A randomized controlled trial comparing customized versus standard headrests for head and neck radiotherapy immobilization in terms of set-up errors, patient comfort and staff satisfaction (ICORG 08-09)

Development of Magnetic Resonance-Compatible Head Immobilization Device and Initial Experience of Magnetic Resonance-Guided Radiation Therapy for Central Nervous System Tumors

PURPOSE

We aimed to develop and investigate positional reproducibility using a fixation device (Unity Brain tumor Immobilization Device [UBID]) in patients with brain tumor undergoing magnetic resonance (MR)-guided radiation therapy (RT) with a 1.5 Tesla (T) MR-linear accelerator (MR-LINAC) to evaluate its feasibility in clinical practice and report representative cases of patients with central nervous system (CNS) tumor.

MATERIALS AND METHODS

Quantitative analysis was performed by comparing images obtained by placing only the MR phantom on the couch with those obtained by placing UBID next to the MR phantom. Twenty patients who underwent RT for CNS tumors using 1.5T MR-LINAC between June and October 2022 were retrospectively analyzed. Among them, 5 did not use UBID, whereas 15 used UBID. The positional reproducibility of UBID was evaluated using the median interfractional and intrafractional errors in the first 10 fractions.

RESULTS

Each MR quality factor of the MR phantom with UBID satisfied the criteria presented by Elekta. Median values of median shifts in the mediolateral, anteroposterior, and craniocaudal axes for interfractional errors were 2.98, 2.35, and 1.40 mm, respectively. For intrafractional errors, the median values were 0.05, 0.03, and 0.06 mm, respectively. The median values of the median rotations in pitch, roll, and yaw for both interfractional and intrafractional rotations were 0.00°. One patient diagnosed with an optic nerve sheath meningioma received RT with motion monitoring during irradiation. In 2 patients, changes in the tumor cavity and residual lesions were observed in the MRI obtained using 1.5T MR-LINAC on the day of the first treatment and immediately before the 21st fraction, respectively; therefore, offline/online adaptation was performed.

CONCLUSIONS

The reproducible and immobile UBID is clinically feasible in patients with CNS tumors receiving RT with 1.5T MR-LINAC. Based on our initial experience, we developed a workflow for 1.5T MR-LINAC treatment of CNS tumors.

A retrospective analysis comparing set up errors from standard versus customised headrests for head and neck radiotherapy

INTRODUCTION

In response to advice from The National Institute for Health and Care Excellence ⁽¹⁾ to reduce hospital visits during COVID-19, standard headrests were introduced for head and neck radiotherapy within Northern Centre for Cancer Care (NCCC). The standard headrest requires one mould room appointment compared to 3 appointments with customised headrests.

METHODS

Two groups of 10 patients treated between December 2019 and June 2020 were retrospectively analysed by 1 observer. Groups were stratified according to age, sex and tumour site. One group had customised headrest and the other had standard headrest. Five hundred and forty seven cone beam computed tomography images were reviewed. A 6 Degree of Freedom match was performed then chin, shoulder and spine position were assessed using dosimetrist drawn structures. Structures out of the tolerance were recorded. A chi-squared test was used for statistical analysis.

RESULTS

The out of tolerance chin position count recorded was 21 for customised headrest and 36 for standard headrest, p-value 0.046. The shoulder position count was 13 for customised headrest and 77 for standard headrest p-value <0.001. The spine position count was 3 for CHR and 21 for standard headrest, p-value <0.001. This means the headrests compared are not equivalent in terms of set up reproducibility. Overall the standard headrest group had 10 set-up re-scans and no set up re-scans were recorded in the customised headrest group.

CONCLUSION

Fewer hospital visits with SHR reduce patient exposure to COVID-19. However, CHR provided a more reliable level of immobilisation in this study.

IMPLICATIONS FOR PRACTICE

The radiotherapy service will be reviewed in line with these findings.

Initial Feasibility and Clinical Implementation of Daily MR-Guided Adaptive Head and Neck Cancer Radiation Therapy on a 1.5T MR-Linac System: Prospective R-IDEAL 2a/2b Systematic Clinical Evaluation of Technical Innovation

PURPOSE

This prospective study is, to our knowledge, the first report of daily adaptive radiation therapy (ART) for head and neck cancer (HNC) using a 1.5T magnetic resonance imaging-linear accelerator (MR-linac) with particular focus on safety and feasibility and dosimetric results of an online rigid registration-based adapt to position (ATP) workflow.

