Interfacility variation in treatment planning parameters in tomotherapy: field width, pitch, and modulation factor

Shimizu, Hidetoshi; Sasaki, Koji; Kubôta, Takashi; Fukuma, Hiroshi; Aoyama, Tomoo; Iwata, Tohru; Tachibana, Hideki; Kodaira, Takeshi

doi:10.1093/jrr/rry042

Cited by 7 publications

(5 citation statements)

References 17 publications

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“…Nevertheless, this MF is reasonable and lower than that recommended in a previous study [33]. In contrast, when the DTF was within the range of 1.2-1.3 and 1.5-1.6 for head and neck and lung cases, respectively, the MF reached 3.0, which is recognized as a much higher value for head and neck plans [34]. A higher MF leads to greater plan complexity in tomotherapy, potentially leading to unacceptable dose delivery [22,23].…”

Section: Discussioncontrasting

confidence: 69%

Impact of delivery time factor on treatment time and plan quality in tomotherapy

Yagihashi

Inoue

Shiba

et al. 2023

Preprint

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Background The delivery time factor (DTF) is a new parameter introduced by the RayStation treatment planning system for tomotherapy treatment planning. This study investigated the effects of this factor on various tomotherapy plans. Methods Overall, 25 patients with cancer (head and neck, 6; lung, 9; prostate, 10) were enrolled in this study. For these patients, helical tomotherapy plans with a field width of 2.5 cm, pitch of 0.287, and DTF of 2.0 were created. All the initial plans were recalculated by changing the DTF parameter from 1.0 to 3.0 in increments of 0.1 (21 plans per patient). For each plan, we calculated the following evaluation indices: the treatment time, modulation factor, conformity index (CI), homogeneity index (HI), and doses to critical organs at risk (OARs). For every index, the values normalized by the corresponding values with a DTF of 1.0 were plotted, and fitted curves with polynomial functions were created as a function of the DTF. These curves were used to evaluate the impact of the DTF on both delivery efficiency and plan quality. Results Treatment time and modulation factor increased monotonically with increasing DTF. Increasing the DTF by 0.1 resulted in an increase in the treatment time and modulation factor by almost 10%. This relationship was similar for all treatment sites. An increase in DTF was found to improve CI, HI, and OAR doses compared to plans with a DTF of 1.0, except for the CI in the lung cancer case. However, the improvement in most indices ceased at a certain DTF; nevertheless, treatment time continued to increase in accordance with an increase in DTF. Conclusions DTF is a critical parameter for improving the quality of tomotherapy plans; however, increase of this factor above a certain level leads to an unnecessary increase in treatment time and deterioration of plan quality. Trial registration: None.

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Section: Discussioncontrasting

confidence: 69%

Impact of delivery time factor on treatment time and plan quality in tomotherapy

Yagihashi

Inoue

Shiba

et al. 2023

Preprint

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“…This relationship has the potential to improve sparing of important anatomical structures. In clinical practice, the MF is known to show marked variation between institutions, 23 but in numerous previous reports, the MF in relation to HS-WBRT was taken to be 3.0, 7,8,13 because the results of the RTOG0933 study were based on a jaw width of 1 cm and an MF of 3.0. 24 In the present study, the dose parameters showed no statistically significant changes with MF reduction from 3.0 to 2.2.…”

Section: Discussionmentioning

confidence: 99%

Influence of Modulation Factor on Treatment Plan Quality and Irradiation Time in Hippocampus-Sparing Whole-Brain Radiotherapy Using Tomotherapy

Ishibashi

Kurosaki

Miura

et al. 2021

Technol Cancer Res Treat

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Objectives: Hippocampus-sparing whole-brain radiotherapy (HS-WBRT) using tomotherapy is known to provide a better dose distribution than volumetric-modulated arc therapy but requires an extended irradiation time. The present study aimed to investigate whether irradiation time can be shortened by reducing the modulation factor (MF) without losing the target dose distribution. Methods: Using six tilted computed tomography images in the head area, the planning target volume (PTV) and hippocampal doses, and the irradiation time was investigated with a jaw width of 1 cm, a pitch of 0.200, and the MF changed from 3.0 to 2.6, 2.2, 1.8, and 1.4. Results: No significant changes in the PTV or hippocampus were found with MF in the range from 3.0 to 1.8, but marked deterioration was found with that of 1.4. The irradiation time showed a linear relationship with the MF within the range from 3.0 to 1.8, with 1334, 1158, 986, and 817 s at modulation factors of 3.0, 2.6, 2.2, and 1.8, respectively. However, when the MF was 1.4, the irradiation time was 808 s. Conclusions: When HS-WBRT is performed with a tilted body position and a jaw width of 1 cm, with a MF of 1.8, a favorable balance between dose parameters and irradiation time is achieved, whereas with a MF of 1.4, the quality of the radiotherapy plan deteriorates, and the irradiation time is approximately the same as that with a MF of 1.8.

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“…The dose to the region of interest (ROI) is presented in Table 1 (Figure 2 , 3 ). Regarding the treatment plan parameters, a dynamic field width of 5 cm, pitch of 0.25, and a modulator factor (MF) of 2.0 were used [ 5 ]. A 3D conformal plan was also developed in order to reduce the treatment time, but dosimetric goals could not be achieved.…”

Section: Case Presentationmentioning

confidence: 99%

Fractionated Total Body Irradiation on an Infant Using Tomotherapy

Abraham¹,

Romaguera²,

Tolakanahalli³

et al. 2022

Cureus

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Total body irradiation (TBI) is used with chemotherapy to induce immunosuppression for hematopoietic cell transplantation and is often administered using lead blocks to minimize lung dose in adults and children. This technique is challenging in infants and young children. A 13-month-old female with acute lymphoblastic leukemia (ALL) was treated with fractionated TBI to a dose of 12 Gy in eight fractions delivered twice daily. Multiple TBI techniques for delivering treatment were considered. Ultimately, treatment using helical tomotherapy was selected in order to spare and accurately quantify the dose to the lung, meet lung dose constraints, and ensure adequate TBI dose coverage. With anesthesia, this technique provided a comfortable and reproducible set-up for the young child. The treatment plan was delivered with intensity-modulated radiotherapy, where 96.4% of the target volume received a prescription dose with a total beam-on time of 16.8 minutes. The mean lung dose was 7.7 Gy for a total lung volume of 245cc. This report describes the challenges faced during the treatment planning and delivery, and how they were resolved.

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Interfacility variation in treatment planning parameters in tomotherapy: field width, pitch, and modulation factor

Cited by 7 publications

References 17 publications

Impact of delivery time factor on treatment time and plan quality in tomotherapy

Impact of delivery time factor on treatment time and plan quality in tomotherapy

Influence of Modulation Factor on Treatment Plan Quality and Irradiation Time in Hippocampus-Sparing Whole-Brain Radiotherapy Using Tomotherapy

Fractionated Total Body Irradiation on an Infant Using Tomotherapy

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