Balanced Turbo Research Articles

Auto-Correction for Inaccurate Auto-Segmentation of Abdominal MRI by Combining Deep Learning and Active Contour Method

Fast and accurate auto-segmentation is crucial during the magnetic resonance-guided adaptive radiation therapy (MRgART). Deep learning auto-segmentation (DLAS) approaches do not always result in clinically acceptable contours, especially for complex abdominal organs. We have previously reported that the inaccurate DLAS for bowels can be refined using deep learning (DL) and/or active contour method (ACM). This study aims to develop an automatic contour correction (ACC) tool by combining DL and ACM techniques to correct for inaccurate DLAS of pancreas and stomach on MRI. The ACC technique consisted of ACM and DL based on UNet system. The ACM utilizes the probability maps generated from DLAS models to establish 2D parameter maps and to initialize contour evolution, thus not requiring initial parameter adjustments. The Organ specific DL-UNet models were trained for pancreas and stomach contours obtained from a research DLAS tool on abdominal MRIs acquired during routine MRgART from a 1.5T MR-Linac using either turbo field-echo or balanced turbo field-echo sequences. The training dataset contained MR slices along with DLAS and ground truth contours from 54 abdominal MRL sets, and 540 additional augmented sets created by shifting and rotating. DLAS contours were classified based on the expected editing effort into the acceptable, minor edit, or major edit category using an in-house developed classification model. Performance of the obtained ACC models were tested on an independent dataset of 11 sets of abdominal MRIs. For pancreas, the DL-UNet model improved 17% (26/153) and 2% (2/95) of the minor and major edits' slices of the testing dataset, respectively, to acceptable and 39% (37/95) of the major edit slices improved to minor edits. The ACM model improved 3% (4/153) of the minor edit slices to acceptable and the 36% (34/95) of the major slices to minor edits. Using the ACC technique with DL and ACM combined, the percentage of acceptable contours increased from 10% (29/277) to 24% (66/277), and minor edits from 55% (153/277) to 61% (170/277), while the percentage of the major edit slices reduced from 35% (95/277) to 15% (41/277). For stomach, the DL model improved 8% (29/366) of the minor edit slices to acceptable and 50% (16/32) of the major edit slices to minor edit slices. The ACM resulted in 2% (6/366) of minor edit slices to acceptable and 41% (13/32) of major edit slices to minor category. Combining both the DL and ACM, the overall percentage of acceptable stomach contours grew from 13% (58/456) to 22% (101/456) and the percentage of major edit slices reduced from 7% (32/456) to 2% (11/456). The ACC method combining both DL and ACM models can substantially improve the quality of inaccurate DLAS contours of pancreas and stomach in a fully automated and fast manner, minimizing the subsequent manual editing time required for MRgART.

An MRI-Based Global Deep Learning Auto-Segmentation Model for Abdominal Organs

<h3>Purpose/Objective(s)</h3> Multi-sequence MRIs are often used in MRI-based radiation treatment (RT) planning and/or MR-guided adaptive RT (MRgART). As MRI sequences are constantly evolving to reflect changing technology and/or tumor specific RT imaging, it is desirable to develop sequence independent deep learning auto-segmentation (DLAS). In this study, we present a global DLAS model that can be used for segmenting abdominal organs on multi-contrast images from multiple machines including those different from training. <h3>Materials/Methods</h3> The global DLAS model was built on a previously investigated 3D neural network for DLAS with multi-site CTs and multi-sequence MRIs. 167 abdominal MRIs acquired with 5 unique sequences with a wide range of acquisition parameters: T2-HASTE and T1-DIXON, fast field echo (FFE), balanced turbo (BTFE) and TFE daily motion-averaged MRI, acquired from a 3T MR simulator and a 1.5T MR-Linac, were used to train the global DLAS model. An additional 81 datasets, including 49 sets of varying image quality and contrast, different to those in the training datasets, were used for testing. The model performance was evaluated by comparing DLAS with manually drawn ground truths, for 10 abdominal organs using 4 metrics: Dice similarity coefficient (DSC), surface DSC (sDSC), mean distance to agreement (MDA), and relative added path length (APL_rel), defined as the APL divided by the organ volume. <h3>Results</h3> The global DLAS model performed well for organs with stable shapes and minimum volume variations (e.g., aorta, liver, kidneys, and spleen) with average DSC = 0.82-0.98, sDSC = 0.67-1, MDA = 0.5-2.2 mm, and APL_rel = 0.1-12 mm/cc, showing considerable invariance to acquisition parameters. High accuracy was also observed for organs with consistent anatomical changes (stomach and large bowel), with average DSC = 0.77-0.94, sDSC = 0.51-0.82, MDA = 0.43-6.3 mm, and APL_rel = 5-18.3 mm/cc. For small bowel, duodenum, and pancreas, reasonable accuracy on the 3T MR simulator images with average DSC = 0.74-0.85, sDSC = 0.65-0.74, MDA = 1.85-3 mm, and APL_rel = 11-21 mm/cc, indicated improved performance for images with higher soft tissue contrast and less motion artifacts. Interestingly accurate segmentation was observed in 23 out of 49 sequences different from training datasets. For the images with relatively poorer quality (e.g., motion artifacts and low signal density in MR-Linac images) and/or distinct contrast (e.g., fat suppressed), the DLAS performance was relatively poorer, indicating inclusion of larger datasets of these images to the model training. <h3>Conclusion</h3> It is feasible to develop an MRI-based, sequence independent, global DLAS model using MRI datasets of limited sequences and assess how well the model output extends to sequences different from training, with variable contrast and image quality. With further improvement using larger training datasets, the global model could be useful, particularly for MRgART where MRI sequences may be updated or adjusted routinely or frequently.

