Image Guided Radiotherapy (IGRT) via Online Cone Beam CT Substantially Reduces Margin Requirements for Stereotactic Lung Radiotherapy

Grills, I.S.; Hugo, Geoffrey D.; Kestin, Larry L.; Chao, K.; Wloch, J.; Yan, Di

doi:10.1016/j.ijrobp.2007.07.280

Cited by 4 publications

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“…Previous works showed that the position and shape of the bladder and rectum vary throughout the course of prostate radiotherapy treatment [ 14 – 16 ]. The application of CBCT can improve the accuracy of radiation therapy in target location and dose delivered [ 17 , 18 ].…”

Section: Discussionmentioning

confidence: 99%

Dosimetric impact of different bladder and rectum filling during prostate cancer radiotherapy

et al. 2016

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BackgroundThe aim of this study was to analyze the influence of volumetric changes of bladder and rectum filling on the 3D dose distribution in prostate cancer radiotherapy.MethodsA total of 314 cone-beam CT (CBCT) image data sets from 19 patients were enrolled in this study. For each CBCT, the bladder and rectum were contoured and volume sizes were normalized to those on their original CT. The daily delivered dose was recalculated on the CBCT images and the doses to bladder and rectum were investigated. Linear regression analysis was performed to identify the mean dose change of the volume change using SPSS 19.ResultsThe data show that the variances of the normalized volume of the bladder and the rectum are 0.13–0.58 and 0.12–0.50 respectively. The variances of V70Gy, V60Gy, V50Gy, V40Gy and V30Gy of bladder are bigger than those of rectum for 17 patients. The linear regression analysis indicates a 10 % increase in bladder volume will cause a 5.6 % (±4.9 %) reduction in mean dose (p <0.05).ConclusionsThe bladder’s volume change is more significant than that of the rectum for the prostate cancer patient. The rectum volume variations are not significant except for air bubbles, which change the shape and the position of the rectum. The bladder volume variations may cause dose changes proportionately. Monitoring the bladder’s volume before fractional treatment delivery will be crucial for accurate dose delivery.

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Section: Discussionmentioning

confidence: 99%

Dosimetric impact of different bladder and rectum filling during prostate cancer radiotherapy

et al. 2016

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“…It is also reported in various studies. [18][19][20] To avoid this situation, Jhigran et al 12 have proposed a method of adding a very large margin to CTV that includes shifts in target position to avoid inadequate dosage of the target volume. But this approach is unacceptable when a high dose of 4,500-5,040 cGy is prescribed to the target site.…”

Section: Discussionmentioning

confidence: 99%

To analyse target volume variations during SIB-IMRT of squamous cell carcinoma of uterine cervix

et al. 2020

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Purpose: To assess volume variations in target site due to changes in bladder filling and rectal content including air bubbles during simultaneous-integrated boost intensity-modulated radiotherapy (SIB-IMRT) of patients suffering from squamous cell carcinoma of uterine cervix. Materials and methods: A total of ten patients of squamous cell carcinoma of uterine cervix were enrolled in this analysis. All patients were planned to undergo SIB-IMRT using 10 MV beam. Planning target volume of the tumour (PTVtumour) and PTVnodal were prescribed with 5,040 and 4,500 cGy doses, respectively. During planning, PTVtumour V95%, PTVnodal V95% and organs at risk (OARs) (bladder, rectum, femoral heads and small bowel) volumes were measured from initial CT planning scans taken with full bladder. CT scans were acquired once in a week over a treatment period of 5·5 weeks. Intra-treatment scans with full bladder were then fused with the planning scans to determine variations in the target volume and the OAR volume. Changes in radiation dose to the PTVtumour and the PTVnodal were also assessed by comparing intra-treatment scans with the planning (first) scans. Results: All patients showed intra-treatment bladder volume larger than the planning bladder volume. Difference between planning bladder and intra-treatment bladder volumes ranged from 4·5 to 49%. Rectal volume varied from 17 to 60 cc. A wide variation between planning and intra-treatment air volumes was found in most of the patients. When comparing initial and inter-fraction air volumes, the maximum difference was 366·67%. Due to bladder and rectal volume variations, PTVtumour V95% and PTVnodal V95% doses did not remain constant throughout the treatment. The maximum discrepancy between intra-treatment PTVtumour dose and planning PTVtumour dose was 12·15%. The maximum difference between planning and inter-fraction PTV V95% was 48·28%. PTVnodal dose observed from scan taken in last week of treatment was 12·87% less than planning PTVnodal dose analysed from planning CT scan. Maximum difference in planning and inter-fraction PTVnodal V95% was 57·78%. Conclusion: Inconsistent bladder and rectal volumes had a significant impact on target volume and dosage during an entire course of SIB-IMRT. For radiotherapy of gynaecological malignancies, data on variations in PTV should be acquired on daily basis to target radiation dose to the tumour site with accuracy.

