Effects of geometric distortion in 0.2T MRI on radiotherapy treatment planning of prostate cancer

Petersch, Bernhard; Bogner, Joachim; Fransson, Annette; Lorang, Thomas; Pötter, Richard

doi:10.1016/j.radonc.2003.12.012

Cited by 53 publications

(47 citation statements)

References 31 publications

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“…Such distortion was minimised in this study by using a high bandwidth turbo spin-echo sequence and by ensuring that the volume of interest was close to the centre of the magnet bore. Various authors have attempted to characterise and/or correct this distortion [41][42][43][44][45] so that MRI could be used to aid computerised RT treatment planning. Some have gone further and promoted the use of planning without a corresponding CT scan [46], with one study using a 3D T 1 FLASH (fast low angle shot) sequence for prostate imaging and quoting a mean distortion of 2 mm in the centre of the pelvis [47].…”

Section: Discussionmentioning

confidence: 99%

An evaluation of four CT–MRI co-registration techniques for radiotherapy treatment planning of prone rectal cancer patients

Dean

Sykes²,

Cooper³

et al. 2012

BJR

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Objectives: MRI is the preferred staging modality for rectal carcinoma patients. This work assesses the CT-MRI co-registration accuracy of four commercial rigid-body techniques for external beam radiotherapy treatment planning for patients treated in the prone position without fiducial markers. Methods: 17 patients with biopsy-proven rectal carcinoma were scanned with CT and MRI in the prone position without the use of fiducial markers. A reference co-registration was performed by consensus of a radiologist and two physicists. This was compared with two automated and two manual techniques on two separate treatment planning systems. Accuracy and reproducibility were analysed using a measure of target registration error (TRE) that was based on the average distance of the mis-registration between vertices of the clinically relevant gross tumour volume as delineated on the CT image. Results: An automated technique achieved the greatest accuracy, with a TRE of 2.3 mm. Both automated techniques demonstrated perfect reproducibility and were significantly faster than their manual counterparts. There was a significant difference in TRE between registrations performed on the two planning systems, but there were no significant differences between the manual and automated techniques. Conclusion: For patients with rectal cancer, MRI acquired in the prone treatment position without fiducial markers can be accurately registered with planning CT. An automated registration technique offered a fast and accurate solution with associated uncertainties within acceptable treatment planning limits. Randomised trials have demonstrated that adjuvant radiotherapy (RT) in patients with resectable rectal cancer offers a statistically significant reduction in the risk of local recurrence compared with surgery alone [1]. Two meta-analyses and a systematic review have confirmed this finding [2-4]: cancer-specific survival was found to be improved when RT was delivered with biological equivalent doses of .30 Gy pre-operatively. Two further trials have confirmed similar benefit when short-course pre-operative RT was combined with total mesorectal excision (TME) [5,6].Three further randomised trials have evaluated the role of pre-operative adjuvant chemoradiotherapy (CRT) for patients with stage T3-T4 or node-positive disease. Two of these studies demonstrated a reduction in local recurrence when pre-operative adjuvant CRT was used rather than long-course adjuvant RT alone [7,8]. The third study demonstrated both reduced local recurrence and reduced acute and late toxicity for pre-operative CRT compared with post-operative CRT [9]. The Cochrane review [4] also examined CRT and concluded that CRT provided incremental benefit in local control, irrespective of the timing of the chemotherapy. These results have led to a significant increase in the use of pre-operative radiation for patients with rectal cancer.MRI offers increased soft-tissue contrast compared with other radiographic imaging modalities such as CT. This improvement allows the accurate...

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Section: Discussionmentioning

confidence: 99%

An evaluation of four CT–MRI co-registration techniques for radiotherapy treatment planning of prone rectal cancer patients

Dean

Sykes²,

Cooper³

et al. 2012

BJR

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“…Previous studies on low-field open magnets have demonstrated large magnitudes of distortions of up to 23 mm. Images acquired on such systems can be successfully corrected by utilising measurements made in a test object containing a grid of MR-visible points [11,12]. In scanners with horizontal tunnel-bore designs, these effects are much less pronounced, although they are still an important consideration when dealing with the demand for high accuracies in radiotherapy planning.…”

