• Progress in Medical Physics
• /
• v.23 no.3
• /
• pp.138-144
• /
• 2012

Dose distribution throughout the clinical organ range of motion was analyzed using a respiratory-motion simulator that was equipped with a polymer gel dosimeter and EBT2 film. The normoxic polymer gel dosimeter was synthesized from gelatin, MAA, HQ, THPC and HPLC. The gel dosimeter and EBT2 film were irradiated with Co-60 gamma rays that were moved along the x-axis and y-axis in ${\pm}1.5cm$ steps at five-second intervals. The field size was $5{\times}5cm^2$. The SSD was 80 cm and set to 10 Gy at a depth of 2 cm. The PDD at a depth of 50 mm was 75.2% in the ion chamber, 82.3% in the static state and 86.1% in the dynamic state in the gel dosimeter. The penumbra for the dynamic state target, which was measured using the gel dosimeter, averaged 10.89 mm, this is a 40.5% increase over the penumbra of the static state target of 7.74 mm. In addition, when measuring with gel dosimetry, the value for the penumbra is 36.6% smaller in the static state and 29.4% smaller in the dynamic state compared to measuring with film. The aim of this study was to investigate the dosimetric properties of a normoxic polymethacrylic acid gel dosimeter in static and dynamic states and to evaluate the potentiality as a relative dosimeter for dynamic therapeutic radiation.

• Progress in Medical Physics
• /
• v.26 no.3
• /
• pp.127-136
• /
• 2015

The purpose of this study is to perform a dosimetric evaluation of amplitude-based respiratory gating for the delivery of volumetric modulated arc therapy (VMAT). We selected two types of breathing patterns, subjectively among patients with respiratory-gated treatment log files. For patients that showed consistent breathing patterns (CBP) relative to the 4D CT respiration patterns, the variability of the breath-holding position during treatment was observed within the thresholds. However, patients with inconsistent breathing patterns (IBP) show differences relative to those with CBP. The relative isodose distribution was evaluated using an EBT3 film by comparing gated delivery to static delivery, and an absolute dose measurement was performed with a $0.6cm^3$ Farmer-type ion chamber. The passing rate percentages under the 3%/3 mm gamma analysis for Patients 1, 2 and 3 were respectively 93.18%, 91.16%, and 95.46% for CBP, and 66.77%, 48.79%, and 40.36% for IBP. Under the more stringent criteria of 2%/2 mm, passing rates for Patients 1, 2 and 3 were respectively 73.05%, 67.14%, and 86.85% for CBP, and 46.53%, 32.73%, and 36.51% for IBP. The ion chamber measurements were within 3.5%, on average, of those calculated by the TPS and within 2.0%, on average, when compared to the static-point dose measurements for all cases of CBP. Inconsistent breathing patterns between 4D CT simulation and treatment may cause considerable dosimetric differences. Therefore, patient training is important to maintain consistent breathing amplitude during CT scan acquisition and treatment delivery.

• Progress in Medical Physics
• /
• v.22 no.2
• /
• pp.99-105
• /
• 2011

The purpose of this study is to evaluate the accuracy of IMRT in our clinic from based on TG119 procedure and establish action level. Five IMRT test cases were described in TG119: multi-target, head&neck, prostate, and two C-shapes (easy&hard). There were used and delivered to water-equivalent solid phantom for IMRT. Absolute dose for points in target and OAR was measured by using an ion chamber (CC13, IBA). EBT2 film was utilized to compare the measured two-dimensional dose distribution with the calculated one by treatment planning system. All collected data were analyzed using the TG119 specifications to determine the confidence limit. The mean of relative error (%) between measured and calculated value was $1.2{\pm}1.1%$ and $1.2{\pm}0.7%$ for target and OAR, respectively. The resulting confidence limits were 3.4% and 2.6%. In EBT2 film dosimetry, the average percentage of points passing the gamma criteria (3%/3 mm) was $97.7{\pm}0.8%$. Confidence limit values determined by EBT2 film analysis was 3.9%. This study has focused on IMRT commissioning and quality assurance based on TG119 guideline. It is concluded that action level were ${\pm}4%$ and ${\pm}3%$ for target and OAR and 97% for film measurement, respectively. It is expected that TG119-based procedure can be used as reference to evaluate the accuracy of IMRT for each institution.

