Non-coplanar whole brain radiotherapy is an effective modality for parotid sparing / 영남의대학술지

BACKGROUND@#The purpose of this study was to evaluate the efficacy and feasibility of non-coplanar whole brain radiotherapy (NC-WBRT) for parotid sparing.@*METHODS@#Fifteen cases, previously treated with WBRT were selected. NC-WBRT plans were generated. The beam arrangement for the non-coplanar plans consisted of superior anterior, right, and left beams. After generation of the non-coplanar plans a field-in-field technique was applied to the bilateral parallel opposed beams in order to reduce maximum dose and increase dose homogeneity. The NC-WBRT plans were subsequently compared with the previously generated bilateral WBRT (B-WBRT) plans. A field-in-field technique was also used with the B-WBRT plans according to our departmental protocol. As per our institutional practice a total dose of 30 Gy in 10 fractions of WBRT was administered 5 days a week.@*RESULTS@#The mean dose to the parotid gland for the two different plans were 16.2 Gy with B-WBRT and 13.7 Gy with NC-WBRT (p < 0.05). In the NC-WBRT plan, the V5Gy, V10Gy, V15Gy, V20Gy, and V25Gy of the parotid were significantly lower (p < 0.05) than those of the B-WBRT plan. The Dmax of the lens was also lower by 10% with NC-WBRT.@*CONCLUSION@#The use of NC-WBRT plans could be a simple and effective method to reduce irradiated volumes and improve the dose-volume parameters of the parotid gland.

Non-coplanar whole brain radiotherapy is an effective modality for parotid sparing / 영남의대학술지

BACKGROUND: The purpose of this study was to evaluate the efficacy and feasibility of non-coplanar whole brain radiotherapy (NC-WBRT) for parotid sparing.METHODS: Fifteen cases, previously treated with WBRT were selected. NC-WBRT plans were generated. The beam arrangement for the non-coplanar plans consisted of superior anterior, right, and left beams. After generation of the non-coplanar plans a field-in-field technique was applied to the bilateral parallel opposed beams in order to reduce maximum dose and increase dose homogeneity. The NC-WBRT plans were subsequently compared with the previously generated bilateral WBRT (B-WBRT) plans. A field-in-field technique was also used with the B-WBRT plans according to our departmental protocol. As per our institutional practice a total dose of 30 Gy in 10 fractions of WBRT was administered 5 days a week.RESULTS: The mean dose to the parotid gland for the two different plans were 16.2 Gy with B-WBRT and 13.7 Gy with NC-WBRT (p < 0.05). In the NC-WBRT plan, the V5Gy, V10Gy, V15Gy, V20Gy, and V25Gy of the parotid were significantly lower (p < 0.05) than those of the B-WBRT plan. The Dmax of the lens was also lower by 10% with NC-WBRT.CONCLUSION: The use of NC-WBRT plans could be a simple and effective method to reduce irradiated volumes and improve the dose-volume parameters of the parotid gland.

Whole brain radiotherapy using four-field box technique with tilting baseplate for parotid gland sparing

PURPOSE: The aim of this study is to evaluate the efficacy and feasibility of four-field box whole brain radiotherapy (FB-WBRT) with tilting baseplate by comparing bilateral WBRT (B-WBRT). METHODS AND MATERIALS: Between March 2016 and September 2018, 20 patients with brain metastases underwent WBRT using the four-field box technique. WBRT is performed with a dose of 30 Gy in 10 fractions daily. Two computed tomography simulations per person were performed. One was in the traditional supine position for B-WBRT and the other by applying the tilting acrylic supine baseplate to elevate the head by 40° for FB-WBRT. The B-WBRT used the field-in-field technique, which is the most commonly used method in our institution. The FB-WBRT comprised anterior, posterior, and bilateral beams. A wedge was applied in anterior and posterior fields to compensate for skull convexity. RESULTS: The average of Dmean of both parotid glands was 10.2 Gy (range, 3.8 to 17.8 Gy) in B-WBRT and 5.4 Gy (range, 2.0 to 11.7 Gy) in FB-WBRT (p < 0.05). Compared to B-WBRT, FB-WBRT reduced the mean dose of the right and left parotid glands from 10.1 Gy to 4.9 Gy and from 10.4 Gy to 5.8 Gy, respectively (p < 0.05). Further, V₅, V₁₀, V₁₅, V₂₀ for the parotid gland decreased significantly in FB-WBRT (p < 0.05). The Dmax and Dmean of lens decreased according to the dose-volume histogram. CONCLUSION: Compared to B-WBRT, FB-WBRT with a tilting baseplate is a simple and effective method that takes feature of noncoplanar beam to protect the parotid gland.

