Method comparison of automated matching software-assisted cone-beam CT and stereoscopic kilovoltage x-ray positional verification image-guided radiation therapy for head and neck cancer: a prospective analysis

Fuller, Clifton D.; Scarbrough, Todd J.; Sonke, Jan‐Jakob; Rasch, Coen R. N.; Choi, Mehee; Wang, Samuel J.; Papanikolaou, Nikos; Rosenthal, David I.

doi:10.1088/0031-9155/54/24/010

Cited by 9 publications

(9 citation statements)

References 82 publications

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“…In HNC treatment, immobilization masks are used to minimize interfractional variation in patient setup and motion during radiation delivery. The amount of error in daily setup in an immobilized patient has been studied previously (33‐35) and CTV‐PTV corrections necessary have been suggested previously using a variety of IGRT devices (7,36) . Interestingly, while studies have been performed to determine the effect that setup error and the movement of a patient as a whole can have on RT accuracy in HNCs, there has been a lack of analysis of the effects of independent TV/OAR/ROI motion, although this data is beginning to emerge (9,21,26,27,29) …”

Section: Discussionmentioning

confidence: 99%

“…However, a significant limitation of most current image‐guided radiation therapy (IGRT) systems is their reliance on a single point reference for corrective setup translations. For example, use of a single isocenter for portal imaging or an index slice or contour for cone‐beam CT data (7) has consequences in the head and neck, where target structures or organs at risk (OARs) are not necessarily fixed to bony landmarks and experience translational motion during delivery of radiation (8‐10) . Consequently, despite excellent setup, TV/OAR displacement from the isocenter may occur in a directionally distinct manner (11) .…”

Section: Introductionmentioning

confidence: 99%

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Estimation of daily interfractional larynx residual setup error after isocentric alignment for head and neck radiotherapy: quality assurance implications for target volume and organs‐at‐risk margination using daily CT on‐rails imaging

Baron

Awan

Mohamed

et al. 2014

J Applied Clin Med Phys

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Larynx may alternatively serve as a target or organ-at-risk (OAR) in head and neck cancer (HNC) image-guided radiotherapy (IGRT). The objective of this study was to estimate IGRT parameters required for larynx positional error independent of isocentric alignment and suggest population–based compensatory margins. Ten HNC patients receiving radiotherapy (RT) with daily CT-on-rails imaging were assessed. Seven landmark points were placed on each daily scan. Taking the most superior anterior point of the C5 vertebra as a reference isocenter for each scan, residual displacement vectors to the other 6 points were calculated post-isocentric alignment. Subsequently, using the first scan as a reference, the magnitude of vector differences for all 6 points for all scans over the course of treatment were calculated. Residual systematic and random error, and the necessary compensatory CTV-to-PTV and OAR-to-PRV margins were calculated, using both observational cohort data and a bootstrap-resampled population estimator. The grand mean displacements for all anatomical points was 5.07mm, with mean systematic error of 1.1mm and mean random setup error of 2.63mm, while bootstrapped POIs grand mean displacement was 5.09mm, with mean systematic error of 1.23mm and mean random setup error of 2.61mm. Required margin for CTV-PTV expansion was 4.6mm for all cohort points, while the bootstrap estimator of the equivalent margin was 4.9mm. The calculated OAR-to-PRV expansion for the observed residual set-up error was 2.7mm, and bootstrap estimated expansion of 2.9mm. We conclude that the interfractional larynx setup error is a significant source of RT set-up/delivery error in HNC both when the larynx is considered as a CTV or OAR. We estimate the need for a uniform expansion of 5mm to compensate for set up error if the larynx is a target or 3mm if the larynx is an OAR when using a non-laryngeal bony isocenter.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Estimation of daily interfractional larynx residual setup error after isocentric alignment for head and neck radiotherapy: quality assurance implications for target volume and organs‐at‐risk margination using daily CT on‐rails imaging

Baron

Awan

Mohamed

et al. 2014

J Applied Clin Med Phys

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“…A previously presented dataset consisting of a series of 100 paired measures using two distinct positional verification techniques in a series of 28 sequential head and neck squamous cell carcinoma patients was utilized. As this manuscript is designed to specify a novel statistical methodology, interested readers are referred to the previous manuscript [ 50 ], wherein imaging parameters have been previously detailed. Briefly, CBCT and stereoscopic kV X-ray were acquired near-simultaneously at approximately biweekly intervals throughout a patient’s course of treatment (dependent upon the scheduling exigencies in the department) for a series of patients with head and neck cancers.…”

