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Objectives Comprehensive training in ultrasound (US) imaging during radiology residency is crucial if radiologists are expected to maintain a substantial role in this widely used imaging modality. This study aimed to evaluate the current curriculum of US training among radiology residency programs across the country via a nationwide survey. Methods A 28-question survey was distributed among all academic radiology departments in the United States and their radiology residents. The survey consisted of 4 sections: general demographic information, training information, clinical competency, and adequacy of training (perspective). The Student t test and 1-way analyses of variance were performed to assess statistical significance. Results Overall, 256 residents from 32 states completed the questionnaire. Only 114 (45%) residents reported having a dedicated rotation for performing US studies. Although 228 (89%) of trainees believed they received adequate experience for interpreting US studies, only 66 (26%) of them had the same belief about performing them. Only 116 (45%) of the residents were comfortable operating the US machines in their departments. Higher years of residency training, having a dedicated rotation for performing US studies, and having more than 10 hours per year of didactic lectures and/or more than 5 hours per year of case conferences dedicated to US had a positive impact on the residents' clinical competency and perspective (all P Conclusions Most radiology residents do not feel confident in performing US examinations by themselves. However, higher clinical competency was reported in the residents who had dedicated rotations for performing US studies and received more hours of US lectures and case conferences throughout their residency.

PURPOSE: Accurate photon attenuation assessment from MR data remains an unmet challenge in the thorax due to tissue heterogeneity and the difficulty of MR lung imaging. As thoracic tissues encompass the whole physiologic range of photon absorption, large errors can occur when using, for example, a uniform, water‐equivalent or a soft‐tissue‐only approximation. The purpose of this study was to introduce a method for voxel‐wise thoracic synthetic CT (sCT) generation from MR data attenuation correction (AC) for PET/MR or for MR‐only radiation treatment planning (RTP). METHODS: Acquisition: A radial stack‐of‐stars combining ultra‐short‐echo time (UTE) and modified Dixon (mDixon) sequence was optimized for thoracic imaging. The UTE‐mDixon pulse sequence collects MR signals at three TE times denoted as UTE, Echo1, and Echo2. Three‐point mDixon processing was used to reconstruct water and fat images. Bias field correction was applied in order to avoid artifacts caused by inhomogeneity of the MR magnetic field. Analysis: Water fraction and R2* maps were estimated using the UTE‐mDixon data to produce a total of seven MR features, that is UTE, Echo1, Echo2, Dixon water, Dixon fat, Water fraction, and R2*. A feature selection process was performed to determine the optimal feature combination for the proposed automatic, 6‐tissue classification for sCT generation. Fuzzy c‐means was used for the automatic classification which was followed by voxel‐wise attenuation coefficient assignment as a weighted sum of those of the component tissues. Performance evaluation: MR data collected using the proposed pulse sequence were compared to those using a traditional two‐point Dixon approach. Image quality measures, including image resolution and uniformity, were evaluated using an MR ACR phantom. Data collected from 25 normal volunteers were used to evaluate the accuracy of the proposed method compared to the template‐based approach. Notably, the template approach is applicable here, that is normal volunteers, but may not be robust enough for patients with pathologies. RESULTS: The free breathing UTE‐mDixon pulse sequence yielded images with quality comparable to those using the traditional breath holding mDixon sequence. Furthermore, by capturing the signal before T2* decay, the UTE‐mDixon image provided lung and bone information which the mDixon image did not. The combination of Dixon water, Dixon fat, and the Water fraction was the most robust for tissue clustering and supported the classification of six tissues, that is, air, lung, fat, soft tissue, low‐density bone, and dense bone, used to generate the sCT. The thoracic sCT had a mean absolute difference from the template‐based (reference) CT of less than 50 HU and which was better agreement with the reference CT than the results produced using the traditional Dixon‐based data. CONCLUSION: MR thoracic acquisition and analyses have been established to automatically provide six distinguishable tissue types to generate sCT for MR‐based AC of PET/MR and for MR‐only RTP.