Selective Radiation Therapy for Ductal Carcinoma In Situ Following Breast-Conserving Surgery According to Age and Margin Width: Korean Radiation Oncology Group 11-04 and 16-02 Studies / 한국유방암학회지

PURPOSE: The optimal indications for omitting adjuvant radiation therapy (RT) after breast-conserving surgery are still controversial in ductal carcinoma in situ (DCIS) of the breast. The purpose of this study was to validate the role of postoperative RT in DCIS patients aged ≤50 years and with tumor margin widths of <1 cm, both of which have been proven to be high-risk features for recurrence in cohorts not receiving RT. METHODS: Using two multicenter retrospective studies on DCIS, a pooled analysis was performed among patients aged ≤50 years and with margin widths < 1 cm. All patients underwent breast-conserving surgery. Two hundred thirty-two patients received postoperative RT, while 54 did not. The median follow-up period was 77 months (range, 2–190 months) and 70 months (range, 5–166 months) in the patients who received RT and those who did not, respectively. RESULTS: The patients who received RT had larger tumors (p < 0.001), higher nuclear grade (p < 0.001), closer margin width (p < 0.001), and negative estrogen receptor expression (p=0.010) compared with those who did not receive RT. During the follow-up period, there were 17 ipsilateral breast tumor recurrences (IBTRs) as follows: invasive carcinoma in 10 patients and DCIS in seven. In the univariate analysis, the treatment with RT and human epidermal growth factor receptor 2 (HER2) status were significant risk factors for IBTR. The 7-year IBTR rates with and without postoperative RT were 3.6% and 13.1%, respectively (p=0.008). HER2-positive tumors had a higher IBTR rate than the HER2-negative tumors (7-year rate, 13.6% vs. 3.9%; p=0.003). CONCLUSION: Postoperative RT following breast-conserving surgery significantly reduced the 7-year IBTR rate in the DCIS patients aged ≤50 years and with margin widths < 1 cm. HER2 positivity was associated with increased IBTR in these patients.

The impact of beam angle configuration of intensity-modulated radiotherapy in the hepatocellular carcinoma

PURPOSE: This treatment planning study was undertaken to evaluate the impact of beam angle configuration of intensity-modulated radiotherapy (IMRT) on the dose of the normal liver in hepatocellular carcinoma (HCC). MATERIALS AND METHODS: The computed tomography datasets of 25 patients treated with IMRT for HCC were selected. Two IMRT plans using five beams were made in each patient; beams with equidistance of 72degrees (Plan I), and beams with a 30degrees angle of separation entering the body near the tumor (Plan II). Both plans were generated using the same constraints in each patient. Conformity index (CI), homogeneity index (HI), gamma index, mean dose of the normal liver (Dmean_NL), Dmean_NL difference between the two plans, and percentage normal liver volumes receiving at least 10, 20, and 30 Gy (V10, V20, and V30) were evaluated and compared. RESULTS: Dmean_NL, V10, and V20 were significantly better for Plan II. The Dmean_NL was significantly lower for peripheral (p = 0.001) and central tumors (p = 0.034). Dmean_NL differences between the two plans increased in proportion to gross tumor volume to normal liver volume ratios (p = 0.002). CI, HI, and gamma indices were not significantly different for the two plans. CONCLUSION: The IMRT plan based on beams with narrow separations reduced the irradiated dose of the normal liver, which would allow radiation dose escalation for HCC.

Comparison of Intensity Modulated Radiation Therapy Dose Calculations with a PBC and AAA Algorithms in the Lung Cancer / 의학물리

