Heart-sparing radiotherapy with three-dimensional printing technology after mastectomy for patients with left breast cancer.

The purpose of this study was to analyze the effectiveness of electron beam therapy (EBT) with patient-tailored bolus (PTB) using three-dimensional printing technology to reduce heart and lung doses during post-mastectomy radiotherapy (PMRT). For 28 patients with left breast cancer, we designed customized virtual bolus for PMRT to compensate for surface irregularities on computed tomography images and developed optimized plans for EBT. As comparison between the PTB and tangential plans, the PTB plan reduced unnecessary exposure to heart and ipsilateral lung with better target coverage compared with the tangential technique.

Is higher dose always the right answer in stereotactic body radiation therapy for small hepatocellular carcinoma?

PURPOSE: This study was conducted to compare clinical outcomes and treatment-related toxicities after stereotactic body radiation therapy (SBRT) with two different dose regimens for small hepatocellular carcinomas (HCC) ≤3 cm in size. Materials and. METHODS: We retrospectively reviewed 44 patients with liver-confined HCC treated between 2009 and 2014 with SBRT. Total doses of 45 Gy (n = 10) or 60 Gy (n = 34) in 3 fractions were prescribed to the 95% isodose line covering 95% of the planning target volume. Rates of local control (LC), intrahepatic failure-free survival (IHFFS), distant metastasis-free survival (DMFS), and overall survival (OS) were calculated using the Kaplan-Meier method. RESULTS: Median follow-up was 29 months (range, 8 to 64 months). Rates at 1 and 3 years were 97.7% and 95.0% for LC, 97.7% and 80.7% for OS, 76% and 40.5% for IHFFS, and 87.3% and 79.5% for DMFS. Five patients (11.4%) experienced degradation of albumin-bilirubin grade, 2 (4.5%) degradation of Child-Pugh score, and 4 (9.1%) grade 3 or greater laboratory abnormalities within 3 months after SBRT. No significant difference was seen in any oncological outcomes or treatment-related toxicities between the two dose regimens. Conclusions: SBRT was highly effective for local control without severe toxicities in patients with HCC smaller than 3 cm. The regimen of a total dose of 45 Gy in 3 fractions was comparable to 60 Gy in efficacy and safety of SBRT for small HCC.

Effect of Radiation Therapy Techniques on Outcome in N3-positive IIIB Non-small Cell Lung Cancer Treated with Concurrent Chemoradiotherapy.

PURPOSE: This study was conducted to evaluate clinical outcomes following definitive concurrent chemoradiotherapy (CCRT) for patients with N3-positive stage IIIB (N3-IIIB) non-small cell lung cancer (NSCLC), with a focus on radiation therapy (RT) techniques. MATERIALS AND METHODS: From May 2010 to November 2012, 77 patients with N3-IIIB NSCLC received definitive CCRT (median, 66 Gy). RT techniques were selected individually based on estimated lung toxicity, with 3-dimensional conformal RT (3D-CRT) and intensity-modulated RT (IMRT) delivered to 48 (62.3%) and 29 (37.7%) patients, respectively. Weekly docetaxel/paclitaxel plus cisplatin (67, 87.0%) was the most common concurrent chemotherapy regimen. RESULTS: The median age and clinical target volume (CTV) were 60 years and 288.0 cm(3), respectively. Patients receiving IMRT had greater disease extent in terms of supraclavicular lymph node (SCN) involvement and CTV ≥ 300 cm(3). The median follow-up time was 21.7 months. Fortyfive patients (58.4%) experienced disease progression, most frequently distant metastasis (39, 50.6%). In-field locoregional control, progression-free survival (PFS), and overall survival (OS) rates at 2 years were 87.9%, 38.7%, and 75.2%, respectively. Although locoregional control was similar between RT techniques, patients receiving IMRT had worse PFS and OS, and SCN metastases from the lower lobe primary tumor and CTV ≥ 300 cm(3)were associated with worse OS. The incidence and severity of toxicities did not differ significantly between RT techniques. CONCLUSION: IMRT could lead to similar locoregional control and toxicity, while encompassing a greater disease extent than 3D-CRT. The decision to apply IMRT should be made carefully after considering oncologic outcomes associated with greater disease extent and cost.

The first private-hospital based proton therapy center in Korea; status of the Proton Therapy Center at Samsung Medical Center.