• Radiation Oncology Journal
• /
• v.28 no.3
• /
• pp.177-183
• /
• 2010

Purpose: Simulation using computed tomography (CT) is now widely available for radiation treatment planning for breast cancer. It is an important tool to help define the tumor target and normal tissue based on anatomical features of an individual patient. In Korea, most patients have small sized breasts and the purpose of this study was to review the margin of treatment field between conventional two-dimensional (2D) planning and CT based three-dimensional (3D) planning in patients with small breasts. Materials and Methods: Twenty-five consecutive patients with early breast cancer undergoing breast conservation therapy were selected. All patients underwent 3D CT based planning with a conventional breast tangential field design. In 2D planning, the treatment field margins were determined by palpation of the breast parenchyma (In general, the superior: base of the clavicle, medial: midline, lateral: mid - axillary line, and inferior margin: 2 m below the inframammary fold). In 3D planning, the clinical target volume (CTV) ought to comprise all glandular breast tissue, and the PTV was obtained by adding a 3D margin of 1 cm around the CTV except in the skin direction. The difference in the treatment field margin and equivalent field size between 2D and 3D planning were evaluated. The association between radiation field margins and factors such as body mass index, menopause status, and bra size was determined. Lung volume and heart volume were examined on the basis of the prescribed breast radiation dose and 3D dose distribution. Results: The margins of the treatment field were smaller in the 3D planning except for two patients. The superior margin was especially variable (average, 2.5 cm; range, -2.5 to 4.5 cm; SD, 1.85). The margin of these targets did not vary equally across BMI class, menopause status, or bra size. The average irradiated lung volume was significantly lower for 3D planning. The average irradiated heart volume did not decrease significantly. Conclusion: The use of 3D CT based planning reduced the radiation field in early breast cancer patients with small breasts in relation to conventional planning. Though a coherent definition of the breast is needed, CT-based planning generated the better plan in terms of reducing the irradiation volume of normal tissue. Moreover it was possible that 3D CT based planning showed better CTV coverage including postoperative change.

• Progress in Medical Physics
• /
• v.16 no.1
• /
• pp.16-23
• /
• 2005

The objective of this study was to construct multi-element ultrasound applicators for the treatment of gynecologic cancer with high dose rate brachytherapy. For the treatment of uterus, piezo-ceramic crystal transducer (PZT -5A) with outer diameter of 4 mm, wall thickness of 1.3 mm, and length of 24.5 mm was selected. For the treatment of cervix or vagina, it should be possible to insert the applicator into the vagina. Thus, a cylindrical PZT -8 material with outer diameter of 24.5 mm, wall thickness of 1.3 mm, and length of 15.2 mm was selected. The operating frequencies determined by vector impedance measurement were 3.2 MHz for the PZT 5A cylinder (OD=4 mm) and 1.7 MHz for the PZT -8 cylinder (OD: 24.5 mm). The ratios of generated acoustic output power to applied electric power were 33% and 61% for the tandem type crystal and the cylinder type crystal, respectively. The radiated acoustic pressure fields from both transducers were calculated using a Matlab code and measured in water using hydrophone. There was good agreement between measured and calculated acoustic pressure field distribution. For a tandem type transducer, the calculated acoustic pressure field decreased from 0.023 MPa at 10 mm to 0.010 Mpa at 30 mm, the reduction of 57%. For the cylinder type transducer which will be used for the treatment of vagina showed 78% reduction at 15 mm and 66% at 25 mm as compared to values at 5 mm from the surface. Based on the characteristics of the transducers, this study demonstrated the possibility of using the crystals as a heating source. Finally, a 3-element and 4-element prototype applicators were constructed. The 3-element applicator is 75 mm long and 4 mm thick and will be used for the treatment of uterus. The 4-element applicator is 61 mm long and 24.5 mm thick and will be used for the treatment of vagina. Using these applicators, it is possible to generate enough power to increase temperature to therapeutic level.

