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Objective To explore the effect of respiratory movement on the dose distribution in the TOMO therapy target area. Methods The motion phantom was used to simulate human respiratory movement. The SNC patient analysis software was used to compare the films of the study group with those of the control group, and the effect of respiratory movement on the dose distribution in the TOMO target area was evaluated by the “pass rate” index. Results Visual observation showed that the distribution of film gray in the head-foot direction (i.e., direction of movement) was significantly different with or without respiratory movement. Film analysis showed that the maximum deviation between the width of the target wrapping curve and the treatment plan value was about 2.4 mm at no respiratory movement and about 27.2 mm at respiratory movement; the penumbra width of the target area was 31 mm (head direction) and 28.5 mm (foot direction) at no respiratory movement and 39.7 mm (head direction) and 37 mm (foot direction) at respiratory movement; the “pass rate” of target dose distribution was only 12.3%. Conclusion Respiratory movement has a great impact on the dose distribution in the TOMO target area in the direction of movement. When making clinical treatment plan, the impact of respiratory movement on the dose distribution in the TOMO target area can not be ignored.
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Due to the influence of respiratory movement in thoracic and abdominal radiotherapy, the real-time tracking technique was effective solution in the contemporarily precise radiotherapy. This article summarized prediction algorithm of several respiratory movement that was used to compensate the delay caused by system response in the real-time tracking radiotherapy, and compared the characteristics, performance and developing situation of various algorithm, and prospected the development and tendency of real-time tracking technique in future.
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Objective To compare the geometric differences of gross tumor volumes(GTV)and displacements of selected clips propagated by rigid image registration(RIR)and deformable image registration (DIR)at end-inhale phase(CT0)and end-exhale phase(CT50)based on four-dimensional computed tomography(4DCT)of the whole breast after breast-conserving surgery(BCS). Methods Forty-four patients who underwent 4DCT simulation scans after BCS were selected. The GTV and displacements of selected metal clips at CT0and CT50were manually delineated by the same radiotherapy physician. Subsequently,the GTV and displacements of selected clips from CT0images were transformed and propagated to CT50images using RIR and DIR.The geometric differences of GTV and displacements of surgical clips from DIR were compared with those from RIR based on the dice similarity coefficient(DSC)and the displacements of the center of mass(COM)in the three-dimensional(3D)directions. Results The mean DSC was 0.86± 0.04 for RIR and 0.87± 0.04 for DIR(P=0.000).The displacements of COM in 3D directions from RIR were significantly greater than those from DIR(1.22 mm vs. 1.10 mm,P=0.000).In the anterior-posterior direction,the displacements from RIR were significantly greater than those from DIR for both GTV and selected clips(P=0.000).However,in the left-right and superior-inferior directions,there were no significant differences in displacements between RIR and DIR for both GTV and the selected clips(all P>0.05). Conclusions DIR can improve the overlap for GTV registration from 4DCT scans at CT0and CT50.Furthermore,DIR is superior to RIR in reflecting GTV and the displacements of selected clips in anterior-posterior direction induced by respiratory movement.
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Objective To study the effect of amplitude of respiratory movements on dose distribution of static intensity-modulated radiotherapy (IMRT),and to provide a basis for dose correction against respiratory movements.Methods A two-dimensional matrix driven by the QUASAR program-controlled respiratory movement instrument was used to simulate human respiratory movements in the head/foot direction.The dose distribution was evaluated on the isocenter plane with different amplitudes of respiratory movements.The Verisoft software and absolute dose analysis were used to analyze dose distribution,percentage errors of absolute dose,and passing rates of radiation field for both collected data and planned dose distribution.Results In spite of little effect on dose distribution in target volume,respiratory movements increased the dose outside the marginal target volume along the movement direction.When the respiratory amplitude was lower than 6 mm,the passing rate of γdistribution met the requirement of clinical dose verification;when the respiratory amplitude was larger than 8 mm,the passing rate of γ distribution was reduced with the increasing respiratory amplitude and fell below the clinical standard.Conclusions Respiratory movements have a blurring effect on static IMRT.It is possible to introduce some compensation methods to static IMRT in the treatment of tumor with periodic respiratory movements.The normal tissue at the edge of target volume along the respiratory movement direction is exposed to a higher radiation dose than expected.Therefore,the radiation dose for the normal tissue around target volume should be made as low as possible in the radiotherapy plan.For the patients with relatively large respiratory amplitude,action should be taken to lower respiratory amplitude and elevate the radiation dose in target volume.
