CBCT-based volumetric and dosimetric variation evaluation of volumetric modulated arc radiotherapy in the treatment of nasopharyngeal cancer patients

Jin, Xiance; Hu, Weigang; Shang, Haijiao; Han, Ce; Jiang, Yi; Zhou, Yanfang; Xie, Conghua

doi:10.1186/1748-717x-8-279

Cited by 22 publications

(17 citation statements)

References 21 publications

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“…Using weekly CT, Robar et al [18] showed that the mean volume of lPG and rPG decreased by 4.4% and 5.0% per week during a 6-week treatment course. Han et al [19] and Lee et al [20] observed a mean and median relative PGs loss rate of 1.1% and 0.7% per treatment day based on used daily megavoltage CT. Jin et al [21] discovered that the left and right part of the PGs underwent a mean volume reduction of 4.4% and 4.7% per week based on weekly CBCT of ten NPC patients treated with IMRT, and the result was in agreement with the findings in Robar et al [18] and ours. All these researches suggested that the OARs have considerable anatomical changes over the treatment course in H & N patients.…”

Section: Discussionsupporting

confidence: 82%

Evaluation of deformable image registration for contour propagation between CT and cone-beam CT images in adaptive head and neck radiotherapy

Zhang

Shi

et al. 2016

THC

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Abstract. Deformable image registration (DIR) is a critical technic in adaptive radiotherapy (ART) to propagate contours between planning computerized tomography (CT) images and treatment CT/Cone-beam CT (CBCT) image to account for organ deformation for treatment re-planning. To validate the ability and accuracy of DIR algorithms in organ at risk (OAR) contours mapping, seven intensity-based DIR strategies are tested on the planning CT and weekly CBCT images from six Head & Neck cancer patients who underwent a 6 ∼ 7 weeks intensity-modulated radiation therapy (IMRT). Three similarity metrics, i.e. the Dice similarity coefficient (DSC), the percentage error (PE) and the Hausdorff distance (HD), are employed to measure the agreement between the propagated contours and the physician delineated ground truths. It is found that the performance of all the evaluated DIR algorithms declines as the treatment proceeds. No statistically significant performance difference is observed between different DIR algorithms (p > 0.05), except for the double force demons (DFD) which yields the worst result in terms of DSC and PE. For the metric HD, all the DIR algorithms behaved unsatisfactorily with no statistically significant performance difference (p = 0.273). These findings suggested that special care should be taken when utilizing the intensitybased DIR algorithms involved in this study to deform OAR contours between CT and CBCT, especially for those organs with low contrast.

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Section: Discussionsupporting

confidence: 82%

Evaluation of deformable image registration for contour propagation between CT and cone-beam CT images in adaptive head and neck radiotherapy

Zhang

Shi

et al. 2016

THC

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“…A large dose gradient always exists between the tumour site and the critical structure in VMAT plans, and so volumetric changes, as mentioned previously, create a potential change in the dose received on the critical structure. Jin et al studied the usefulness of the CBCT images-based VMAT plan adaptation in nasopharyngeal tumour patients and found that there was a reduction of 4.5 cm 3 in parotid volume during the course of treatment and, as a result, the dose received was increased up to 8.8% than the planned value [24]. CBCT can be used to monitor such changes on a daily basis and reconstruct the dose apart from providing actual set up information of the patient.…”

Section: Discussionmentioning

confidence: 99%

Analysis of Dosimetric Impacts of Cone Beam Computed Tomography–Based Volumetric Modulated Arc Therapy Planning

Noufal

Abdullah

Niyas

et al. 2016

Journal of Medical Imaging and Radiation Sciences

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Objective: To quantify the Hounsfield unit (HU) variations between computed tomography (CT) and cone beam CT (CBCT) and study its impact on volumetric modulated arc therapy (VMAT) plans. Methods: HU number variations in CT and CBCT images were evaluated using the Catphan-504 phantom, and changes in seven different materials within the phantom (air, polymethylpentene, low-density polyethylene, polystyrene, acrylic, Delrin, and Teflon) were studied. The HU variations in half-fan and full-fan modes of CBCT were evaluated. The effect of variations in the shape of the body cross sections was assessed by reducing the body of the Catphan by 0.5 cm and 1.0 cm. CBCT-based VMAT plans in 27 patients (10 prostate, 10 brain, and 7 head and neck (HN)) were compared with corresponding CT-based plans. The dosimetric variations were assessed referring to different points on the dose volume histogram (D 5% , D 50% , and D 95% for PTVs and D 1% , D max , and D mean for organs at risk). The relative percentage of difference (DD (%)) between CT-and CBCT-based VMAT plans were examined on these points. To evaluate the dosimetric accuracy, dose distributions were compared using Omnipro-I'mRT software. The VMAT plans were evaluated based on 3 mm-3%, 2 mm-2%, and 1 mm-1% gamma criteria. Results: The HU difference in CT and CBCT was highest for air, Delrin, and Teflon, whereas the difference was less than 20 HU for the other materials. The dose volume histograms of both CTand CBCT-based plans were in excellent agreement in both phantom and patients, except in HN cases where the difference was 7%. The average 3 mm-3% gamma pass points in brain, prostate, and HN patients were 97 AE 0.2%, 96 AE 0.06%, and 93.3 AE 1.1%, respectively. The gamma pass rates reduced to 88.8 AE 0.06%, 91 AE 0.04%, and 79 AE 6% in 2 mm-2%, and further declined to 76.6 AE 0.09%, 75.2 AE 0.5%, and 60 AE 6% using the stringent 1 mm-1% gamma criteria for brain, prostate, and HN cases, respectively. Conclusion: Based on the results of this study, it is our belief that CBCT images can be used as a tool for evaluating the dosimetric variation in patient VMAT plans. The author(s) has no financial disclosures or conflicts of interest to declare.