• Radiation Oncology Journal
• /
• v.11 no.2
• /
• pp.369-376
• /
• 1993

226 patients with carcinoma of the uterine cervix treated with curative radiation therapy at the Department of Therapeutic Radiology, Dongsan hospital, Keimyung university, School of medicine, from July,1988 to May,1991 were evaluated. The patients with all stages of the disease were included in this study. The maximum and mean follow up durations were 60 and 43 months. The radiation therapy consisted of external irradiation to the whole pelvis (2700~4500 cGy) and boost parametrial doses (for a total of 4500~6300 cGy)with midline shild $(4{\times}10\;cm),$ and combined with intracavitary irradiation (5700~7500 cGy to point A). The distribution of patients according to the stage was as follows: stage IB 37 $(16.4\%),$ stage IIA 91 $(40.3\%),$ stage IIB 58 $(25.7\%),$ stage III 32 $(13.8\%),$ stage IV 8 $(3.5\%).$ The overall failure rate was $23.9\%$ (54 patients). The failure rate increased as a function of stage from $13.5\%$ in stage IB to $15.4\%$ in stage IIA, $25.9\%$ in stage IIB, $46.9\%$ in stage III, and $62.5\%$ in stage UV. The pelvic failure alone were 32 patients and 11 patients were as a components of other failure, and remaining 11 patients had distant metastasis only. Among the 43 patients of locoregional failure,28 patients were not controlled initially and in other words nearly half of total failures were due to residual tumor. The mean medial paracervical (point A) doses were 6700 cGy in stage IIB,7200 cGy in stage IIA,7450 cGy in stage IIB,7600 cGy in stage III and 8100 cGy in stage IV. The medial paracervical doses showed some correlation with tumor control rate in early stage of disease (stage Ib, IIA), but there were higher central failure rate in advanced stage in spite of higher paracervical doses. In advanced stage, failure were not reduced by simple increment of paracervical doses. To improve a locoregional control rate in advanced stages, it is necessary to give additional treatment such as concomitant chemoradiation.

• Radiation Oncology Journal
• /
• v.16 no.2
• /
• pp.195-202
• /
• 1998

Purpose : In order to obtain basic data for treatment plan in radiosurgery, we measured small fields of 6 MV X-rays and compared the measured data with our Monte Carlo simulations for the small fields. Materials and Methods : The small fields of 1.0, 2.0 and 3.0 cm in diameter were used in this study. Percentage depth dose (PDD) and beam Profiles of those fields were measured and calculated. A small semiconductor detector, water phantoms, and a remote control system were used for the measurement Monte Carlo simulations were Performed using the EGS4 code with the input data prepared for the energy distribution of 6 MV X-rays, beam divergence, circular fields and the geometry of the water phantoms. Results : In the case of PDD values, the calculated values were lower than the measured values for all fields and depths, with the differences being 0.3 to 5.7% at the depths of 20 to 20.0 cm and 0.0 to 8.9% at the surface regions. As a result of the analysis of beam profiles for all field sizes at a depth of loom in water phantom, the measured 90% dose widths were in good agreement with the calculated values, however, the calculated Penumbra radii were 0.1 cm shorter than measured values. Conclusion : The measured PDDs and beam profiles agreement with the Monte Carlo calculations approximately. However, it is different when it comes to calculations in the area of phantom surface and penumbra because the Monte Carlo calculations were performed under the simplified geometries. Therefore, we have to study how to include the actual geometries and more precise data for the field area in Monte Carlo calculations. The Monte Carlo calculations will be used as a useful tool for the very complicated conditions in measurement and verification.

