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Background : Adequate dose to Clinical Target Volume is needed to control tumour and to deliver adequate dose without missing the target, this Clinical Target Volume must be encompassed by two margins for uncertainties; first, Internal margin uncertainties and second, set up margin uncertainty will form Planning Target Volume. Three mm setup error of couch location resulted in 38% decrease of minimum target radiation dose and 42 % increase of minimal Spinal Cord and Parotid Gland radiation dose. Aims and Objectives : Objectives of this retrospective study are, before implementation of high precession radiotherapy technique for Head and Neck Malignancy, we want determine optimal 3-dimensional Clinical Target Volume to planning target volume margin and to assess our setup accuracy in our institute, NRS Medical College & Hospital, Kolkata. Material and Methods : We analyzed retrospectively set up error from 691 set Cone Beam CT images of 94 patients. According to Standard Guidelines Target Volume delineated and for creation Clinical Target Volume to Planning target volume margin, we have used 5-7 mm margin around Clinical Target Volume. Results : In 99% patients’ setup deviation were within 0.5 cm. The population systematic error (?) in in Super Inferior; mediolateral; and anterior posterior direction were 0.13 cm, 0.12 cm and 0.14 cm respectively. The population random error in Super Inferior; mediolateral; and anterior posterior direction were 0.021 cm, 0.022 cm and 0.173 cm respectively. Using van Herk formula Clinical Target Volume to Planning Target Volume margin in Super Inferior; mediolateral; and anterior posterior direction were 0.34, 0.47 and 0.32 cm respectively. Corresponding values with Stroom formula 0.28, 0.40 and 0.26 cm respectively. Conclusions : In our study Set up margin of 5mm all around the CTV to create PTV is found to be safe and adequete
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Objective:To compare the difference between breast bracket combined with polyurethane foam and single polyurethane foam in the accuracy of immobilization, providing a better immobilization for breast cancer radiotherapy.Methods:Fifty breast cancer patients who received radiotherapy in Sun Yat-sen University Cancer Center from March 2021 to July 2021 were selected. Among them, 25 patients were immobilized with polyurethane foam (foam group), and the other 25 patients were immobilized with polyurethane foam combined with breast bracket (combination group). All patients were scanned by CBCT once a week to obtain setup errors in the SI, LR and AP directions for t-test. The formula M PTV=2.5 Σ+0.7 σ was used to calculate the margin of the planning target volume(M PTV). Results:The setup errors in the foam group were SI (2.0±3.26) mm, LR (0.88±2.76) mm, AP (1.22±3.55) mm, Rtn -0.24°±0.85°, Pitch 0.16°±1.11°, Roll -0.32°±1.05°, and the M PTV were 6.75 mm, 8.46 mm and 8.73 mm, respectively. The setup errors in the combination group were SI (1.0±3.01) mm, LR (0.62±2.74) mm, AP (1.82±3.21) mm, Rtn 0.64°±0.59°, Pitch 0.71°±1.22°, Roll 0.29°±0.73°, and the M PTV were 6.35 mm, 7.47 mm, and 7.61 mm, respectively. After comparing the setup errors in the three-dimensional directions between two groups, the t value of LR, SI, AP and Rtn, Pitch, Roll was -4.304, -2.681, 1.384, and -9.457, -3.683, -5.323, respectively. And the differences in the LR, SI, Rtn, Pitch and Roll directions were statistically significant (all P<0.05). Conclusions:The immobilization effect of polyurethane foam combined with breast bracket is better and the M PTV is also smaller than those of polyurethane foam alone. Therefore, it is recommended to use polyurethane foam combined with breast bracket for immobilization in breast cancer radiotherapy.