Deep Learning Auto-Segmentation on Multi-Sequence MRI for MR-Guided Adaptive Radiation Therapy

<h3>Purpose/Objective(s)</h3> Robust auto-segmentation based on daily MRI is highly desirable for MR-guided adaptive radiation therapy (MRgART). However, it is generally challenging particularly if the daily MRI is acquired with multiple sequences or if it is for imaging complex anatomy, e.g., abdomen. To overcome these issues, we developed a deep learning algorithm to segment abdominal organs quickly and automatically on multi-sequence MRI. <h3>Materials/Methods</h3> The deep learning auto-segmentation model was developed using a modified U-net, ResUnet3D, with end-to-end mapping, and was trained with 85 daily MRI sets acquired during MRgART on a 1.5T MR-Linac for 37 patients with abdominal tumors. The daily MRI sets were motion averaged images derived from 4D MRI acquired with multiple sequences, including Fast Field Echo (FFE), Balanced Turbo Field Echo (BTFE) and TFE. Each daily MRI was paired with a CT. All MRIs were pre-processed using bias field correction and intensity standardization. The ground truth contours were created manually based on existing guidelines. For the training datasets, field-of-view extension via online random 3D elastic transform/deformation was utilized to augment and improve the quality of datasets. During the model training, a patient-based z-score normalization method was employed to standardize the multi-contrast images. Two models were trained, one for 11 organs: aorta, duodenum, kidneys, liver, pancreas, spinal cord, spleen, stomach, large bowel, and small bowel, and another for 10 organs with combined large and small bowel. Performance of the obtained models was evaluated using 11 test datasets in terms of dice similarity coefficient (DSC), mean distance to agreement (MDA) and time efficiency using an Intel Xeon CPU (2.4 GHz, 64GB RAM) hardware. <h3>Results</h3> For the challenging bowels, the auto-segmentation accuracy for the model trained with the combined bowel was better, with MDA/DSC of 2.1/0.86 versus 6.8/0.76 (large bowel) and 6.1/0.68 (small bowel) for the separate-bowel model. Average DSC for the obtained contours of aorta, left kidney, right kidney, liver, spinal cord, spleen, and stomach was 0.93, 0.93, 0.94, 0.94, 0.83, 0.92 and 0.88, respectively from both models. While no significant difference in model performance was observed with BTFE versus TFE testing datasets, a slightly improved segmentation was seen on the BTFE images for pancreas and duodenum, DSC 0.71 and 0.72. This improvement may be attributed to the enhanced contrast seen in BTFE images when compared to the TFE and FFE images. The time required to generate all organs on an MRI was 20-24 seconds. <h3>Conclusion</h3> We have developed deep learning auto-segmentation models based on multi-sequence MRI sets for abdominal organs. The models performed reasonably well. With further development using large datasets, the models may be integrated in MRgART for fast, fully automated, and accurate contouring of abdominal organs on daily MRI.