Purpose: MR-based pseudo-CT has an important role in MR-based radiation therapy planning and PET attenuation correction. The purpose of this study is to establish a clinically feasible approach, including image acquisition, correction, and CT formation, for pseudo-CT generation of the brain using a single-acquisition, undersampled ultrashort echo time (UTE)-mDixon pulse sequence. Methods: Nine patients were recruited for this study. For each patient, a 190-s, undersampled, single acquisition UTE-mDixon sequence of the brain was acquired (TE = 0.1, 1.5, and 2.8 ms). A novel method of retrospective trajectory correction of the free induction decay (FID) signal was performed based on point-spread functions of three external MR markers. Two-point Dixon images were reconstructed using the first and second echo data (TE = 1.5 and 2.8 ms). R2∗ images (1/T2∗) were then estimated and were used to provide bone information. Three image features, i.e., Dixon-fat, Dixon-water, and R2∗, were used for unsupervised clustering. Five tissue clusters, i.e., air, brain, fat, fluid, and bone, were estimated using the fuzzy c-means (FCM) algorithm. A two-step, automatic tissue-assignment approach was proposed and designed according to the prior information of the given feature space. Pseudo-CTs were generated by a voxelwise linear combination of the membership functions of the FCM. A low-dose CT was acquired for each patient and was used as the gold standard for comparison. Results: The contrast and sharpness of the FID images were improved after trajectory correction was applied. The mean of the estimated trajectory delay was 0.774 μs (max: 1.350 μs; min: 0.180 μs). The FCM-estimated centroids of different tissue types showed a distinguishable pattern for different tissues, and significant differences were found between the centroid locations of different tissue types. Pseudo-CT can provide additional skull detail and has low bias and absolute error of estimated CT numbers of voxels (−22 ± 29 HU and 130 ± 16 HU) when compared to low-dose CT. Conclusions: The MR features generated by the proposed acquisition, correction, and processing methods may provide representative clustering information and could thus be used for clinical pseudo-CT generation.

What's known on the subject? and What does the study add? In a recent rtMRI study, we were able to show that, during initiation of voiding, there was both funnelling of the bladder neck and simultaneous contraction of the ventral prostate. We presumed that the vertical contraction of the ventral prostate contributes to the initiation of successful micturition. The question remained as to whether this shortening of the ventral prostate is predominantly caused by contractile elements in the organ itself, or by surrounding contractile elements of the pelvic floor. In our study we provide insight in to anatomical changes, and biometric and functional analysis of the prostate during micturition. A sagittal contraction of the ventral prostate and the longitudinal smooth muscle elements at the onset of voiding, which can be observed on MRI, is likely to shorten and open up the prostatic urethra. Objective To investigate if in vitro contractile strength of the prostate and the prostatic urethra might correlate with the shortening of the ventral prostate seen on real-time magnetic resonance imaging (rtMRI). Micturition is a complex process that includes anatomical and neurological interactions for successful voiding. Recently we described on rtMRI that vertical contraction of the ventral prostate precedes initiation of male micturition and may contribute to the funnelling of the bladder neck. Patients and Methods In all, 10 patients undergoing radical prostatectomy (RP) were enrolled. Approval was obtained from all patients and by the local Ethics Committee. Preoperative rtMRI during voiding was performed as described before in eight patients undergoing RP, measuring the difference of the cranio-caudal distance of the ventral prostate (VP). To roughly estimate the amount of force required to deform the prostate in a vertical direction as seen on rtMRI, we uniaxially compressed the organ immediately after surgery by the same distance, assuming incompressibility and isotropy of prostatic tissue. A muscle strip (3 × 3 mm) from the ventral prostate, dorsal prostate and prostatic urethra was obtained after pathological evaluation. Contraction was elicited by electrical-field stimulation (EFS: 0.1 ms pulses at 2, 4, 8, 16, 32 and 64 Hz for 4 s). Results There was a mean cranio-caudal contraction of the ventral prostate by 7.6 mm at the onset of micturition on rtMRI (P = 0.002). The mean (sd) contractile force of strips elicited by EFS at 32 Hz was 1472.44 (706.88) mN for the ventral prostate, 1044.24 (894.66) mN for the dorsal prostate, and 639.10 (785.06) mN for the prostatic urethra (P = 0.02). Extrapolating these values to the whole organ diameter, we calculated comparable force as observed in compression experiments. Conclusions Our functional and biometric in vitro analyses of prostate tissue showed sufficient contractile strength of the ventral prostate to induce a shortening of the organ as seen on rtMRI. There was significant higher contractile strength in the ventral prostate than in the dorsal prostate or the proximal urethra. The consistency of in vivo and in vitro results underlines the significance of the ventral prostate for the initiation of normal micturition.

