Influence of daily imaging on plan quality and normal tissue toxicity for prostate cancer radiotherapy

Bell, Katharina; Heitfeld, Marina; Licht, Norbert; Rübe, Christian; Dzierma, Yvonne

doi:10.1186/s13014-016-0757-9

Cited by 19 publications

(9 citation statements)

References 30 publications

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“…Such a trade-off would be interesting to perform, but remains outside the scope of this study as a number of combinations (margin vs. imaging scenario) would need to be compared. Similar approaches have been presented for other treatment sites [ 11 , 27 ]. As a rule-of-thumb, dose from kV imaging is relatively small and it might be expected that the positive influence of dose sparing from margin reduction would be dominant in this scenario.…”

Section: Discussionmentioning

confidence: 88%

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Imaging dose and secondary cancer risk in image-guided radiotherapy of pediatric patients

et al. 2018

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BackgroundDaily image-guided radiotherapy (IGRT) can contribute to cover extended body volumes with low radiation dose. The effect of additional imaging dose on secondary cancer development is modelled for a collective of children with Morbus Hodgkin.MethodsEleven radiotherapy treatment plans from pediatric patients with Hodgkin’s lymphoma were retrospectively analyzed, including imaging dose from scenarios using different energies (kV/MV) and planar/cone-beam computed tomography (CBCT) techniques. In addition to assessing the effect of imaging dose on organs at risk, the excess average risk (EAR) for developing a secondary carcinoma of the lung or breast was modelled.ResultsAlthough the variability between the patients is relatively large due to the different target volumes, the additional EAR due to imaging can be consistently determined. For daily 6MV CBCT, the EAR for developing a secondary cancer at age 50 is over 3 cases per 104 PY (patient-years) for the female breast and 0.7–0.8 per 104 PY for the lungs. This can be decreased by using only planar images (< 1 per 104 PY for the breast and 0.1 for the lungs). Similar values are achieved by daily 360° kV CBCT (0.44–0.57 per 104 PY for the breast and 0.08 per 104 PY for the lungs), which is again reduced for daily 200° kV CBCT (0.02 per 104 PY for the lungs and 0.07–0.08 per 104 PY for the breast). These values increase if an older attained age is considered (e.g., for 70 years, by a factor of four for the lungs).ConclusionsDaily imaging can be performed with an additional secondary cancer risk of less than 1 per 104 PY if kV CBCT is applied. If MV modalities must be chosen, a similar EAR can be achieved with planar images. A further reduction in risk is possible if the imaging geometry allows for sparing of the breast by a partial rotation underneath the patient.

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Section: Discussionmentioning

confidence: 88%

“…Dose calculation of the summation plans was carried out in the Philips Pinnacle TPS Version 9.0–9.6 on a 2 mm dose grid using the collapsed cone algorithm (for a detailed explanation of the procedure, compare [ 11 ]). Dose-volume histogram (DVH) values are considered to assess dose to the organs at risk (OARs).…”

Section: Methodsmentioning

confidence: 99%

Imaging dose and secondary cancer risk in image-guided radiotherapy of pediatric patients

et al. 2018

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“…Afterwards kilovoltage (kV) cone beam CT (CBCT) is performed to match anterior rectal wall and ERB to the planning CT. Using daily CBCT for patient positioning is a widely understood method for ART procedures [2,3,[18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Adaptive radiotherapy and the dosimetric impact of inter- and intrafractional motion on the planning target volume for prostate cancer patients