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“…Determination of the discrepancy between the intended and actual treatment position with the aid of cone-beam computed tomography (CBCT) is an integral part of IGRT. 1 This discrepancy is calculated as a shift in treatment field position comparing the CBCT images against its corresponding reference which is known as digitally reconstructed radiographs (DRRs). Set-up error comprises a systematic and random component 2 and is calculated over a horizontal axis or right-left (X), longitudinal axis or superior-inferior (Y), and depth or anterior-posterior (Z) axis.…”

Section: Introductionmentioning

confidence: 99%

Set-up Errors and Determination of Planning Target Volume Margins Protocol for Different Anatomical Sites in a Newly Established Tertiary Radiotherapy Centre in India

Mandal

Singh

Bera

et al. 2020

ASJO

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Abstract Objective Our study aimed to assess the set-up errors for image-guided radiotherapy at a newly established tertiary radiation center in India and to establish the departmental protocol of clinical target volume–planning target volume (CTV–PTV) margins for different anatomical sites. Materials and Methods This study enrolled the first 200 patients who were treated with curative intent at All India Institute of Medical Sciences, Patna, from February 2019 to September 2019. Number of patients were 53, 26, 53, 11, 6, 47, and 4 for head and neck, brain, breast, thorax, abdomen, pelvis, and craniospinal irradiation (CSI), respectively. The translational vectors for total 1,463 kV cone-beam computed tomography (CBCT) images were collected from the treatment record. Results For the systematic error, the largest value is found for the thoracic subset on the X and Y directions, and for breast patients on Z axis, whereas the smallest values were found for CSI. For random error, the largest value was found for pelvic in the X, Y direction, and for breast subset on Z axis, whereas the smallest values on X and Z axes were found in the brain and for head and neck on the Y axis. Largest value for systemic error is smaller than 5 mm in all directions and for all anatomical subsets. The highest random error value is 5.07 mm in Y axis for pelvic subset. The largest values for CTV–PTV margin are found for thoracic subset and the smallest for CSI followed by the brain. Significant reduction of set-up error observed for the last hundred patients as compared to the first half of the patient population. Conclusion Use of thermoplastic cast along with breast board and respiratory motion management should be recommended to reduce set-up error for breast and thoracic subset. Six degrees of freedom robotic couch system can also further rectify the set-up error in image-guided radiotherapy.

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Image Guided Radiotherapy (IGRT) via Online Cone Beam CT Substantially Reduces Margin Requirements for Stereotactic Lung Radiotherapy

Cited by 4 publications

References 0 publications

Dosimetric impact of different bladder and rectum filling during prostate cancer radiotherapy

Dosimetric impact of different bladder and rectum filling during prostate cancer radiotherapy

To analyse target volume variations during SIB-IMRT of squamous cell carcinoma of uterine cervix

Set-up Errors and Determination of Planning Target Volume Margins Protocol for Different Anatomical Sites in a Newly Established Tertiary Radiotherapy Centre in India

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