Five patients with novel coronavirus Omicron variant of concern infection / 中华危重病急救医学

Objective:To analyze clinical characteristics of patients with novel coronavirus Omicron variant of concern infection, and to provide practical data and experience for subsequent clinical treatment.Methods:A retrospective analysis was performed for the clinical data of 5 cases with novel coronavirus Omicron variant of concern infection treated in the First Hospital of Jiaxing from December 18, 2021 to January 28, 2022. The patients' clinical data were recorded, including gender, age, length of hospital stay, vaccination status, clinical symptoms, laboratory indicators [white blood cell count (WBC), lymphocyte count (LYM), eosinophil count (EOS), hypersensitivity C-reactive protein (hs-CRP), novel coronavirus antibody immunoglobulin (IgG and IgM)], chest CT, treatment course and disease outcome.Results:All 5 patients were male, aged 24-37 years old. Four patients were vaccinated with novel coronavirus vaccine (one patient received 3 doses of the vaccine and 3 patients received only the first 2 doses of the vaccine), and no infection was found in chest CT. Laboratory examination showed that WBC, LYM, EOS and hs-CRP levels were normal, and only showed mild symptoms of upper respiratory tract infection. One patient was not vaccinated with novel coronavirus vaccine, and signs of viral pneumonia could be seen in chest CT, laboratory examination showed that WBC and hs-CRP levels increased, suggesting that bacterial infection, fever, cough, sputum and other respiratory symptoms were obvious, and the treatment time was long. All 5 patients were treated with Chinese medicine Lotus antipyretic and Baihu Yinqiao decoction based on routine antiviral therapy.Conclusions:Patients with novel coronavirus Omicron variant of concern infection vaccinated with the novel coronavirus vaccine have milder clinical symptoms, with less obvious chest CT findings and faster recovery. Chinese medicine Lotus antipyretic and Baihu Yinqiao decoction has obvious therapeutic effect on such patients.

Installation product acceptance of Varian Halcyon accelerator / 中华放射肿瘤学杂志

Objective:To understand the components, performance, acceptance test and quality assurance (QA) protocols of the new Varian Halcyon accelerator through the procedures of installation product acceptance (IPA).Methods:Per Varian IPA protocol, TG-142 for LINAC and TG-148 for tomotherapy QA protocols, the software license, safety interlock, mechanical accuracy, dosimetric performance and imager system were checked thoroughly. Some parameters were benchmarked to the conventional TrueBeam system.Results:The system has been fully licensed. Safety interlock was normal. Mechanical accuracy: The maximum deviation of beam stability per gantry rotation was 1.13%. The size of isocenter was>0.59mm. The offsets of MV imager, collimation rotation and absolute gantry rotation were 0.09mm, -0.21° and 0.11°, respectively. The maximum offsets of couch, virtual-to-isocenter were 0.15mm (vertical) and -0.04mm (vertical), respectively. Beam performance: The depth deviation of maximum dose was 0.1cm. The offset of percentage depth dose at 10cm was 0.5%. The maximum deviations of off-axis-intensity, symmetry, and repeatability were 0.9%, 0.94% and -0.44%, respectively. MV imager: The dark field mean pixel value, noise, corrected pixels, defective lines, sensitivity and linearity disparity of dose were 614, 4.4, 3626, 0, 19177, and 0.47%, respectively. All values were within the range of tolerance. Visual check of contrast resolution and small object detection was all satisfactory.Conclusions:Without Halcyon-specific TG report or guidelines, manufacture-provided IPA manual can be helpful with the installation of acceptance and QA protocols. IPA has been successfully performed for Halcyon at Peking University Cancer Hospital. The automated workflow improves the clinical efficiency by simplifying the operations.