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Context: Head-and-neck cancer patients undergoing chemoradiation. Aims: The aim of the study was to see if there is any correlation between the planning target volume (PTV) and mucositis. Settings and Design: This was a single-arm prospective study. Subjects and Methods: A total of forty head-and-neck cancer patients undergoing chemoradiation were assessed for mucositis at the 5th week. The grades of mucositis were correlated with PTVs of low risk (54 Gy) and high risk (60–66 Gy). Statistical Analysis Used: The data were analyzed using the statistical software, SPSS Inc. Release 2009, predictive analytics software statistics for windows version 20.0, Chicago. Log transformation was done as the data were skewed. Independent t-test was used to compare between the two grades of toxicity. P <0.01 was considered for statistical significance. Results: The mean PTVlow risk was 522cc (228–771) and PTVhigh risk was 254cc (20–780). Grade II mucositis was seen in 27 (67%) patients and Grade III in 11 (28%) patients. The mean PTVlow risk was higher for patients, who had Grade III compared to Grade II mucositis (571 vs. 517 cc, P = 0.052). Conclusions: The same was seen for PTVhigh risk(367 vs. 222 cc, P = 0.017). PTV is a better predictor of mucositis, and those patients with larger PTV require close monitoring and early intervention of mucositis
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Introduction: Radiotherapy in head and neck cancers is treated for several weeks and daily setup and reproducibility is a challenge. This daily variability causes setup errors which accounts planning target volume margins. Reduced PTV margins have to be taken to decrease the dose to the parotid glands, without compromising on loco regional control rates. The present study is done to identify setup errors and see the feasibility to decrease the PTV margins by creating dummy radiotherapy plans in order to decrease dose to parotid glands. Material and Methods: 420 portal images were evaluated for setup errors in three dimensions (Antero Posterior, Left to Right and Superior to Inferior) which were performed in ten patients of oropharyngeal squamous cell carcinoma. All patients were treated in supine position using immobilization cast. After target volume delineation a PTV margin of 7mm was given. Dosimetric parameters of PTV and organs at risk were assessed. PTV margins were calculated according to three methods proposed by Stroom, Van Herk and ICRU 62. Dummy radiotherapy plans were generated using new PTV margins and compared with 7mm PTV margins. The data was analyzed using 3-way ANNOVA test for statistical significance. Results: The optimum PTV margins were 4mm in LR and SI direction and 7mm in AP direction. The PTV parameters (V95, D95, Dmax, Dmean, HI and CI) had no significant difference among different radiotherapy plans with different PTV margins. There was a significant decrease in the dose to right parotid (39.12 Gy to 32.88Gy; p-0.04), left parotid (37.90 to 31.21Gy; p-0.03) and parotid combined (38.65 to 31.45 Gy; p-0.01) when 7mm PTV margins were reduced to 4mm PTV margins. The results of dummy radiotherapy plans using asymmetric PTV margins (LR-4mm, SI-4mm and AP-7mm) and symmetrical PTV margins (4mm in all directions) are compared with PTV margins (7mm in all directions), in terms of PTV and OAR dosimetric parameters. Conclusion: The decreased PTV margins of 4mm decreases the dose to the parotid significantly. The implementation of radiotherapy plans needs to be supplemented by daily IGRT.
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Background: Conformal Radiotherapy techniques adapting to the ballistics of delineated volumes allowed significant reduction in excess radiation induced mortality however the increasing number of long-term survivors and expanding use of cardiotoxic drug highlight the persistent need for maximal cardiac possible sparing. The low dose volume of left ventricle are better predictor of acute coronary events than mean heart dose. Materials and Methods: 38 post-MRM patients were randomized to treatment by 3Dimensional Conformal Radiotherapy (3D CRT) and Intensity Modulated Radiotherapy (IMRT) technique. Two tangential beams were used in 3D CRT technique while five to seven (mostly tangential beams) were used in inversely planned IMRT technique. The dose volume parameters of planning target volume, heart and left ventricle were compared. Results: The dosimetry of Planning target volume showed significantly better coverage in IMRT technique (D90, D95) however the D50 was comparable in both the techniques. In dosimetry of heart, the high dose volumes (V30, V40) were nearly comparable in both the techniques. The other dose volume parameters (V5, V10, V20, V25, D33, D67, D100) and the mean dose were significantly lesser in 3D CRT technique along with significantly better sparing of left ventricle (Dmean and V5). Conclusion: The dosimetry of target volume was better with IMRT technique, but this was accompanied by a huge increase in dose to whole heart and specifically the left ventricle which has strong potential to translate into an increased cardiotoxicity. A better distribution of the target region may be obtained by multiple segmentation of the two tangential fields in 3D CRT plans with further reduction in dose to heart and left ventricle.