Compressed SENSE single-breath-hold and free-breathing cine imaging for accelerated clinical evaluation of the left ventricle

To assess the accuracy of compressed SENSE (CS-SENSE) cine cardiac magnetic resonance imaging (CMR) with and without breath-hold in comparison to standard cine CMR with breath-hold for the assessment of left ventricular (LV) function. Thirty-three healthy volunteers underwent balanced turbo field-echo cine CMR with breath-hold (BTFE-BH; reference standard), single breath-hold CS-SENSE (csBTFE-BH) cine CMR, and free-breathing (FB) CS-SENSE (csBTFE-FB) cine CMR on a 3 T MRI system. All images were acquired in stacks of eight short-axis sections. Image quality was assessed and compared by the Wilcoxon matched-pairs signed-rank test. End-diastolic volume, end-systolic volume, stroke volume, ejection fraction, LV end-diastolic (LVED) mass, regional myocardial wall motion, and scan time were compared by paired t-test, linear regression, and Bland-Altman analyses. All techniques provided acceptable image quality (score ≥3) for LV volumetric analysis in all participants (BTFE-BH [reference standard]: 5.00±0.00; csBTFE-BH: 4.03±0.17 [p<0.001]; csBTFE-FB: 3.76±0.44 [p<0.001]), with good agreement in LV function assessment; however, there was a slight but significant underestimation of LVED mass by csBTFE-FB (csBTFE-FB: 73.63±17.31 g versus BTFE-BH [reference standard]: 75.12±18.18 g, p=0.037). All methods showed a strong correlation with quantitative regional myocardial wall motion. Acquisition times for both csBTFE-BH and csBTFE-FB were significantly shorter than that for BTFE-BH (BTFE-BH [reference standard]: 89.3±5.70 seconds; csBTFE-BH: 24.42±2.18 seconds [p<0.001]; csBTFE-FB: 22.48±1.85 seconds [p<0.001]). LV function assessment with the novel CS-SENSE cine CMR is not inferior to standard cine CMR, irrespective of BH; however, LVED mass is underestimated by csBTFE-FB.

254. Fast T1,T2, M0 mapping in clinical MRI: Look-locker based inversion recovery balanced turbo field echo

Purpose T1, T2 maps in MRI allows to evaluate quantitatively the state of organs and to recognize anomalies. Look-Locker based Inversion Recovery Balanced Turbo Field Echo (LL-IR-BTFE) is a distortion free sequence that hold high SNR allowing fast mapping in every region of the body, in particular myocardial tissue, liver and brain. This study investigated a method to achieve fast T1, T2, M0 maps of phantoms and their accuracy. Methods The Philips MRI phantom has been used centred in the head coil of the Philips scanner Ingenia 3T. After local shimming, the scans have been performed using conventional spin echo pulse sequences to find the real T1 and T2. Next the phantoms have been scanned using the LL-IR- BTFE. We recovered an estimation of T1, T2 and M0 (in arbitrary units) using 3 parameter fit and correction expressions [1] , next we compared the maps obtained increasing flip angles and profile corrections [2] . Results The images were free of distortion but the susceptibility artifact was found, the percentage difference between the T1 in a central ROI using IR-BTFE and spin echo is less than 8% for the scans at different flip angles in the full T1 range after profile correction. The standard deviation was around 1.2% of T1 and T2; the values are reproducible in identical scans with percent differences of 1.3%. Conclusions The process needs an accurate choice of parameters to maximize the accuracy in maps and the range of T1,T2 involved must be known in advance in order to find the best flip angle.

The Visibility of the Terminal Thoracic Duct Into the Venous System Using MR Thoracic Ductography with Balanced Turbo Field Echo Sequence

Magnetic resonance thoracic ductography (MRTD) with balanced turbo field echo (bTFE) can visualize both the thoracic duct and its surrounding vessels. This study aimed to investigate the visibility of the terminal thoracic duct into the venous system in the subclavian region using MRTD with bTFE. MRTD was performed with bTFE as a preoperative workup comprising respiratory gating on a 1.5-T magnetic resonance system for patients with esophageal cancer. The portion and the number of terminal thoracic ducts into the venous system and preterminal branching in the left subclavian region were assessed using MRTD in 132 patients. The confidence level of the visibility using MRTD was also evaluated. The most frequent terminal portion of the thoracic duct was the jugulovenous angle (92 patients, 69.7%), followed by the subclavian vein (27 patients, 20.5%) and the internal jugular vein (8 patients, 6.1%). Four patients also exhibited double entry of the thoracic duct into the venous system. The preterminal branching was single in 96 patients (72.7%) and multiple in 36 patients (27.3%). The confidence level of the visibility of the thoracic duct using MRTD was absolutely certain in 112 patients (84.8%) and was somewhat certain in 20 patients (15.2%). MRTD with bTFE is a robust imaging modality to visualize the terminal portion of the thoracic duct into the venous system in the subclavian region.

Simultaneous detection of hepatocellular carcinoma and vessel thrombus by using SPIO-enhanced B-TFE with the T2 preparation pulse technique.

