Initial clinical experience with a radiation oncology dedicated open 1.0T MR‐simulation

Glide-Hurst, Carri K; Hearshen, David; Kim, Joshua; Pantelic, Milan; Zhao, Bo; Mancell, Tina; Levin, Kenneth; Movsas, Benjamin; Chetty, Indrin J.; Siddiqui, M. Salim

doi:10.1120/jacmp.v16i2.5201

Cited by 23 publications

(19 citation statements)

References 56 publications

(71 reference statements)

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“…Using a 1.0 T Panorama high‐field open vertical‐bore system (Philips Medical Systems, Best, The Netherlands), a vendor‐supplied 3D distortion phantom consisting of docusate sodium capsules within a foam structure (17) was scanned using a 3D T1 spoiled gradient echo sequence (voxel size

0.938 \times 0.938 \times 2 {mm}^{3}, 450 \times 450 \times 400 {mm}^{3}

FOV, 385 Hz/pixel, TE/TR/flip angle: 3.77 ms/30 ms/60°, 3D correction algorithm applied). ACT of this phantom was also acquired.…”

Section: Methodsmentioning

confidence: 99%

MRI geometric distortion: Impact on tangential whole‐breast IMRT

Walker

Metcalfe

Liney

et al. 2016

J Applied Clin Med Phys

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The purpose of this study was to determine the impact of magnetic resonance imaging (MRI) geometric distortions when using MRI for target delineation and planning for whole‐breast, intensity‐modulated radiotherapy (IMRT). Residual system distortions and combined systematic and patient‐induced distortions are considered. This retrospective study investigated 18 patients who underwent whole‐breast external beam radiotherapy, where both CT and MRIs were acquired for treatment planning. Distortion phantoms were imaged on two MRI systems, dedicated to radiotherapy planning (a wide, closed‐bore 3T and an open‐bore 1T). Patient scans were acquired on the 3T system. To simulate MRI‐based planning, distortion maps representing residual system distortions were generated via deformable registration between phantom CT and MRIs. Patient CT images and structures were altered to match the residual system distortion measured by the phantoms on each scanner. The patient CTs were also registered to the corresponding patient MRI scans, to assess patient and residual system effects. Tangential IMRT plans were generated and optimized on each resulting CT dataset, then propagated to the original patient CT space. The resulting dose distributions were then evaluated with respect to the standard clinically acceptable DVH and visual assessment criteria. Maximum residual systematic distortion was measured to be 7.9 mm (95%<4.7mm) and 11.9 mm (95%<4.6mm) for the 3T and 1T scanners, respectively, which did not result in clinically unacceptable plans. Eight of the plans accounting for patient and systematic distortions were deemed clinically unacceptable when assessed on the original CT. For these plans, the mean difference in PTV normalV95 (volume receiving 95% prescription dose) was 0.13±2.51% and −0.73±1.93% for right‐ and left‐sided patients, respectively. Residual system distortions alone had minimal impact on the dosimetry for the two scanners investigated. The combination of MRI systematic and patient‐related distortions can result in unacceptable dosimetry for whole‐breast IMRT, a potential issue when considering MRI‐only radiotherapy treatment planning.PACS number(s): 87.61.‐c, 87.57.cp, 87.57.nj, 87.55.D‐

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0.938 \times 0.938 \times 2 {mm}^{3}, 450 \times 450 \times 400 {mm}^{3}

FOV, 385 Hz/pixel, TE/TR/flip angle: 3.77 ms/30 ms/60°, 3D correction algorithm applied). ACT of this phantom was also acquired.…”

Section: Methodsmentioning

confidence: 99%

MRI geometric distortion: Impact on tangential whole‐breast IMRT

Walker

Metcalfe

Liney

et al. 2016

J Applied Clin Med Phys

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“…First, images were generated by taking the maximum intensity projection of each of all 13 slices for each scan, which is consistent with our clinical protocol. 15 Control point detection was then conducted on each image with a combination of masking and thresholding, while a connectivity algorithm was used to further separate control points from increased noise at the field boundaries. The x and y positions (horizontal and vertical axes, respectively) were determined by finding the centroid of each control point and were compared to a binary template generated from the factory schematic of the phantom.…”

