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Intensity-modulated radiation therapy (IMRT) in the treatment of head-and-neck (H&N) cancer provides the opportunity to diminish normal tissue toxicity profiles and thereby enhance patient quality of life. However, highly conformal treatment techniques commonly establish steep dose gradients between tumor and avoidance structures. Daily setup varia...
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Context 1
... 20 advanced H&N cancer patients were analyzed in the context of this report; 10 treated with conventional 3D treatment planning and 10 treated with IMRT. Basic patient and tumor characteristics are listed in Table 1. The mean absolute setup error in any single dimension for conven- tional 3D treatment averaged 3.33 mm. ...
Citations
... RT requires a high degree of precision; hence reproducibility of daily patient treatment setup is recommended due to the vicinity of head and neck anatomical structures (Hong et al. 2005). In this situation, it is not only possible to reduce the spectrum of toxicities to the adjacent normal critical structures but also to maximize the radiation dose to the target (Burnet et al. 2004, Yeh 2010. ...
This study assessed the efficiency of offline setup correction protocol and the use of a thermoplastic mask for head and neck cancer (HNC) patients treated with three-dimensional conformal radiotherapy at Ocean Road Cancer Institute. A prospective study was conducted from April to August 2021 to verify 62 patients’ treatment setup using an offline setup correction protocol while immobilized with a thermoplastic mask. Megavoltage images were matched with digitally reconstructed radiographs obtained during CT simulation to determine the gross set-up deviations. Box plots were used to show the deviations on three consecutive days of the first week and a successive weekly set-up verification in lateral, longitudinal, and vertical directions. The associations between thermoplastic mask types and weekly deviations were analyzed using repeated test ANOVA. A p-value ˂ 0.05 was considered statistically significant. The observed deviations after the use of correction protocol were lower in all three translational directions. There was no statistical significance between types of thermoplastic mask and setup deviations in lateral (p < 0.65), longitudinal (p = 0.19), and vertical (p = 0.12) directions. The offline correction protocol can be used in settings with limited resources and high workloads of patients. Both types of thermoplastic masks are effective in immobilizing HNC patients.
... They have substantial dosimetric effects on delivered doses to targets and OARs. Previous studies found that interfractional translational and rotational errors significantly alter the delivered dose to target volumes and OARs [22][23][24][25][26][27][28][29][30][31]. Many such studies have employed various methods to mimic the dosimetric impact of setup errors. ...
... Many such studies have employed various methods to mimic the dosimetric impact of setup errors. These methods include dose simulation on planning computed tomography (pCT), cone-beam CT (CBCT), and dose accumulation using deformable image registration of pCT and CBCT [22][23][24][25][26][27][28][29][30][31][32]. Most previous studies simulated and evaluated the dosimetric impact of interfractional setup errors on pCT with weekly or lower imaging frequencies of setup verification [22][23][24][25][26][27][28][29]. ...
... These methods include dose simulation on planning computed tomography (pCT), cone-beam CT (CBCT), and dose accumulation using deformable image registration of pCT and CBCT [22][23][24][25][26][27][28][29][30][31][32]. Most previous studies simulated and evaluated the dosimetric impact of interfractional setup errors on pCT with weekly or lower imaging frequencies of setup verification [22][23][24][25][26][27][28][29]. The dosimetric impact of 6-dimensional (6D) interfractional setup errors in head and neck cancer has been studied in previous studies. ...
Background:
This study aimed to evaluate the dosimetric influence of 6-dimensional (6D) interfractional setup error in tongue cancer treated with intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) using daily kilovoltage cone-beam computed tomography (kV-CBCT).
Materials and methods:
This retrospective study included 20 tongue cancer patients treated with IMRT (10), VMAT (10), and daily kV-CBCT image guidance. Interfraction 6D setup errors along the lateral, longitudinal, vertical, pitch, roll, and yaw axes were evaluated for 600 CBCTs. Structures in the planning CT were deformed to the CBCT using deformable registration. For each fraction, a reference CBCT structure set with no rotation error was created. The treatment plan was recalculated on the CBCTs with the rotation error (RError), translation error (TError), and translation plus rotation error (T+RError). For targets and organs at risk (OARs), the dosimetric impacts of RError, TError, and T+RError were evaluated without and with moderate correction of setup errors.
Results:
The maximum dose variation ΔD (%) for D98% in clinical target volumes (CTV): CTV-60, CTV-54, planning target volumes (PTV): PTV-60, and PTV-54 was -1.2%, -1.9%, -12.0%, and -12.3%, respectively, in the T+RError without setup error correction. The maximum ΔD (%) for D98% in CTV-60, CTV-54, PTV-60, and PTV-54 was -1.0%, -1.7%, -9.2%, and -9.5%, respectively, in the T+RError with moderate setup error correction. The dosimetric impact of interfractional 6D setup errors was statistically significant (p < 0.05) for D98% in CTV-60, CTV-54, PTV-60, and PTV-54.
