Assessing the image quality of pelvic MR images acquired with a flat couch for radiotherapy treatment planning

McJury, M.; O’Neill, A.; Lawson, Michael; McGrath, Clare; Grey, Arthur; Page, Walter

doi:10.1259/bjr/27295679

Cited by 30 publications

(25 citation statements)

References 12 publications

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“…However, in future, it is expected that vendors will bring to market more dedicated RF coils that will allow the acquisition of treatment position images across a number of sites. This will allow the radiotherapy community to build on the experience of other groups that have been so far restricted by diagnostic devices [20][21][22]. In the context of the current study, the addition of an anterior chest element to the oncology coil would extend coverage of the neck lower down and therefore remedy its current shortcoming.…”

Section: Discussionmentioning

confidence: 97%

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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Section: Discussionmentioning

confidence: 97%

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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“…The eight-channel cardiac coil was not used for the MRI RT scan because this coil is curved and rigid, so there would have been a greater distance between the patient and the posterior section of the coil than with the four-channel cardiac coil. This would have resulted in a reduced SNR of approximately 14% [23] and could potentially have prevented very large patients participating in the study, owing to the restrictions of the magnet bore size.…”

Section: Mri Scanning Protocolmentioning

confidence: 99%

The influence of MRI scan position on image registration accuracy, target delineation and calculated dose in prostatic radiotherapy

Hanvey¹,

Sadozye²,

McJury³

et al. 2012

BJR

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Objective: To investigate the necessity of performing MRI in the radiotherapy position when using MRI for prostatic radiotherapy. Methods: 20 prostate patients received a CT, diagnostic MRI and an MRI scan in the radiotherapy position. The quality of registration between CT and MRI was compared between the two MRI set-ups. The prostate and seminal vesicles were contoured using all scans and intensity modulated radiotherapy (IMRT) plans were generated. Changes in the target volume and IMRT plans were investigated. Two-tailed paired Student's ttests determined the statistical significance.Results: There was a decrease in the mean distance from the centre of the bony anatomy between CT and MRI (from 3.9 to 1.9 mm, p-value,0.0001) when the MRI scan was acquired in the radiotherapy position. Assuming that registering CT with an MRI scan in the radiotherapy position is the gold standard for delineating the prostate and seminal vesicles, using a planning target volume delineated on the CT with a diagnostic MRI scan viewed separately, resulted in a mean conformation number of 0.80 instead of the expected 0.98 (p,0.0001). Conclusion: By registering CT with an MRI scan in the radiotherapy position, there is a statistically significant improvement in the registration and IMRT quality. Advances in knowledge: To achieve an acceptable registration and IMRT quality in prostatic radiotherapy, neither CT with a separate diagnostic MRI nor CT registered to a diagnostic MRI will suffice. Instead, a CT registered with an MRI in the radiotherapy position should be used.

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“…The dedicated MR examination for radiotherapy treatment planning involves issues not present in the diagnostic setting. The patient should ideally be imaged in the same position as during treatment, including fixations [6] which influence both the coil setup and image quality [7,8]. The geometric accuracy of the images is crucial which increase demands on the choice of sequences and bandwidth [9] and the sequences and image planes should be optimized for determination of the precise geometrical extent of an already known pathology.…”

Section: Introductionmentioning

confidence: 99%

Variability in prostate and seminal vesicle delineations defined on magnetic resonance images, a multi-observer, -center and -sequence study

et al. 2013

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BackgroundThe use of magnetic resonance (MR) imaging as a part of preparation for radiotherapy is increasing. For delineation of the prostate several publications have shown decreased delineation variability using MR compared to computed tomography (CT). The purpose of the present work was to investigate the intra- and inter-physician delineation variability for prostate and seminal vesicles, and to investigate the influence of different MR sequence settings used clinically at the five centers participating in the study.MethodsMR series from five centers, each providing five patients, were used. Two physicians from each center delineated the prostate and the seminal vesicles on each of the 25 image sets. The variability between the delineations was analyzed with respect to overall, intra- and inter-physician variability, and dependence between variability and origin of the MR images, i.e. the MR sequence used to acquire the data.ResultsThe intra-physician variability in different directions was between 1.3 - 1.9 mm and 3 – 4 mm for the prostate and seminal vesicles respectively (1 std). The inter-physician variability for different directions were between 0.7 – 1.7 mm and approximately equal for the prostate and seminal vesicles. Large differences in variability were observed for individual patients, and also for individual imaging sequences used at the different centers. There was however no indication of decreased variability with higher field strength.ConclusionThe overall delineation variability is larger for the seminal vesicles compared to the prostate, due to a larger intra-physician variability. The imaging sequence appears to have a large influence on the variability, even for different variants of the T2-weighted spin-echo based sequences, which were used by all centers in the study.

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Assessing the image quality of pelvic MR images acquired with a flat couch for radiotherapy treatment planning

Cited by 30 publications

References 12 publications

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

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

The influence of MRI scan position on image registration accuracy, target delineation and calculated dose in prostatic radiotherapy

Variability in prostate and seminal vesicle delineations defined on magnetic resonance images, a multi-observer, -center and -sequence study

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