Study of scanning method of T 1WI_Star_VIBE_FS in MRI simulation of neck radiotherapy / 中华放射肿瘤学杂志

Objective:To compare and analyze the image quality, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of T 1WI_Star_VIBE_FS sequence in MRI simulation of neck tumors with different scanning methods, aiming to determine the optimal scanning method. Methods:A retrospective analysis of 78 patients receiving MRI contrast scan was performed. All patients were randomly divided into three groups according to three different scanning methods including bolus mode (group A, n=23), segmentation splicing mode (group B, n=18) and the combination mode (group C, n=37). The image quality, SNR and CNR of the anterior soft tissues of neck were statistically compared. Results:A higher image quality score was obtained in group C. The mean SNR and CNR in three groups were calculated as 214.70±148.78, 91.95±59.26, 307.61±127.80, and 208.74±148.27, 85.79±59.50, 301.58±127.48, respectively. The image quality score, SNR and CNR in group C were significantly better compared with those in group A and B (all P<0.01). Conclusion:Combination of bolus and segmentation splicing modes is a recommended approach in MRI simulation during radiotherapy of neck tumors.

Dose response characterization of novel presage sheets for radiotherapy dose verification / 中华放射医学与防护杂志

Objective:To characterize the key dose response properties of the novel presage sheet dosimeters for radiotherapy dose verification, including absorption spectra, linearity, dose range and stability.Methods:The same batch of presage sheet dosimeters were irradiated by a radiotherapy linac. The absorption spectra within 400-700 nm were read out with a spectrophotometer, and the R-G-B3 absorption changes read out with a film flatbed scanner was compared before and after irradiation.Results:An absorption peak was clearly identified at 628 nm, where absorptions change in high linearity with delivered doses ( R2=0.9999). A flat valley region is identified around 490 nm, where dose induced absorption changes were negligible. The readout sensitivity of the R-channel of the flatbed scanner was higher than both in green and blue channels. In the dose range below 10 Gy, the R-channel absorptions are in significant linearity with doses ( R2=0.9999), with absorptions change in an obvious quadratic trend in the range beyond 10 Gy ( R2=0.9999). The dose range of presage sheets was more than 94.6 Gy. The absorptions were well preserved within 1 h post-irradation, and then are shown to increase gradually, where the increase speeds are dose-related. The post-irradiation integrity of dose falloff gradients are shown with negligible gradient blurring. Conclusions:The novel presage sheets shown to have reasonable dose response linearity, large dose range, desirable post-irradiation dose gradient integrity and negligible fractionation effect, which indicates its great potentials in integral dose verification of high-dose and multiple target radiotherapy deliveries.

A feasibility study of local adaptation of Lung SBRT RapidPlan commercial model / 中华放射医学与防护杂志

Objective:To explore the feasibility and optimization effect of modifying the Henry Ford Hospital (HFHS) RapidPlan model for stereotactic body radiation therapy planning based on local requirements.Methods:The following changes were made based on Henry Ford Health System(HFHS) Rapid Plan Lung SBRT model, taking the latest clinical guideline evidence and local clinical practice into account: Internal gross target volume(IGTV) and organ at risk(OAR) structure, lung, were added and set corresponding parameters.The upper value of planning target volume (PTV) was adjusted from 109% to 125%. The original training library was replaced with 73 local historical simultaneous integrated boosting plans, and statistical verification and outlier cleaning of the initial trained model were performed using Model Analytics software. Totally 10 cases not included in the model library were selected for independent verification, and automatic optimization result of the models before and after modifying were compared under the same beam condition. The following dosimetric parameters were compared after target dose normalization: conformal index (CI) of target volume, the mean doses, maximum doses and dose-volume parameters of OARs.Results:The " tail" of the PTV′s DVH and the " shoulder" and " tail" of the IGTV′s DVH of model M (local) validation plan (M (local)_P) performs higher than the original model HFHS (HFHS_P). The PTV_CI (1.07±0.13) of M local_P were significantly smaller than HFHS_P (1.25±0.24) ( Z=-2.497, P<0.05). Except for Heart_ D15 cm 3 and Heart_ Dmax, most of the M local_P dosimetric parameters of OARs were lower than HFHS_P, and the standard deviation was smaller. However, the difference of between two plans was no more than 3.06%. 10 HFHS_P plans don′t satisfy dose parameters requirement, two of which PTV_CI values are 1.52 and 1.74, far beyond the clinically acceptable range. Conclusions:Commercial model HFHS could be localized by replacing training library and adjusting parameters. Moreover, plans optimized by the modified model are local clinical acceptable in the aspects of target volume conformity and hotspots, and have a better performance in terms of OAR sparing and plan consistency.