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Objective@#To assess the interobserver variations in delineating the planning target volume (PTV) and organs at risk (OAR) using different contouring methods during intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC), aiming to provide references for the quality control of multi-center clinical trials.@*Methods@#The PTV and OAR of CT image of 1 NPC patient manually delineated by 10 physicians from 8 different radiation centers were defined as the " manual contour group" , and the OAR auto-contoured using the ABAS software and modified by the physicians were defined as the " auto+ manual contour group" . The maximum/minimum ratio (MMR) of the PTV and OAR volumes, and the coefficient of variation (CV) for different delineated contours were comparatively evaluated.@*Results@#Large variation was observed in the PTV and OAR volumes in the manual contour group. The MMR and CV of the PTV were 1.72-3.41 and 0.16-0.39, with the most significant variation in the PTVnd (MMR=3.41 and CV=0.39 for the PTVnd-L). The MMR and CV of the manually contoured OAR were 1.30-7.89 and 0.07-0.67. The MMR of the temporal lobe, spinal cord, temporomandibular joint, optic nerve and pituitary gland exceeded 2.0. Compared with the manual contour group, the average contouring time in the auto+ manual group was shortened by 68% and the interobserver variation of the OAR volume was reduced with an MMR of 1.04-2.44 and CV of 0.01-0.37.@*Conclusions@#Large variation may occur in the PTV and OAR contours during IMRT plans for NPC delineated by different clinicians from multiple medical centers. Auto-contouring+ manually modification can reduce the interobserver variation of OAR delineation, whereas the variation in the delineation of small organs remains above 1.5 times. The consistency of the PTV and OAR delineation and the possible impact upon clinical outcomes should be reviewed and evaluated in multi-center clinical trials.
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Objective To assess the interobserver variations in delineating the planning target volume (PTV) and organs at risk (OAR) using different contouring methods during intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC),aiming to provide references for the quality control of multi-center clinical trials.Methods The PTV and OAR of CT image of 1 NPC patient manually delineated by 10 physicians from 8 different radiation centers were defined as the "manual contour group",and the OAR auto-contoured using the ABAS software and modified by the physicians were defined as the "auto+manual contour group".The maximum/minimum ratio (MMR) of the PTV and OAR volumes,and the coefficient of variation (CV) for different delineated contours were comparatively evaluated.Results Large variation was observed in the PTV and OAR volumes in the manual contour group.The MMR and CV of the PTV were 1.72-3.41 and 0.16-0.39,with the most significant variation in the PTVnd (MMR=3.41 and CV =0.39 for the PTVnd-L).The MMR and CV of the manually contoured OAR were 1.30-7.89 and 0.07-0.67.The MMR of the temporal lobe,spinal cord,temporomandibular joint,optic nerve and pituitary gland exceeded 2.0.Compared with the manual contour group,the average contouring time in the auto+ manual group was shortened by 68％ and the interobserver variation of the OAR volume was reduced with an MMR of 1.04-2.44 and CV of 0.01-0.37.Conclusions Large variation may occur in the PTV and OAR contours during IMRT plans for NPC delineated by different clinicians from multiple medical centers.Auto-contouring+ manually modification can reduce the interobserver variation of OAR delineation,whereas the variation in the delineation of small organs remains above 1.5 times.The consistency of the PTV and OAR delineation and the possible impact upon clinical outcomes should be reviewed and evaluated in multi-center clinical trials.
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Objective Bladder filling in patients with cervical cancer before and after operation during intensity-modulated radiotherapy (IMRT) was controlled by using bladder volume measurement instrument (BVI 9400).The displacement errors of the target area and the changes of the irradiation dose and the morphology of the filling bladder were compared.The significance of consistency of preoperative and postoperative bladder filling in IMRT for cervical cancer was investigated.Methods Forty-five patients with cervical cancer treated with radiotherapy in our hospital in 2018 were recruited and divided into A,B and C groups (n=15).In group A,patients did not undergo surgery,patients in group B received radical resection of cervical cancer (bladder volume measurement (BVI 9400) was utilized to monitor the bladder urine volume in both A and B groups before treatment).In group C,patients who self-controlled urination without monitoring bladder urine volume before treatment were randomly selected.All patients in three groups underwent KV-CBCT scan before treatment for online registration analysis.The displacement errors in the x-(left and right),y-(head and foot),z-axis directions (ventral and dorsal),PTV coverage volume percentage (V10o) and percentage difference (△ V100) of the prescription dose were calculated.Results The average displacement errors in the x-,y-,z-axis directions were as follows:1.67 mm,1.55 mm and 1.67 mm in group A,1.43 mm,1.58 mm and 1.84 mm in group B,and 2.27 mm,2.30 mm and 2.08 mm in group C,respectively.In group A,the V1oo was calculated as 96.96％ and △ V1oo was 1.17％.In group B,V1oo was 9 5.9 ％ and △ V10o was 1.2 9 ％.In group C,V10o was 9 4.0 2 ％ and △ V100 was 2.1 7 ％.Conclusions Controlling the consistency of bladder filling can reduce the effect of inconsistency of bladder filling upon the displacement errors to certain extent,which can guarantee the accuracy of the target location and the irradiation dose of the target,protect the bladder,small intestine and rectum,and alleviate the radiation-induced response of cervical cancer patients.