Study Type – Diagnostic (exploratory cohort) Level of Evidence 2b What’s known on the subject? and What does the study add? Micturition cysturethrography or video urodynamics can show sequences of the micturition cycle, but are limited to show all participating structures at one. MRI is a non invasive imaging methodology to describe the anatomy of physiological voiding or voiding dysfunction. In our study we provide preliminary insight in anatomical changes in the lower urinary tract during physiological micturition in males. This imaging methodology may help detecting anatomical differences in individuals with voiding disorders. Further, we presume that the vertical contraction of the ventral prostate seem to contribute to the initiation of successful micturition, additionally to the funnelling of the bladderneck. OBJECTIVE • To investigate the interactions between the bladder, urethra, pelvic floor and the function of the prostate during ‘normal’ voiding. PATIENTS AND METHODS • In all, 16 men with no history of urinary incontinence, urgency or obstructive voiding dysfunction were enrolled. We analysed the interaction between the bladder, urethra, pelvic floor and changes in the prostate during the Valsalva manoeuvre and voiding using real-time magnetic resonance imaging (rtMRI). • The axis through the external sphincter (AES) to pubo-coccygeal line (PC-line) and the angle between the axis of the os pubis (AOP) and ventral prostate (VP) was measured before and at the end of voiding. Additionally, the angle between the AOP and the VP was measured during the Valsalva manoeuvre. • Change of position, or contraction, of the VP was measured. RESULTS • The mean age of the men was 69.8 years and mean prostate volume 33.1 mL. • Before voiding, the mean AES to PC-line was 10.5 mm. At the end of voiding, the mean AES to PC-line was 20 mm. • The mean angle between AOP/VP was 31.6° in the storage phase and increased to a mean of 54.5° during voiding. • During the Valsalva manoeuvre, the angle between the AOP/VP remained constant. • There was a mean vertical contraction of the VP of 48.25 mm before voiding and a declining of the cranio-caudal distance of the VP with a mean of 33.92 mm during voiding. CONCLUSIONS • All the men in our study showed relaxation of the pelvic floor, followed by a descent of the bladder neck. Voiding could not be initiated unless the prostate rotated around the symphysis. • The study suggests that both the rotation and a vertical contraction of the prostate precede voiding. • The anatomy of physiological voiding or voiding dysfunction can be investigated non-invasively using rtMRI.