The purpose of this study was to compare between superparamagnetic iron oxide (SPIO)-enhanced three-dimensional balanced turbo field-echo (B-TFE) sequence with T2 preparation pulse (T2 prep) and T2*-weighted imaging (T2*WI) for the simultaneous detection of hepatocellular carcinoma (HCC) and vessel thrombus. For 1.5-T magnetic resonance imaging, SPIO was administered to 23 patients with a portal or venous tumor thrombus, and B-TFE with T2 prep and T2*WI were acquired. Regions of interest in the B-TFE and T2*WI were selected for the tumor, liver, tumor thrombus, and vessels. The contrasts of the HCC in the liver and the tumor thrombus in the vessels were determined from clinical image. Contrast was calculated using the mean value of the signal intensity on the HCC to the liver and tumor thrombus to vessels. The mean contrasts between HCC and the liver with the use of B-TFE and T2*WI were 0.61±0.05 and 0.70±0.04, respectively. The contrast of HCC to the liver was significantly higher in T2*WI than in B-TFE (p<0.05). The mean contrasts between the tumor thrombus and vessels with the use of B-TFE and T2*WI were 0.28±0.02 and 0.10±0.02, respectively. The contrast of tumor thrombus in the vessels was higher in B-TFE than in T2*WI (p<0.01). Kupffer imaging can be used to assess liver function and acquire morphological images using three-dimensional B-TFE with T2 prep. This technique would be helpful for simultaneous detection of HCC and tumor thrombus.

Improved diagnosis of common bile duct stone with single-shot balanced turbo field-echo sequence in MRCP.

To evaluate the value of adding single-shot balanced turbo field-echo (b-TFE) sequence to conventional magnetic resonance cholangiopancreatography (MRCP) for the detection of common bile duct (CBD) stone. One hundred thirty-seven consecutive patients with suspected CBD stone underwent MRCP including single-shot b-TFE sequence. Twenty-five patients were confirmed with CBD stone by endoscopic retrograde cholangiopancreatography or ultrasonography. Two radiologists reviewed two image protocols: protocol A (conventional MRCP protocol: unenhanced T1-, T2-, and respiratory-triggered three-dimensional fat-suppressed single-shot turbo spin-echoMRCP sequence) and protocol B (protocol A plus single-shot b-TFE sequence). The sensitivity, specificity, positive (PPV) and negative predictive value (NPV), and area under the receiver-operating-characteristic (ROC) curve (AUC) for the detection of CBD stone were compared. The sensitivity (72%) and NPV (94%) were the same between the two protocols. However, protocol B was greater in the specificity (99%) and PPV (94%) than protocol A (92% and 67%, respectively) (P=0.0078 and 0.031, respectively). The AUC was significantly greater for protocol B (0.93) than for protocol A (0.86) (P=0.026). Inclusion of single-shot b-TFE sequence to conventional MRCP significantly improved the specificity and PPV for the detection of CBD stone.

Shared versus non-shared prepulse perfusion MR sequence in absolute myocardial perfusion quantification

Methods In this substudy of the NOMI-trial (ClinicalTrials.gov identifier: NCT01398384), quantitative perfusion analysis was compared between patients that underwent an MR first pass perfusion sequence with a shared (n=25) and a non-shared prepulse (n=25), at 4 months after revascularized myocardial infarction. Perfusion imaging consisted of 3 short-axis slices acquired every heartbeat, with a balanced turbo gradient echo sequence in a 1.5 tesla MR unit (Achieva, Philips Medical Systems, The Netherlands) and was performed at rest and during adenosine (140 μg/kg/min) stress. MBF was quantified using Fermi deconvolution with a single bolus (SB, 0.05 mmol/kg) and dual bolus (DB, equal volumes of 0.0027 mmol/kg followed by 0.05 mmol/kg of contrast agent) analysis technique, in 6 segments of basal and midventricular short axis slices. Apical segments and segments with infarct scar on the corresponding late gadolinium enhancement-images were excluded. Results Baseline characteristics of both patient groups were comparable. MBF values were significantly higher with SP than with NSP sequence for the SB analysis technique. For DB, MBF was not different for rest perfusion,

Utility of Two Types of MR Cisternography for Patency Evaluation of Aqueduct and Third Ventriculostomy Site: Three Dimensional Sagittal Fast Spin Echo Sequence and Steady-State Coherent Fast Gradient Echo Sequence