• Radiation Oncology Journal
• /
• v.25 no.2
• /
• pp.101-108
• /
• 2007

[ $\underline{Purpose}$ ]: To compare radiation therapy alone to combined modality therapy about survival rate and tolerance of elderly patients ($70=or{\geq}$) with non-small-cell lung cancer (NSCLC). $\underline{Materials\;and\;Methods}$: Between 1998 and 2002, 57 patients given radiation therapy due to NSCLC (Stage III) were analysed retrospectively. Radiation therapy alone (RT), concurrent chemoradiation (CRT), and sequential chemoradiation (SCRT) was done to 33, 16 and 8 patients, respectively. Patients' median age was 74 (range $70{\sim}85$). Male and female are 51 patients and 6 patients, respectively. 23 patients were stage IIIa and 34 were stage IIIb. Patients' characteristic distribution of RT and CRT was not significantly different except mass size that RT has a bigger than CRT. The fraction size of radiation therapy was 1.8 Gy in CRT and $1.8{\sim}3\;Gy$ in other groups. Total radiation dose was $51{\sim}63\;Gy$ according to the fraction size. If the prescribed total radiation dose was successfully irradiated, we stated that it was completion of radiation therapy. $\underline{Results}$: 52 patients were dead. Median period of radiation therapy was as follow: RT, 35 days, CRT, 60.5 days and SCRT, 35 days. Overall median survival time (MST) was 10.1 months. The 1 yr- and 2 yr-overall survival rate was 39.8% and 17.6%, respectively. MST of RT, CRT and SCRT was 8.9, 8.2 and 11.7 months, respectively. The 1 yr survival rate of RT, CRT and SCRT was 38.4%, 37.5% and 50% (not significant). Patients given incomplete radiation therapy were 12 (RT, 5 CRT, 6 SCRT, 1). N stage (p=0.081) and the difference of treatment methods (p=0.079) were the factors affecting incompletion of radiation therapy, but it was not significant. In case of combined-agents chemotherapy, 4 of 8 ceased radiation therapy. T stage ($T{\geq}3$), mass size (${\geq}5\;cm$), Karnofsky performance scale (${\leq}70$) and completion of radiation therapy were the prognostic factors in uni- and multi-variate analysis. $\underline{Conclusion}$: In elderly patients with NSCLC, radiation therapy alone was a treatment method with similar survival period compared with other methods. Generally, patients given radiation therapy alone was tolerable to a treatment. Before planning concurrent chemoirradiation in elderly patients with NSCLC, physicians pay attention to a selection of patients and chemotherapy agents considering general condition and toxicity.

• Radiation Oncology Journal
• /
• v.25 no.2
• /
• pp.118-124
• /
• 2007

[ $\underline{Purpose}$ ]: This study was to evaluate the survival and pattern of failure after radiation therapy of sino-nasal cancer using partial attenuation filer and wedged beams and to help radiotherapy planning of sino-nasal cancer. $\underline{Materials\;and\;Methods}$: Between February 1992 and March 2003, 17 patients with sino-nasal cancers underwent radiation therapy using partial attenuation filter at Dongsan Medical Center, Keimyung university. There were 9 male and 8 female patients. Patients' age ranged from 40 to 75 years (median 59 years). There were 10 patients of maxillary sinus cancer, 7 patiens of nasal cancer. The histologic type was squamous cell carcinoma in 11, adenoid cystic carcinoma in 4 and olfactory neuroblastoma in 2. The distribution of clinical stage by the AJCC system was 3 for stage II, 7 for III and 6 for IV. The five patients were treated with radiation alone and 12 patients were treated with surgery and postoperative radiation therapy. The range of total radiation dose delivered to the primary tumor was from 44 to 76 Gy (median 60 Gy). The follow-up period ranged from 3 to 173 months with median of 78 months. $\underline{Results}$: The overall 2 year survival rate and disease free survival rate was 76.4%. The 5 year and 10 year survival rate were 76.4% and 45.6% and the 5 year and 10 year disease free survival rate was 70.6%. The 5 year disease free survival rate by treatment modality was 91.6% for postoperative radiation group and 20% for radiation alone group, statistical significance was found by treatment modality (p=0.006). There were no differences in survival by pathology and stage. There were local failure in 5 patients (29%) but no distant failure and no severe complication required surgical intervention. $\underline{Conclusion}$: Radiation therapy of sino-nasal cancer using partial attenuation filter was safe and effective. Combined modality with conservative surgery and radiation therapy was more advisable to achieve loco-regional control in sino-nasal cancer. Also we considered high precision radiation therapy with dose escalation and development of multi-modality treatment to improve local control and survival rate in advanced sino-nasal cancer.

