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Objective:The respiratory waveform of lung cancer patients based on 4D-CT respiratory gating was analyzed to evaluate the accuracy of gating during radiotherapy, and to explore the off-target in the 4D-CT respiratory gating radiotherapy.Methods:Clinical data of 18 patients with lung cancer admitted to Radiotherapy Department of Jiangsu Cancer Hospital were collected to obtain the respiratory waveform data during 4D-CT respiratory gating radiotherapy. The waveform in each treatment working cycle was compared with the waveform in 4D-CT scan to study whether there was a possibility of the off-target in the treatment of lung cancer patients.Results:There were 154 treatment sessions and 20,790 treatment breathing cycles in 18 patients, among which the threshold of gated opening beam miss amplitude (Δm-en) was greater than 0 in 95 treatment breathing cycles in 7 patients, accounting for 0.46% of all breathing cycles, and the threshold of gated closing beam miss amplitude (Δm-dis) was greater than 0 in 1419 treatment breathing cycles in 13 patients, accounting for 6.83% of all cycles. Among the 13 patients withΔm-dis greater than 0, actual tumor range of motion (R G) was greater than the sum of the value of target margin (M) and the value of plan tumor range of motion (R T) in 7 patients, R G was more than 1.5 times of M+R T in 7 patients, and there were also 7 patients in the phase of rapid rise and fall of respiratory curve. The correlation efficients between R G-M-R T and the percentage of beam on miss phase (T en%) and the percentage of beam closing off phase (T dis%) were 0.41 and 0.57, respectively. Conclusion:When R G is more than 1.5 times of M+R T value and the gating beam on phase contains the phases in the rapid rise and fall of the respiratory curve, the possibility of the off-target during radiotherapy is significantly increased.
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Objective The aim of this study was to investigate the dosimetric advantages of Gating in the treatment of prima-ry hepatic cancer with large segmentation. Methods A retrospective analysis of 10 patients with primary liver cancer from August 2017 to November 2018 after interventional therapy was performed using three consecutive phases of end-tidal phase to achieve pa-tient-controlled large-segment radiotherapy. Ten patients underwent 4DCT localization scan,and 10 respiratory phase sequences were reconstructed by respiratory wave-form,and the images were transmitted to the MIM6. 7. 6 workstation. In the MIM workstation, full-time phase maximum density projection(MIP-10),full-time phase average density projection(Mean-10),end-expiration 3 phase maximum density projection(MIP-3) and end-expiration 3 phase average density projection( Mean-3) were generated re-spectively,where MIP was used for target delineation and Mean for dose calculation. The radiotherapy doctor delineated IGTV-10 and IGTV-3 on the MIM workstation,and released CTV-10,CTV-3,PTV-10 and PTV-3 to compare the volume differences of the target area. After the target area was drawn,the image was transmitted from the MIM workstation to the Eclipse treatment planning sys-tem,and the full-time phase plan(Plan-10)with the same conditions and three consecutive phase-phase gating plans(Plan-3) were prepared. The prescriptive dosage was given at 50 Gy/10 f/2weeks. Comparing the HI and CI of the target area,the comparison of organs at risk included: the average dose of liver Dmean,the irradiation volume of liver less than 15Gy,the Dmax of small intestine, the Dmax of colon, the Dmax of stomach, the average dose of the kidney Dmean, the heart Dmax, and the spinal cord Dmax. Results The volume of the target area delineated at the end of expiratory phase was less than that of the target area outlined by the full-time phase in IGTV,CTV and PTV,and the difference was statistically significant(P<0. 05). In the two groups of seven field coplanar lage-segment radiotherapy plans,the 3-phase respiratory gating plan significantly reduced the dose of the organs at risk, and the difference was statistically significant(P<0. 05). At the same time,there was no statistically difference in the HI and CI be-tween of the two groups(P>0. 05). Conclusion The gated target area delineation and planning design of the three consecutive pha-ses of end-tidal phase reduce the volume of IGTV,CTV and PTV target regions compared with the selection of full-time phase,and have obvious advantages in the planned dosimetry. The irradiation dose that threatens the organs is worthy of being promoted and ap-plied in the large-scale radiotherapy of liver cancer.
