21%, 27%, and 52% of patients, respectively. Hormone therapy was given to 65% of patients. Toxicity was scored according to the CTC scale version 3.0. RESULTS: median age was 69 years and median follow-up was 39 months (range, 16-61 months). Acute and late grade 2 gastrointestinal (GI) toxicity occurred in 2% and 5% of patients, respectively, while acute and late grade 3 GI toxicity was absent. Grade 2 and 3 pretreatment genitourinary (GU) morbidity (PGUM) were 15% and 2%, respectively. Acute grade 2 and 3 GU toxicity were 43% and 5% and late grade 2 and 3 GU toxicity were 21% and 1%, respectively. After multiple Cox regression analysis, PGUM was an independent predictor of decreased late ≥ grade 2 GU toxicity-free survival (hazard ratio = 9.4 (95% confidence interval: 4.1, 22.0), p < 0.001). At the end of follow-up, the incidence of late grade 2 and 3 GU toxicity decreased to 7% and 1%, respectively. CONCLUSION: GI toxicity rates after IMRT with daily image-guidance were excellent. GU toxicity rates were acceptable and strongly related to PGUM.

3D computational study of non-invasive patient-specific microwave hyperthermia treatment of breast cancer.

Non-invasive microwave hyperthermia treatment of breast cancer is investigated using three-dimensional (3D) numerical breast phantoms with anatomical and dielectric-properties realism. 3D electromagnetic and thermal finite-difference time-domain simulations are used to evaluate the focusing and selective heating efficacy in four numerical breast phantoms with different breast tissue densities. Beamforming is used to design and focus the signals transmitted by an antenna array into the breast. We investigate the use of propagation models of varying fidelity and complexity in the design of the transmitted signals. An ideal propagation model that is exactly matched to the actual patient's breast is used to establish a best-performance baseline. Simpler patient-specific propagation models based on a homogeneous breast interior are also explored to evaluate the robustness of beamforming in practical clinical settings in which an ideal propagation model is not available. We also investigate the performance of the beamformer as a function of operating frequency and compare single-frequency and multiple-frequency focusing strategies. Our study suggests that beamforming is a robust method of non-invasively focusing microwave energy at a tumor site in breasts of varying volume and breast tissue density.

Dosimetric evaluation of high-dose-rate interstitial brachytherapy boost treatments for localized prostate cancer.

PURPOSE: To quantitatively evaluate the dose distributions of high-dose-rate (HDR) prostate implants regarding target coverage, dose homogeneity, and dose to organs at risk. MATERIAL AND METHODS: Treatment plans of 174 implants were evaluated using cumulative dose-volume histograms (DVHs). The planning was based on transrectal ultrasound (US) imaging, and the prescribed dose (100%) was 10 Gy. The tolerance doses to rectum and urethra were 80% and 120%, respectively. Dose-volume parameters for target (V90, V100, V150, V200, D90, D(min)) and quality indices (DNR [dose nonuniformity ratio], DHI [dose homogeneity index], CI [coverage index], COIN [conformal index]) were calculated. Maximum dose in reference points of rectum (D(r)) and urethra (D(u)), dose to volume of 2 cm(3) of the rectum (D(2ccm)), and 0.1 cm(3) and 1% of the urethra (D(0.1ccm) and D1) were determined. Nonparametric correlation analysis was performed between these parameters. RESULTS: The median number of needles was 16, the mean prostate volume (V(p)) was 27.1 cm(3). The mean V90, V100, V150, and V200 were 99%, 97%, 39%, and 13%, respectively. The mean D90 was 109%, and the D(min) was 87%. The mean doses in rectum and urethra reference points were 75% and 119%, respectively. The mean volumetric doses were D(2ccm) = 49% for the rectum, D(0.1ccm) = 126%, and D1 = 140% for the urethra. The mean DNR was 0.37, while the DHI was 0.60. The mean COIN was 0.66. The Spearman rank order correlation coefficients for volume doses to rectum and urethra were R(D(r),D(2ccm)) = 0.69, R(D(u),D0.(1ccm)) = 0.64, R(D(u),D1) = 0.23. CONCLUSION: US-based treatment plans for HDR prostate implants based on the real positions of catheters provided acceptable dose distributions. In the majority of the cases, the doses to urethra and rectum were kept below the defined tolerance levels. For rectum, the dose in reference points correlated well with dose-volume parameters. For urethra dose characterization, the use of D1 volumetric parameter is recommended.

Music therapy CD creation for initial pediatric radiation therapy: a mixed methods analysis.