Purpose: We aimed to evaluate the utility of two types of MR cisternography [fast spin echo sequence and steady-state coherent gradient echo (GRE) sequence] in addition to phase contrast-cine imaging (PC-cine), for assessing patency at the aqueduct and third ventriculostomy site. Materials and Methods: 43 patients (35 patients with suspected aqueductal stenosis and 8 patients with third ventriculostomy) were retrospectively analyzed. PCcine, 3 dimensional sagittal fast spin echo sequence [driven-equilibrium imaging (DRIVE) or volumetric isotrophic T2-weighted acquisition (T2 VISTA)] and steadystate coherent fast GRE sequence (balanced turbo field echo; bTFE) imaging were performed in all patients. The patency of the aqueduct or third ventriculostomy site was scored. Some pitfalls of each sequence were also analyzed in individual cases. Results: 93% of all cases showed consistent scores in PC-cine, DRIVE/T2 VISTA, and bTFE imaging. DRIVE/T2 VISTA imaging provided functional information of cerebrospinal fluid flow with flow-related artifacts, while bTFE imaging allowed direct visualization of the aqueduct or ventriculostomy site. However, evaluation of anatomical structures was difficult in three cases with strong flow-related artifacts on DRIVE/T2 VISTA and in 2 cases with susceptibility artifacts on bTFE. Conclusion: Both DRIVE/T2 VISTA and bTFE imaging have complementary roles in evaluating the patency of the aqueduct and 3rd ventriculostomy site. Index terms Aqueductal Stenosis Third Ventriculostomy Volumetric Isotrophic T2-Weighted Acquisition Driven-Equilibrium Imaging Balanced Turbo Field Echo

T2 prepを併用したSPIO造影B-TFEによるHCCと腫瘍栓同時検出の基礎的検討

T2 prepを併用したSPIO造影B-TFEによるHCCと腫瘍栓同時検出の基礎的検討

Global Small Bowel Motility: Assessment with Dynamic MR Imaging

To assess the repeatability in human volunteers of software-quantified small bowel motility captured with magnetic resonance (MR) imaging and to test the ability to detect changes in motility induced by pharmacologic agents. The study was approved by the Royal Free Research Ethics Committee, and all subjects gave full written informed consent. Twenty-one healthy volunteers (14 men, seven women; mean age, 28 years) underwent cine MR imaging with a three-dimensional balanced turbo field-echo sequence to capture small bowel motility. Volume blocks (15 cm thick) were acquired every second during a 20-second breath hold. A randomized, blinded, placebo-controlled crossover study of either 0.5 mg neostigmine or saline (n = 11) or 20 mg intravenous butylscopolamine or saline (n = 10) was performed with motility MR imaging at baseline and repeated at a mean of 4 weeks (range, 2-7 weeks). Two readers independently drew regions of interest around the small bowel, and motility was quantified by using a registration algorithm that provided a global motility metric in arbitrary units. Repeatability of the motility measurements at baseline was assessed by using Bland-Altman and within-subject coefficient of variation measures. Changes in mean motility measurements after drug administration were compared with those after placebo administration by using paired t testing. The repeatability between baseline measurements of motility was high; the Bland-Altman mean difference was -0.0025 (range, 0.28-0.4), the 95% limit of agreement was ±0.044 arbitrary units (au), and the within-subject coefficient of variation was 4.9%. Measured motility with neostigmine (mean, 0.39 au) was significantly higher than that with placebo (mean, 0.34 au; P < .001), whereas that with butylscopolamine (mean, 0.13 au) was significantly lower than that with placebo (mean, 0.30 au; P < .001). Quantification of small bowel motility with use of MR imaging in healthy volunteers is repeatable and sensitive to changes induced by means of pharmacologic manipulation. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13130151/-/DC1.

Global Small Bowel Motility: Assessment with Dynamic MR Imaging

To assess the repeatability in human volunteers of software-quantified small bowel motility captured with magnetic resonance (MR) imaging and to test the ability to detect changes in motility induced by pharmacologic agents. The study was approved by the Royal Free Research Ethics Committee, and all subjects gave full written informed consent. Twenty-one healthy volunteers (14 men, seven women; mean age, 28 years) underwent cine MR imaging with a three-dimensional balanced turbo field-echo sequence to capture small bowel motility. Volume blocks (15 cm thick) were acquired every second during a 20-second breath hold. A randomized, blinded, placebo-controlled crossover study of either 0.5 mg neostigmine or saline (n = 11) or 20 mg intravenous butylscopolamine or saline (n = 10) was performed with motility MR imaging at baseline and repeated at a mean of 4 weeks (range, 2-7 weeks). Two readers independently drew regions of interest around the small bowel, and motility was quantified by using a registration algorithm that provided a global motility metric in arbitrary units. Repeatability of the motility measurements at baseline was assessed by using Bland-Altman and within-subject coefficient of variation measures. Changes in mean motility measurements after drug administration were compared with those after placebo administration by using paired t testing. The repeatability between baseline measurements of motility was high; the Bland-Altman mean difference was -0.0025 (range, 0.28-0.4), the 95% limit of agreement was ±0.044 arbitrary units (au), and the within-subject coefficient of variation was 4.9%. Measured motility with neostigmine (mean, 0.39 au) was significantly higher than that with placebo (mean, 0.34 au; P < .001), whereas that with butylscopolamine (mean, 0.13 au) was significantly lower than that with placebo (mean, 0.30 au; P < .001). Quantification of small bowel motility with use of MR imaging in healthy volunteers is repeatable and sensitive to changes induced by means of pharmacologic manipulation. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13130151/-/DC1.

