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Objective To compare bone marrow-sparing intensity-modulated radiotherapy (BMS-IMRT) with conventional intensity-modulated radiotherapy (IMRT) without considering pelvic bone marrow (PBM) as a planning constraint in the treatment of cervical cancer after hysterectomy. Methods BMS-IM-RT and IMRT planning were separately designed in a cohort of 10 patients with cervical cancer after hysterec-tomy. The prescribed dose was 95% planning target volume receiving 45 Gy/25 f. A commercially available TPS with convolution/superposition (CS) algorithm was used for dose calculation. Plans were compared ac-cording to dose-volume histogram (DVH) analysis in terms of PTV homogeneity (HI), conformity index (CI) as well as dose and volume parameters of organ at risks (OARs). Results BMS-IMRT was better than IMRT in terms of CI, but inferior to the latter for HI. When compared with IMRT, V_5, V_(10), V_(20), V_(30) and V_(40) of PBM in BMS-IMRT were reduced by 1.81% ,8.61% ,31.81% ,29.50% and 28.29%, respec-tively. No statistically significant differences were found between BMS-IMRT and IMRT for dose distritutions of the small bowel, bladder or rectum. Conclusions For patients with cervical cancer after hysterectomy, BMS-IMRT can reduce the PBM volume irradiated by low dose, which may reduce acute hematologic toxici-ties.
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Objective: To compare inverse three-dimensional conformal radiotherapy (Inv 3D-CRT) and intensity modulated ra-diotherapy (IMRT) for non-small cell lung cancer. Methods: For a cohort of 10 patients, Inv 3D-CRT and three groups of IMRT plannings were designed for per patient. The prescribed dose was 60 Gy/2 Gy/30f, 95% of the planning target volume received this dose. Dose was computed with a commercially available TPS using convolution/superposition (CS) algorithm. Plans were compared according to the PTV_(95)V_(20) ratio (PTV_(95)V_(20)) and D_(max)-D_(min). Results: Compared with Inv 3D-CRT, the PTV_(95)V_(20) ratio of three groups of IMRT increased by 1.08 (P = 0.014), 0.72 (P = 0.089) and 0.42 (P = 0.318), respectively. Conclusions: For NSCLC, IMRT can reduce the dose to the lungs compared with inverse 3D-CRT by improving the conformity of the plan and is worth spreading in clinical work.
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Objective:To compare bone marrow-sparing intensity-modulated radiotherapy(BMS-IMRT)with conventional (four-field box[3DCRT]and anteroposterior-posteroanterior[CRT])techniques in the treatment of cervical cancer.Methods:For a cohort of 10 patients,BMS-IMRT,3DCRT and CRT planning were designed.The prescribed dose was 45Gy/1.8Gy/25f,95%of the planning target volume received this dose.Doses were computed with a commercially available TPS.Plans were compared according to dose-volume histogram (DVH)analysis in terms of PTV homogeneity and conformity indices(HI and CI)as well as OARs dose and volume parameters.Results:BMS-IMRT had an advantages over 3DCRT and CRT in terms of CI,but inferior to the latter two for HI.BMS-IMRT was superior to 3DCRT in reducing the dose to PBM,small bowel,bladder and rectum.Compared with CRT,BMS-IMRT reduced the volume irradiated to the doses from 30Gy to 40Gy,but increased the volume irradiated to the low doses from 5Gy to 20Gy.In addition,BMS-IMRT reduced the volume of small bowel,bladder,rectum at nearly all dose levels.Conclusion:BMS-IMRT reduced irradiation of PBM compared with 3DCRT technique.Compared with CRT technique,BMS-IMRT reduced the volume of PBM irradiated to high doses.Therefore,for patients with cervical cancer after hysterectomy,BMS-IMRT might reduce acute hematologic toxicity(HT)compared with conventional techniques.