PURPOSE: The purpose of this report is to describe the proton therapy system at Samsung Medical Center (SMC-PTS) including the proton beam generator, irradiation system, patient positioning system, patient position verification system, respiratory gating system, and operating and safety control system, and review the current status of the SMC-PTS. MATERIALS AND METHODS: The SMC-PTS has a cyclotron (230 MeV) and two treatment rooms: one treatment room is equipped with a multi-purpose nozzle and the other treatment room is equipped with a dedicated pencil beam scanning nozzle. The proton beam generator including the cyclotron and the energy selection system can lower the energy of protons down to 70 MeV from the maximum 230 MeV. RESULTS: The multi-purpose nozzle can deliver both wobbling proton beam and active scanning proton beam, and a multi-leaf collimator has been installed in the downstream of the nozzle. The dedicated scanning nozzle can deliver active scanning proton beam with a helium gas filled pipe minimizing unnecessary interactions with the air in the beam path. The equipment was provided by Sumitomo Heavy Industries Ltd., RayStation from RaySearch Laboratories AB is the selected treatment planning system, and data management will be handled by the MOSAIQ system from Elekta AB. CONCLUSION: The SMC-PTS located in Seoul, Korea, is scheduled to begin treating cancer patients in 2015.

Different effects of bladder distention on point A-based and 3D-conformal intracavitary brachytherapy planning for cervical cancer.

This study sought to evaluate the differential effects of bladder distention on point A-based (AICBT) and three-dimensional conformal intracavitary brachytherapy (3D-ICBT) planning for cervical cancer. Two sets of CT scans were obtained for ten patients to evaluate the effect of bladder distention. After the first CT scan, with an empty bladder, a second set of CT scans was obtained with the bladder filled. The clinical target volume (CTV), bladder, rectum, and small bowel were delineated on each image set. The AICBT and 3D-ICBT plans were generated, and we compared the different planning techniques with respect to the dose characteristics of CTV and organs at risk. As a result of bladder distention, the mean dose (D50) was decreased significantly and geometrical variations were observed in the bladder and small bowel, with acceptable minor changes in the CTV and rectum. The average D2 cm(3)and D1 cm(3)showed a significant change in the bladder and small bowel with AICBT; however, no change was detected with the 3D-ICBT planning. No significant dose change in the CTV or rectum was observed with either the AICBT or the 3D-ICBT plan. The effect of bladder distention on dosimetrical change in 3D-ICBT planning appears to be minimal, in comparison with AICBT planning.

Development of a video-guided real-time patient motion monitoring system.

PURPOSE: The authors developed a video image-guided real-time patient motion monitoring (VGRPM) system using PC-cams, and its clinical utility was evaluated using a motion phantom. METHODS: The VGRPM system has three components: (1) an image acquisition device consisting of two PC-cams, (2) a main control computer with a radiation signal controller and warning system, and (3) patient motion analysis software developed in-house. The intelligent patient motion monitoring system was designed for synchronization with a beam on/off trigger signal in order to limit operation to during treatment time only and to enable system automation. During each treatment session, an initial image of the patient is acquired as soon as radiation starts and is compared with subsequent live images, which can be acquired at up to 30 fps by the real-time frame difference-based analysis software. When the error range exceeds the set criteria (δ(movement)) due to patient movement, a warning message is generated in the form of light and sound. The described procedure repeats automatically for each patient. A motion phantom, which operates by moving a distance of 0.1, 0.2, 0.3, 0.5, and 1.0 cm for 1 and 2 s, respectively, was used to evaluate the system performance. The authors measured optimal δ(movement) for clinical use, the minimum distance that can be detected with this system, and the response time of the whole system using a video analysis technique. The stability of the system in a linear accelerator unit was evaluated for a period of 6 months. RESULTS: As a result of the moving phantom test, the δ(movement) for detection of all simulated phantom motion except the 0.1 cm movement was determined to be 0.2% of total number of pixels in the initial image. The system can detect phantom motion as small as 0.2 cm. The measured response time from the detection of phantom movement to generation of the warning signal was 0.1 s. No significant functional disorder of the system was observed during the testing period. CONCLUSIONS: The VGRPM system has a convenient design, which synchronizes initiation of the analysis with a beam on/off signal from the treatment machine and may contribute to a reduction in treatment error due to patient motion and increase the accuracy of treatment dose delivery.