A mixed methods research design was used to investigate the effects of a music therapy CD (MTCD) creation intervention on pediatric oncology patients' distress and coping during their first radiation therapy treatment. The music therapy method involved children creating a music CD using interactive computer-based music software, which was "remixed" by the music therapist-researcher to extend the musical material. Eleven pediatric radiation therapy outpatients aged 6 to 13 years were randomly assigned to either an experimental group, in which they could create a music CD prior to their initial treatment to listen to during radiation therapy, or to a standard care group. Quantitative and qualitative analyses generated multiple perceptions from the pediatric patients, parents, radiation therapy staff, and music therapist-researcher. Ratings of distress during initial radiation therapy treatment were low for all children. The comparison between the two groups found that 67% of the children in the standard care group used social withdrawal as a coping strategy, compared to 0% of the children in the music therapy group; this trend approached significance (p = 0.076). MTCD creation was a fun, engaging, and developmentally appropriate intervention for pediatric patients, which offered a positive experience and aided their use of effective coping strategies to meet the demands of their initial radiation therapy treatment.

Design and evaluation of a methodology to perform personalized visual biofeedback for reducing respiratory amplitude in radiation treatment.

A methodology to perform personalized visual biofeedback aimed to the reduction of respiratory amplitude is here proposed. A custom-made software allows to adapt the biofeedback parameters to a patient's respiratory pattern by calculating a limiting range for respiratory amplitude obtained from data acquired during free breathing. The proposed methodology has been tested on ten healthy volunteers and on five lung cancer patients undergoing radiotherapy treatment. The protocol for volunteers consisted of 3 min of data acquisition during the subject's free breathing, 2 min of visual biofeedback within the limits, and 3 min of free breathing. The patients' free breathing was acquired in 3 min and the visual biofeedback performed during all the sessions of the radiotherapy treatment, i.e., an average of eight sessions and an average total treatment time of 2000 s each patient. All the volunteers and three patients of the five found the protocol comfortable. The settlement time needed for considering the limiting range stabilized during free breathing has been calculated as 120 +/- 10 s (p < 0.05). During visual biofeedback the baseline shift was removed and the average respiratory amplitude was reduced by about 40% for all the subjects. The variability of the breathing amplitude remained unaltered during biofeedback. Eight volunteers and three patients remained within the limiting range for more than 90% of the biofeedback period; all subjects remained within the limiting range for more than 80% of the biofeedback period. During the biofeedback period both groups, volunteers and patients, showed a significant increase in breathing frequency which was mostly doubled. Patients with shallow breathing performed comfortably the biofeedback.

Solid water as phantom material for dosimetry of electron backscatter using low-energy electron beams: a Monte Carlo evaluation.

This study evaluated the dosimetry of electron backscatter when Solid Water is used to substitute water as phantom in electron radiotherapy. Monte Carlo simulation (EGSnrc-based code) was employed to predict electron energy spectra and depth doses for the 0.5 and 1 cm of Solid Water and water slabs above 3 mm of lead (Pb) layers using electron beams with energies of 4 and 6 MeV. For comparison, Monte Carlo simulations were repeated with Pb layers taken out from the phantoms using the same experimental configuration. Analyses on electron energy spectra for the 4 and 6 MeV electron beams showed that deviations of electron energy distributions between the Solid Water and water phantom were more significant in the high-energy range (i.e., close to the maximal electron energy) than the lower range corresponding to the electron backscatter. These deviations of electron energy spectra varied with depth and were mainly due to the electron fluence or beam attenuation. Dosimetry results from Monte Carlo simulations showed that the Solid Water phantom had lower depth dose compared to water with the same experimental setup. For the 4 MeV electron beams with 0.5 cm of Solid Water, depth doses were 1.8%-3.9% and 2.3%-4.4% lower than those in water, with and without the Pb layer underneath, respectively. Thicker Solid Water of 1 cm resulted in different decreases in depth doses of 1.8%-4.6% (with Pb) and 2.3%-4.4% (without Pb) compared to water. For higher nominal electron beam energy of 6 MeV with 0.5 cm of Solid Water, depth doses decreased 1.7%-2.9% (with Pb) and 1.6%-2.1% (without Pb) compared to water. These decreases in depth doses changed to 1.7%-3.7% (with Pb) and 1.7%-3% (without Pb) when the thickness of Solid Water was increased to 1 cm. The dosimetry data in this study are useful in determining the correction factor when using Solid Water to substitute water for the electron backscatter measurement in electron radiotherapy.