Dynamic susceptibility contrast MRI (DSC-MRI) is the current standard for the measurement of Cerebral Blood Flow (CBF) and Cerebral Blood Volume (CBV), but it is not suitable for the measurement of Extraction Flow (EF) and may not allow for absolute quantification. The objective of this study was to develop and evaluate a methodology to measure CBF, CBV, and EF from T1-weighted dynamic contrast-enhanced MRI (DCE-MRI). A two-compartment modeling approach was developed, which applies both to tissues with an intact and with a broken Blood-Brain-Barrier (BBB). The approach was evaluated using measurements in normal grey matter (GM) and white matter (WM) and in tumors of 15 patients. Accuracy and precision were estimated with simulations of normal brain tissue. All tumor and normal tissue curves were accurately fitted by the model. CBF (mL/100 mL/min) was 82 +/- 21 in GM and 23 +/- 14 in WM, CBV (mL/100 mL) was 2.6 +/- 0.8 in GM and 1.3 +/- 0.4 in WM. EF (mL/100 mL/min) was close to zero in GM (-0.009 +/- 0.05) and WM (-0.03 +/- 0.08). Simulations show an overlap between CBF values of WM and GM, which is eliminated when Contrast-to-Noise (CNR) is improved. The model provides a consistent description of tracer kinetics in all brain tissues, and an accurate assessment of perfusion and permeability in reference tissues. The measurement sequence requires optimization to improve CNR and the precision in the perfusion parameters. With this approach, DCE-MRI presents a promising alternative to DSC-MRI for quantitative bolus-tracking in the brain.

Purpose To investigate the image quality and vessel depiction of renal MRA with integrated parallel imaging techniques (iPAT) using acceleration factors of 2 and 3. Materials and Methods In this prospective study renal MRA was performed on 14 and 12 patients with acceleration factors of 3 and 2, respectively. For the MRA a 3D-GRE sequence with an acquired spatial resolution of 0.9 × 0.8 × 1.0 mm3 was applied (TR/TE = 3.79 msec/1.39 msec, FOV = 400 mm × 320 mm, acquired matrix = 512 × 384, flip angle = 25°) on a 32-channel 1.5T MR scanner. The acquisition time was 26 seconds with iPAT 2, and 19 seconds with iPAT3. All parameters other than acquisition time and acceleration factor were kept constant. To assess the signal-to-noise ratio (SNR) we performed repetitive phantom measurements using iPAT 2 and 3. The images were rated by two radiologists in terms of noise, artifacts, and the quality of vessel depiction for the proximal, segmental, and subsegmental renal artery. A Mann-Whitney U-test and kappa-test were used for statistical analysis. Results SNR decreased significantly with iPAT 3 in the phantom measurements. The two readers found no difference in noise, but significantly fewer artifacts with iPAT 3. The depiction of segmental vessels was significantly better for both readers with iPAT 3, and the subsegmental vessels were rated significantly better by one reader. iPAT 3 also resulted in a better interreader agreement. Conclusion The use of iPAT 3 for renal MRA enables a better depiction of the distal parts of the renal artery. The decrease in SNR is not diagnostically impairing. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc.

Purpose To compare high-resolution T2-weigthed images of the liver with and without integrated parallel acquisition techniques (iPAT) using either breath-hold sequences in combination with prospective acquisition motion correction (PACE) or respiratory triggering. Materials and Methods Ten volunteers and 10 patients underwent each four different high-resolution fast spin echo (FSE) T2-weigthed sequences with 5 mm slice thickness and a full 320 matrix: a multi-breath-hold FSE sequence with and without iPAT and PACE and a respiratory-triggered FSE sequence with and without iPAT. Image quality was rated with a five-point scale by two independent readers. Signal intensity measurements were performed on a water phantom. Results The sequences with iPAT required a substantially shorter acquisition time without loss of image quality. Overall image quality was rated equal for all sequences by both readers. Image time for nine slices with iPAT was 13 seconds (19 seconds without iPAT) with multi-breath-hold and on average 4:00 minutes (7:02 minutes without iPAT) with respiratory triggering. Imaging with the PACE technique resulted in more correct positioning of the image stacks. Conclusion T2-weighted fast imaging with iPAT is feasible and results in high-quality images within a short acquisition time. Overall image quality is not negatively affected by iPAT. J. Magn. Reson. Imaging 2004;20:443–450. © 2004 Wiley-Liss, Inc.