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Resumen: El presente trabajo muestra una aplicación del algoritmo Chan-Vese para la segmentación semi-automática de estructuras anatómicas de interés (pulmones y tumor pulmonar) en imágenes de 4DCT de tórax, así como su reconstrucción tridimensional. La segmentación y reconstrucción se realizó en 10 imágenes de TAC, las cuales conforman un ciclo inspiración-espiración. Se calculó el desplazamiento máximo para el caso del tumor pulmonar usando las reconstrucciones del inicio de la inspiración, el inicio de la espiración, y la información del voxel. El método propuesto logra segmentar de manera apropiada las estructuras estudiadas sin importar su tamaño y forma. La reconstrucción tridimensional nos permite visualizar la dinámica de las estructuras de interés a lo largo del ciclo respiratorio. En un futuro se espera poder contar con mayor evidencia del buen desempeño del método propuesto y contar con la retroalimentación del experto clínico, ya que el conocimiento de características de estructuras anatómicas, como su dimensión y posición espacial, ayuda en la planificación de tratamientos de Radioterapia (RT), logrando optimizar las dosis de radiación hacia las células cancerosas y minimizarla en órganos sanos. Por lo tanto, la información encontrada en este trabajo puede resultar de interés para la planificación de tratamientos de RT.
Abstract: This paper presents an application of the Chan-Vese algorithm for a semi-automatic segmentation of anatomical structures of interest (lungs and lung tumor) in thorax 4DCT images, as well as its threedimensional reconstruction. Segmentations and reconstructions were performed in 10 CT images, which conform an inspiration-expiration cycle. The maximum displacement of the lung tumor was calculated using the reconstructions of the beginning of inspiration, beginning of expiration, and the voxel size information. The proposed method was able to succesfully segment the studied structures regardless of their size and shape. The threedimensional reconstruction allow us to visualize the dynamics of the structures of interest throughout the respiratory cycle. In the near future, we are expecting to be able to have more evidence of the good performance of the proposed segmentation approach, and to have feedback from a clinical expert, giving the fact that the knowledge of anatomical structures characteristics, such as their size and spatial location, may help in the planning of radiotherapy treatments (RT), optimizing the radiation dose to cancer cells and minimizing it in healthy organs. Therefore, the information found in this work may be of interest for the planning of RT treatments.
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Objective To investigate the difference of lung and target volume and dosimetry characteristics features of deep inhalation breathing holding-active breathing control (ABC) and the four dimensional CT (4D-CT) free breathing in stereotactic body radiation therapy (SBRT) technology for patients with lung cancer.Methods 10 patients with pulmonary malignant tumor who were proposed SBRT treatment were selected,and received CT under free breath (FB-CT),4D-CT scan under quiet respiration (4D-CT) and active breathing control CT scan (ABC-CT),respectively.With SBRT technology under the same condition designed four corresponding plans,FB-CT,ABC-CT,4D-CT and 4D-CT0 which was the end inspiratory phase of 4D-CT respectively.The lung volume(V),PTV,V5,V20,mean lung dose(MLD) and normal tissue complication probability(NTCP) of four treatment programs were counted and compared.Results Compared with FB-CT,V,PTV,V5,V20,MLD and NTCP of ABC-CT were 51.48％,-65.34％,-42.64％,-56.62％,-40.22％ and-98.53％ (t=-7.14 to6.16,P＜0.05);PTV,V5,V20,MLD and NTCP of 4D-CT were-40.14％,-16.90％,-37.16％,-17.85％ and-90.96％ (t =0.54 to 3.22,P＜0.05);PTV,V5,V20,MLD and NTCP of 4D-CT0 were-68.98％,-30.21％,-48.49％,-37.45％ and-95.82％ (t=1.32 to 5.46,P＜0.05),respectively.Compared with FB-CT,the lung volume of 4D-CT and 4D-CT0 had no statistical difference (P ＞ 0.05).Conclusions ABC-CT methods have ideal clinical characteristics,with larger double lung volume,smaller artifacts of image,and higher target matching precision.ABC-CT methods reduce the dose of normal lung tissues significantly.
