The sensitivity of ArcCHECK-based gamma analysis to manufactured errors in helical tomotherapy radiation delivery

AbstractThe biplanar diode arrays Delta4PT and Delta4+ has been used in our hospital since the introduction of the TomoTherapy in 2013 to ensure a good agreement between the calculated and the measured dose distributions in patient-related QA with helical TomoTherapy. The aim of this presentation is to evaluate the quality of the measurement procedure with the Delta4 phantoms Delta4PT and (since January 2016) Delta4+. This includes the influence of a cross calibration with a treatment plan with low modulation.Two analyses were performed: (i) All treatment plans in a period of three months (n=86) were not only calculated and measured with Delta4PT or Delta4+ but also with an ionization chamber (Exradin A1SL) in the homogeneous “cheese phantom”. (ii) All data measured from January 2016 to April 2017 (Delta4+, n=132) were analyzed regarding median dose deviation, Gamma analysis and others.The comparison with chamber measurements shows that all measurements with Delta4 and almost all with the ionization chambers (79 of 86) yield a deviation of measured vs. planned dose in the PTV of less than 2.5%, but with a lower variation of the Delta4 measurements. However, a strong correlation between both was not observed.The separate analysis of the measurements with the newer Delta4+ (since January 2016) shows a mean dose deviation in the PTVs of only 0.14% with a standard deviation (S.D.) of 0.69%. Before every measurement a cross calibration has been performed. Without this cross calibration, the deviation would be 0.96% with an increased standard deviation of 0.93%.It is concluded that the Delta4 systems are well suited for patient-related QA for helical TomoTherapy treatment plans. The comparison with chamber measurements shows a plausible accordance between both systems whereas the variation of single measurements is quite different.With the help of a daily cross calibration the variability of the Delta4 results is further decreased and the results show higher accuracy and reliability. According to our experience, a daily cross calibration is mandatory for a reliable patient-related QA.

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Dosimetric comparison of helical tomotherapy, volume-modulated arc therapy, and fixed-field intensity-modulated radiation therapy in nasopharyngeal and cervical cancers

10.21203/rs.3.rs-45988/v1 ◽

2020 ◽

Author(s):

Deyang Yu ◽

Shan Lu ◽

Lei Wang ◽

Xueyuan Hu ◽

Xin Li ◽

...

Keyword(s):

Radiation Therapy ◽

Field Intensity ◽

Helical Tomotherapy ◽

Intensity Modulated Radiation Therapy ◽

Conformity Index ◽

High Dose ◽

Fixed Field ◽

Intensity Modulated ◽

Radiation Delivery ◽

Arc Therapy

Abstract Background: To compare the dosimetric parameters of different radiotherapy plans, helical tomotherapy(HT), volume-modulated arc therapy (VMAT), and fixed-field intensity-modulated radiation therapy (FF-IMRT) for nasopharyngeal carcinoma (NPC) and cervical cancer (CC).Methods: A total of 15 patients with NPC and 15 patients with CC were chosen for retrospective analysis and replanned for HT, VMAT, and FF-IMRT. The prescribed doses of the planning target were 2.12/69.96 Gy, 1.8/59.4 Gy for NPC and 1.8/45 Gy for CC, respectively. The dosimetric parameters of the planning target, organs at risk (OARs), and the efficiency of radiation delivery were assessed and compared using the paired-samples t-test.Results: Compared with VMAT and FF-IMRT, HT plans significantly improved the mean conformity index (CI) and homogeneity index (HI). For the OARs, the HT plans reduced the maximum doses of most organs, such as brainstem, spinal cord, and optic nerves in NPC, and significantly reduced the volume of the high-dose region in NPC and the V30 and V40 of small bowel, rectum, and bladder in CC. However, VMAT evidently reduced the treatment time and improved the efficiency of radiation delivery than HT.Conclusions: For NPC and CC, results showed that HT and VMAT possessed better homogeneity and conformity of the target and better sparing of OARs compared with the conventional FF-IMRT, and HT achieved the best effect. VMAT had the shortest radiation delivery time. The results of this study can provide guidance for the selection of appropriate radiation technologies for patients with NPC and CC who are undergoing concurrent chemoradiotherapy.

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Poster - Wed Eve-45: Imaging and Radiation Delivery in Helical Tomotherapy: Phantom Study of a Moving Target

Medical Physics ◽

10.1118/1.3244149 ◽

2009 ◽

Vol 36 (9Part2) ◽

pp. 4312-4312

Author(s):

C Gallagher ◽

S Yartsev ◽

S Gaede ◽

J Van Dyk

Keyword(s):

Helical Tomotherapy ◽

Phantom Study ◽

Moving Target ◽

Radiation Delivery

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Dosimetric comparison between helical tomotherapy, volume modulated arc-therapy and Fixed-Field intensity modulated radiation therapy in postoperative adjuvant radiotherapy for cervical cancer

10.21203/rs.3.rs-58107/v1 ◽

2020 ◽

Author(s):

Deyang Yu ◽

Lei Wang ◽

Xueyuan Hu ◽

Xin Li ◽

Yanling Bai ◽

...