• Korean Journal of Head & Neck Oncology
• /
• v.14 no.2
• /
• pp.156-163
• /
• 1998

Background & Objectives: Frameless fractionated stereotactic radiotherapy(FFSRT) is a modification of stereotactic radiosurgery(SRS) with radiobiologic advantage of fractionation without losing mechanical accuracy of SRS. Local recurrence of head and neck cancer at or near skull base benefit from reirradiation. Main barrier to successful palliation is dose limitation secondary to normal tissue tolerance. We try to evaluate the efficacy and safety of FFSRT as a new modality of reirradaton in these challenging patients. Materials & Methods: Seven patients with recurrent head & neck cancer involving at or near skull base received FFSRT from September 1995 to November 1997. Six patients with nasopharyngeal cancer had received induction chemotherapy and curative radiation therapy. One patient with maxillary sinus cancer had received total maxillectomy and postoperative radiation therapy as a initial treatment. Follow-up ranged from 11 to 32 months with median of 24 months. Three of 7 patients received hyperfractionated radiation therapy(1.1-1.2Gy/fraction, bid, total 19.8-24Gy) just before FFSRT. All patients received FFSRT(3-5Gy/fraction, total 15-30Gy/5-10fractions). Chemotherapy(cis-platin $100mg/m^2$) were given concurrently with FFSRT in four patients. Second course of FFSRT were given in 4 patients with progression or recurrence after initial FFSRT. Because IF(irregularity factor; ratio of surface area of target to the surface area of sphere with same volume as a target) is too big to use conventional stereotactic RT using multiple arc method for protection of radiation damage to critical normal tissue, all patients received FFSRT with conformal method using irregular static ports. Results: Five of 7 patients showed complete remission in follow-up CT &/or MRI. Three of these five patients who developed marginal, in-field, and out-field recurrences, respectively. Another one of complete responders has been dead of G-I bleeding without evidence of local recurrence. One partial responder who showed progressive disease 15 months after initial FFSRT has received additional FFSRT, and then he is well-being with symptomatic improvement. One minmal responder who showed progression of locoregional disease 9 months after $1^{st}$ FFSRT has received 2nd FFSRT, and then he is alive with stable disease. Five of 7 case had showed direct invasion to skull base and had complaint headache and various symptoms of cranial nerve involvement. Four of these five case showed improvement of neurologic symptoms after FFSRT. No significant neurologic complicaltion related to FFSRT was observed during follow-up periods. Tumor volumes were ranged from 3.9 to 50.7 cc and surface area ranged from 16.1 to $114.9cm^2$. IF ranged from 1.21 to 1.74. The average ratio of volume of prescription isodose shell to target volume was 1.02 that indicated the improvement of target coverage and dose distribution with FFSRT with conformal method compared to target coverage with FFSRT with multiple arc method. Conclusion: Our initial experience suggests that FFSRT with conformal method was relatively effective and safe modality in the treatment of recurrent head and neck cancer involving at or near skull base. Treatment benefit included good palliation of symptoms and reasonable radiographic response. However, more experience and additional follow-up are needed to better assess its ultimate role in treating these challenging patients.