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Objective To investigate the clinical target volume (CTV)-planned target volume (PTV) setup margins during intensity-modulated radiotherapy (IMRT) for cervical cancer patients with different body mass index (BMI),aiming to provide reference for precise individual therapy.Methods Forty patients diagnosed with cervical cancer undergoing IMRT in Cancer Hospital of Fudan University between March and September 2017 were recruited and assigned into the BMI ≤ 18.4,18.5-23.9,24.0-27.9 and ≥ 28 kg/m2 groups according to the BMI classification criteria proposed by National Health and Family Planning Commission (NHFPC) of the People's Republic of China.Assisted with the bladder volume measurement device,9 cycles of kilo-voltage cone beam computed tomography (CBCT) images were subject to online registration and imaging analysis.CTV-PTV setup margins were calculated based on the formula of MPTV =2.5∑+0.7σamong four groups.Single factor variance analysis was performed.LSD test was utilized for two-group comparison.Results Among four groups,the CTV-PTV setup margins in the x,y and z directions were (6.87 mm,6.06 mm,8.49 mm),(3.13 mm,3.02 mm,3.14 mm),(4.70 mm,4.86 mm,5.31 mm) and (7.63 mm,8.28 mm,8.54 mm),respectively (P=0.038,0.048 and 0.004).Conclusions The setup errors in the BMI ≤ 18.4 and ≥28 kg/m2 groups are significantly larger compared with those in the remaining groups Consequently,CTV-PTV setup margins should be enlarged to certain extent for patients with BMI≤ 18.4 and ≥≥28 kg/m2.
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Objective To explore the inter-fraction setup errors and affecting factors from data of daily fan-beam megavoltage computed tomography(MVCT). Methods A total of 37consecutive NPC patients treated with tomotherapy were hospitalized during the period of February 2015 to September 2015. For each patient,one MVCT scan was obtained after conventional positioning ,online correction and tomotherapy delivery daily ,and the scans were put into the planning computed tomography to determine inter-fraction setup errors. The MPTV was calculated with the equation:MPTV=2.5∑+0.7σ(∑:systematic error;σ:random error). Results The average absolute errors of the inter-fraction were(2.102 ± 0.0406)mm,(1.490 ± 0.0348)mm,(1.306 ± 0.335)mm and(1.392 ± 0.0384)° at three dimensions. The total MPTV accounting for inter-error was 3.4675 mm,2.9795 mm,and 2.8885 mm. Gradual increases in both inter-fraction three-dimensional displacement were observed with time and treatment(P < 0.05). Univariate analysis revealed that weight loss and retraction of neck lymph nodes were affecting factors of set-up errors. Conclusions 3 mm margins uniformly expended from clinical target volume to planning target volume may not be suitable. The personalized margin should be adopted for the design of IMRT planning. Displacement increases as a treatment course is prolonged.
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Objective To determine the margins of planning target volume (MPTV) in primary cervical cancer patients with tomotherapy and evaluate the importance of automatic registration(AR) plus manual registration.Methods The setup errors of 29 primary cervical cancer patients receiving external radiation from June 2012 to Dec 2014 were measured by megavoltage computed tomography (MVCT),which were performed at least two times weekly before treatment and were registered with the planning CT.The setup errors between automatic registration and total shift (TS) including both AR and manual registration were compared MPTV was calculated.Results Setup errors were collecte from 443 sets of MVCT in 29 patients.AR and total shift (TS) values in the x,y,z directions and rotation angle were (-0.9±2.3),(0.0±3.1),(1.0±2.6) mm,0.2° ±0.8° and (-0.8±1.8),(-0.4±3.4),(l.4 ± 2.5) mm,0.1° ± 0.5°,respectively.There were statistically significant differences between the two groups in all directions except for the x axis (t =5.1,-5.2,3.2,P ＜ 0.05).MPTV were 4.6,5.7,3.3 mm in the x,y,z directions,respectively.Conclusions Manual registration is necessary after automatic registration in cervical cancer patients with tomotherapy.For patients with cervical cancer treated by tomotherapy,planning target volume MPTV parameters are suggested to be 5,6,4 mm in the x,y,z directions.
