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Objective:To investigate the feasibility of individualized primary clinical target volume (CTV) delineation in intensity-modulated radiotherapy for nasopharyngeal carcinoma (NPC).Methods:Clinical data of 87 consecutive patients newly diagnosed with lateralized NPC in Jiangsu Cancer Hospital between October 2016 and February 2018 were retrospectively analyzed. Lateralized NPC is defined as tumor invasion not exceeding the contralateral wall. According to the tumor spread, the primary CTV was optimized as follows: CTV2 only covered the medial part of the contralateral pterygopalatine fossa, whereas the contralateral foramen oval was not included; on the level of parapharyngeal space, the contralateral side of CTV only covered the posterior lateral lymph nodes, whereas the contralateral internal jugular vein was not regularly covered. Failure patterns and 5-year survival [local control rate (LCR), progression-free survival (PFS) and overall survival (OS)] were evaluated by Kaplan-Meier method. Paired t-test and rank-sum test were used to analyze the dose variation in the optimized region and adverse reactions. Results:The median follow-up time was 59.5 months. The 5-year LCR, PFS, and OS were 98.9%, 86.5% and 92.1%, respectively. There was no local recurrence in the optimized area of CTV. Dosimetric comparison results showed that the doses of parotid gland, temporal lobe, cochlea and middle ear on the contralateral side were reduced by 13.45%, 9.14%, 38.83%, and 29.36%, respectively. Four cases (4.6%) developed grade 3 hearing loss, all on the ipsilateral side. The optimized scheme significantly alleviated the hearing loss on the contralateral side compared to that on the ipsilateral side ( P<0.001). Other grade 3 late adverse reactions included cranial nerve injury, subcutaneous fibrosis in the neck and visual impairment, with 1 case each. Conclusion:Individualized primary CTV for lateralized NPC is feasible and safe, with obvious dosimetric advantages and reduced adverse reaction rate, which is worthy of clinical promotion.
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Objective:The respiratory waveform of lung cancer patients based on 4D-CT respiratory gating was analyzed to evaluate the accuracy of gating during radiotherapy, and to explore the off-target in the 4D-CT respiratory gating radiotherapy.Methods:Clinical data of 18 patients with lung cancer admitted to Radiotherapy Department of Jiangsu Cancer Hospital were collected to obtain the respiratory waveform data during 4D-CT respiratory gating radiotherapy. The waveform in each treatment working cycle was compared with the waveform in 4D-CT scan to study whether there was a possibility of the off-target in the treatment of lung cancer patients.Results:There were 154 treatment sessions and 20,790 treatment breathing cycles in 18 patients, among which the threshold of gated opening beam miss amplitude (Δm-en) was greater than 0 in 95 treatment breathing cycles in 7 patients, accounting for 0.46% of all breathing cycles, and the threshold of gated closing beam miss amplitude (Δm-dis) was greater than 0 in 1419 treatment breathing cycles in 13 patients, accounting for 6.83% of all cycles. Among the 13 patients withΔm-dis greater than 0, actual tumor range of motion (R G) was greater than the sum of the value of target margin (M) and the value of plan tumor range of motion (R T) in 7 patients, R G was more than 1.5 times of M+R T in 7 patients, and there were also 7 patients in the phase of rapid rise and fall of respiratory curve. The correlation efficients between R G-M-R T and the percentage of beam on miss phase (T en%) and the percentage of beam closing off phase (T dis%) were 0.41 and 0.57, respectively. Conclusion:When R G is more than 1.5 times of M+R T value and the gating beam on phase contains the phases in the rapid rise and fall of the respiratory curve, the possibility of the off-target during radiotherapy is significantly increased.