Section: Methodsmentioning

confidence: 99%

Comparison of measurement methods with a mixed effects procedure accounting for replicated evaluations (COM3PARE): method comparison algorithm implementation for head and neck IGRT positional verification

et al. 2015

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PurposeComparison of imaging measurement devices in the absence of a gold-standard comparator remains a vexing problem; especially in scenarios where multiple, non-paired, replicated measurements occur, as in image-guided radiotherapy (IGRT). As the number of commercially available IGRT presents a challenge to determine whether different IGRT methods may be used interchangeably, an unmet need conceptually parsimonious and statistically robust method to evaluate the agreement between two methods with replicated observations. Consequently, we sought to determine, using an previously reported head and neck positional verification dataset, the feasibility and utility of a Comparison of Measurement Methods with the Mixed Effects Procedure Accounting for Replicated Evaluations (COM3PARE), a unified conceptual schema and analytic algorithm based upon Roy’s linear mixed effects (LME) model with Kronecker product covariance structure in a doubly multivariate set-up, for IGRT method comparison.MethodsAn anonymized dataset consisting of 100 paired coordinate (X/ measurements from a sequential series of head and neck cancer patients imaged near-simultaneously with cone beam CT (CBCT) and kilovoltage X-ray (KVX) imaging was used for model implementation. Software-suggested CBCT and KVX shifts for the lateral (X), vertical (Y) and longitudinal (Z) dimensions were evaluated for bias, inter-method (between-subject variation), intra-method (within-subject variation), and overall agreement using with a script implementing COM3PARE with the MIXED procedure of the statistical software package SAS (SAS Institute, Cary, NC, USA).ResultsCOM3PARE showed statistically significant bias agreement and difference in inter-method between CBCT and KVX was observed in the Z-axis (both p − value<0.01). Intra-method and overall agreement differences were noted as statistically significant for both the X- and Z-axes (all p − value<0.01). Using pre-specified criteria, based on intra-method agreement, CBCT was deemed preferable for X-axis positional verification, with KVX preferred for superoinferior alignment.ConclusionsThe COM3PARE methodology was validated as feasible and useful in this pilot head and neck cancer positional verification dataset. COM3PARE represents a flexible and robust standardized analytic methodology for IGRT comparison. The implemented SAS script is included to encourage other groups to implement COM3PARE in other anatomic sites or IGRT platforms.

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“…Nonetheless, despite widespread implementation [3], quality assurance/quality improvement assessments of image-guidance systems may often be overlooked [4]. As distinct IGRT systems may provide distinct data distributions with regard to setup error [5], aggressive efforts at optimizing not only image acquisitions, but also optimizing human performance in radiotherapy tasks is a critical consideration [6]. …”

Section: Introductionmentioning

confidence: 99%

Improved human observer performance in digital reconstructed radiograph verification in head and neck cancer radiotherapy

et al. 2014

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Purpose Digitally reconstructed radiographs (DRRs) are routinely used as an a priori reference for setup correction in radiotherapy. The spatial resolution of DRRs may be improved to reduce setup error in fractionated radiotherapy treatment protocols. The influence of finer CT slice thickness reconstruction (STR) and resultant increased resolution DRRs on physician setup accuracy was prospectively evaluated. Methods Four head and neck patient CT-simulation images were acquired and used to create DRR cohorts by varying STRs at 0.5, 1, 2, 2.5, and 3 mm. DRRs were displaced relative to a fixed isocenter using 0–5 mm random shifts in the three cardinal axes. Physician observers reviewed DRRs of varying STRs and displacements and then aligned reference and test DRRs replicating daily KV imaging workflow. A total of 1,064 images were reviewed by four blinded physicians. Observer errors were analyzed using nonparametric statistics (Friedman’s test) to determine whether STR cohorts had detectably different displacement profiles. Post hoc bootstrap resampling was applied to evaluate potential generalizability. Results The observer-based trial revealed a statistically significant difference between cohort means for observer displacement vector error (p = 0.02) and for Z-axis (p < 0.01). Bootstrap analysis suggests a 15% gain in isocenter translational setup error with reduction of STR from 3 mm to ≤2 mm, though interobserver variance was a larger feature than STR-associated measurement variance. Conclusions Higher resolution DRRs generated using finer CT scan STR resulted in improved observer performance at shift detection and could decrease operator-dependent geometric error. Ideally, CT STRs ≤2 mm should be utilized for DRR generation in the head and break neck.

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Method comparison of automated matching software-assisted cone-beam CT and stereoscopic kilovoltage x-ray positional verification image-guided radiation therapy for head and neck cancer: a prospective analysis

Cited by 9 publications

References 82 publications

Estimation of daily interfractional larynx residual setup error after isocentric alignment for head and neck radiotherapy: quality assurance implications for target volume and organs‐at‐risk margination using daily CT on‐rails imaging

Estimation of daily interfractional larynx residual setup error after isocentric alignment for head and neck radiotherapy: quality assurance implications for target volume and organs‐at‐risk margination using daily CT on‐rails imaging

Comparison of measurement methods with a mixed effects procedure accounting for replicated evaluations (COM3PARE): method comparison algorithm implementation for head and neck IGRT positional verification

Improved human observer performance in digital reconstructed radiograph verification in head and neck cancer radiotherapy

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