Soah Park

Dosimetric comparison of four different external beam partial breast irradiation techniques: Three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, helical tomotherapy, and proton beam therapy

BACKGROUND AND PURPOSE As an alternative to whole breast irradiation in early breast cancer, a variety of accelerated partial breast irradiation (APBI) techniques have been investigated. The purpose of our study is to compare the dosimetry of four different external beam APBI (EB-APBI) plans: three-dimensional conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), helical tomotherapy (TOMO), and proton beam therapy (PBT). METHODS AND MATERIALS Thirty patients were included in the study, and plans for four techniques were developed for each patient. A total dose of 30Gy in 6Gy fractions once daily was prescribed in all treatment plans. RESULTS In the analysis of the non-PTV breast volume that was delivered 50% of the prescribed dose (PD), PBT (mean: 16.5%) was superior to TOMO (mean: 22.8%), IMRT (mean: 33.3%), and 3D-CRT (mean: 40.9%) (p<0.001). The average ipsilateral lung volume percentage receiving 20% of the PD was significantly lower in PBT (0.4%) and IMRT (2.3%) compared with 3D-CRT (6.0%) and TOMO (14.2%) (p<0.001). The average heart volume percentage receiving 20% and 10% of the PD in left-sided breast cancer (N=19) was significantly larger with TOMO (8.0%, 19.4%) compared to 3D-CRT (1.5%, 3.1%), IMRT (1.2%, 4.0%), and PBT (0%, 0%) (p<0.001). CONCLUSIONS All four EB-APBI techniques showed acceptable coverage of the PTV. However, effective non-PTV breast sparing was achieved at the cost of considerable dose exposure to the lung and heart in TOMO.

Randomised clinical trial: the efficacy of a 10‐day sequential therapy vs. a 14‐day standard proton pump inhibitor‐based triple therapy for Helicobacter pylori in Korea

Aliment Pharmacol Ther 2011; 34: 1098–1105

Secondary Neutron Doses for Several Beam Configurations for Proton Therapy

PURPOSE To compare possible neutron doses produced in scanning and scattering modes, with the latter assessed using a newly built passive-scattering proton beam line. METHODS AND MATERIALS A 40 x 30.5 x 30-cm water phantom was irradiated with 230-MeV proton beams using a gantry angle of 270 degrees , a 10-cm-diameter snout, and a brass aperture with a diameter of 7 cm and a thickness of 6.5 cm. The secondary neutron doses during irradiation were measured at various points using CR-39 detectors, and these measurements were cross-checked using a neutron survey meter with a 22-cm range and a 5-cm spread-out Bragg peak. RESULTS The maximum doses due to secondary neutrons produced by a scattering beam-delivery system were on the order of 0.152 mSv/Gy and 1.17 mSv/Gy at 50 cm from the beam isocenter in the longitudinal (0 degrees ) and perpendicular (90 degrees ) directions, respectively. The neutron dose equivalent to the proton absorbed dose, measured from 10 cm to 100 cm from the isocenter, ranged from 0.071 mSv/Gy to 1.96 mSv/Gy in the direction of the beam line (i.e., phi = 0 degrees ). The largest neutron dose, of 3.88 mSv/Gy, was observed at 135 degrees and 25 cm from the isocenter. CONCLUSIONS Although the secondary neutron doses in proton therapy were higher when a scattering mode rather than a scanning mode was used, they did not exceed the scattered photon dose in typical photon treatments.