Evaluation of Pediatric Thoracic Disorders: Comparison of Unenhanced Fast-Imaging-Sequence 1.5-T MRI and Contrast-Enhanced MDCT

The purpose of this study was to investigate the efficacy of thoracic MRI with fast imaging sequences without contrast administration at 1.5 T for evaluating thoracic abnormalities by comparing MRI findings with contrast-enhanced MDCT findings. A prospective study included consecutively registered pediatric patients who from December 2009 to January 2012 underwent thoracic MDCT followed within 2 days by MRI for evaluation of thoracic abnormalities. The final study sample consisted of 71 children (36 boys, 35 girls; mean age, 8.6 ± 4.5 years; range, 2 months-16 years) and 71 paired thoracic MRI and MDCT studies. Thoracic MRI was performed in the axial and coronal planes with the following fast imaging sequences: T1-weighted fast-field echo inversion prepulse, T2-weighted balanced fast-field echo multiple 2D, T1- and T2-weighted turbo spin-echo cardiac-triggering parallel imaging technique without cardiac monitoring, and STIR. Thoracic MDCT was performed with i.v. contrast administration. Two pediatric radiologists independently reviewed each MRI and MDCT study for abnormalities in the lung, large airways, and mediastinal, pleural, and musculoskeletal structures. The sensitivity, specificity, and overall accuracy of MRI were calculated. Interobserver agreement was measured with the kappa coefficient. With MDCT as the reference standard, 51 of 71 (72%) patients had abnormal findings on MDCT studies, including infections in 21 (42%) cases, neoplasms in 19 (37%) cases, interstitial lung disease in seven (14%) cases, pleural effusion in three (6%) cases, and congenital bronchogenic cyst in one (2%) case. The overall diagnostic accuracy, sensitivity, and specificity of MRI for detecting thoracic abnormalities were 69 of 71 (97%), 49 of 51 (96%), and 20 of 20 (100%). Two undiagnosed findings with MRI that were detected with MDCT were mild bronchiectasis and small pulmonary nodule (3 mm). Almost perfect interobserver agreement was found between two reviewers with 70 of 71 agreements (κ = 0.97; 95% CI, 0.92-1.00; p < 0.001). CONCLUSION; MRI with fast imaging sequences without contrast administration is comparable to contrast-enhanced MDCT for detecting thoracic abnormalities in pediatric patients. Use of MRI with fast imaging sequences without contrast administration as a first-line cross-sectional imaging study in lieu of contrast-enhanced MDCT has the potential to benefit this patient population owing to reduced radiation exposure and i.v. contrast administration.

TH‐C‐141‐11: Evaluation of MR Images as the Planning and Reference Dataset for Daily CBCT‐Based IGRT of the Prostate

Purpose: An important question rarely discussed in the CT vs. MRI simulation debate is whether MRI reference images provide an adequate image‐set to use with daily localization such as cone‐beam CT (CBCT). This study compares clinical couch shifts based on daily CBCT images to shifts measured from MR images as the reference dataset for prostate IMRT treatment. Methods: Eight patients undergoing a pilot study had MR imaging along with CT simulation with the intent of evaluating a MR‐simulation process. Patients had T1, T2 and bTFE (balanced Turbo Field Echo) sequences. The remainder of the treatment planning process continued using traditional procedures using CT. Therapists used only the CT scan as a reference for localization. Retrospectively, an observer measured shifts between daily CBCT images and MR reference images. Results: The differences in shift positions for the cohort between therapists and the observer are −0.16cm ± 0.25cm (AP), 0.04cm ± 0.19cm (SI), and — 0.01cm ± 0.14cm (LR). The mean group error for the therapists and the observer were less than 2 mm in all directions. Based on these shifts, the calculated margins for the therapists would be 0.87cm (AP), 0.65cm (SI), and 0.71cm (LR) and for the observer would be 1.1cm (AP), 0.66cm (SI), and 0.70cm (LR). For SI and LR directions both sets of margins are very close to one another. An outlier impacted the AP margin difference by 2.3mm and should be investigated further. This initial analysis suggests that each modality can be considered clinically sufficient for daily localization. Conclusion: The results of this study suggest that MR reference image‐sets can be used for daily image‐guided localization of prostate cancers with at least the same accuracy as current methods. MR simulation provides substantial soft‐tissue contrast and can improve tissue targeting in radiation oncology, as a Result further investigation is warranted.