Purpose: To evaluate volumetric coverage of a Mick Radionuclear titanium Split-Ring applicator (SRA) with/without interstitial needle compared to an intracavitary Vienna applicator (VA), interstitial-intracavitary VA, and intracavitary ring and tandem applicator (RTA). Methods: A 57 year-old female with FIGO stage IIB cervical carcinoma was treated following chemoradiotherapy (45Gy pelvic and 5.4Gy parametrial boost) with highdose- rate (HDR) brachytherapy to 30Gy in 5 fractions using a SRA. A single interstitial needle was placed using the Ellis Interstitial Cap for the final three fractions to increase coverage of left-sided gross residual disease identified on 3T-MRI. High-risk (HR) clinical target volume (CTV) and intermediate-risk (IR) CTV were defined using axial T2-weighted 2D and 3D MRI sequences (Philips PET/MRI unit). Organs-at-risks (OARs) were delineated on CT. Oncentra planning system was used for treatment optimization satisfying GEC-ESTRO guidelines for target coverage and OAR constraints. Retrospectively, treatment plans (additional 20 plans) were simulated using intracavitary SRA (without needle), intracavitary VA (without needle), interstitial-intracavitary VA, and intracavitary RTA with this same patient case. Plans were optimized for each fraction to maintain coverage to HR-CTV. Results: Interstitial-intracavitary SRA achieved the following combined coverage for external radiation and brachytherapy (EQD2): D90 HR-CTV =94.6Gy; Bladder_2cc =88.9Gy; Rectum_2cc =65.1Gy; Sigmoid_2cc =48.9Gy; Left vaginal wall (VW) =103Gy, Right VW =99.2Gy. Interstitial-intracavitary VA was able to achieve identical D90 HR-CTV =94.6Gy, yet Bladder_2cc =91.9Gy (exceeding GEC-ESTRO recommendations of 2cc 80Gy without severely overdosing OARs. Conclusion: The Ellis Interstitial Cap for the SRA offered superior dosimetric coverage as compared to the interstitialintracavitary VA. This represents the first reported use for this devise, and further investigation is warranted.

Purpose: Accurate and robust photon attenuation derived from MR is essential for PET/MR and MR-based radiation treatment planning applications. Although the fuzzy C-means (FCM) algorithm has been applied for pseudo-CT generation, the input feature combination and the number of clusters have not been optimized. This study aims to optimize both for clinically practical pseudo-CT generation. Methods: Nine volunteers were recruited. A 190-second, single-acquisition UTE-mDixon with 25% (angular) sampling and 3D radial readout was performed to acquire three primitive MR features at TEs of 0.1, 1.5, and 2.8 ms: the free-induction-decay (FID), the first and the second echo images. Three derived images, Dixon-fat and Dixon-water generated by two-point Dixon water/fat separation, and R2* (1/T2*) map, were also created. To identify informative inputs for generating a pseudo-CT image volume, all 63 combinations, choosing one to six of the feature images, were used as inputs to FCM for pseudo-CT generation. Further, the number of clusters was varied from four to seven to find the optimal approach. Mean prediction deviation (MPD), mean absolute prediction deviation (MAPD), and correlation coefficient (R) of different combinations were compared for feature selection. Results: Among the 63 feature combinations, the four that resulted in the best MAPD and R were further compared along with the set containing all six features. The results suggested that R2* and Dixon-water are the most informative features. Further, including FID also improved the performance of pseudo-CT generation. Consequently, the set containing FID, Dixon-water, and R2* resulted in the most accurate, robust pseudo-CT when the number of cluster equals to five (5C). The clusters were interpreted as air, fat, bone, brain, and fluid. The six-cluster Result additionally included bone marrow. Conclusion: The results suggested that FID, Dixon-water, R2* are the most important features. The findings can be used to facilitate pseudo-CT generation for unsupervised clustering. Please note that the project was completed with partial funding from the Ohio Department of Development grant TECH 11-063 and a sponsored research agreement with Philips Healthcare that is managed by Case Western Reserve University. As noted in the affiliations, some of the authors are Philips employees