MICROSCOPIC GOLD PARTICLE-BASED FIDUCIAL MARKERS FOR PROTON THERAPY OF PROSTATE CANCER

PURPOSE We examined the feasibility of using fiducial markers composed of microscopic gold particles and human-compatible polymers as a means to overcome current problems with conventional macroscopic gold fiducial markers, such as dose reduction and artifact generation, in proton therapy for prostate cancer. METHODS AND MATERIALS We examined two types of gold particle fiducial marker interactions: that with diagnostic X-rays and with a therapeutic proton beam. That is, we qualitatively and quantitatively compared the radiographic visibility of conventional gold and gold particle fiducial markers and the CT artifacts and dose reduction associated with their use. RESULTS The gold particle fiducials could be easily distinguished from high-density structures, such as the pelvic bone, in diagnostic X-rays but were nearly transparent to a proton beam. The proton dose distribution was distorted <5% by the gold particle fiducials with a 4.9% normalized gold density; this was the case even in the worst configuration (i.e., parallel alignment with a single-direction proton beam). In addition, CT artifacts were dramatically reduced for the gold particle mixture. CONCLUSION Mixtures of microscopic gold particles and human-compatible polymers have excellent potential as fiducial markers for proton therapy for prostate cancer. These include good radiographic visibility, low distortion of the depth-dose distribution, and few CT artifacts.

Variations in dose distribution and optical properties of GafchromicTM EBT2 film according to scanning mode

PURPOSE The authors aim was to investigate the effects of using transmission and reflection scanning modes, the film orientation during scanning, and ambient room light on a dosimetry system based on the Gafchromic(TM) EBT2 film model. METHODS For calibration, the films were cut to 3 × 3 cm(2) and irradiated from 20 to 700 cGy at the depth of maximum dose using 6 and 10 MV photon beams in a 10 × 10 cm(2) field size. Absolute dose calibration of the linear accelerator was done according to the TRS398 protocol. An FG65-G ionization chamber was used to monitor the dose while irradiating the films in solid water. The film pieces were scanned with an EPSON Expression 1680 Pro flatbed scanner in transmission and reflection modes. Authors investigated the effect of orientation on films and examined the optical properties of EBT2 film using an ellipsometer and an ultraviolet (UV)/visible spectrometer to explain the dosimetric dependence of the film on orientation during the scanning process. To investigate the effect of ambient room light, films were preirradiated in 6 and 10 MV photon beams with intensity-modulated radiotherapy (IMRT) quality assurance (QA) plans, and then exposed to room light, either directly for 2 days in a workroom or for 2 months in a film box. Gamma index pass criteria of (3%, 3 mm) were used. RESULTS The dose response curves based on net optical density (NOD) indicated that the reflection scanning mode can provide a better dose sensitivity than the transmission scanning mode, whereas the standard deviation of the dose is greater in reflection mode than in transmission mode. When the film was rotated 90° from the portrait orientation, the average dose of the EBT2 film decreased by 11.5-19.6% in transmission mode and by 1.5-2.3% in reflection mode. Using an ellipsometer, variation of the refractive index of EBT2 film-the birefringence property-was found to be the largest between 45° (1.72 and 1.71) and 135° (1.8 and 1.77) for 300 and 800 cGy. Absorption spectra of EBT2 films measured with spectrometer were the function of film orientation. The readings in reflection scanning mode were more stable against room light than those in transmission scanning mode, although dose readings increased in both modes after the films were exposed to room light. CONCLUSIONS The transmission scanning mode exhibited a strong dependence on film orientation during scanning and a change in optical density resulting from room light exposure, so a constant scanning orientation and minimal exposure to light can reduce uncertainty in the measured dose (23 ± 3%). The angular dependence was analyzed using Jones matrices and optical properties of EBT2 film were obtained using an ellipsometer and an UV/visible spectrometer. The reflection scanning mode has relatively good stability with respect to room light and film orientation on a scanner, although the large standard deviation of dose is a disadvantage in measurements of absolute dose. Reflection scanning mode can offer a potential advantage for film dosimetry in radiotherapy, although transmission scanning mode is still recommended for dosimetry as it provides better uncertainty results.