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Objective To evaluate the impact of respiratory motion on lung dosimetry using 4D-CT during lung cancer radiotherapy.Methods Ten cases were randomly selected from non-small cell lung cancer (NSCLC) patients treated in our department.The 4D-CT machine was adopted for simulation before treatment and 10 respiratory phases were obtained for each patient.Target volumes were delineated on the maximum intensity projection (MIP) images,and plans were generated on average intensity projection (ALP) images.Plans were transferred to CT images of each respiratory phase,and we calculated the dosage on lungs and subsequently evaluated the volume dosage to lungs and the entire body.Results The mean dosage to lungs are greatly affected by the respiratory phase.This difference also depended on tumor location.When it was inside the lung,the average dosage shows the same trend as the respiratory motion,with the change rate of 2.18％,which was less than the change of lung volume 4.49％ (t =4.189,P ＜ 0.05).When the tumor was located nearby the lung,the mean dosage showed the opposite trend with respiratory motion,with the change rate of 3.76％,which was also less than the change of lung volume 4.49％ (t =25.007,P ＜ 0.05).The effect of respiratory motion on V5,V10,V20 of body was small,and the magnitude of change for whole body dosages were 0.47％,0.28％,0.17％ respectively,which was smaller than the change of lung volume 4.49％ (t =11.371,11.188,11.377,P ＜ 0.05).Volume dose of lung V5,V10,V20 and lung volume change trends were the same,and the magnitude of change for lung volume dosages were 2.39％,1.91％,1.80％ respectively,and were smaller than the change of lung volume 4.49％ (t =2.279,2.298,2.485,P ＜ 0.05).Conclusions The mean dosage to lungs shows a great difference between different respiratory phases.More attention should be paid when evaluating the lung volume during treatment planning.
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Objective To explore the effect of respiration on dose accumulation for target volume and normal liver in radiotherapy for hepatocellular carcinoma (HCC) while applying 4D-CT and deformable registration.Methods Nineteen HCC patients who had received transcatheter arterial chemoembolization were enrolled in this study.All patients underwent 3D-and 4D-CT simulation in free breathing.The 3D dose (Dose-3D) was calculated from the treatment planning designed on the 3D-CT image.The Dose-3D then was recalculated on ten phases of 4D-CT images respectively,and the end-inspiration and end-expiration doses were defined as Dose El and Dose-EE.The 4D dose (Dose-4D) was obtained by deforming and accumulating ten-phase doses of 4D-CT images on the end-expiration phase image.The dosimetric differences of planning target volume and normal liver were compared among Dose-3D,Dose-4D,Dose-EI and Dose-EE.Results The D99 and D95of planning target volume (PTV) in Dose-3D were higher than those of Dose-4D,Dose-Fl and Dose EE (x2 =32.75,26.31,P ＜ 0.05).The conformal index (CI) and homogeneity index (HI) in Dose-3D were better than those of Dose-4D,Dose-E1 and Dose-EE,in which CI decreased from 0.78 to0.63,0.60 and 0.57,while HI increased from 0.08 to 0.15,0.16 and 0.19 (x2 =37.80,31.86,P ＜0.05).No statistically significant differences were found in dosimetric indices of PTV between Dose-4D and Dose EI,Dose-EE,and between Dose-El and Dose-EE (P ＞ 0.05).The mean dose (D),V5,V10,V20,V30 and V40 of normal liver were similar among four dose distributions (P ＞ 0.05).Conclusions More objective and precise dose distribution for target volume and normal liver could be obtained by applying both 4D-CT and deformable registration,which is beneficial to accurately predicting the dosevolume indices of radiation-induced liver injury and offering more reliable evidence of escalation for target dose.
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Locally advanced non-small cell lung cancer (NSCLC) encompasses a heterogeneous collection of tumour and nodal stages. Despite recent advances, the overall survival for this group remains poor. Radical radiotherapy remains the mainstay of treatment. The complexities involved in the delivery of radical radiotherapy to the lung pertain to tumour volume definition, intra- and inter-fraction motion (namely tumour motion caused by respiration and GTV migration during treatment) and the proximity of organs at risk to the high-dose region. Here we discuss a selection of strategies to manage these complexities. Motion management can be addressed by 4D CT planning, radiotherapy gating and on-board imaging, including cone beam CT. Advanced planning methods such as intensity modulated radiotherapy may potentially allow dose escalation and sparing of normal tissue toxicity. Functional imaging has already improved our ability to stage tumours and more carefully select appropriate candidates for radical treatment. Better imaging also improves GTV definition. However, the complexities of image acquisition and interpretation need to be accounted for and agreed consensus protocols have yet to be defined. Novel imaging methods such as 4D PET-CT and 4D MRI may also yield improvements for the future and these are briefly discussed.