METHODS AND MATERIALS

Ten patients with HNC received daily ART on a 1.5T/7MV MR-linac, 6 using ATP only and 4 using ATP with 1 offline adapt-to-shape replan. Setup variability with custom immobilization masks was assessed by calculating the mean systematic error (M), standard deviation of the systematic error (Σ), and standard deviation of the random error (σ) of the isocenter shifts. Quality assurance was performed with a cylindrical diode array using 3%/3 mm γ criteria. Adaptive treatment plans were summed for each patient to compare the delivered dose with the planned dose from the reference plan. The impact of dosimetric variability between adaptive fractions on the summation plan doses was assessed by tracking the number of optimization constraint violations at each individual fraction.

RESULTS

The random errors (mm) for the x, y, and z isocenter shifts, respectively, were M = -0.3, 0.7, 0.1; Σ = 3.3, 2.6, 1.4; and σ = 1.7, 2.9, 1.0. The median (range) γ pass rate was 99.9% (90.9%-100%). The differences between the reference and summation plan doses were -0.61% to 1.78% for the clinical target volume and -11.74% to 8.11% for organs at risk (OARs), although an increase greater than 2% in OAR dose only occurred in 3 cases, each for a single OAR. All cases had at least 2 fractions with 1 or more constraint violations. However, in nearly all instances, constraints were still met in the summation plan despite multiple single-fraction violations.

CONCLUSIONS

Daily ART on a 1.5T MR-linac using an online ATP workflow is safe and clinically feasible for HNC and results in delivered doses consistent with planned doses.

Assessment of set-up errors in the radiotherapy of patients with head and neck cancer: standard vs. individual head support

Background

The aim of the study was to (a) compare the accuracy of two different immobilization strategies for patients with head and neck tumors, and (b) compare the set-up errors on treatment units with different portal imaging systems.

Patients and methods

Variations in the position of the isocenter (IC) relative to the reference point determined on the computed tomography simulator were measured in a vertical (anterior-posterior), longitudinal (superior-inferior), and lateral (medial-lateral) direction in 120 head and neck cancer patients irradiated with curative intent. Depending on the treatment unit (unit A - 2D/2D image previews; unit B- 2D image previews) and the time of irradiation, patients were divided into 6 groups of 20 patients. In patients irradiated in 2014, standard head supports were used (groups 1 and 2), whereas in those treated in 2015 and 2017 (groups 3–6) individual head supports were employed. The clinical-to-planning target volume safety margin was calculated according to the formula proposed by Van Herk.

Results

In total, 2,454 portal images and 3,681 set-up errors were analysed. Implementation of individual head supports in 2015 resulted in a statistically significant reduction in the average inter-fraction displacement in the vertical direction and in decreased number of IC displacements in the vertical and longitudinal direction (applies to both treatment units). The largest reduction of the safety margin was calculated in the longitudinal direction and the safety margins were larger for unit B than for unit A.

Conclusions

The use of individual head supports and a more advanced imaging system were found to increase set-up precision.

A comparative study between open-face and closed-face masks for head and neck cancer (HNC) in radiation therapy

Aim

To determine the setup reproducibility in the radiation treatment of Head and Neck (HN) patients using open face head and shoulder masks (OHSM) with customized headrest (CHR) versus standard closed head and shoulder masks (CHSM) and to determine the patient's level of comfort and satisfaction for both masks.

Methods

Forty patients were prospectively randomized into two groups using simple random sampling. Group 1 was assigned with CHSMs, immobilized with a standard HR (SHR) while Group 2 was assigned with OHSMs, and immobilized with CHR. Cone beam computed tomography (CBCT) was taken the first 3 days, followed by weekly CBCT (prior treatment) with results registered to the planning CT to determine translational and rotational inter-fraction shifts and to verify accuracy. Mean (M) and standard deviation (SD) of the systematic and random setup errors of the 2 arms in the translational and rotational directions were analyzed, using Independent t-test and Mann-Whitney U test. Patient comfort was measured using a Likert questionnaire.

Results

The vertical, lateral, longitudinal and Z/roll rotational shifts were not significantly different between the two masks. X/yaw and Y/pitch rotational shifts were significantly greater in Group 2 versus Group 1, for both systematic (p = 0.009 and 0.046, respectively) and random settings (p = 0.016 and 0.020) but still within three degrees. Patients reported higher neck and shoulder comfort (p = 0.020) and overall satisfaction (p = 0.026) using the OHSM with the CHR versus the CHSM with the SHR during CT simulation.

Conclusion

Open masks provide comparable yet comfortable immobilization to closed masks for HN radiotherapy.