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“…Daha önceki çalışmalarda da gösterildiği gibi akciğer olgularında, CBCT tedavi süresine yaklaşık üç dakika eklmesine rağmen ve toplam tedavi dozuna katkısı kV-kV görüntülemeye göre daha fazla olsa da hedef hacmin fraksiyonlar arası lokalizasyonunu belirmede ve set-up sapmalarını azaltmada 2B görüntülemelere göre daha üstün olduğu sonucuna varıldı. [8,22,32,33] İstatiksel olarak araştırıldığında baş boyun hastalarında set-up hatalarını belirlemede kV-kV ve kV CBCT için anlamlı farklılık bulunmaz iken akciğer hastalarında iki görüntüleme arasındaki (p<0.05) fark anlamlı bulunmuştur. Bu nedenle akciğer hastalarında IGRT protokollerinde kV CBCT ve online düzeltme protokolü kullanıldı-ğında PTV oluşturmak için CTV'ye verilecek marj küçülecek ve PTV hacmi daha küçük olacağından kritik organ koruması daha iyi olacaktır.…”

Section: Discussionunclassified

Definition of the set-up error using 2D radiographic images and 3D computed tomography and dosimetric effect of set-up errors for head and neck/lung radiotherapy patients

Ceylan¹

2015

TJ Oncol

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OBJeCTIVesIn this study, the comparison of the set-up accuracy using twodimensional kilo voltage (kV-kV) imaging and three-dimensional cone beam CT (CBCT) in head and neck/lung radiotherapy patients was done. MeTHOds404 images of all 8 head and neck and 9 lung patients studied to find 2D and 3D set-up errors. CTV to PTV margins were obtained using calculated set-up errors. The plans of the selected head and neck and lung patients were calculated to investigate dosimetric effect of the set-up errors. ResuLTskV-kV and CBCT detected average set-up errors for head and neck patients were less than 2 mm. kV-kV and CBCT detected average set-up errors for lung patients were less than 7 mm. While there was a statistically differences (p<0.05) for lung patients, no statistically differences was found for head and neck cases as compared kV-kV and CBCT image data sets. The calculated margin using CBCT image data sets was found bigger than the calculated margin using kV-kV image data sets. The adequate and clinically accepted margins were calculated for both IGRT approach. The neglible dosimetric effects were observed for both data sets. CONCLusIONWe conclude that the 2D radiographic image of head and neck radiotherapy patient reduces positioning errors. While 3D registration of CBCT and planning CT of head and neck cases adds little improvement comparing with 2D images, 3D CBCT images of lung radiotherapy patients provided more accurate information of the set-up errors.Key words: Set-up; CBCT; kV-kV. AMAÇBu çalışmada baş-boyun ve akciğer hastalarının iki boyutlu kVkV ve üç boyutlu kV CBCT ile belirlenen set-up hataları karşı-laştırıldı. GeReÇ Ve yÖNTeMÇalışmada sekiz baş-boyun, dokuz akciğer hastasının IGRT sü-reçlerinde elde edilen 404 kV-kV ve CBCT görüntüleri incelendi. İki boyutta ve üç boyutta belirlenen set-up farklılıkları tespit edildi. Bu farklar kullanılarak PTV marjlarının yeterliliği araştırıldı. Set-up farklılıklarının doz dağılımına etkisine bakıldı. BuLGuLARBaş-boyun hastaları için ortalama x, y, z yönündeki sapmalar kv-kV ve CBCT görüntülemelerde sırasıyla ≤2 mm ve akciğer hastalarında her iki görüntüleme için <7 mm bulundu. Her hasta gurubu için kV-kV ve CBCT görüntüleme teknikleri karşılaştı-rıldığında baş-boyun hastalarında anlamlı farklılık bulunmadı. Akciğer hastalarında anlamlı farklılık (p<0.05) tespit edildi. Sapmalara göre PTV çin gereken marj her iki tedavi bölgesi için kVkV kullanıldığında CBCT için hesaplanan marj değerinden daha fazla bulundu. Bu marj değerleri klinik marj değerlerinin içinde bulunduğundan CTV hacimlerini kapsanmasında dozimetrik etkinin göz ardı edilebileceği görüldü. sONuÇÇalışmada baş-boyun hastalarında haftada iki kez kV-kV görün-tülemenin pozisyon hatalarını azaltacağı gösterilmiştir. Akciğer olgularında set-up hatalarını minimuma indirmek için CBCT ile hastalarının tedavi pozisyonlandırılmasının daha doğru yapılabi-lirken baş-boyun olgularında kV-kV görüntülemenin yeterli olduğu, CBCT ile planlama CT'sinin 3D eşlemesinin anlamlı fayda sağlamadığı gösterilmiştir.Anahtar söz...

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CBCT-based volumetric and dosimetric variation evaluation of volumetric modulated arc radiotherapy in the treatment of nasopharyngeal cancer patients

Cited by 22 publications

References 21 publications

Evaluation of deformable image registration for contour propagation between CT and cone-beam CT images in adaptive head and neck radiotherapy

Evaluation of deformable image registration for contour propagation between CT and cone-beam CT images in adaptive head and neck radiotherapy

Analysis of Dosimetric Impacts of Cone Beam Computed Tomography–Based Volumetric Modulated Arc Therapy Planning

Definition of the set-up error using 2D radiographic images and 3D computed tomography and dosimetric effect of set-up errors for head and neck/lung radiotherapy patients

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