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Objective To investigate the impact of movement frequency on gross tumor volume (GTV) of moving tumors and coordinate position of the central point based on three-and four-dimensional CT scans.Methods The respiratory motion platform from Modus and 8 phantoms with different shapes and volumes were used to simulate the movement of lung tumors.Three-and four-dimensional CT scans were performed at movement frequencies of 10,15,and 20 times/min.GTV (GTV10,GTV15,and GTV20) and IGTV (IGTV10,IGTV15,and IGTV20) were delineated,and the coordinate position of the central point was obtained.The Friedman test was performed for GTV10,GTV15,GTV20,IGTV10,IGTV15,IGTV20,and the coordinate position of the central point.Results GTV10,GTV15,and GTV20 at the three movement frequencies were 12.41±14.26 cm3,10.38±11.18 cm3,and 12.50±15.23 cm3,respectively (P=0.687),and the positional values were-8.2±96.2 mm,-8.6±96.1 mm,and-8.6±95.7 mm in x-axis (P=0.968),108.2±25.0 mm,110.4±22.5 mm,and 109.0±24.2 mm in y-axis (P=0.028),and 65.2±13.7 mm,65.4± 13.4 mm,and 65.4± 13.2 mm in z-axis (P =0.902).IGTV10,IGTV15,and IGTV20 at the three movement frequencies were 17.78± 19.42 cm3,17.43± 19.56 cm3,and 17.44± 18.80 cm3,respectively (P=0.417),and the positional values were-7.7±95.9 mm,-7.9±95.6 mm,and-7.9±95.1 mm in x-axis (P=0.325),109.4±24.5 mm,109.6±24.1 mm,and 109.2±24.3 mm in y-axis (P=0.525),and 65.5±13.3 mm,65.6±13.4 mm,and 65.5±13.3 mm in z-axis (P=0.093).Conclusions During simulated positioning of thoracic tumors,respiratory movement frequency has no significant impact on target volume established by four-dimensional CT scan.There are no significant differences in three-dimensional target volume established at different respiratory frequencies,but respiratory frequency has a significant impact on the position of the central point of the target volume in y-axis.
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Objective To study the effect of the respiratory amplitude on the dose distribution of volumetric modulated arc therapy (VMAT).Methods Respiratory motion simulation phantom (QUASAR) was used to simulate the respiratory movement from head to toe,and a two-dimensional ionization chamber matrix was used to collect the dose distribution in isocenter with different respiratory amplitude.Verisoft software and absolute dose analysis were used to analyze dose distribution,percentage errors of absolute dose in isocenter,passing rates of radiation field for the data collected,and results were compared to planned dosage.Results The effect on isocenter target dose of respiratory motion was below dose tolerance 5％ (t =-22.614--10.756,P ＜ 0.05).The respiratory movement made the dose on the edge of the target area higher,with fewer hot spots and more cold spots in the target area.As the respiratory amplitude increased,the effect of respiratory movement on the overall dose distribution in the target area was greater.The difference of the whole beam γ passing rate between 6,8,10 mm and stationary state was significant (t =3.095,8.685,14.096,P ＜ 0.05).The difference of target γ passing rate between 8,10 mm and stationary state was significant (t =6.081,9.841,P ＜0.05).Conclusions The respiratory movement could cause the dose transmission errors of VMAT,the error increased with increased range of motion.The actual radiation dose for normal tissues along the direction of respiratory movement on the target edge was higher than what was planned.
