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Image guidance protocols: balancing imaging parameters against scan time.

ABSTRACT: Optimisation of imaging protocols is essential to maximise the use of image-guided radiotherapy. This article evaluates the time for daily online imaging with TomoTherapy® (Accuray®, Sunnyvale, CA), separating mechanical scan acquisition from radiographer-led image matching, to estimate the time required for a clinical research study (VoxTox).Over 5 years, 18 533 treatments were recorded for 3 tumour sites of interest (prostate, head and neck and central nervous system). Data were collected for scan length, number of CT slices, slice thickness, scan acquisition time and image matching time.The proportion of coarse thickness scans increased over time, with a move of making coarse scans as the default. There was a strong correlation between scan time and scan length. Scan acquisition requires 40 s of processing time. For coarse scans, each additional centimetre requires 8 s for acquisition. Image matching takes approximately 1.5 times as long, so each additional centimetre needs 20 s extra in total. Modest changes to the imaging protocol have minimal impact over the course of the day.This work quantified the effect of changes to clinical protocols required for research. The results have been found to be reassuring in the busy National Institutes of Health department.This novel method of data collection and analysis provides evidence of the minimal impact of research on clinical turnover. Whilst the data relate specifically to TomoTherapy, some aspects may apply to other platforms in the future.

SUBMITTER: Bates AM

PROVIDER: S-EPMC3854571 | biostudies-other | 2013 Dec

REPOSITORIES: biostudies-other

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Project description:PurposeIn this paper we compared two different 3D ultrasound (US) modes (3D free-hand mode and 3D wobbler mode) to see which is more suitable to perform the 3D-US/3D-US registration for clinical guidance applications. The typical errors with respect to their impact on the final localization error were evaluated step by step.MethodsMulti-point target and Hand-eye calibration methods were used for 3D US calibration together with a newly designed multi-cone phantom. Pointer based and image based methods were used for 2D US calibration. The calibration target error was computed by using a different multi-cone phantom. An egg-shaped phantom was used as ground truth to compare distortions for both 3D modes along with the measurements of the volume. Finally, we compared 3D ultrasound images acquired by 3D wobbler mode and 3D free-hand mode with respect to their 3D-US/3D-US registration accuracy using both, phantom and patient data. A theoretical step by step error analysis was performed and compared to empirical data.ResultsTarget registration errors based on the calibration with the 3D Multi-point and 2D pointer/image method have been found to be comparable (∼1mm). They both outperformed the 3D Hand-eye method (error >2mm). Volume measurements with the 3D free-hand mode were closest to the ground truth (around 6% error compared to 9% with the 3D wobbler mode). Additional scans on phantoms showed a 3D-US/3D-US registration error below 1 mm for both, the 3D free-hand mode and the 3D wobbler mode, respectively. Results with patient data showed greater error with the 3D free-hand mode (6.50mm - 13.37mm) than with the 3D wobbler mode (2.99 ± 1.54 mm). All the measured errors were found to be in accordance to their theoretical upper bounds.ConclusionWhile both 3D volume methods showed comparable results with respect to 3D-US/3D-US registration for phantom images, for patient data registrations the 3D wobbler mode is superior to the 3D free-hand mode. The effect of all error sources could be estimated by theoretical derivations.

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Image guidance protocols: balancing imaging parameters against scan time.

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