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Objective To investigate the differences in position and volume between planning target volumes (PTV) based on positron emission tomography?computed tomography (PET?CT) images with an standardized uptake value ( SUV) no less than 2?5, 20% of the maximum SUV ( SUVmax ), or 25% of SUVmax , three?dimensional ( 3D ) CT, and four?dimensional ( 4D ) CT in thoracic esophageal cancer. Methods Eighteen patients with thoracic esophageal cancer sequentially received chest 3DCT, 4DCT, and [18F]fluoro?2?deoxy?D?glucose (FDG) PET?CT scans. PTV3D was obtained by conventional expansion of 3DCT images;PTV4D was obtained by fusion of target volumes from 10 phases of 4DCT images. The internal gross tumor volumes ( IGTV) , IGTVPET2.5 , IGTVPET20%, and IGTVPET25%, were generated based on PET?CT images with an SUV no less than 2?5, 20% of SUVmax , and 25% of SUVmax , respectively. These IGTVs were expanded longitudinally by 3?5 cm and radically by 1 cm to make PTVPET2.5 , PTVPET20%, and PTVPET25%, respectively. Results PTV3D was significantly larger than both PTV4D and PTVPET(P=0?000 -0?044), while there was no significant difference between PTV4D and PTVPET ( P= 0?216 -0?633 ) . The mutual degrees of inclusion ( DIs ) between PTV3D and PTV4D were 0?70 and 0?95, respectively, which were negatively correlated with 3D?Vector ( P=0?039). The mutual DIs between PTVPET2.5, PTVPET20%, and PTVPET25% were 0?74, 0?72, 0?78, 0?73, 0?77, and 0?70, respectively, which showed no correlation with 3D?Vector (P=0?150 -0?822). The mutual DIs between PTV3D and PTVPET were 0?86, 0?84, 0?88, 0?63, 0?67, and 0?59, respectively. Conclusions It is difficult to achieve complete volumetric overlap of PTVs based on 3DCT, 4DCT and PET?CT in thoracic esophageal cancer due to different target volume information. PET scan during free breathing should be used with caution to generate PTVs in thoracic esophageal cancer.
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Objective To study the PTV by ng 4DCT and compare target,target displacement and dose distribution of 3D and 4D planning for thoracic middle or lower esophageal cancer,evaluate the clinical value of 4DCT in esophageal cancer radiotherapy.Methods From Jan to Dec 2012patients with primary esophageal cancer underwent 3DCT simulation scans first,then followed by 4DCT simulation scan.PTV and OARs were sketched in the ordinary 3DCT and 4DCT respectively.And designing two sets of radiotherapy plan for each patient:3D and 4D plan.We compare PTV,PTV displacement and OARs dosimetry's differences in the 3D plan and 4D plan.Using the paired t-test or Wilcoxon sign-rank test to compare the difference between the two sets of plans.Results The volume of PTV4D was larger than the PTV3D (195.19 cm3 vs.175.67 cm3,P =0.001) in all patients.The center displacement had only significantly difference (displacement was 0.25 cm,P =0.014) in left-right direction for 10 patients of thoracic middle esophageal cancer.The center displacement had no significantly different in the three direction for 9 patients of thoracic under esophageal cancer (P=0.722,0.307,0.208).The dose target area of V100,V95 and V90 in Plan3DC were significantly than those in Plan-3D for 19 patients of thoracic middle-lower esophageal cancer (88.62％ vs.95.69％,P=0.000;95.17％ vs.99.79％,P=0.001;97.19％ vs.99.99％,P=0.001).In 4D plan the lung V5,V20 and Dmean of heart were higher than that in 3D plan for all patients (39.49％vs.37.44％,P=0.016;19.93％ vs.18.87％,P=0.018 and 2607.74 cGy vs.2389.16 cGy,P=0.004).Conclusions 4DCT positioning technology can accuracy determine individualized expanding boundary by target area of radiotherapy for thoracic middle or lower esophageal cancer.The enlarging target volume increase the dose of radiotherapy for lung,and in the dose range in the 4D plan,but the increased dose of heart should be noted.