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Objective To measure the setup errors and organ movements of patients with esophagus carcinoma during radiotherapy and find a reasonable margin from the clinic target volume (CTV) to the planning target volume (PTV). Methods (1) Set-up veri cation: Forty-two cases of untreated esophageal cancer were enrolled into this study. The physicist firstly made the planning according to the doctor requests and ensured the best distribution at the target. Thereafter, the 0° and 90° digitally reconstructed radiograph (DRR) was transmitted to the iView GT workshop. Meanwhile, two copies of cross-cut electronic portal image (EPI) were required before radiotherapy. Two doctors confirmed the variance of the osteal mark from the EPI and DRR,and output a 3D direction (left to right, superior to inferior, anterior to posterior) of the setup errors through the iView GT software. (2)Breathing motion:Ten cases of untreated esophageal cancer were enrolled into this study.Three distinct breathing levels were deflned: FB (free breathing), EBH (expiration with breath-held) and IBH (inspiration with breath-held). We gave the treatment planning in FB, then by moving the isocenter to EBH and IBH, we recalculated the dose distribution without changing the field angle, shape and weighing (Mus). Displacements were analyzed at four points (anterior, posterior, right lateral and left lateral) and five levels of target (upper, quarter, isocenter, three-quarter and lower). Results (1) The systematic setup errors were -0.23 cm, -0.02 cm and -0.06 cm, and the random errors were 0.44 cm, 0.45 cm and 0.44 cm at the direction of left to right(LR), superior to inferior (SI), anterior to posterior(AP), respectively. (2) The organ movements were 0.3 cm, 0.6cm and 0.3cm at the LR, SI, AP, respectively. Conclusions As an alternative, the root-sum-of-squares of set-up error and organ motion are suggested by σtot=√ (σITV2+σSM2). The CTV to PTV margins are 0.8cm left to right, 0.78cm superior to inferior, 0.5cm anterior to posterior.
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Objective To invesigate the influence of breathing motion on intensity-modulated radiotherapy (IMRT) of chest wall after radical mastectomy,and explore clinical value of accurately determined target volume.Methods A total of 17 radical mastectomy patients underwent 3DCT simulation scans sequentially followed by 4DCT simulation scans during free breathing.The targets and normal organs was determined based on CT images respectively.Three sets of radiotherapy plan were designed for each patient:plan 3D,plan 4D and plan 3D-A.The Plan 3D and plan 4D was designed based on 3D and 4D targets respectively.Plan 3D was copied to 4D target with the same isocenter coordinates.The dose distribution was calculated separately to evaluate the dose-volume histograms parameters for PTV,ipsilateral lung and heart,respectively.Two planning parameters was compared with paired t-test or Wilcoxon sign-rank test.Results The average volume of PTV4D was (10.35 ± 4.80) ％ larger than PTV3D (P =0.000).Compared with plan 3D,the V100,V95,V90,D95,D90,Dmin of plan 3D-A were reduced,that were (0.78 -18.0)％ (P=0.000),(0.01-3.90)％ (P=0.000),(0-2.12)％ (P=0.000),(13-222) cGy (P=0.000),(1-118) cGy (P=0.000),(6-1 910) cGy (P=0.000).However,the V20,V10,V5,Dmean of the ipsilateral lung and V30 of heart were same between 3D plan and 4D plan (P =0.288,0.407,0.435,0.758,0.575).Conclusions The respiratory motion may reduce the target dose and its coverage in chest wall treatments,so 4DCT plan could accurately define target volume without increasing the exposure dose of normal tissues.