Keyword(s):

Cervical Cancer ◽

Radiation Therapy ◽

Helical Tomotherapy ◽

Treatment Time ◽

Intensity Modulated Radiation Therapy ◽

High Dose ◽

Intensity Modulated ◽

Radiation Delivery ◽

Arc Therapy ◽

Dose Volumes

Abstract Background: To evaluate the dosimetric parameters among three different radiotherapy techniques in patients with postoperative cervical cancer, including the Helical Tomotherapy (HT), the Volume Modulated Arc-Therapy (VMAT), and the Fixed-Field intensity modulated radiation therapy (FF-IMRT). Methods: Fifteen cervical cancer patients treated with postoperative radiotherapy were re-planning with HT, VMAT and FF-IMRT. The prescribed target dose of the patients was 1.8/45Gy. The paired-samples t-test was used to compare the dosimetric parameters of the planning target and OARs (Organs at risk), and the efficiency of radiation delivery. Results: Compared with the VMAT and FF-IMRT, the HT plans showed significant improvement in the conformity index (CI) and the homogeneity index (HI). In addition, the HT plans also significantly reduced the volume of high-dose region of the OARS, especially in the V30, V40 of small bowel, rectum and bladder. Meantime, the advantage of VMAT is that it reduced the treatment time and improved the efficiency of radiation delivery obviously, compared with the HT (293.8 ± 12.8s Vs. 557.6 ± 51.9s, P < 0.001) and FF-IMRT (293.8 ± 12.8s Vs. 581.8 ± 26.1s, P < 0.001). Conclusion: Our result reveals that HT showed better CI and HI for the target and reduced high dose volumes to OARs compared with VMAT and FF-IMRT, but the lower dose volumes to OARs increased slightly. As for the benefit of VMAT, it demonstrated the shortest treatment time. Our results could provide guidance for selecting the appropriate radiation technologies for cervical cancer patients who undergoing postoperative adjuvant pelvic radiotherapy.

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Helical Tomotherapy for Skull Base Tumors: A Preliminary Report

Journal of Neurological Surgery Part B Skull Base ◽

10.1055/s-0034-1384186 ◽

2014 ◽

Vol 75 (S 02) ◽

Author(s):

Wan-Soo Yoon ◽

D. Chung

Keyword(s):

Skull Base ◽

Preliminary Report ◽

Helical Tomotherapy ◽

Skull Base Tumors

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Helical tomotherapy for advanced esophageal cancer improves target conformity and homogeneity: A comparison with fixed-field intensity-modulated radiotherapy

JOURNAL OF ADVANCES IN PHYSICS ◽

10.24297/jap.v11i3.471 ◽

2015 ◽

Vol 11 (3) ◽

pp. 3146-3155

Author(s):

Luhua Wang

Keyword(s):

Esophageal Cancer ◽

Field Intensity ◽

Helical Tomotherapy ◽

Intensity Modulated Radiotherapy ◽

Matched Pair ◽

Conformity Index ◽

Target Coverage ◽

Advanced Esophageal Cancer ◽

Fixed Field ◽

Intensity Modulated

Purpose: To evaluate the usefulness of helical tomotherapy (HT) in the treatment of advanced esophageal cancer (EC) and compare target homogeneity, conformity and normal tissue doses between HT and fixed-field intensity-modulated radiotherapy (ff-IMRT).Methods: In all, 23 patients with cT3-4N0-1M0-1a thoracic EC (upper esophagus, 9 patients; middle esophagus, 6; distal esophagus, 6 and esophagogastric junction, 2) who were treated with ff-IMRT (60 Gy in 30 fractions) were re-planned for HT and ff-IMRT with the same clinical requireÂments. Comparisons were performed using the Wilcoxon matched-pair signed-rank test.Results: Compared with ff-IMRT, HT significantly reduced the homogeneity index for thoracic, upper, middle and distal ECs by 38%, 31%, 36% and 33%, respectively (P < 0.05). The conformity index was increased by HT for thoracic, upper and middle ECs by 9%, 9% and 18%, respectively (P < 0.05). Target coverage was improved by 1% with HT (P < 0.05). The mean lung dose was significantly reduced by HT for thoracic and upper ECs (P < 0.05). The V20 (volume receiving at least 20 Gy) and higher dose volumes of the lungs were decreased by HT in all cases, but the differences were significant for thoracic, upper and distal ECs (P < 0.05), with reductions of 2.1%, 3.1% and 2.2%, respectively. HT resulted in a larger lung V5 for thoracic, upper, middle and distal ECs, with increases of 3.5%, 1.5%, 7.2% and 3.2%, respectively. Heart sparing was significantly better with HT than with ff-IMRT in terms of the V30 and V40 for thoracic, upper, middle and distal ECs (P < 0.05).Conclusions: Compared to ff-IMRT, HT provides superior target coverage, conformity and homogeneity, with reduced the volume of high doses to the lungs and heart for advanced EC. HT may be a treatment option for advanced EC, especially upper EC.

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