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Objective To evaluate the similarities and differences between four-dimensional radiotherapy (4D-CT ) and active breathing control techniques(ABC) in respiratory management in lung radiotherapy ,and investigate the indications and feasibility of different breathing control techniques for different patients .Methods Twenty-one patients treated with lung radiotherapy received respiratory management .4D-CT technology was used in 11 patients ,while ABC technology was adopted in the rest 10 .The ratios of planning target volume(PGTV) to gross tumor volume(GTV)[(PGTV/GTV)] were calculated .The differences between these two respiratory management technologies were compared in terms of the PGTV ,positioning time ,planning time and treatment time to investigate the indications .Results 4D-CT technology had higher PGTV/GTV ratio ,and shorter positioning time and irradiation time than ABC technology(P0 .05) .In patients with ABC and 4D-CT technology ,objective response rates were 50 .0% ,45 .5% ,respectively ,and the radiation pneumonitis rates were 30 .0% ,27 .3% ,respectively .There was no significant difference in both groups (P>0 .05) .Conclusion In lung tumor radiothera-py ,ABC can reduce irradiation volume ,suitable for patients with good performance status .4D-CT is time-saving and well tolerated , suitable for patients with smaller tumors .
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ObjectiveTo analyze the correlation between primary tumor volume (PTV) and prognosis of nasopharyngeal carcinoma ( NPC ) treated by intensity-modulated radiotherapy ( IMRT ).Methods330 NPC patients treated by IMRT were included.Pretreatment computerized tomography image were input into tree-dimensional treatment-planning system,in which the primary tumor volume were calculated automatically.The receiver operating characteristic curve was used to determine the best cut-off point of PTV.Within the framework of UICC 2002 T stage,The PTV was divided into four groups:V1 ＜ 10cm3,V2 10-25 cm3,V3 ＞ 25-50 cm3 and V4 ＞ 50 cm3.Kaplan-Meier and Logrank test was used to analyze the survival,Cox proportion risk regression model were used to analysis the correlation between PTV and prognosis.ResultsThe mean PTV for all NPC patients was ( 34.2 ± 27.1 ) cm3 with the range of 0.4- 153.7 cm3.The 3-year overall survival for V1,V2,V3 and V4 stage were 88.6％,90.0％,91.2％ and 74.2％,respectively (x2 =12.83,P =0.005 ).There was no significant difference among V1,V2 and V3in terms of overall survival ( x2 =1.96,P =0.376).The 3-year distant metastasis-free survival and diseasesfree survival or overall survival were decrease in PTV ＞50 cm3 and PTV≤50 cm3 (77.4％:89.9％,x2 =7.24,P=0.007and 64.5％:85.1％,x2 =13.95,P=0.000 or 74.2％:90.3％,x2 =11.76,P=0.001).Multivariate analysis revealed that PTV was a adverse prognostic factors for overall survival (x2 =0.00,P =2.580).ConclusionOur data showed that the primary tumor volume had significantly impacted on the prognosis of NPC patients treated by intensity modulated radiotherapy.