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Objective To evaluate the respiration-induced target volume motion in 3D-CRT for mid-thoracic esophageal carcinoma in order to guide the radiation oncologist to choose the expansion marginfor ITV.Methods Ten patients with mid-thoracic esophageal carcinoma were scanned by multi-spiral CTsimulator respectively in free breathing(FB),breath.hold after normal inspiration and expiration(IBH and EBH)with the same scanning range.Then the CT images of three series were transfefred to the treatmentplanning system.The target volume was outlined following the same standard.The motion of the centerpoint of GTV,the center point of each slice of GTV and the edge of the GTV in selected slice weremeasured respectively to obtain the comprehensive value of GTV motion。in order to find the appropriate IMvalue according to the 95％confidence interval of the GTV motion.Results①The GTV motion betweenIBH and EBH was(0.19±0.16)cm in the left.right direction,(0.54±0.19)cm in the cranial andcaudal irection.and(0.16±0.14)cm in anterior.posterior directions for the center of GTV,.For thecenter point of each slice of GTV.they ere(0.19±0.15)cm,(0.54±0.16)cm,(0.16±0.13)cm in three directions above.respectively.For the edge of the GTV in selected slice.they were(0.26±0.19)cm,(0.54±0.18)cm,(0.24±0.19)cm,respectively.The comprehensive value of GTV motion between IBH and EBH was(0.23±0.17)cm,(0.54±0.17)cm,(0.21±0.17)cm.respectively.The 95％confidence interval was 0.21-0.25 cm.0.53-0.56 cm and 0.19-0.22 cm in three directions.②The direction of GTV motion：No motion was noticed in 8.2％.while 73.3％to the right side and 18.5％to the left side in the left-right direction when IBH were compared with EBH.100％were moved to caudal in the the cranial and caudal direction[(0.54±0.17)cm].In the anterior-posterior direction,no motion was noticed in 8.2％,while 16.6％to the posterior and 75.2％to the anterior when IBH were compared with EBH.③The GTV motion was correlated with the vafiance of 1ung volumes in IBH-EBH(r=0.683,P=0.032)and not with GTV volume and length.Conclusions Respiration can induce target volume motion in 3 DCRT for mid-thoracic esophageal carcinoma.Compared to EBH.the GTV tends to move to the caudal,the anterior and the ight side in IBH.
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Objective To evaluate the respiration-induced dosimetric variance in 3DCRT for midthoracic esophageal carcinoma, in order to guide the radiation oncologist to choose the expansion margin. Methods Ten patients with mid-thoracic esophageal carcinoma were scanned by multi-spiral CT simulator respectively in free breathing ( FB), breath-hold after normal inspiration and expiration ( IBH and EBH )with the same scanning range. Then the CT images of three series were transferred to the treatment planning system. The target volume was outlined following the same standard. Plan1 was designed in the images of FB and transported completely to the images of IBH and EBH as Plan2 and Plan3 respectively to observe the dosimetric variance in target volume. Results For GTV, there was a statistical difference only in V100 of the three plans ( H = 6.423, P = 0.040 ) and no significant difference was found in other indexes. For CTV, the V100 and V95 were better in Plan1 (F=3.992, P=0.030; H=9.920, P=0.007) and no significant difference was found in other indexes. While ()TV, the Dmin, V100 and V95 was better in Plan1 ( F = 3.677, P = 0.039; F = 4.539, P = 0.020; H = 6.846, P = 0.033 ) and no significant difference was found in other indexes. There were no significant differences in all the indexes for the spinal cord and lung in the three plans. Conclusions The change in dose distribution was not so much with the standard expansion. It can meet the needs of clinical treatment.
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Objective To compare the difference of decreasing radiation-induce lung injure among CT scans including active breathing control (ABC), slow CT scan and general axial CT scan under free breathing (FB) in precise radiotherapy of peripheral non-small cell lung cancer (NSCLC). Methods Ten patients of peripheral NSCLC were included. For each patient, three CT scans were obtained: (1) the general axial CT scans under FB;(2) the fast spiral CT scans under ABC;(3) the slow CT scans under FB. Three treatment plans based on three CT scans were optimized. Gross tumor volume (GTV), clinical target volume (CTV) and planning target volume (PTV) along with V20 (lung volume accepted > 20 Gy/all lung volume ×100%) and Dmean (average dosage accepted irradiation of all lung)of three treatment plans were calculated and compared. Results The GTV and CTV of the slow CT plan seem in largest, and those of ABC plan in smallest, but no statistics signification among the three plans (F = 1.513, P = 0.238;F = 1.376, P = 0.270). However, The PIV of the FB plan was largest, and the difference of PTV between plans of ABC and FB, plans of slow CT scans and FB were statistics significant (F = 26. 148, P = 0.000). The differences of V20 and Dmean between plans of FBand ABC, plans of FB and slow CT scans were statistics significant yet (F = 7.623, P = 0.002;F = 18.217, P = 0.000). Conclusion Compared with FB conditions, ABC or the slow CT scan method in precise radiotherapy of peripheral NSCLC can decrease radiation volume and dose to normal tissues as well as the probability of decreasing radiation-induce lung injure.