Conclusions:
The uncorrected interfractional 6D setup errors could significantly impact the delivered dose to targets and OARs in tongue cancer. That emphasized the importance of daily 6D setup error correction in IMRT and VMAT.
... This might have led to the detection of higher average value of setup error in our study. Hong et al. 15 observed that mean absolute set up error in any single direction was 3.33 mm with a population size of ten patients. Daily imaging in first week was done followed by weekly imaging. ...
Reproducibility of daily position is necessary forefficacious delivery of radiotherapy. There are uncertaintiesduring the delivery of radiotherapy which increases the risk ofinadequate dose delivery to the target as well as unnecessaryirradiation of nearby normal tissues. These uncertainties, knownas setup errors, should be clinically in order to attain optimumplanning target volume (PTV) margins. The present study aimsto find out the optimum PTV margins in our department withexisting immobilization system and imaging facilities.
... Beltran et al. have suggested daily setup verification which decreases the PTV margin and minimizes insufficient tumor coverage caused due to setup uncertainties. [16] Similarly, several studies in other organs have demonstrated daily setup variability, for example, Hong [17] In our department, the standard practice was to apply a PTV margin of 0.5 cm over the CTV when the conventional couch was used and errors were corrected in three dimensions, namely, vertical, lateral, and longitudinal. In this study, we retrospectively reviewed and analyzed 630 fractions of radiotherapy delivered in patients with GBM. ...
Objectives
Image-guided radiotherapy maximizes therapeutic index of brain irradiation by reducing setup errors during treatment. The aim of study was to analyze setup errors in the radiation treatment of glioblastoma multiforme and if decrease in planning target volume (PTV), margin is feasible using daily cone beam CT (CBCT) and 6D couch correction.
Materials and Methods
Twenty-one patients (630 fractions of radiotherapy) were studied in which corrections were made in 6° of freedom. We determined setup errors, impact of setup errors of initial three fractions CBCT versus rest of the treatment with daily CBCT, and mean difference in setup errors with or without application of 6D couch and volumetric benefit of reduction of PTV margin from 0.5 cm to 0.3 cm.
Results
The mean shift in the conventional directions, namely, vertical, longitudinal, and lateral was 0.17 cm, 0.19 cm, and 0.11 cm. There was significant change in vertical shift when first three fractions were compared with rest of the treatment with daily CBCT. When the effect of 6D couch was nullified, all directions showed increased error with longitudinal shift being significant. The number of setup errors of magnitude >0.3 cm was more significant when only conventional shifts were applied as compared with 6D couch. There was significant decrease in volume of brain parenchyma irradiated when margin of PTV was reduced from 0.5 cm to 0.3 cm.
Conclusion
Daily CBCT along with 6D couch correction can reduce setup error which allows reduction in PTV margin during radiotherapy planning in turn improving the therapeutic index.
... Over the treatment, the anatomic change derived from a combination of treatment response, weight loss, and radiation effects on normal tissues is inevitable. The changes in internal organs and surface must be non-trivial especially in intensity modulated radiotherapy (IMRT), currently dominant radiation treatment scheme, that try to maximally conform the dose to the target volume, and avoid organ-at-risks (OARs) than the 3D conformal radiotherapy (3D-CRT) [7][8][9]. The notion of on-line and off-line adaptive radiation therapy (ART) [10] was introduced to take preemptive option on the worst case scenario. ...
Deep convolutional neural network (CNN) helped enhance image quality of cone-beam computed tomography (CBCT) by generating synthetic CT. Most of the previous works, however, trained network by intensity-based loss functions, possibly undermining to promote image feature similarity. The verifications were not sufficient to demonstrate clinical applicability, either. This work investigated the effect of variable loss functions combining feature- and intensity-driven losses in synthetic CT generation, followed by strengthening the verification of generated images in both image similarity and dosimetry accuracy. The proposed strategy highlighted the feature-driven quantification in (1) training the network by perceptual loss, besides L1 and structural similarity (SSIM) losses regarding anatomical similarity, and (2) evaluating image similarity by feature mapping ratio (FMR), besides conventional metrics. In addition, the synthetic CT images were assessed in terms of dose calculating accuracy by a commercial Monte-Carlo algorithm. The network was trained with 50 paired CBCT-CT scans acquired at the same CT simulator and treatment unit to constrain environmental factors any other than loss functions. For 10 independent cases, incorporating perceptual loss into L1 and SSIM losses outperformed the other combinations, which enhanced FMR of image similarity by 10%, and the dose calculating accuracy by 1–2% of gamma passing rate in 1%/1mm criterion.