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ObjectiveTo measure the displacement of solitary pulmonary lesion (SPL) using fourdimensional CT (4DCT), and to compare the planning target volume using 4D maximum intensity projection (MIPMIP) ( PTV4DMIP ) with the empirical PTV3D.Methods Data were acquired from 24 consecutive patients with SPL. For each patient, respiration-synchronized 4DCT images and standard axial CT scans were obtained during free breathing.In lung window setting,the 4D technique was used to measure the displacement of SPL in three dimensions. We compared an PTV created using the MIP (PTV4DMIP) to the PTV created from the gross tumor volume (GTV) enlarged isotropically for each spatial direction by 1.0 cm and 1. 5 cm in the PTV3D1.0cm and PTV3D1.5cm. Results The SPL located in the lower lobe showed significant difference with the upper and middle lobe in y axis (0. 44 cm,0. 92 cm, t =2. 87, P =0. 000),but there was no difference in both x and z axis (0. 27 cm,0. 39 cm,t =1.44 ,P =0. 116 and 0. 29 cm,0. 40 cm,t =1.51, P =0. 227). SPL showed significantly greater displacement in y axis than in both x and z axis [0.60 cm and0. 31 cm (t =4.23,P=0.000) ,0.60 cm and 0.32 cm (t =4.65,P=0. 000)], but there was no significant difference between x and z axis (0. 31 cm,0. 32 cm,t =0. 33 ,P =0. 741 ). There was no statistically difference between the peripheral lung cancer and the pulmonary metastasis tumor in three directions ( x axis : 0. 37 cm,0. 32 cm, t =0. 52, P =0. 223 ; y axis : 0. 54 cm, 0. 95 cm, t =- 1.38, P =0.061;z axis:0.42 cm,0.37 cm, t=0.29, P=0.859).Both PTV3D1.0cm and PTV3D1.5cm showed significantly greater volume than PTV4DMIP(46. 73 cm3 ,86. 52 cm3 and 30. 02 cm3 ,t =- 11.35, - 12. 09,P =0. 000,0. 000). ConclusionsThe displacement of SPL in y axis is much greater than x and z axis. The empirical PTV3D is much bigger than PTV4DMIP, which suggests that 4DMIP provide adequate coverage of the moving target and minimize dose to normal tissues.
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Objecttve To compare the positional and volumetric differences of planning target volumes(PTVs)based on axial three-dimensional CT(3D-CT)and four-dimensional CT(4D-CT)for the primary tumor of non-small cell lung cancer(NSCLC).Methods Sixteen NSCLC patients with lesions located in the upper lobe and 12 patients with lesions in middle and lower lobes,totally 28 patients, initially underwent three-dimensional CT scans followed by 4D-CT scans of the thorax under normal free breathing.PTVvector was defined on gross tumor volume (GTV) contoured on 3D-CT and its motion vector. The clinical target volumes(CTVs)were created by adding 7 mm to GTVs,then, internal target volume (ITVs)were produced by enlarging CTVs isotropically based on the individually measured amount of motion in the 4D-CT,lastly,PTVs were created by adding 3 mm setup margin to ITVs. PTV4D was defined on the fusion of CTVs on all phases of the 4D data.The CTV wag generated by adding7 mm to the GTV on each phase.then,PIVs were produced by fusing CTVs on 10 phases and adding 3 mm setup margin.The position of the target center,the volume of target and the degree of inclusion(DI)were compared reciprocally between the PTVvector and the PTV 4D The difference of the position,volume and degree of inclusion of the targets between PTVvecter and PTV4D were compared,and the relevance between the relative characters of the targets and the three-dimensional vector was analyzed based on the groups of the patients. Results The median of the 3 D motion vector for the lesions in the upper lobe was 2.8 mm, significantly lower than that for the lesions in the middle and lower lobe ( 7.0 mm, z = - 3. 485, P < 0. 05 ). In the upper lobe group there was only significant spatial difference between the PTVvector and PTV4D targets in the center coordinate at the x axe (z = -2. 010, P < 0. 05 ), while in the middle and lower lobes there was only significant spatial difference between the PTVvector and PTV4D targets in the center coordinates at the z axe (z = -2. 136,P <0.05). The median of ratio of PTV4D and PTVvector, of the upper lobe group was 0. 75, significantly higher than that of the middle and lower lobes group (0. 52, z = - 2. 949, P < 0. 05 ).A significant correlation was found for the motion vector and the ratio of PTV and PTV4D in both groups ( r = - 0. 638, - 0. 850, P < 0. 05 ). For all patients, the median of D[ of PTV4D in PTVvector was 66. 39% ,while the median of DI of PTVvector, in PTV4D was 99. 55% , both showed a positive significant correlation with the motion vector (r = -0. 814,0. 613 ,P < 0. 05). Conclusions PTV4D defined based on 4D-CT simulation images is obviously less than PTV defined based on 3D-CT simulation images. The ratio and DI of both targets are related with the three-dimensional motion vector of the tumor.