Section: C Image Analysismentioning

confidence: 99%

“…We have previously reported on our magnet's B 0 field inhomogeneity and found that it was within American College of Radiology guidelines. 15 This technical note focuses on the technical characterization of gradient nonlinearity (GNL) for large fields of view (FOVs), develops and evaluates a correction scheme, and then quantifies the temporal stability of the measurements for a clinically available MR-SIM system. GNL is the focus of this work, because it is one of the dominant sources of image distortion 16,17 and is insensitive to the acquisition sequence.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Characterization and correction of gradient nonlinearity induced distortion on a 1.0 T open bore MR‐SIM

et al. 2015

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“…Coronal acquisitions are performed to ensure high spatial resolution in the superior–inferior direction where liver motion is dominant (3) . 4D MRIs were acquired on a 1.0T Philips Panorama High Field Open (HFO) magnetic resonance system (RT Oncology Configuration, v3.5.2, Philips Medical Systems, Cleveland, OH), which has been described in detail elsewhere 16 , 20 . Respiratory triggering was performed based on a signal derived from an air‐filled cushion placed on the abdomen that was used as an external surrogate.…”

Section: Methodsmentioning

confidence: 99%

Impact of incorporating visual biofeedback in 4D MRI

Kim

Price

et al. 2016

J Applied Clin Med Phys

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Precise radiation therapy (RT) for abdominal lesions is complicated by respiratory motion and suboptimal soft tissue contrast in 4D CT. 4D MRI offers improved contrast although long scan times and irregular breathing patterns can be limiting. To address this, visual biofeedback (VBF) was introduced into 4D MRI. Ten volunteers were consented to an IRB‐approved protocol. Prospective respiratory‐triggered, T2‐weighted, coronal 4D MRIs were acquired on an open 1.0T MR‐SIM. VBF was integrated using an MR‐compatible interactive breath‐hold control system. Subjects visually monitored their breathing patterns to stay within predetermined tolerances. 4D MRIs were acquired with and without VBF for 2‐ and 8‐phase acquisitions. Normalized respiratory waveforms were evaluated for scan time, duty cycle (programmed/acquisition time), breathing period, and breathing regularity (end‐inhale coefficient of variation, EI‐COV). Three reviewers performed image quality assessment to compare artifacts with and without VBF. Respiration‐induced liver motion was calculated via centroid difference analysis of end‐exhale (EE) and EI liver contours. Incorporating VBF reduced 2‐phase acquisition time (4.7±1.0 and 5.4±1.5trueprefixmin with and without VBF, respectively) while reducing EI‐COV by 43.8%±16.6%. For 8‐phase acquisitions, VBF reduced acquisition time by 1.9±1.6trueprefixmin and EI‐COVs by 38.8%±25.7% despite breathing rate remaining similar (11.1±3.8 breaths/min with vs. 10.5±2.9 without). Using VBF yielded higher duty cycles than unguided free breathing (34.4%±5.8% vs. 28.1%±6.6%, respectively). Image grading showed that out of 40 paired evaluations, 20 cases had equivalent and 17 had improved image quality scores with VBF, particularly for mid‐exhale and EI. Increased liver excursion was observed with VBF, where superior–inferior, anterior–posterior, and left–right EE‐EI displacements were 14.1±5.8, 4.9±2.1, and 1.5±1.0 mm, respectively, with VBF compared to 11.9±4.5, 3.7±2.1, and 1.2±1.4 mm without. Incorporating VBF into 4D MRI substantially reduced acquisition time, breathing irregularity, and image artifacts. However, differences in excursion were observed, thus implementation will be required throughout the RT workflow.PACS number(s): 87.55.‐x, 87.61.‐c, 87.19.xj

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Initial clinical experience with a radiation oncology dedicated open 1.0T MR‐simulation

Cited by 23 publications

References 56 publications

MRI geometric distortion: Impact on tangential whole‐breast IMRT

MRI geometric distortion: Impact on tangential whole‐breast IMRT

Technical Note: Characterization and correction of gradient nonlinearity induced distortion on a 1.0 T open bore MR‐SIM

Impact of incorporating visual biofeedback in 4D MRI

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