... 3D fast spin-echo (FSE) with variable flip angle, MR imaging allows for reconstruction in multiple planes using voxels acquired isotopically with no gap. The partial volume effect is minimized, resulting in improved spatial resolution and potentially better diagnostic performance [7,8]. Measurement in 3D planes may thus allow for more accurate delineation of cervical MRI staging [9,10]. ...
Objective: The effect of obesity on MRI image quality of the cervical spine is not fully understood. The aim of this study was to examine the image quality for the degenerative diseases of obese patients by using the three-dimensional T2 weighted Turbo Spin Echo (3DT2W TSE) MRI sequence. Patients and Method: Thirty-five patients have been diagnosed with cervical spine degenerative complications. The patients were divided into two groups according to their BMI, the obese and non-obese. The MRI examinations were performed by using 3DT2W TSE sequence which was produced by a 1.5 Tesla Philips scanner MRI device to generate images for the cervical spines (C5-C6, C6-C7). The signal intensities were measured by using the region of interest (ROI) in two tissues being compared. Results: A significant difference was found in the MR image contrast between the obese and non-obese patients (P˂ 0.03) for (C5-C6, C6-C7) and the same result was found specifically with (C6-C7), where (P˂ 0.04). While the other physical measurements were not significantly differed between the two groups. Conclusion: Using of 3DT2W TSE MRI sequence is efficient for the imaging of the cervical spine’s complications of the obese patients.
... Many studies, for this reason, have pointed out that it is not easy to perform accurate patient setups with a thermoplastic mask only. Therefore, it is recommended to use additional monitoring mechanisms such as x-ray-based guidance systems (for example, electronic portal imaging device, kV planar imaging, and/or cone-beam computed tomography) to reduce setup errors (Karger et al., 2001;Hong et al., 2005;Tae-Ho et al., 2012). ...
Purpose: Thermoplastic masks keep patients in an appropriate position to ensure accurate radiation delivery. For a thermoplastic mask to maintain clinical efficacy, the mask should wrap the patient's surface properly and provide uniform pressure to all areas. However, to our best knowledge, no explicit method for achieving such a goal currently exists. Therefore, in this study, we intended to develop a real-time thermoplastic mask compression force (TMCF) monitoring system to measure compression force quantitatively. A prototype system was fabricated, and the feasibility of the proposed method was evaluated.
Methods: The real-time TMCF monitoring system basically consists of four force sensor units, a microcontroller board (Arduino Bluno Mega 2560), a control PC, and an in-house software program. To evaluate the reproducibility of the TMCF monitoring system, both a reproducibility test using a micrometer and a setup reproducibility test using a head phantom were performed. Additionally, the reproducibility tests of mask setup and motion detection tests were carried out with a cohort of six volunteers.
Results: The system provided stable pressure readings in all 10 trials during the sensor unit reproducibility test. The largest standard deviation (SD) among trials was about 36 gf/cm² (∼2.4% of the full-scale range). For five repeated mask setups on the phantom, the compression force variation of the mask was less than 39 gf/cm² (2.6% of the full-scale range). We were successful in making masks together with the monitoring system connected and demonstrated feasible utilization of the system. Compression force variations were observed among the volunteers and according to the location of the sensor (among forehead, both cheekbones, and chin). The TMCF monitoring system provided the information in real time on whether the mask was properly pressing the human subject as an immobilization tool.
Conclusion: With the developed system, it is possible to monitor the effectiveness of the mask in real time by continuously measuring the compression force between the mask and patient during the treatment. The graphical user interface (GUI) of the monitoring system developed provides a warning signal when the compression force of the mask is insufficient. Although the number of volunteers participated in the study was small, the obtained preliminary results suggest that the system could ostensibly improve the setup accuracy of a thermoplastic mask.
... The impact of daily setup variations on head-and-neck IMRT was studied by Hong et al [3]. They demonstrated that daily set up errors could result in significant ''cold spots'' and underdosing 1% of the tumor subvolume by 20% could lead to a loss of 11% in expected tumor control. ...