State of the art of gel dosimeters for three-dimensional radiotherapy dose verification / 中华放射医学与防护杂志

Dose verification, as part of the radiotherapy QA chain, is a significant method to ensure the patients' safety and efficacy of treatment. The increasing application of precision radiotherapy techniques in clinic has advanced the need of three-dimensional ( 3D) dose verification. Gel dosimeters, prevailing for its intrinsic 3D high-resolution measurement and good tissue equivalence, can serve as effective supplement to the clinical radiotherapy dosimetric system. This paper reviews the method ology, dose response mechanism, characterizations of the state-of-the-art gel dosimeters. Gel dosimeters, outstanding for 3D dose measurement, have a great potential to explore both for clinical application and academic research.

A comparative study of dosimetric verification of HalcyonTM treatment plans using Varian Portal Dosimetry and PTW array 1500 / 中华放射医学与防护杂志

Objective To compare two pretreatment plan QA methods for HalcyonTM accelerator using Portal Dosimetry (PD),and PTW OCTAVIUS 1500 detector array + Octagonal phantom (Oct 1500)respectively.Methods Parallel measurement-based pretreatment QA using two methods was performed for 22 IMRT/VMAT plans (74 fields) that have been used to treat 20 patients recruited in the Halcyon clinical trial.Several γ 2D comparisons were also applied to provide guidelines for Halcyon planning QA.Results Using Oct1500 method,the γ 2D passing rates for 74 fields in 22 Plans were 95.26±3.59,95.01±3.62 (Local Dose),99.05± 1.35,98.57± 1.96 (Max Dose) respectively.Two-related samples non-parametric tests suggested that the differences between the evaluation criteria were of statistical significance (Z =-7.220,-4.108,P＜0.05).For PD method,the γ 2D passing rates were 84.11％ ± 1.35％ (1 mm/1％),99.07％± 1.35％ (2 mm/2％),and 99.86％ ± 1.35％ (3 mm/3％).Two-related samples non-parametric tests suggested that the differences between evaluation criteria of PD method were statistically significant (Z =-7.475,-7.475,-6.906,P＜0.05).For 74 fields and max dose,3 mm/3％ evaluation criteria,two-related samples non-parametric tests suggested that the differences between PD and Oct1500 method were statistically significant (Z=-5.072,P＜0.05).Conclusions Both methods can be used for Halcyon pretreatment plan QA.PD is superior to Oct1500 with respect to efficiency and spatial resolution-induced verification accuracy.The criteria of 2 mm/2％ for PD,and Max Dose/3 mm/3％ for Oct1500 was suggested.

Impact of immobilization base plates composed of various materials on the imaging quality of MR simulation during radiotherapy / 中华放射肿瘤学杂志

Objective To compare the impact of immobilization base plates composed of 7 types of materials on the MR-simulation imaging quality used for radiotherapy,aiming to provide reference data for clinical applications.Methods Using identical T1 and T2 sequences of Siemens MR-simulator,the MR images of ACR Large Phantom were acquired on the Orfit carbon fiber laminate,polycarbonate (PC),high precision base plate (HP),Jinan Huayuxin BR,WR,KP and SP materials,respectively.The imaging quality without any plate was used as the baseline data.The following metrics were compared:1.High-contrast spatial resolution:the sharpness of 3 pairs of hole arrays was observed,which represented resolutions of 1.1 mm,1.0 mm and 0.9 mm on the LR and AP directions;2.Image intensity uniformity in terms of percent integral uniformity (PIU):PIU =100× [1-((high-low)/(high +low)];3.Low-contrast resolution:distinguishable spokes representing resolutions of 5.1％,3.6％,2.5％ and 1.4％ were recorded.According to ACR recommendations,high-contrast resolution of 1.0 mm,PIU of T1WI and T2＞82％and low-contrast spoke difference＜3 were considered as clinically acceptable.Results High-contrast T1WI and T2WI resolutions of no plate,PC plate,HP plate and KP material were all 0.9 mm,and those of the remaining materials were =worse than 0.9 mm.The T1WI and T2WI PIU of no plate was＞87％,and the PIU of carbon fiber plate was reduced by＞ 25％.The PIU decrease of remaining materials was within ±4％.Except the carbon fiber plate,the low-contrast spokes of the remaining materials were within ±3 compared with the reference.Conclusions In clinical settings,carbon fiber plate exerts the most significant effect upon the MR-simulation imaging quality,which is unsuitable for MR simulation.Imaging quality of PC and HP plates are consistent with that of no plate.BR and KP materials exert slight effect upon MR signal.The remaining materials are of potential values for the manufacture of immobilization devices and accessories.