Influence of Lipiodol Agent on Proton Beam Range in Radiotherapy Planning Using Computed Tomography for Hepatocellular Carcinoma

PURPOSE To evaluate the influence of lipiodol on the proton beam range, which has not yet been determined. METHODS AND MATERIALS Two computed tomography (CT) data sets were obtained with a T25-flask containing lipiodol and water that was placed above a water phantom. The plan with the lipiodol CT images was performed, and then a verification plan was applied to the water CT images. The actual proton beam ranges in the lipiodol and water were measured under same conditions, and we compared the calculated proton beam range in the treatment planning system with measured values. RESULTS The calculated distal range in the treatment planning system was 12 cm in water, which was 3.87 cm longer than that in lipiodol (8.13 cm). In contrast, the measured distal range was 12 +/- 0.01 cm in water, which was 0.21 +/- 0.01 cm longer than that of lipiodol (11.78 +/- 0.01 cm). A 3.65 +/- 0.01-cm range shift was found in the calculated range compared with the measured range. For 10 hepatocellular carcinoma patients, the distal range in the verification plan with the corrected CT images in which the Hounsfield unit (HU) value of lipiodolized lesion was replaced with the average HU value of the surrounding tissue was 0.61 +/- 0.26 cm (range, 0.26-0.99) longer than that in the plan with uncorrected CT images. CONCLUSIONS It could be relevant for the purposes of range calculation of proton beams in the treatment planning system that the HU value of a lipiodolized lesion is replaced by the average HU value of the surrounding normal tissue.

CHARACTERISTICS OF MOVEMENT-INDUCED DOSE REDUCTION IN TARGET VOLUME: A COMPARISON BETWEEN PHOTON AND PROTON BEAM TREATMENT

We compared the main characteristics of movement-induced dose reduction during photon and proton beam treatment, based on an analysis of dose-volume histograms. To simulate target movement, a target contour was delineated in a scanned phantom and displaced by 3 to 20 mm. Although the dose reductions to the target in the 2 treatment systems were similar for transverse (perpendicular to beam direction) target motion, they were completely different for longitudinal (parallel to beam direction) target motion. While both modalities showed a relationship between the degree of target shift and the reduction in dose coverage, dose reduction showed a strong directional dependence in proton beam treatment. Clinical simulation of target movement for a prostate cancer patient showed that, although coverage and conformity indices for a 6-mm lateral movement of the prostate were reduced by 9% and 16%, respectively, for proton beam treatment, they were reduced by only 1% and 7%, respectively, for photon treatment. This difference was greater for a 15-mm target movement in the lateral direction, which lowered the coverage and conformity indices by 34% and 54%, respectively, for proton beam treatment, but changed little during photon treatment. In addition, we found that the equivalent uniform dose (EUD) and homogeneity index show similar characteristics during target movement. These results suggest that movement-induced dose reduction differs significantly between photon and proton beam treatment. Attention should be paid to the target margin in proton beam treatment due to the distinct characteristics of heavy ion beams.

Serum gastrin levels in different stages of distal gastric carcinogenesis: is there a role for serum gastrin in tumor growth?

BACKGROUND/AIMS Elevated levels of serum gastrin (SG) have been associated with tumorigenic effects in a number of gastrointestinal cancers. We decided to investigate the relationship between SG and gastric epithelial lesions. MATERIALS AND METHODS A total of 90 patients with gastric epithelial lesions (hyperplastic polyp, 12; adenoma, 41; early gastric cancer, 29; advanced gastric cancer, 8) were enrolled as the case group and 79 patients without epithelial lesions were enrolled as the control group. RESULTS Serum gastrin levels were significantly different between the case and control groups (p<0.001). A high SG level (>80 pg/mL), intestinal metaplasia, and a pepsinogen I/II ratio <3 were independently associated with an increased risk of epithelial lesions (odds ratio: 14.6, 9.4, and 4.1, respectively, p<0.05). SG levels in case subjects showed a unimodal distribution pattern as the disease progressed. The mean SG level was highest in those with hyperplastic polyps and then decreased significantly to the control level in the gastric cancer group. Higher SG levels in each disease category were not associated with increased tumor size, synchronicity, invasiveness, presence of lymph node metastasis, or a higher cellular proliferation index (p>0.05). CONCLUSION An increased SG level was an independent and potent risk factor for gastric epithelial lesions. However, it does not seem to relate with distal gastric tumor growth. Serial decreases in SG levels should be considered a warning sign in index hypergastrinemic patients with no prior Helicobacter pylori eradication.