Purpose: Emerging technologies such as dedicated PET/MRI and MR-therapy systems require robust and clinically practical methods for determining photon attenuation. Herein, we propose using novel MR acquisition methods and processing for the generation of pseudo-CTs. Methods: A single acquisition, 190-second UTE-mDixon sequence with 25% (angular) sampling density and 3D radial readout was performed on nine volunteers. Three water-filled tubes were placed in the FOV for trajectory-delay correction. The MR data were reconstructed to generate three primitive images acquired at TEs of 0.1, 1.5 and 2.8 ms. In addition, three derived MR images were generated, i.e. two-point Dixon water/fat separation and R2* (1/T2*) map. Furthermore, two spatial features, i.e. local binary pattern (S-1) and relative spatial coordinates (S-2), were incorporated. A direct-mapping operator was generated using Artificial Neural Networks (ANNs) for transforming the MR features to a pseudo-CT. CT images served as the training data and, using a leave-one-out method, for performance evaluation using mean prediction deviation (MPD), mean absolute prediction deviation (MAPD), and correlation coefficient (R). Results: The errors between measured CT and pseudo-CT declined dramatically when the spatial features, i.e. S-1 and S-2, were included. The MPD, MAPD, and R were, respectively, 5±57 HU, 141±41 HU, and 0.815±0.066 for results generated by the ANN trained without the spatial features and were 32±26 HU, 115±18 HU, and 0.869±0.035 with the spatial features. The estimation errors of the pseudo-CT were smaller when both the S-1 and S-2 were used together than when either the S-1 or the S-2 was used. Pseudo-CT generation (256×256×256 voxels) by ANN took < 0.5 s using a computer having an Intel i7 3.4GHz CPU and 16 GB RAM. Conclusion: The proposed direct-mapping ANN approach is a technically accurate, clinically practical method for pseudo-CT generation and can potentially help improve the accuracy of MR-AC and MR-RTP applications. Please note that the project was completed with partial funding from the Ohio Department of Development grant TECH 11-063 and a sponsored research agreement with Philips Healthcare that is managed by Case Western Reserve University. As noted in the affiliations, some of the authors are Philips employees

Purpose: Radiotherapy plans for patients with cervical cancer treated with EBRT followed by HDR brachytherapy are optimized by constraining dose to organs at risk (OARs). Risk of treatment related toxicities is estimated based on the dose received to the hottest 2cc (D2cc) of the bladder, bowel, rectum, and sigmoid. To account for intrafractional variation in OAR volume and positioning, a dose deformation method is proposed for more accurate evaluation of dose distribution for these patients. Methods: Radiotherapy plans from five patients who received 50.4Gy pelvic EBRT followed by 30Gy in five fractions of HDR brachytherapy, using split-ring and tandem applicators, were retrospectively evaluated using MIM Software version 6.0. Dose accumulation workflows were used for initial deformation of EBRT and HDR planning CTs onto a common HDR planning CT. The Reg Refine tool was applied with user-specified local alignments to refine the deformation. Doses from the deformed images were transferred to the common planning CT. Deformed doses were scaled to the EQD2, following the linear-quadratic BED model (considered α/β ratio for tumor as 10, and 3 for rest of the tissues), and then combined to create the dose composite. MIM composite doses were compared to the clinically-reported plan assessments based upon the American Brachytherapy Society (ABS) guidelines for cervical HDR brachytherapy treatment. Results: Bladder D2cc exhibited significant reduction (−11.4%±3.85%, p 0.05 for all) relative to the calculated values used clinically. Conclusion: Application of deformable dose composite techniques may lead to more accurate total dose reporting and can allow for elevated dose to target structures with the assurance of not exceeding dose to OARs. Further study into deformable dose composition and correlation with clinical outcomes is warranted.