Application of MRI simulation in delineation of gross tumor volume in pre-operative radiotherapy for low rectal carcinoma / 中华放射医学与防护杂志

Objective To explore the value of MRI simulation in the pre-operative radiotherapy for locally advanced low rectal carcinoma.Methods A total of 40 patients diagnosed with locally advanced low rectal carcinoma by endoscopic biopsy and radiological staging examinations were included in this study.There were 22 male and 18 female with nedian age 58 years (range 31-80).Patients underwent CT and MRI simulation scanning in the same position and fixing device.GTV under CT images and MRI inages were delineated respectively by two experienced radiologists.Primary tumor length,tumor volume and distance of distal tumor from the anal verge were calculated by treatment planning system(TPS).The two groups of data were compared.Results The distance of distal tumor to the anal verge were all no more than 5 cm on digital examination.The mean length of GTVcT was remarkably longer than that of GTVMRI [(5.21 ±1.65) cm vs.(4.46 ± 1.51) cm,t =5.059,P ＜0.05].The mean volume of GTVcTWaS significantly larger than that of GTVMRI[(55.71 ±31.57) cm3vs.(44.02 ±25.11) cm3,t=6.977,P＜ 0.05)].The mean distance of distal tumor to the anal verge was (3.72 ± 0.93) cm,significantly longer than that of lower bounds of GTVCT to the anal verge,which had a high consistency with GTVMRI.The IMRT plan was based on CT-MRI fusion images.There were no 3-4 grade adverse effects of radiotherapy.The overall pCR rate was 32.5％.Conclusions MRI simulation could define smaller GTV and more precise lower bounds than CT.With improved accuracy of target volumes contours,the application of MRI simulation may promote the efficacy of radiotherapy and result in a reduction in the incidence of toxicities.

Preparation and characterization of docetaxel incorporated in phosphatidylcholine-sodium desoxycholate mixed micelles / 军事医学

Objective To prepare and characterize docetaxel incorporated phosphatidylcholine -sodium desoxycholate mixed micelles (DOX EPC/SDC MMs).Methods Docetaxel mixed micelles (DOX MMs) were prepared using the co-precipitation method .An optimized formulation was obtained by single factor method , which was used to study the effect of several factors on water solubility of DOX in MMs, including EPC/total(EPC+SDC)concentration, total(EPC+SDC) concentration, the pH and ionic strength of the hydrated solution .Then, the obtained DOX MMs were characterized by investigating particle size distribution and morphology , and by conducting dilute experiments to examin micelle stability . Results The EPC/total ( EPC+SDC) concentration ratio was 0.4.The total supplementary material concentration was 2.5%.Pure water was used to disperse the film .The drug loaded MMs had an average size of 18.56 nm and average zeta potential of -24.3 mV.A roundlike shape was observed under a transmission electron microscope ( TEM).Conclusion DOX EPC/SDC MMs, prepared by a simple and convenient method , can enhance water solubility , is physically compatible with injection solutions and is expected to become a new drug delivery system .