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The purpose of this study was to develop the respiratory training system using individual characteristic guiding waveform to reduce the impact of respiratory motion that causes artifact in radiotherapy. In order to evaluate the improvement of respiratory regularity, 5 volunteers were included and their respiratory signals were acquired using the in-house developed belt-type sensor. Respiratory training system needs 10 free breathing cycles of each volunteer to make individual characteristic guiding waveform based on Fourier series and it guides patient's next breathing. For each volunteer, free breathing and guided breathing which uses individual characteristic guiding waveform were performed to acquire the respiratory cycles for 3 min. The root mean square error (RMSE) was computed to analyze improvement of respiratory regularity in period and displacement. It was found that respiratory regularity was improved by using respiratory training system. RMSE of guided breathing decreased up to 40% in displacement and 76% in period compared with free breathing. In conclusion, since the guiding waveform was easy to follow for the volunteers, the respiratory regularity was significantly improved by using in-house developed respiratory training system. So it would be helpful to improve accuracy and efficiency during 4D-RT, 4D-CT.
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Artifacts , Displacement, Psychological , Fourier Analysis , RespirationABSTRACT
In this study, we evaluated feasibility of applying MTV (Metabolic Target Volume) to respiratory gated radiotherapy for more accurate treatment using various SUV (Standard Uptake Value) from PET images. We compared VOI (Volume of Interest) images from 50%, 30% and 5% SUV (standard uptake volume) from PET scan of an artificial target with GTV (Gross Tumor Volume) images defined by percentage of respiratory phase from 4D-CT scan for respiratory gated radiotherapy. It is found that the difference of VOI of 30% SUV is reduced noticeably comparing with that of 50% SUV in longitudinal direction with respect to total GTV of 4D-CT image. Difference of VOI of 30% SUV from 4D-PET image defined by respiratory phase from 25% inhalation to 25% exhalation, and GTV from 4D-CT with the same phase is shown below 0.6 cm in maximum. Thus, it is better to use 4D-PET images than conventional PET images for applying MTV to gated RT. From the result that VOI of 5% SUV from 4D-PET agrees well with reference image of 4D-CT in all direction, and the recommendation from department of nuclear medicine that 30% SUV be advised for defining tumor range, it is found that using less than 30% SUV will be more accurate and practical to apply MTV for respiratory gated radiotherapy.
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Exhalation , Inhalation , Nuclear Medicine , Positron-Emission TomographyABSTRACT
PURPOSE: 4DCT scans performed for radiotherapy were retrospectively analyzed to assess the possible benefits of respiratory gating in non-small cell lung cancer (NSCLC) and established the predictive factors for identifying patients who could benefit from this approach. MATERIALS AND METHODS: Three treatment planning was performed for 15 patients with stage I~III NSCLC using different planning target volumes (PTVs) as follows: 1) PTVroutine, derived from the addition of conventional uniform margins to gross tumor volume (GTV) of a single bin, 2) PTVall phases (patient-specific PTV), derived from the composite GTV of all 6 bins of the 4DCT, and 3) PTVgating, derived from the composite GTV of 3 consecutive bins at end-exhalation. RESULTS: The reductions in PTV were 43.2% and 9.5%, respectively, for the PTVall phases vs. PTVroutine and PTVgating vs. PTVall phases. Compared to PTVroutine, the use of PTVall phases and PTVgating reduced the mean lung dose (MLD) by 18.1% and 21.6%, and V20 by 18.2% and 22.0%, respectively. Significant correlations were seen between certain predictive factors selected from the tumor mobility and volume analysis, such as the 3D mobility vector, the reduction in 3D mobility and PTV with gating, and the ratio of GTV overlap between 2 extreme bins and additional reductions in both MLD and V20 with gating. CONCLUSION: The additional benefits with gating compared to the use of patient-specific PTV were modest; however, there were distinct correlations and differences according to the predictive factors. Therefore, these predictive factors might be useful for identifying patients who could benefit from respiratory-gated radiotherapy.