Prognostic Significance of Hemodynamic and Clinical Stages in the Prediction of Hepatocellular Carcinoma.

Background & Goals: Early identification of hepatocellular carcinoma (HCC) is associated with improved survival for patients with chronic liver disease (CLD). We evaluated the prognostic significance of hemodynamic stage (HS) and clinical stage (CS) in predicting HCC in CLD patients. Methods: Between January 2006 and May 2014, 801 patients with CLD who underwent hepatic venous pressure gradient (HVPG) measurement were prospectively enrolled. HS was classified by HVPG (mm Hg) as follows: HS-1 (HVPG⩽6), HS-2 (6<HVPG⩽10), HS-3 (10<HVPG⩽12), HS-4 (12<HVPG⩽20), and HS-5 (20<HVPG). CS was classified as follows: CS-0 (no cirrhosis), CS-1 (cirrhosis without varix), CS-2 (cirrhosis with varix), CS-3 (varix bleeding without other complications), CS-4 (first nonbleeding decompensating event), and CS-5 (any second decompensating event). The HCC development and risk factors for HCC were evaluated in all patients and patients with cirrhosis, respectively. Results: HCC developed in 53 patients (6.6%). The incidence densities of HCC according to HS-1 to HS-5 and CS-0 to CS-5 were 4, 16, 36, 45, and 49/1000 person years and 0, 15, 25, 33, 36, and 53/1000 person years of observation, respectively. Ascites aggravation [P=0.008, odd ratio (OR)=2.33], HVPG>12 mm Hg (P=0.033, OR=2.17), CS>2 (P=0.039, OR=2.36), and alpha-fetoprotein (AFP; P=0.017, OR=1.01) were significant predictors of HCC development in all patients. For patients with cirrhosis, ascites aggravation (OR=2.51), HVPG >12 mm Hg (OR=2.46), and CS >2 (OR=2.62) were correlated with HCC development. Areas under receiver operating characteristic curves of the prediction-model, CS, HVPG score, and AFP were 0.797, 0.707, 0.701, and 0.653, respectively. Conclusions: HCC development correlates with advancing liver fibrosis or disease as measured by HS and CS. In addition, ascites aggravation and elevated AFP appears to be associated with increased incidence of HCC.

Clinical features and treatment outcomes of skin cancer arising from burn scar: a single-institution experience.

Aims and Background This study was conducted to investigate the clinicopathological features and long-term outcomes of patients with skin cancer arising from burn scar (SCBS). Patients and Methods We retrospectively reviewed the medical records of patients diagnosed with SCBS between January 2000 and May 2012. A total of 44 patients were enrolled in this study. Results The median latent period between burn injury and development of SCBS was 32 years (range, 8–78 years). The most frequent sites of SCBS were the lower limbs (68.2%) followed by the upper limbs (15.9%) and trunk (11.4%). Most patients (95.4%) had squamous cell carcinoma. Of 34 patients with localized disease at the time of diagnosis, 33 patients are alive with no evidence of recurrence. Of 10 patients with regional lymph node metastasis (referred to as locally advanced disease), 4 died of disease progression and 5 are alive with metastatic disease in the lymph nodes, bone or lung. Patients with localized disease survived longer than patients with locally advanced disease (P = 0.000). In patients with locally advanced disease, the median overall survival time was 16 months (95% CI, 2.88–29.4 months). Conclusions While localized SCBS is a potentially curable disease, locally advanced SCBS has a poor prognosis in spite of aggressive treatment. These results suggest that early recognition and aggressive treatment are essential to improve the outcomes of SCBS.