Introduction Head and neck cancers represent the sixth most common malignancy worldwide. It is the most common malignancy among males in India [1]. Radiotherapy plays an important role in the management of head and neck cancers. It is the standard non surgical treatment modality for locally advanced head and neck cancers. Radiotherapy is also used as adjuvant treatment with or without concurrent chemotherapy, after definitive surgery. Abstract Introduction: 3DCRT and IMRT demands high accuracy in patient positioning and accurate and faithful reproducibility of the treatment position right from the day of acquisition of planning scans and throughout the entire duration of radiation treatment delivery. Inadequacies in the accurate reproduction of the treatment positions during each fraction can lead to setup variations which can significantly compromise the ultimate precision of idealized treatment delivery. Materials and methodology: We retrospectively analysed the daily setup variations in patients with head and neck malignancies who received radical or adjuvant radiotherapy from January 2018 to June 2018. A CTV-PTV margin of 0.5 cm is used at our centre. The average displacement from the reference treatment position in lateral, longitudinal and vertical directions were calculated based on CBCT shifts recorded during the entire course of treatment. Results: 101 patients were included in the study (45.54% radical radiotherapy and 54.45% postoperative radiotherapy). The mean shift in any direction was between 0.13 cm and 0.19 cm in the study population as a whole, in radically treated patients and postoperative patients. The shift in any direction of more than 0.5 cm occurred only once or twice during the entire treatment period per patient, except one postoperative patient. The frequency of shift was more in postoperative patients. The mean shifts in the lateral and longitudinal directions were significantly more for postoperative patients (p 0.008 and 0.014 respectively). Conclusions: The CTV to PTV expansion margin used at our institute is adequate for radically treated patients with head and neck cancers both in definitive and postoperative settings. The smaller mean shifts (<2mm) and low frequency of shifts points to the potential for reducing the current CTV to PTV expansion, which needs to be validated in larger studies.
... This step is done to ensure quality treatment and limit inaccurate dose deposition and thus ensures that the delivered dose matches the planned dose. QA also includes the verification and safety steps taken to ensure reliable and repeatable setup of the patient to guarantee optimal placement of the doses given the importance of setup in treatment accuracy [15]. In conventional RT, adaptive workflows require a new CT sim, plan, and QA at each adaptation point and is thus a resource intensive approach. ...
Simple Summary
Normal tissue toxicities in head and neck cancer persist as a cause of decreased quality of life and are associated with poorer treatment outcomes. The aim of this article is to review organ at risk (OAR) sparing approaches available in MR-guided adaptive radiotherapy and present future developments which hope to improve treatment outcomes. Increasing the spatial conformity of dose distributions in radiotherapy is an important first step in reducing normal tissue toxicities, and MR-guided treatment devices presents a new opportunity to use biological information to drive treatment decisions on a personalized basis.
Abstract
MR-linac devices offer the potential for advancements in radiotherapy (RT) treatment of head and neck cancer (HNC) by using daily MR imaging performed at the time and setup of treatment delivery. This article aims to present a review of current adaptive RT (ART) methods on MR-Linac devices directed towards the sparing of organs at risk (OAR) and a view of future adaptive techniques seeking to improve the therapeutic ratio. This ratio expresses the relationship between the probability of tumor control and the probability of normal tissue damage and is thus an important conceptual metric of success in the sparing of OARs. Increasing spatial conformity of dose distributions to target volume and OARs is an initial step in achieving therapeutic improvements, followed by the use of imaging and clinical biomarkers to inform the clinical decision-making process in an ART paradigm. Pre-clinical and clinical findings support the incorporation of biomarkers into ART protocols and investment into further research to explore imaging biomarkers by taking advantage of the daily MR imaging workflow. A coherent understanding of this road map for RT in HNC is critical for directing future research efforts related to sparing OARs using image-guided radiotherapy (IGRT).
... The impact of daily setup variations on head-and-neck IMRT was studied by Hong et al [3]. They demonstrated that daily set up errors could result in significant ''cold spots'' and underdosing 1% of the tumor subvolume by 20% could lead to a loss of 11% in expected tumor control. ...
Introduction: 3DCRT and IMRT demands high accuracy in patient positioning and accurate and faithful reproducibility of the treatment position right from the day of acquisition of planning scans and throughout the entire duration of radiation treatment delivery. Inadequacies in the accurate reproduction of the treatment positions during each fraction can lead to setup variations which can significantly compromise the ultimate precision of idealized treatment delivery. Materials and methodology: We retrospectively analysed the daily setup variations in patients with head and neck malignancies who received radical or adjuvant radiotherapy from January 2018 to June 2018. A CTV-PTV margin of 0.5 cm is used at our centre. The average displacement from the reference treatment position in lateral, longitudinal and vertical directions were calculated based on CBCT shifts recorded during the entire course of treatment. Results: 101 patients were included in the study (45.54% radical radiotherapy and 54.45% postoperative radiotherapy). The mean shift in any direction was between 0.13 cm and 0.19 cm in the study population as a whole, in radically treated patients and postoperative patients. The shift in any direction of more than 0.5 cm occurred only once or twice during the entire treatment period per patient, except one postoperative patient. The frequency of shift was more in postoperative patients. The mean shifts in the lateral and longitudinal directions were significantly more for postoperative patients (p 0.008 and 0.014 respectively). Conclusions: The CTV to PTV expansion margin used at our institute is adequate for radically treated patients with head and neck cancers both in definitive and postoperative settings. The smaller mean shifts (<2mm) and low frequency of shifts points to the potential for reducing the current CTV to PTV expansion, which needs to be validated in larger studies.