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Objective:To evaluate the effect of leaf position error of Varian high-definition multi-leaf collimator (HD120) on the dosimetry of stereotactic body radiation therapy (SBRT) for lung tumors.Methods:Nine SBRT plans based on HD120 for lung tumors were selected as the reference plans. The parameters of the plans were modified by the in-house program based on the Varian Eclipse 15.6 scripting application program interface to generate the simulation plans with three types of leaf position errors including the isotropic systematic error, the anisotropic systematic error and the random error, respectively. Then, the dosimetric metric deviation between each simulation plan and the corresponding reference plan was calculated and regression analysis was performed to evaluate the dosimetric effect of three types of leaf position errors of HD120 on SBRT.Results:The planning target volume (PTV) D 99%, D 2cm and V 5Gy of double lungs were decreased quadraticly with the increase of the absolute value of the isotropic systematic error. The first-order sensitivity was -0.06%/mm to -0.26%/mm, and the second-order sensitivity was -0.55%/mm 2 to -1.17%/mm 2 ( R2=0.96-0.99, P<0.01). The maximum change of PTV D 99% was -3.13%. The linear regression analysis of the effects of the anisotropic systematic error and random error showed that the sensitivity of CI was 25.16%/mm ( R2=0.98, P<0.01) and -4.84%/mm( R2=0.99, P<0.01), and the sensitivity of other dosimetric deviations with the anisotropic systematic error was 4.80%/mm to 5.12%/mm ( R2=0.96-0.98, P<0.01), whereas the sensitivity with the random error was -0.47%/mm to -1.01%/mm ( R2=0.96-0.99, P=0-0.02). Conclusions:The dosimetric deviation of SBRT plan based on HD120 for lung cancer is highly sensitive to the anisotropic systematic error of leaf position, but less sensitive to the random error. In addition, the isotropic systematic error of leaf position will lead to the decrease of target coverage to a certain extent. Consequently, it is necessary to strictly control the systematic error of HD120 leaf position in the implementation of SBRT plan in clinical work.
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The motion of the tumor limits further improvement in the accuracy of radiotherapy. Real-time monitoring and tracking of tumor location is an emerging technology to improve the accuracy of tumor radiotherapy. According to the adopted methods, it can be broadly divided into non-radiation-based and radiation-based systems. The former system includes ultrasound guidance, nuclear magnetic resonance guidance, electromagnetic tracking, optical image guidance, artificial intelligence-based technologies, and the latter system consists of KV, MV-grade X-ray imaging system and CT-based guidance system. In this review, research progresses on real-time tumor monitoring and tracking technology in radiotherapy, respective advantages and disadvantages and current clinical application were summarized.
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Objective:To compare the dosimetric difference between IMRT and VMAT plans for ovarian protection after cervical cancer ovarian transposition surgery.Methods:Thirty-one patients who had received both cervical cancer resection and ovarian transposition were selected for adjuvant radiotherapy. The 9-field evenly divided IMRT and the dual-arc VMAT technology were performed for the treatment planning. The difference of the ovarian mean dose between the two techniques was explored. The relationship between the position of the ovarian-target interval and the ovarian dose was also analyzed.Results:A total of 54 ovaries in 31 patients were effectively transposed and moved out of the target area. Among them, 9 ovaries were located above the upper boundary of the PTV. For these cases, the ovarian mean dose of IMRT and VMAT were (177.8±90.7) and (166.7±70.6) cGy, respectively, which was not statistically different( P>0.05).45 ovaries were located in the same level with PTV. For these cases, the ovarian mean dose of IMRT and VMAT were (459.1±239.9) and (428.3±238.2) cGy, respectively ( z=3.11, P=0.002). The ovarian mean dose has the highest correlation and negative correlation with the closest lateral distance from the ovarian volume center to the PTV surface (IMRT, r=-0.922, P=0.001; VMAT, r=-0.865, P=0.001). To reduce the ovarian mean dose to 500 cGy, the lateral closest distance between the ovarian volume center and the PTV surface should be 3.6 cm and 3.3 cm for IMRT and VMAT respectively. Conclusions:There is no difference between the two planned ovarian doses when the ovaries were located above the upper boundary of the PTV. When the ovaries were located in the same level with PTV, the VMAT plan is better than IMRT in both ovarian dose and treatment efficiency. The ovarian dose could be predicted by the lateral closest distance from the ovarian volume center to the PTV.
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Objective To compare the dose distribution between volumetric-modulated arc therapy ( VMAT ) and intensity-modulated radiotherapy ( IMRT ) in patients with brain metastases receiving hippocampus-sparing whole brain radiotherapy. Methods Forty-six patients with brain metastases admitted to our hospital from 2013 to 2016 were recruited in this study. After fusing the CT and MRI images, the hippocampus was delineated on the fusion images. The three-grade hippocampal avoidance regions were created by using a volumetric expansion of 3,5 and 10 mm surrounding the hippocampus. The planning target volume ( PTV) was calculated by subtracting the 5-mm expansion surrounding the hippocampus from the whole brain. The prescription dose was 30 Gy/10 fractions. The 7-field IMRT and single arc VMAT were designed for each case. The dose distribution of PTV,hippocampus and other organs at risk ( OARs) were evaluated in both plans. Results The PTV was statistically compared between VMAT and IMRT:V95:95. 90％ and 94. 97％( P=0. 000 );V90:98. 17％ and 97. 48％( P=0. 000 );CI:0. 825 and 0. 813 ( P=0. 013);HI:0. 277 and 0. 289(P=0. 025).The hippocampal dose was also compared between VMAT and IMRT:the Dmax of hippocampus was 1698. 9 cGy for VMAT and 1784. 9 cGy for IMRT (P=0. 002).TheDmean of hippocampus was 1183. 8 cGy for VMAT and 1112. 7 cGy for IMRT (P=0. 000).No statistical significance was observed between IMRT and VMAT in protecting the OARs except the chiasma opticum ( 3262. 6 cGy and 3529. 3 cGy,P=0. 000).The MU and treatment time of VMAT and IMRT were 651 and 2768( P=0. 000) ,and 188 s and 504 s ( P=0. 000) . Conclusions The dose distribution of PTV in VMAT is significantly better than that in IMRT. VMAT is advantageous in protecting the hippocampus than IMRT. VMAT can significantly shorten treatment time and MU and enhance the equipment utilization. Besides, VMAT can achieve the goal of protecting the hippocampus and meet the prescription dose requirement of PTV.