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Objective To compare dosimetrie difference of treatment planning of three-dimensional conformal radiotherapy (3D-CRT) and simplified intensity-modulated radiotherapy (slMRT) for non-small cell lung cancer (NSCLC). Methods Ten NSCLC patients treaded by radiotherapy were investigated. 3D-CRT and slMRT plannings were designed for each patient. The prescribed dose was 60 Gy(2 Gy/f), the 95 % of the planning target volume was received with this dose for each patient. The dose was computed with treatment planning system of ADAC Pinnacle3 using convolution/superpasition algorithm. Two plans were compared according to the homogeneity index (HI) and conformity index (CI) of dosimetry in the planning target volume and the parameters of dose-volume histogram (DVH) in normal tissue. Results In the terms of HI and CI, sIMRT had slight vantages over 3D-CRT. In the terms of DVH, compared with 3D-CRT, mean lung dose, V5, V10 and V20 of slMRT reduced by 14.81 %, 17.88 %, 19.15 % and 27.78 %, respectively. The dosimetric differences were not statistically significant between 3D-CRT and sIMRT in terms of esophagus, heart and spinal cord. Conclusions For NSCLC, sIMRT has some irreplaceable advantages over 3D-CRT and is worth spreading in clinical work.
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Objective To study the effect of the location and volume of tumors on the normal lung dose-volume parameters for lung cancer. Methods An sphere with a diameter of 2 cm made of tissue-equiv-alent material used for simulating tumor was inserted into the superior lobe, middle lobe, inferior lobe of the right lung, and superior lobe, inferior lobe of the left lung of the Rando phantom, respectively. 5-field sIM-RT plans were designed. The prescribed dose was 60 Gy/2 Gy/30 f, and 99% of the planning target volume received this dose. Dose-volume parameters of normal lung tissue including V_5, V_(10), V_(20), V_(30), V_50 and mean lung dose were analyzed and compared. Results For the dose-volume parameters, the diameter and the po-sition of the tumor have a significant effect (P < 0.05). With the diameter expanding from 2 cm to 3 cm,the parameters associated with tumor in various lobes increased by a range between 3.83%-125.38%,while the parameters linked with tumor in different lobes increased by a range between 10.46%-51.46% with the diameter expanding from 3 cm to 4 cm. Conclusions Location and diameter of sphere-like tumor have obvious effect on dose-volume parameters. Knowing about the degree of influence will help oncologists and physicists to evaluate treatment planning better and reduce radiation pneumonitis.
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Objective To establish an efficiency calibration method without a radioactive source for Inspector 2000 gamma spectroscopy system.Methods At the fwst step,geometry parameters of the detector were properly specified by comparisons of FEPE(Full Energy Peak Efficiency)between Monte Carlo(MC)calculations and the average measured values of HPGe and NaI detectors using point sources(137 Cs).The differences between calculations and measurements were generally within ±10% for gamma rays.Then,Monte Carlo simulation was used to evaluate the counting efficiency of Nal(TI)and HPGe detectors for BOMAB phantoms.Corresponding efficiency curves and functions were fitted.Results The counting efficiency received from the fitted efficiency functions had a good agreement with those from MC simulation.The bias for Nal detector ranged from-19% to 18%,while the bias for HPGe detector ranged from-11% to 17%.The above errors were totally acceptable in the on-site deployment during nuclear and radiological emergency events.Conclusions Monte Carlo method is simple,time and laborsaving in determing the counting efficiency of gamma spectroscopy system.
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The procedure of quality assurance(QA) and quality control(QC) is introduced. Then,the necessity of performing the QA and QC combining the corresponding international technical report and clinical practice is discussed. On the above basis,a system of QA and QC suitable to our daily work is established,which provides the guarantee for high quality service to patients and achieve economic and social benefits simultaneously.
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Objective To evaluate the effect of conformal radiotherapy for elderly patients with adva nced non-small-cell lung cancer. Methods From November 1998 to June 2001, 24 elderly patients with advanced non-small -cell lung cancer were treated with conformal radiotherapy. ResultsOne-year, two-year and three-year overall survival rate for the entire group are 91 67%, 54 16%, 43 33%. No patients developed acute radiation pneumonitis . According to the univariate analysis, significant prognostic factors included superior vena cava syndrome, Karnofsky performance status scores and gross tumo r volume. Conclusions Conformal radiotherapy improve the effect in elderly patients with advanced no n-small-cell lung cancer.
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The relationships in using efficiency and economic benefits of large-scale equipment and the cycle of turning back cost are discussed, and then the standards of full-load operation of large-scale equipment are discussed according to the analysis of utilization rate and a variety of radiotherapy techniques of large-scale equipment in past five years. On the above basis, some rational advices are proposed about how to reasonably use large-scale medical equipment and advanced treatment technique, providing high quality service for patients and achieving economic and social benefits simultaneously.