The influence of a six degrees of freedom couch and an individual head support in patient positioning in radiotherapy of head and neck cancer

Reproducible patient positioning is important in radiotherapy (RT) of head-and-neck cancer. We therefore compared set-up errors in head-and-neck RT resulting from three different patient positioning systems. Patients were either treated with a standard head support (SHS) and conventional treatment couch (SHS-3, n = 10), a SHS and rotational couch (SHS-6, n = 10), or an individual head support (IHS) and rotational couch (IHS-6, n = 10). Interfraction mean translation vector lenghts were significantly lower for IHS-6 compared to SHS-3 (0.8 ± 0.3 mm vs. 1.4 ± 0.7 mm, P = 0.001). Intrafraction displacement was comparable among cohorts. This study showed that the use of a six degrees of freedom couch combined with an IHS in head-and-neck RT resulted in better interfraction reproducibility.

A comparison of interfraction setup error, patient comfort, and therapist acceptance for 2 different prostate radiation therapy immobilization devices

PURPOSE

Our purpose was to investigate interfraction setup error of the immobilization device required to implement transperineal ultrasound compared with the current, standard immobilization device. Patient comfort and radiation therapist (RT) satisfaction were also assessed.

METHODS AND MATERIALS

Cone beam computed tomography images were acquired before 4069 fractions from 111 patients (control group, n = 56; intervention group, n = 55) were analyzed. The intervention group was immobilized using the Clarity Immobilization System (CIS), comprising a knee rest with autoscan probe kit and transperineal ultrasound probe (n = 55), and control group using a leg immobilizer (LI) (n = 56). Interfraction setup errors were compared for both groups. Weekly questionnaires using a 10-point visual analog scale were administered to both patient groups to measure and compare patient comfort. RT acceptance for both devices was also compared using a survey.

RESULTS

There was no significant difference in the magnitude of interfraction cone beam computed tomography-derived setup shifts in the lateral and anteroposterior direction between the LI and CIS (P = .878 and .690, respectively). However, a significant difference (P = .003) was observed in the superoinferior direction between the 2 groups of patients. Patient-reported level of comfort and stability demonstrated no significant difference between groups (P = .994 and .132). RT user acceptance measures for the LI and CIS were ease of handling (100% vs 53.7%), storage (100% vs 61.1%), and cleaning of the devices (100% vs 64.8%), respectively.

CONCLUSIONS

The CIS demonstrated stability and reproducibility in prostate treatment setup comparable to LI. The CIS device had no impact on patient comfort; however, RTs indicated a preference for LI over the CIS mainly because of its weight and bulkiness.

Positioning reproducibility with and without rotational corrections for 2 head and neck immobilization systems

PURPOSE

The purpose of this study was to evaluate the impact of offline rotational corrections and assess intrafraction motion for head and neck (H&N) cancer patients immobilized with and without a custom neck cushion.

METHODS AND MATERIALS

Fifty H&N cancer patients were immobilized and imaged with pretreatment and posttreatment cone beam computed tomography (CBCT) for each treatment fraction. Of these patients, 25 had a custom neck cushion added to their immobilization. Each CBCT was registered to the simulation computed tomography offline. Registrations were performed with automatching tools and a matching volume of interest that consisted of a 5-mm expansion around the mandible, occipital bone, C1/C2, and C7/T1. To determine positioning accuracy, the registration was inspected to confirm these bony anatomy structures were contained within a 3- or 5-mm expansion of the simulation position. If not, the registration was repeated with rotational corrections included and re-evaluated. For each fraction, intrafraction motion was also quantified through the difference between the pretreatment and posttreatment CBCT registration coordinates.

RESULTS

For translational registrations, the bony anatomy in pretreatment imaging was outside the 3-mm or 5-mm expansion structure, respectively, for 49% and 15% of fractions on average for patients without a custom headrest and for 48% and 13% of fractions on average for patients with a custom headrest. The addition of rotational corrections reduced these numbers to 21% and 4% and to 28% and 6%, respectively. Intrafraction motion was significantly lower for patients immobilized with the addition of a custom neck cushion: 1.0 ± 0.5 mm compared with 1.8 ± 1.6 mm for patients with the standard headrest only (P = .02). This was reflected in posttreatment positioning accuracy, which was significantly reduced in the case of the standard headrest compared with pretreatment imaging (P values of < .001 to .048).

CONCLUSIONS

Rotational corrections significantly improved pretreatment patient positioning accuracy (P < .001). Intrafraction motion was reduced significantly through the addition of a custom neck cushion and resulted in an increase in posttreatment positioning accuracy for these patients.