The diagnostic accuracy of quantitative CMR perfusion imaging may not be the same for all coronary arteries

Background Absolute quantification of myocardial perfusion with cardiac magnetic resonance (CMR) is an emerging technique and its diagnostic accuracy remains to be fully established. Furthermore it is not known whether there are any differences in the accuracy of coronary artery disease (CAD) detection between coronary arteries. Methods 41 patients with known or suspected CAD underwent 1.5T perfusion imaging prior to coronary angiography. Perfusion imaging k-t balanced Turbo Field Echo sequence, shortest TE (range 1.35-1.54ms), shortest TR (range 2.64-3.12ms), 50°flip angle; 90° prepulse, 100ms prepulse delay and typical acquired resolution 1.7x1.9x10mm. 3 short axis slices were acquired every heartbeat. Stress imaging preceded rest by 14±2 minutes. A dual bolus (0.01mmol/kg then 0.1mmol/kg 20 seconds later) of contrast agent was used. Blinded experts performed all data analysis. Mean segmental perfusion values were obtained using dedicated prototype Philips ViewForum software and Fermi deconvolution. Each segment was assigned to a perfusion territory according to standard definitions. Myocardial perfusion reserve (MPR) was defined as stress perfusion divided by rest perfusion. The mean of the 2 lowest MPR for each perfusion territory was used for analysis. X-ray angiography Quantitative coronary angiography (QCA) was performed on all arteries ≥2mm and a mean diameter stenosis ≥70% regarded as significant. The accuracy of MPR to detect significant CAD as defined by QCA was determined by receiver-operating characteristic (ROC) curves. Results

Resolution enhanced T1-insensitive steady-state imaging.

Resolution enhanced T(1)-insensitive steady-state imaging (RE-TOSSI) is a new MRI pulse sequence for the generation of rapid T(2) contrast with high spatial resolution. TOSSI provides T(2) contrast by using nonequally spaced inversion pulses throughout a balanced steady-state free precession (SSFP) acquisition. In RE-TOSSI, these energy and time intensive adiabatic inversion pulses and associated magnetization preparation are removed from TOSSI after acquisition of the data around the center of k-space. Magnetization evolution simulations demonstrate T(2) contrast in TOSSI as well as reduction in the widening of the point spread function width (by up to a factor of 4) to a near ideal case for RE-TOSSI. Phantom experimentation is used to characterize and compare the contrast and spatial resolution properties of TOSSI, RE-TOSSI, balanced SSFP, Half-Fourier Acquisition Single-Shot Turbo Spin Echo (HASTE), and turbo spin echo and to optimize the fraction of k-space acquired using TOSSI. Comparison images in the abdomen and brain demonstrate similar contrast and improved spatial resolution in RE-TOSSI compared with TOSSI; comparison balanced SSFP, HASTE, and turbo spin echo images are provided. RE-TOSSI is capable of providing high spatial resolution T(2)-weighted images in 1 s or less per image.

Cardiac magnetic resonance imaging of mucopolysaccharidosis type II cardiomyopathy