Absolute dose calibration and output factor simulation for flattened and flattening filter-free Monte Carlo model of 6 MV photon beams / 中华放射医学与防护杂志

Objective To explore the Monte Carlo calculation methods for the absolute dose calibration and output factor of 6 MV flattening-filter ( FF) and flattening-filter free ( FFF) photon beams based on TrueBeam accelerator .Methods The BEAMnrc code was used to model the LINAC head of FF and FFF modes.The BEAM_up covers the components from the target to the monitor chamber , and BEAM_down includes the structures beneath the chamber , the dose deposit to the monitor chamber contributed by the incidence electrons and scattered particles from the secondary collimators were calculated respectively .The incidence electron-induced dose at certain depths on the central axis were simulated by means of the DOSXYZnrc code .By means of dose calibration equation , the calibration factor for the standard field (10 cm ×10 cm) and the output factors for various fields (1 cm ×1 cm-40 cm ×40 cm) were computed respectively .Results For the 6 MV FF and FFF beams under the standard 10 cm ×10 cm field, 1 MU equals to 7.747 ×1013 ±3.099 ×1011 and 3.248 ×1013 ±1.624 ×1011 electrons to the target , respectively , which deposited 21.53 and 35.01 cGy to the monitor chamber of the virtual accelerator respectively .The difference between the simulated and calculated output factors were 0.72%±1.4%and 0.56%±0.78%for FF and FFF , respectively .Conclusions The model generated and measured output factors agree well , indicating the good accuracy of the dose calculation by the model , which would provides basis for further clinical dosimetric studies .

Knowledge-based semi-automated optimization of intensity-modulated radiotherapy plans using a volume modulated arc therapy-configured model / 中华放射肿瘤学杂志

Objective To evaluate the feasibility and dosimetric features of a volume modulated arc therapy (VMAT)-configured model in knowledge-based optimization of fixed-field dynamic intensitymodulated radiotherapy (IMRT) plans based on the Varian RapidPlan system.Methods ① A dose-volume histogram prediction model was trained with 81 qualified preoperative VMAT plans for rectal cancer and then statistically verified.② For clinically approved 10 IMRT plans with the same dose prescription,the above model was used to automatically generate new optimization parameters and dynamic muhileaf collimator (MLC) sequences with field geometry and beam energy unchanged.③ In order to rule out the disparities between different versions,a single algorithm was used to calculate the absolute doses of the original and new plans.④ Statistical analyses were performed on dosimetric parameters after comparable target dose coverage was achieved in the two plans by appropriate normalization.Results On the basis of similar target dose homogeneity and coverage,RapidPlan significantly reduced the doses to the urinary bladder (D50％ by 9.01 Gy,P =0.000;Dmean by 8.08 Gy,P =0.005) and the femoral head (D50％ by 4.20 Gy,P =0.000;Dmean by 3.84 Gy,P=0.005) but significantly elevated the mean total number of monitor units (1211±99 vs.771±79,P=0.000) and the number of fields with multiple MLC carriage groups.The knowledge-based semi-automated optimization caused a significantly larger number of high-dose hotspots but a similar D2％ (52.54 vs.52.71 Gy,P=0.239).Conclusions The VMAT model can be used for the knowledge-based semi-automated optimization of IMRT plans to enhance the efficiency and OAR protection.However,the resulting high-dose hotspots need further manual intervention.

Clinical observation of different dose of clopidogrel on the neural function in patients with ischemic stroke / 药学实践杂志

Objective To explore the clinical effects of different dose of clopidogrel on the neural functions in patients with ischemic stroke.Methods 120 patients with ischemic stroke were randomly divided into low dose group (clopidogrel 75 mg daily) or high dose group (clopidogrel 150 mg daily).All the patients received the same basic treatment plus clopidogrel for 3 month.Both groups were evaluated and compared for their NIHSS scores, platelet count, platelet aggregation rate, neurologic deterioration rate, recurrence rate of cerebral infarction and intracranial bleeding rate at the time of admission, one month and three month.Results Compared to the scores at the time of admission, NIHSS scores decreased in both groups after one month treatment with statistical significance (P<0.05).The high dose group dropped more obviously.The NIHSS scores at 3 month in the low dose group had no difference statistically compared to 1 month (P>0.05), while high dose group declined significantly (P<0.05).The platelet count and platelet aggregation were decreased significantly in high dose group at 3 month(P<0.05), while there was no significant change in the low dose group(P>0.05).The neurologic deterioration rate, recurrence rate of cerebral infarction in the low dose group were 11.7％, 10.0％ respectively, significantly higher than that of high dose group (5.0％, 5.0％, respectively), which was statistically significant (P<0.05).However, there was no statistically significant difference (P>0.05) between two groups in intracranial bleeding rate (5.0％ and 6.7％ respectively).Conclusion Patients on clopidogrel 150 mg exhibited much better recovery of neural functions and greater reduction in the recurrence of cerebral infarction and atherosclerosis related cardiovascular events.