et al. 2020

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Purpose To investigate the dosimetric influence of daily interfractional (inter) setup errors and intrafractional (intra) target motion on the planning target volume (PTV) and the possibility of an offline adaptive radiotherapy (ART) method to correct larger patient positioning uncertainties in image-guided radiotherapy for prostate cancer (PCa). Materials and methods A CTV (clinical target volume)-to-PTV margin ranging from 15 mm in LR (left-right) and SI (superior-inferior) and 5-10 mm in AP (anterior-posterior) direction was applied to all patients. The dosimetric influence of this margin was retrospectively calculated by analysing systematic and random components of inter and intra errors of 31 consecutive intermediate-and high-risk localized PCa patients using daily cone beam computed tomography and kV/kV (kilo-Voltage) imaging. For each patient inter variation was assessed by observing the first 4 treatment days, which led to an offline ART-based treatment plan in case of larger variations. Results: Systematic inter uncertainties were larger (1.12 in LR, 2.28 in SI and 1.48 mm in AP) than intra systematic errors (0.44 in LR, 0.69 in SI and 0.80 mm in AP). Same findings for the random error in SI direction with 3.19 (inter) and 2.30 mm (intra), whereas in LR and AP results were alike with 1.89 (inter) and 1.91 mm (intra) and 2.10 (inter) and 2.27 mm (intra), respectively. The calculated margin revealed dimensions of 4-5 mm in LR, 8-9 mm in SI and 6-7 mm in AP direction. Treatment plans which had to be adapted showed smaller variations with 1.12 (LR) and 1.72 mm (SI) for Σ and 4.17 (LR) and 3.75 mm (SI) for σ compared to initial plans with 1.77 and 2.62 mm for Σ and 4.46 and 5.39 mm for σ in LR and SI, respectively. Conclusion The currently clinically used margin of 15 mm in LR and SI and 5-10 mm in AP direction includes inter and intra uncertainties. The results show that offline ART is feasible which becomes a necessity with further reductions in PTV margins.

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“…Moreover, most studies regarding imaging dose primarily concentrate on the dose by itself [ 6 – 13 ], only few have the focus on the clinical consequences for plan quality [ 14 – 18 ]. There is one study to evaluate systematically the influence of different imaging scenarios on plan quality, however, this study deals with prostate treatment [ 19 ]. The effect of dose smearing is also sparsely examined by now, most studies on this topic rely on rather theoretical models of the average positioning errors and the resulting dose volume histogram [ 1 , 3 , 20 – 23 ].…”

Section: Introductionmentioning

confidence: 99%

Image guidance and positioning accuracy in clinical practice: influence of positioning errors and imaging dose on the real dose distribution for head and neck cancer treatment

et al. 2018

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BackgroundModern radiotherapy offers the possibility of highly accurate tumor treatment. To benefit from this precision at its best, regular positioning verification is necessary. By the use of image-guided radiotherapy and the application of safety margins the influence of positioning inaccuracies can be counteracted. In this study the effect of additional imaging dose by set-up verification is compared with the effect of dose smearing by positioning inaccuracies for a collective of head-and-neck cancer patients.MethodsThis study is based on treatment plans of 40 head-and-neck cancer patients. To evaluate the imaging dose several image guidance scenarios with different energies, techniques and frequencies were simulated and added to the original plan. The influence of the positioning inaccuracies was assessed by the use of real applied table shifts for positioning. The isocenters were shifted back appropriately to these values to simulate that no positioning correction had been performed. For the single fractions the shifted plans were summed considering three different scenarios: The summation of only shifted plans, the consideration of the original plan for the fractions with set-up verification, and the addition of the extra imaging dose to the latter. For both effects (additional imaging dose and dose smearing), plans were analyzed and compared considering target coverage, sparing of organs at risk (OAR) and normal tissue complication probability (NTCP).ResultsDaily verification of the patient positioning using 3D imaging with MV energies result in non-negligible high doses. kV imaging has only marginal influence on plan quality, primarily related to sparing of organs at risk, even with daily 3D imaging. For this collective, sparing of organs at risk and NTCP are worse due to potential positioning errors.ConclusionRegular set-up verification is essential for precise radiation treatment. Relating to the additional dose, the use of kV modalities is uncritical for any frequency and technique. Dose smearing due to positioning errors for this collective mainly resulted in a decrease of OAR sparing. Target coverage also suffered from the positioning inaccuracies, especially for individual patients. Taking into account both examined effects the relevance of an extensive IGRT is clearly present, even at the expense of additional imaging dose and time expenditure.

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Influence of daily imaging on plan quality and normal tissue toxicity for prostate cancer radiotherapy

Cited by 19 publications

References 30 publications

Imaging dose and secondary cancer risk in image-guided radiotherapy of pediatric patients

Imaging dose and secondary cancer risk in image-guided radiotherapy of pediatric patients

Adaptive radiotherapy and the dosimetric impact of inter- and intrafractional motion on the planning target volume for prostate cancer patients

Image guidance and positioning accuracy in clinical practice: influence of positioning errors and imaging dose on the real dose distribution for head and neck cancer treatment

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