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Humans , Carcinoma, Non-Small-Cell Lung , Lung , Retrospective Studies , Tumor BurdenABSTRACT
PURPOSE : To assess the respiratory tumor movement using 4D-CT (4-dimensional computed tomography) for minimizing setup and target volume uncertainty of body-frame based stereotactic radiosurgery (SRS) in lung tumor. MATERIALS AND METHODS : Fifty-seven stereotactic radiation therapies with respiratory gating system in 44 patients (two targets in seven patients and three in three patients) were executed in Asan Medical Center from May 2005 to June 2006. We used respiratory gating system consisted of RPM (Real-time Positioning Management system, Varian, USA) and 4D-CT (GE healthcare, USA), if tumor movement was exceeding 5 mm by respiration on fluoroscopy. Accurate tumor movement on reconstructed 4D-CT image was determined for respiratory gated therapy. Respiratory gated therapy was done if tumor movement was exceeding 5 mm, and non-gated therapy was done if it was below 5 mm. RESULTS : Forty-five tumors were treated with supine position, and the other twelve were with prone position. Median tumor movement (3-dimensional) by respiration was 8.78+/-5.30 mm, and it was mostly affected by superior-inferior movement (8.53+/-5.23 mm). Tumor movements were different by tumor location, whether upper (5.38+/-2.85 mm) or lower (10.12+/-5.08 mm) lobe (p=0.015). Tumor movement was exceeding 5 mm in 27 (47.3%) tumors, and below 5 mm in 30 tumors in 4D-CT evaluation. Tumor movements on adopted respiratory gated phase were wholly below 5 mm, and its median value was 3.70+/-1.13 mm. CONCLUSION : Assessment of respiratory tumor movement using 4D-CT and gating system was helpful for minimizing target volume uncertainty. As a result, image-guided radiation therapy could improve the treatment accuracy of high precision stereotactic radiosurgery
Subject(s)
Humans , Delivery of Health Care , Fluoroscopy , Four-Dimensional Computed Tomography , Lung , Prone Position , Radiosurgery , Radiotherapy, Image-Guided , Respiration , Supine Position , UncertaintyABSTRACT
PURPOSE: Reduction of respiratory motion artifacts in PET images was studied using respiratory-gated PET (RGPET) with moving phantom. Especially a method of generating simulated helical CT images from 4D-CT datasets was developed and applied to a respiratory specific RGPET images for more accurate attenuation correction. MATERIALS AND METHODS: Using a motion phantom with periodicity of 6 seconds and linear motion amplitude of 26 mm, PET/CT (Discovery ST; GEMS) scans with and without respiratory gating were obtained for one syringe and two vials with each volume of 3, 10, and 30 ml respectively. RPM (Real-Time Position Management, Varian) was used for tracking motion during PET/CT scanning. Ten datasets of RGPET and 4D-CT corresponding to every 10% phase intervals were acquired. From the positions, sizes, and uptake values of each subject on the resultant phase specific PET and CT datasets, the correlations between motion artifacts in PET and CT images and the size of motion relative to the size of subject were analyzed. RESULTS: The center positions of three vials in RGPET and 4D-CT agree well with the actual position within the estimated error. However, volumes of subjects in non-gated PET images increase proportional to relative motion size and were overestimated as much as 250% when the motion amplitude was increased two times larger than the size of the subject. On the contrary, the corresponding maximal uptake value was reduced to about 50%. CONCLUSION: RGPET is demonstrated to remove respiratory motion artifacts in PET imaging, and moreover, more precise image fusion and more accurate attenuation correction is possible by combining with 4D-CT.
Subject(s)
Artifacts , Dataset , Periodicity , Positron Emission Tomography Computed Tomography , Syringes , Tomography, Spiral ComputedABSTRACT
For Stereotactic Radiosurgery of lung tumor, 4 dimensional CT was done during for free breathing of the patient. The movement of the treated target was measured in the CT images, and appropriate breathing cycle was selected for treatment. For patient A, the movement of the treatment target was 10.1 mm during full breathing cycle, and 5.4 mm for treated breathing cycle, 30~70%. For patient B, the movement was 13 mm, and 3.5 mm for full breathing cycle and treated breathing cycle, respectively.