Imaging dose and risk of Varian thoracic cone beam CT to the ICRP computational reference phantom / 中华放射肿瘤学杂志

Objective To investigate the dose distribution and radiation risk of Varian thoracic cone beam computed tomography (CBCT) with default parameters with reference to Monte Carlo simulation and International Commission on Radiological Protection (ICRP) report 110.Methods EGSnrc/BEAMnrc code was used to simulate the material, thickness, and geometry of the kV CBCT source (kVS) to establish the kVS model.A benchmarked MCSIM code was applied to calculate the dose distribution in the ICRP phantom after the scan with the standard thoracic parameters (110 kV, 20 mA, and 262 mAs), and the conversion coefficient of absolute dose was obtained in a spherical phantom following the TG-61 protocol.The results of Monte Carlo simulation were validated by PDD and Profile in a water phantom and the measurement of the absolute dose in the computed tomography dose index (CTDI) phantom and Alderson phantom.The models including BEIR VⅡ were used to evaluate the radiation risks.Results With reference to the criterion of 3%/1 mm, the uncertainties of PDD and Profile were less than 2%.The difference between the measured and calculated values was<2.9% in the CTDI phantom and ≤0.05 cGy in the Alderson phantom.In the ICRP110 phantom, the doses to the left lung, right lung, left breast, right breast, heart, thyroid, trachea, cancellous bone, and cortical bone were 1.28, 1.39, 1.74, 1.80, 1.46, 0.48, 0.88, 0.85, and 1.84 cGy, respectively.The relative risks of ischemic heart disease, breast cancer, lung cancer, thyroid cancer, and tracheal cancer in a standard scan were1.001 , 1.009, 1.019, 1.000, and 1.008, respectively. Conclusions The accumulated dose and long-term risks of CBCT during image-guided thoracic radiotherapy cannot be neglected and should be effectively controlled.

The model training of knowledge-based radiotherapy treatment planning and its preliminary application / 中华放射肿瘤学杂志

Objective Knowledge?based radiotherapy ( KBRT ) can reduce the plan quality variability induced by different experiences between physicians and improve the quality of treatment plans. Methods The Varian Rapid Plan system was used to train a dose?volume histogram ( DVH) prediction model. The obtained model was preliminarily applied to semi?automatic design of the preoperative treatment plans for rectal cancer. Eighty high?quality volumetric modulated arc therapy plans were imported into the model training set of the Rapid Plan system. The structures of the plans were matched to the corresponding labels and codes as listed in the library. The training started after the verification of prescription. The residual plots,regression curves,geometric plots for organ at risk ( OAR) ,in?field DVH plots,and model training logs were examined. After removal of the mismatch, the original plans were assessed to rule out outliers and influential data points. More similar plans may be added for another round of training. Ten KBRT plans were designed using the final model and compared with the clinical plans. Results For the two major OARs,the femoral head and bladder,the average goodness of fit of the principal component were 0?999 415/1.0 and 0?999 963/1.0 for the DVH model,and 0?999 651/1.0 and 0?999 945/1.0 for geometry?based expected dose model,respectively. In all the plans, 11 had Cook ’ s distance values exceeding the tolerance and 4 had studentized residual values exceeding the tolerance. The outliers were all kept in the training set to generalize the scope of the model. The 10 KBRT plans had significantly improved homogeneity indices for PGTV and PTV than the original plans (P=0?00,0?04).The 10 KBRT plans also had significantly reduced D50% to the femoral head and bladder as well as significantly reduced mean doses to the bladder than the original plans (P=0?042,0?000,0?005). Conclusions In this study,the Rapid Plan system is used to train a KBRT model for design of preoperative radiotherapy plans for rectal cancer. The results of preliminary application meet the clinical requirements.