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confidence: 99%

Commissioning of a new wide-bore MRI scanner for radiotherapy planning of head and neck cancer

Liney

Owen²,

Beaumont³

et al. 2013

BJR

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Objective: A combination of CT and MRI is recommended for radiotherapy planning of head and neck cancers, and optimal spatial co-registration is achieved by imaging in the treatment position using the necessary immobilisation devices on both occasions, something which requires wide-bore scanners. Quality assurance experiments were carried out to commission a newly installed 1.5-T widebore MRI scanner and a dedicated, flexible six-channel phased array head and neck coil. Methods: Signal-to-noise ratio (SNR) and spatial signal uniformity were quantified using a homogeneous aqueous phantom, and geometric distortion was quantified using a phantom with water-filled fiducials in a grid pattern. Volunteer scans were also used to determine the in vivo image quality. Clinically relevant T 1 weighted and T 2 weighted fat-suppressed sequences were assessed in multiple scan planes (both sequences fast spin echo based). The performance of two online signal uniformity correction schemes, one utilising low-resolution reference scans and the other not utilising low-resolution reference scans, was compared. Results: Geometric distortions, for a 635-kHz bandwidth, were ,1 mm for locations within 10 cm of the isocentre rising to 1.8 mm at 18 cm away. SNR was above 50, and uniformity in the axial plane was 71% and 95% before and after uniformity correction, respectively. Conclusion: The combined performance of the wide-bore scanner and the dedicated coil was adjudged adequate, although superior-inferior spatial coverage was slightly limited in the lower neck. Advances in knowledge: These results will be of interest to the increasing number of oncology centres that are seeking to incorporate MRI into planning practice using dedicated equipment.

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“…System‐dependent distortion mainly stems from gradient nonlinearities, static field inhomogeneities, and eddy currents created by the switching of field gradients and maladjustments of both the gradient offsets and the radio frequency 20. For the purpose of radiotherapy, it is particularly important to check whether the geometrical accuracy of image is sufficient to allow precise target and OARs delineation.…”

Section: Discussionmentioning

confidence: 99%

Quantitative analysis of image quality for acceptance and commissioning of an MRI simulator with a semiautomatic method

Chen

Dai

2018

J Applied Clin Med Phys

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Magnetic Resonance Imaging (MRI) simulation differs from diagnostic MRI in purpose, technical requirements, and implementation. We propose a semiautomatic method for image acceptance and commissioning for the scanner, the radiofrequency (RF) coils, and pulse sequences for an MRI simulator. The ACR MRI accreditation large phantom was used for image quality analysis with seven parameters. Standard ACR sequences with a split head coil were adopted to examine the scanner's basic performance. The performance of simulation RF coils were measured and compared using the standard sequence with different clinical diagnostic coils. We used simulation sequences with simulation coils to test the quality of image and advanced performance of the scanner. Codes and procedures were developed for semiautomatic image quality analysis. When using standard ACR sequences with a split head coil, image quality passed all ACR recommended criteria. The image intensity uniformity with a simulation RF coil decreased about 34% compared with the eight‐channel diagnostic head coil, while the other six image quality parameters were acceptable. Those two image quality parameters could be improved to more than 85% by built‐in intensity calibration methods. In the simulation sequences test, the contrast resolution was sensitive to the FOV and matrix settings. The geometric distortion of simulation sequences such as T1‐weighted and T2‐weighted images was well‐controlled in the isocenter and 10 cm off‐center within a range of ±1% (2 mm). We developed a semiautomatic image quality analysis method for quantitative evaluation of images and commissioning of an MRI simulator. The baseline performances of simulation RF coils and pulse sequences have been established for routine QA.

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Effects of geometric distortion in 0.2T MRI on radiotherapy treatment planning of prostate cancer

Cited by 53 publications

References 31 publications

An evaluation of four CT–MRI co-registration techniques for radiotherapy treatment planning of prone rectal cancer patients

An evaluation of four CT–MRI co-registration techniques for radiotherapy treatment planning of prone rectal cancer patients

Commissioning of a new wide-bore MRI scanner for radiotherapy planning of head and neck cancer

Quantitative analysis of image quality for acceptance and commissioning of an MRI simulator with a semiautomatic method

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