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The Hi-Art system for TomoTherapy allows only three (1.0 cm, 2.5 cm, 5.0 cm) field widths and this can produce different dose distribution around the end of PTV (Planning target volume) in the direction of jaw movement. In this study, we investigated the effect of field width on the dose difference around the PTV using DQA (Delivery quality assurance) phantom and real clinical patient cases. In the analysis with DQA phantom, the calculated dose and irradiated films showed that the more dose was widely spreaded out in the end region of PTV as increase of field width. The 2.5 cm field width showed a 1.6 cm wider dose profile and the 5.0 cm field width showed a 4.2 cm wider dose profile compared with the 1.0 cm field width in the region of 50% of maximum dose. The analysis with four patient cases also showed the similar results with the DQA phantom which means that more dose was irradiated around the superior and inferior end of PTV as an increase of field width. The 5.0 cm field width produced the remarkable high dose distribution around the end region of PTV and we could evaluate the effect quantitatively with the calculation of DVH (Dose volume histogram) of the virtual PTVs which were delineated around the end of PTV in the direction of jaw variation. From these results, we could verify that the margin for PTV in the direction of table movement should be reduced compared with the conventional margin for PTV when the large field such as 5.0 cm was used in TomoTherapy.
Subject(s)
Humans , JawABSTRACT
Objective To investigate the feasibility of online and offline cone-beam CT (CBCT) guided radiotherapy for lung cancer. Methods Fourteen patients with lung tumor treated by three-dimen-sional conformal radiotherapy were investigated. Online kV CBCT scan,image registration and setup correc-tion were performed before and immediately after radiotherapy. CBCT online-guided correction data were used to calculate the population-based CTV-PTV margins under the condition of non-correction and correction in every fraction respectively. The numbers of initial images and the population-based CTV-PTV margins af-ter the offline compensation of the system setup error were evaluated with the permission of 0.5 mm and 1.5 mm maximal residue error,respectively. Results Under the condition of non-correction,the required mar-gins for total error were 5.7 mm,8.0 mm and 7.8 mm in the left-right(x axis) ,cranio-caudal(y axis) and anterior-posterior(z axis) directions, respectively. When the tumor was corrected in every fraction, the re-quired margins for intra-fraction error were 2.4 mm,2.4 mm and 2.3 mm in x,y and z axes, respectively. To correct the systematic setup error,9 sets of CBCT images for 3.3 mm,3.7 mm and 3.6 mm PTV margins, and 7 sets of CBCT images for 3.9 mm,4.3 mm and 4.3 mm PTV margins in x,y and z axes were necessary when 0. 5 mm and 1.5 mm maximal residue errosr were permited respectively. Conclusions Both of the online CBCT correction and the offline adaptive correction can markedly reduce the impact of setup error and reduce the required PTV margins accordingly. It is feasible to deliver the online and offline image guided ra-diation for patients with lung tumor.
ABSTRACT
Objective To investigate how much the patient setup accuracy for irradiation of head and neck cancer can be improved by online setup verification and offline setup verification using cone-beam computed tomography(CBCT), and the feasibility of image-guided adaptive correction procedure to reduce the PIN margin.Methods 16 patients of head-and-neck cancer treated with three-dimensional conformal radiotherapy (3D-CRT)or intensity modulated radiotherapy(IMRT)were investigated. The first online kV CBCT scan, rigid image registration, setup correction were performed before radiotherapy. The second kV CBCT scan were acquired immediately after treatment and analysis was performed as above. CBCT scans were acquired at two or three fractions weekly during the entire course of radiotherapy and CBCT online-guided correction data were recorded. The data was used to calculate the population-based CTV-PTV margins under the condition of non-correction, correction every fraction and compensation of the systematic setup error respectively. The number of initial images required to predict systematic setup error was evaluated with the permission of 0.5 mm residue error. Results Total of 320 sets of CBCT images were analyzed for 16 patients. Under the condition of non-correction, the margins required to account for total error are 5.7 mm,5.6 mm,and 7.3 mm in the left-right(X axis),cranio-eaudal(Y axis), and anterior-posterior (Z axis)directions respectively, when the tumor was corrected every fraction, the margins required to account for intrafraetion error are 1.7 mm,1.7 mm,and 2.3 mm in X, Y,and Z axis.To correct the systematic setup error,8 sets of CBCT images are adequate. After compensation for the effect of the systematic setup error, 2.7 mm,2.5 mm, and 3.6 mm PTV margins are necessary in X, Y, and Z axis respectively. Conclusions There exists some extent of setup error in head and neck 3D-CRT or IMRT.The on-line CBCT correction and the approach based on off-line adaptive correction both can be used to reduce the impact of setup error obviously, the required margins for the PTV was reduced accordingly.