Role of large-diameter MRI simulation in target volume delineation in radiotherapy for nasopharyngeal carcinoma / 中华放射肿瘤学杂志

Objective To investigate the role of large-diameter magnetic resonance imaging (MRI) simulation in target volume delineation in radiotherapy for nasopharyngeal carcinoma (NPC).Methods Eighteen patients with NPC underwent computed tomography (CT) simulation and MRI simulation scans and localization in the same body position,with SOMATOM Sensation Open 40-row 82-cm large-diameter CT simulator and Siemens 3T MRI MAGNETOM Skyra 70-cm large-diameter simulator,respectively.The gross tumor volume (GTV) and parotid glands were delineated on all images according to the ICRU Report 50/62,and MRI was applied to observe the changes in GTV and parotid volume during radiotherapy.Paired t-test was applied to analyze the differences between GTVCT and GTVMRI and between GTVnx-CT and GTVnx-MRI.Results GTVMRI decreased significantly compared with GTVCT,and the average volume decreased from (213.64±84.59) cm3 to (199.68±84.69) cm3(p=0.006).As for the volume of primary lesions in the nasopharynx,GTVnx-MRI was significantly smaller than GTVnx-CT,and the volume decreased from (95.75± 24.76) cm3 to (88.12±26.25) cm3 (P =0.001);as for the volume of cervical lymph nodes,GTVnd-MRI was significantly smaller than GTVnd-CT,and the volume decreased from (117.89± 72.69) cm3 to (111.56± 70.69) cm3 (P=0.018).The targets delineated by CT and MRI did not overlap completely,with major differences in skull base bone and cervical soft tissue.The volume of both parotid glands delineated on MRI image was higher than that delineated on CT image,with a major difference in the deep lobe.MRI showed that GTV was reduced by 82.64± 16.87％ during radiotherapy,and the volumes of the left and right parotid glands were reduced by (32.7± 23.95) ％ and (34.7± 21.72) ％,respectively.Conclusions The delineation of target volume based on MRI simulation is more accurate than that based on CT simulation and can achieve a smaller volume range,which helps to guide target volume delineation in radiotherapy for NPC accurately.

Performance comparison of four common LINAC daily QA instruments / 中华放射医学与防护杂志

Objective To compare the performances of four commercially available LINAC daily QA instruments.Methods The dosimetric stability of a LINAC including central axis output,flatness and symmetry were verified and fine-tuned using a 3-dimensional water phantom,dosimeters and ionization chambers.The baseline of the four instruments including LINA-C,QUICK-C,BEAM-C and QA3 were set thereafter.Daily measurements of LINAC were conducted with these instruments respectively and the results were compared.Arbitrary errors (CAX and SYM) beyond TG-142 tolerances were introduced to the LINAC to test the sensibilities of each instrument in detecting these changes.Results Relative to the baseline that were measured by the 3-dimensional water phantom and dosimeters,the results monitored by the four instruments were comparable.The maximum disparities of the CAX,FLAT,and SYM were 0.5％ (LINA-C),-0.45％ (QUICK-C),and 0.5％ (BEAM-C),respectively.All checkers detected the known errors successfully.Conclusions The stabilities of all the four evaluated instruments met the requirements of daily QA for LINAC.LINA-C verifies CAX only.QUICKE-C,BEAM-C and QA3 can be used to perform all the daily QA protocols as suggested by AAPM TG 142 report.They also provide unique additional functions.The setup of baseline determines if the morning checkers could measure the LINAC dosimetric parameters correctly.When an error is alarmed by the morning checker,it is recommended to verify the performance of the instrument first rather than recalibrating the LINAC immediately.