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Objective To report the total skin electron irradiation(TSEI) to treat the mycosis fungoides and the related acute toxicity,short-term efficacy and long-term results.Methods Five patients with pathologically confirmed mycosis fungoides were enrolled from 1990 to 2011,including 4 males and 1 female.Median age was 51 years old(range 14-56 years old).Dose homegeneity within the field were ± 10％ of the prescribed dose with a skin surface dose of about 90％ of the prescribed dose.Four cases received a total dose of about 30 Gy in 30-32 fractions in 8 weeks,and the other case received an electron boost of 5 Gy to the residual tumor after irradiation with 31 Gy within 31 fractions in 8 weeks,who had received 6 cycles chemotherapy before TSEI.Results 4 cases with a follow-up time of more than 15 years achieved complete response 6 months after radiotherapy.For the recently treated case,a great partial response was achieved after radiotherapy.Acute toxicities for all patients were acceptable.Two patients survived after a follow-up of more than 15 years while the other two cases died of visceral involvement at 1 and 3 years later,respectively.The case treated recently survived 2 months later.Conclusions A total TSEI dose of about 30 Gy within 30-32 fractions during 8 weeks could be proved to be very effective and safe in skin lesion control.Visceral involvement is the main failure type.
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Objective To investigate the influence of random setup error on dose distribution in radiotherapy and determine the margin from ITV to PTV. Methods A random sample approach was used to simulate the fields position in target coordinate system. Cumulative effect of random setup error was the sum of dose distributions of all individual treatment fractions. Study of 100 cumulative effects might get shift sizes of 90%dose point position. Margins from ITV to PTV caused by random setup error were choosen by 95% probability. Spearman's correlation was used to analyze the influence of each factor. Results The average shift sizes of 90%dose point position was 0.62,1.84,3.13,4.78,6.34 and 8.03 mm if random setup error was 1,2,3,4,5 and 6 mm,respectively. Univariate analysis showed the size of margin was associated only by the size of random setup elror. Conclusions Margin of ITV to PTV is 1.2 times random setup error for head-and-neck cancer and 1.5 times for thoracic and abdominal cancer. Field size, energy and target depth. unlike random setup error, have no relation with the size of the margin.
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Objective To fit the functional relation between Percentage Depth Dose and depth by Newton Interpolation. Methods After analyzing the data of Percentage Depth Dose from different manufacturers' linear accelerators, the average of Percentage Depth Dose with same depth was calculated, and then the average data was determined. The interval was set and the interpolation node was selected for simulating the cubic polynomial with PDD and depth. Results Comparing the calculated values by the function with the measured ones, the error was less than 1%. Conclusion The function simulated with Newton Interpolation is applicable in routine clinical radiotherapy and research.
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Objective To evaluate the clinical results of three dimensional conformal radiotherapy (3DCRT) for esophageal carcinoma. Methods From May 1999 to May 2001, 104 patients with pathologically confirmed esophageal carcinoma were randomly divided into conventional radiotherapy (CT) and three dimensional conformal radiotherapy(3DCRT) groups, with 52 patients in each arm. The patients in CT group received conventional radiotherapy in 2.0?Gy/f, 5 fractions a week to a total dose of 70?Gy in 7 weeks. The patients in 3DCRT group were first treated by the same fractionation in CT group to the dose of 40?Gy, and then treated by 3DCRT in 3.0?Gy/f, 5 fractions a week to the total dose of 70?Gy in 6 weeks. Results The 1-and 3-year local control rates were 80.2% and 60.5% in 3DCRT group and 61.6% and 31.7% in CT group(?2 = 4.87, P