⁎ Corresponding author. Pole de Cardiologie, CHRU Lille, EA 2693, Universite Lille 2, Bvd Pr Leclercq, 59037 Lille Cedex, France. Tel.: +33 320445045; fax: +33 320444881. E-mail address: frederic.mouquet@univ-lille2.fr (F. Mouquet). We report the case of a 26 year old patient, referred for cardiology evaluation before lung transplantation in a context of mucopolysaccharidosis type II (MPS or Hunter's syndrome). The patient had no history of cardiovascular disease. EKG showed a sinus rhythm with a negative T wave in precordial leads. Echocardiography showed a left ventricle with normal systolic function and paradoxal septum motion, and a dilated and hypokinetic right ventricle. Color Doppler flow showed a mild grade mitral regurgitation with stiffened posterior mitral leaflet, as well as stiffened anterior tricuspid leaflet. However, the image quality was limited because of a pectus excavatum. In order to accurately characterize the cardiac involvement before lung transplantation, we performed cardiac MRI with a Philips Intera 1.5 T magnet (Philips Medical Systems, Best, The Netherlands) and a phase array synergy cardiac coil. Electrocardiogram gated cine images were performed with the use of segmented balanced turbo fast-field echo sequence (b-TFE, repetition time and echo time respectively 3 and 1.6 ms; 5 mm of thickness sections) in short axis, four chambers, and long axis. Thereafter, 0.2 mmol/kg of Gd-DTPA (Dotarem, Guerbet France) was administrated intravenously. Ten minutes after injection, contrasted enhanced images were acquired in short axis, and four chambers view with a segment tree-dimensional inversion-recovery turbo fast-field echo pulse sequence and linear k space order. The inversion time selected to optimally null the myocardium was validated by visual inspection with the use of a specific sequence to determine the best time of inversion (look locker sequence). Left ventricular systolic function was 54% (end diastolic volume= 119 mL, 71 mL/m; end systolic=55mL, 33 mL/m; LV mass=118 g and 73 g/m) with paradoxal motion of the septum. The right ventricle was dilated and hypokinetic (ejection fraction=26%) (Fig. 1, online movie 1). Cine imaging showed immobile posteriormitral leaflet which appeared thickened and stiffened (Fig. 1, online movie 1). Similar abnormalities were observed for the anterior tricuspid leaflet (Fig. 1, onlinemovie 2). No flowvoidwas perceptible but flowvelocity encoded imaging revealed amildmitral regurgitation (Fig. 2). Late enhancement imaging revealed no myocardial fibrosis. To thebest of our knowledge,wedescribe for thefirst time the ability of cardiacMRI to identify the featureofMPStype II cardiomyopathy.MPS type II is a rare X-linked recessive disease characterized by cellular accumulation of glycosaminoglycans and proteoglycans in all organs, caused by lysosomal dysfunction [1]. In most patients, death occurs in thefirst or second decade of life. Clinicalmanifestations associate severe airway obstruction and pulmonary restriction, neurological disorders and skeletal deformities. Cardiac involvement includes myocardial hypertrophy, systolic dysfunction and valve dysfunction due to leaflet Fig.1.MRI horizontal long axis view. The right ventricle is enlarged. The posterior leaflet of the mitral valve is thickened (white arrow head) as well as the anterior leaflet of the tricuspid valve (black arrow head).

Ｂａｌａｎｃｅｄ Ｔｕｒｂｏ Ｆｉｅｌｄ Ｅｃｈｏを用いた骨盤腔静脈叢描出のための至適撮像条件の検討

Evaluating the relation between the developing range and the extent of invasion of a malignant tumor around the pelvic venous plexus is an important index for making strategic therapeutic decisions. In this study, we tried to depict a venous plexus in the pelvis using Balanced Turbo Field Echo (B-TFE). At first, we used an original phantom (derived from one layer of lard and another of agar (0.1%Gd-DTPA, 0.9%NaCl), each 500 ml, and we changed the Start Up Echo (SUE); 0-30, SPAIR inversion delay time (delay time); 0-200 ms, shot interval (SI); 1150, 1500 ms and evaluated the degree of fat suppression in SNR, CNR (the air signal method). The fat suppression-effect was found to be high in delay time; 120 ms in SUE; 0, SI; 1150 ms and 160 ms in SUE; 0, SI; 1500 ms was different SUE>0 each delay time. As for the images of healthy volunteers (5 men and 5 women), after fixing optimum conditions, we evaluated the images visually, as assessed by two radiologists and two radiographers, comparing between SUE; 0-30 and SI; 1150 and 1500 ms. According to the visual evaluation, the fat suppression-effect was worse, more than with the delay time; 20. We judged the best image of the venous plexus in the pelvis as being at SUE; 10, SI; 1500 ms. We think that using the B-TFE can help distinguish pelvic venous plexuses, by setting an optimum sequence.

Quantitative analysis of first‐pass contrast‐enhanced myocardial perfusion MRI using a patlak plot method and blood saturation correction

The objectives of this study were to develop a method for quantifying myocardial K(1) and blood flow (MBF) with minimal operator interaction by using a Patlak plot method and to compare the MBF obtained by perfusion MRI with that from coronary sinus blood flow in the resting state. A method that can correct for the nonlinearity of the blood time-signal intensity curve on perfusion MR images was developed. Myocardial perfusion MR images were acquired with a saturation-recovery balanced turbo field-echo sequence in 10 patients. Coronary sinus blood flow was determined by phase-contrast cine MRI, and the average MBF was calculated as coronary sinus blood flow divided by left ventricular (LV) mass obtained by cine MRI. Patlak plot analysis was performed using the saturation-corrected blood time-signal intensity curve as an input function and the regional myocardial time-signal intensity curve as an output function. The mean MBF obtained by perfusion MRI was 86 +/- 25 ml/min/100 g, showing good agreement with MBF calculated from coronary sinus blood flow (89 +/- 30 ml/min/100 g, r = 0.74). The mean coefficient of variation for measuring regional MBF in 16 LV myocardial segments was 0.11. The current method using Patlak plot permits quantification of MBF with operator interaction limited to tracing the LV wall contours, registration, and time delays.