The pencil beam convolution (PBC) algorithms in radiation treatment planning system have been widely used to calculate the radiation dose. A new photon dose calculation algorithm, referred to as the anisotropic analytical algorithm (AAA), was released for use by the Varian medical system. The aim of this paper was to investigate the difference in dose calculation between the AAA and PBC algorithm using the intensity modulated radiation therapy (IMRT) plan for lung cancer cases that were inhomogeneous in the low density. We quantitatively analyzed the differences in dose using the eclipse planning system (Varian Medical System, Palo Alto, CA) and I'mRT matirxx (IBA, Schwarzenbruck, Germany) equipment to compare the gamma evaluation. 11 patients with lung cancer at various sites were used in this study. We also used the TLD-100 (LiF) to measure the differences in dose between the calculated dose and measured dose in the Alderson Rando phantom. The maximum, mean, minimum dose for the normal tissue did not change significantly. But the volume of the PTV covered by the 95% isodose curve was decreased by 6% in the lung due to the difference in the algorithms. The difference dose between the calculated dose by the PBC algorithms and AAA algorithms and the measured dose with TLD-100 (LiF) in the Alderson Rando phantom was -4.6% and -2.7% respectively. Based on the results of this study, the treatment plan calculated using the AAA algorithms is more accurate in lung sites with a low density when compared to the treatment plan calculated using the PBC algorithms.

A Correction Method of Dose to Attenuation Rate of Transmitting Photon Beam Through Couch Top for Radiosurgery Using Novalis / 의학물리

This study has its own goal to deliver the accurate dose on the target volume by calculating and modifying the attenuation rate of photon beam transmitting the couch top with geometric model. The experiment was that the transmission rate and attenuation rate of photon beam transmitting the couch top was predicted by the geometric model, then compared and analyzed with what was measured experimentally based on that. The result showed that the predicted value by the geometric model accorded closely with the experimental value. In addition, in order to judge whether the practical clinical application is available, the point dose, measured after modifying the attenuation rate modelinged according to the treatment plan of a patient of spine radiosurgery, was compared with the one done nothing. The result was that the former showed decreased error range with treatment planned one than the latter. This papers calculated the transmission and attenuation rate with the geometric model transmitting the couch top and verified it experimentally. This method is expected to be very useful in not only the radiosurgery using Novalis but also the general radiation therapy.

The Effects of Nanoparticles for Irradiation / 영남의대학술지

BACKGROUND: To evaluate the changes in the radiation dose and temperature distribution on irradiated egg albumin and nanoparticle (Fe3O4) powder mixed egg albumin. METHODS: A new type of phantom was designed by fabricating a 30x30x30cm acryl square inside a 3x3x3cm small square and dividing it into two parts. In the control group, only egg albumin was irradiated, and in the test group, 25nm 20mg/cc, 25nm 40mg/cc, and 1 um 40 mg/cc nanoparticles with egg albumin were irradiated. The radiation isodose distributions and temperature changes were then observed. RESULTS: No significant changes were observed in the radiation dose and temperature distribution. CONCLUSION: The nanoparticles were considered not to have had any effect on the radiation dose and temperature distribution under the experimental conditions. Further studies can be conducted based on the changes in the mixture material.

Hypothyroidism after Radiotherapy of Locally Advanced Head and Neck Cancer / 대한방사선종양학회지

PURPOSE: The aim of the present study was to retrospectively evaluate the incidence of hypothyroidism in locally advanced head and neck cancer patients who received radiotherapy (RT) either with or without neck dissection. MATERIALS AND METHODS: From January 2000 to December 2005, 115 patients with locally advanced head and neck cancer and who received definitive RT or postoperative RT including standard anterior low-neck field were recruited to be part of this study. Nineteen patients had undergone ipsilateral neck dissection, whereas, 18 patients underwent bilateral neck dissection, and 78 patients were received RT alone. Patients' ages ranged from 28 to 85 years (median, 59 years) and there were a total of 73 male and 42 female patients. The primary tumor sites were the oral cavity, oropharynx, hypopharynx, larynx, and other sites in 18, 40, 28, 22 and 7 patients, respectively. Radiation dose to the thyroid gland ranged from 44 Gy to 66 Gy with a median dose of 50 Gy. Follow-up time ranged from 2 to 91 months, with a median of 29 months. RESULTS: The 1- and 3-year incidence of hypothyroidism was 28.7% (33 patients) and 33.0% (38 patients), respectively. The median time to detection of hypothyroidism was 8.5 months (range, 0 to 36 months). A univariate analysis revealed that neck node dissection was a risk factor for hypothyroidism (p=0.037). However, no factor was statistically significant from the results of a multivariate analysis. CONCLUSION: Patients treated for advanced head and neck cancer with radiotherapy with or without neck dissection will develop hypothyroidism. It is important to check the thyroid function periodically in these patientsespecially with the risk factor of neck node dissection.