Analysis of changes in dose distribution due to respiration during IMRT.

PURPOSE: Intensity modulated radiation therapy (IMRT) is a high precision therapy technique that can achieve a conformal dose distribution on a given target. However, organ motion induced by respiration can result in significant dosimetric error. Therefore, this study explores the dosimetric error that result from various patterns of respiration. MATERIALS AND METHODS: Experiments were designed to deliver a treatment plan made for a real patient to an in-house developed motion phantom. The motion pattern; the amplitude and period as well as inhale-exhale period, could be controlled by in-house developed software. Dose distribution was measured using EDR2 film and analysis was performed by RIT113 software. Three respiratory patterns were generated for the purpose of this study; first the 'even inhale-exhale pattern', second the slightly long exhale pattern (0.35 seconds longer than inhale period) named 'general signal pattern', and third a 'long exhale pattern' (0.7 seconds longer than inhale period). One dimensional dose profile comparisons and gamma index analysis on 2 dimensions were performed RESULTS: In one-dimensional dose profile comparisons, 5% in the target and 30% dose difference at the boundary were observed in the long exhale pattern. The center of high dose region in the profile was shifted 1 mm to inhale (caudal) direction for the 'even inhale-exhale pattern', 2 mm and 5 mm shifts to exhale (cranial) direction were observed for 'slightly long exhale pattern' and 'long exhale pattern', respectively. The areas of gamma index >1 were 11.88%, 15.11%, and 24.33% for 'even inhale-exhale pattern', 'general pattern', and 'long exhale pattern', respectively. The long exhale pattern showed largest errors. CONCLUSION: To reduce the dosimetric error due to respiratory motions, controlling patient's breathing to be closer to even inhaleexhale period is helpful with minimizing the motion amplitude.

Comparison of film dosimetry techniques used for quality assurance of intensity modulated radiation therapy.

PURPOSE: Accurate dosimetry is essential to ensure the quality of advanced radiation treatments, such as intensity modulated radiation therapy (IMRT). Therefore, a comparison study was conducted to assess the accuracy of various film dosimetry techniques that are widely used in clinics. METHODS: A simulated IMRT plan that produced an inverse pyramid dose distribution in a perpendicular plane of the beam axis was designed with 6 MV x rays to characterize the large contribution of scattered photons to low dose regions. Three film dosimetry techniques, EDR2, EDR2 with low-energy photon absorption lead filters (EDR2 WF), and GafChromic EBT, were compared to ionization chamber measurements as well as Monte Carlo (MC) simulations. The accuracy of these techniques was evaluated against the ionization chamber data. Two-dimensional comparisons with MC simulation results were made by computing the gamma index (gamma) with criteria ranging from 2% of dose difference or 2 mm of distance to agreement (2%/2 mm) to 4%/4 mm on the central vertical plane (20 x 20 cm2) of a square solid water phantom. Depth doses and lateral profiles at depths of 5, 10, and 15 cm were examined to characterize the deviation of film measurements and MC predictions from ionization chamber measurements. RESULTS: In depth dose comparisons, the deviation between the EDR2 films was 9% in the low dose region and 5% in high dose region, on average. With lead filters, the average deviation was reduced to -1.3% and -0.3% in the low dose and high dose regions, respectively. EBT film results agreed within 1.5% difference on average with ionization chamber measurements in low and high dose regions. In two-dimensional comparisons with MC simulation, EDR2 films passed gamma tests with a 2%/2 mm criterion only in the high dose region (gamma < or = 1, total of 63.06% of the tested region). In the low dose region, EDR2 films passed gamma tests with 3%/3 mm criterion (gamma < or = 1, total of 98.4% of the tested region). For EDR2 WF and GafChromic EBT films, gamma tests with a 2% /2 mm criterion (gamma < or = 1) in the tested area was 97.3% and 96.8% of the tested region, respectively. CONCLUSIONS: The EDR2 film WF and GafChromic EBT film achieved an average accuracy level of 1.5% against an ionization chamber. These two techniques agreed with the MC prediction in 2%/2mm criteria evaluated by the gamma index, whereas EDR2 without filters achieved an accuracy level of 3%/3 mm with the decision criteria of agreement greater than 95% of the tested region. The overall results will provide a useful quantitative reference for IMRT verifications.