Phased-array Coil Research Articles

L’IRM 3 Tesla multi-paramétrique dans le staging du cancer prostatique en pratique courante

To analyse the detection ability of a multiparametric 3T MRI with phased-array coil in comparison with the pathological data provided by the prostatectomy specimens. Prospective study of 30 months, including 74 patients for whom a diagnosis of prostate cancer had been made on randomized prostate biopsies, and all eligible to a radical prostatectomy. They all underwent multiparametric 3T MRI with pelvic phased-array coil including T2-weighted imaging (T2W), dynamic contrast-enhanced (DCE) and diffusion-weighted imaging (DWI) with an ADC mapping. Each gland was divided in octants. Three specific criteria have been sought (detection ability, capsular contact [CC] and extracapsular extension [ECE]), in comparison with the pathological data provided by the prostatectomy specimens. Five hundred and ninety-two octants were considered with 124 significant tumors (volume ≥ 0.1cm(3)). The general ability of tumor detection had a sensitivity, specificity, PPV and NPV respectively to 72.3%, 87.4%, 83.2% and 78.5%. The estimate of the CC and ECE had a high negative predictive power with specificities and VPN respectively to 96.4% and 95.4% for CC, and 97.5 and 97.7% for ECE. Multiparametric 3T MRI with pelvic phased-array coil appeared to be a reliable imaging technique in clinical and routine practice for the detection of localized prostate cancer. Estimation of the CC and millimeter ECE remains to be clarified, even if the negative predictive power for these parameters seems encouraging.

Diffusion-tensor MRI and tractography of the esophageal wall ex vivo.

To demonstrate the feasibility of diffusion-tensor magnetic resonance imaging (MRI) and tractography as a means of evaluating the individual layers of the normal esophageal wall by using esophageal specimens containing carcinoma. Twelve esophageal specimens each containing a carcinoma that were preserved in formalin were studied with a 7.0-T small-bore MR system equipped with a four-channel phased-array surface coil. Diffusion-tensor MR images were obtained with a field of view of 50-60 × 25-30 mm, matrix of 256 × 128, section thickness of 1 mm, b value of 1000 sec/mm(2) , and motion-probing gradient in seven noncollinear directions. The diffusion-weighted images, apparent diffusion coefficient (ADC) maps, fractional anisotropy (FA) maps, direction-encoded color FA maps, and tractographic images in the 12 esophageal specimens were compared with the histopathologic findings, which served as the gold standard. The diffusion-weighted images, ADC maps, FA maps, and direction-encoded color FA maps depicted the normal esophageal wall in all 12 specimens (100%) as consisting of eight layers, which clearly corresponded to the tissue layers of the esophageal wall. The ADC, FA, λ1 , λ2 , and λ3 values of each layer of the normal esophageal wall were significantly different from the corresponding values of the adjacent layer or layers of the esophageal wall. Diffusion-tensor tractographic images were able to selectively display the layers of the normal esophageal wall. By looking at the normal part of esophageal specimens containing carcinoma, we have demonstrated that diffusion-tensor MRI and tractography are capable of depicting the individual tissue layers of the normal esophageal wall.

Is the Transport of a Gadolinium-Based Contrast Agent Decreased in a Degenerated or Aged Disc? A Post Contrast MRI Study

A post contrast magnetic resonance imaging study has been performed in a wide population of low back pain patients to investigate which radiological and phenotypic characteristics influence the penetration of the contrast agent in lumbar discs in vivo. 37 patients affected by different pathologies (disc herniation, spondylolisthesis, foraminal stenosis, central canal stenosis) were enrolled in the study. The selected population included 26 male and 11 female subjects, with a mean age of 42.4±9.3 years (range 18–60). Magnetic resonance images of the lumbar spine were obtained with a 1.5 T scanner (Avanto, Siemens, Erlangen, Germany) with a phased-array back coil. A paramagnetic non–ionic contrast agent was injected with a dose of 0.4 ml/kg. T1-weighted magnetic resonance images were subsequently acquired at 5 time points, 5 and 10 minutes, 2, 4 and 6 hours after injection. Endplates presented clear enhancement already 5 minutes after injection, and showed an increase in the next 2 hours followed by a decrease. At 5 and 10 minutes, virtually no contrast medium was present inside the intervertebral disc; afterwards, enhancement significantly increased. Highly degenerated discs showed higher enhancement in comparison with low and medium degenerated discs. Discs classified as Pfirrmann 5 showed a statistically significant higher enhancement than Pfirrmann 1, 2 and 3 at all time points but the first one, possibly due to vascularization. Disc height collapse and Modic changes significantly increased enhancement. Presence of endplate defects did not show any significant influence on post contrast enhancement, but the lack of a clear classification of endplate defects as seen on magnetic resonance scans may be shadowing some effects. In conclusion, disc height, high level of degeneration and presence of Modic changes are factors which increase post contrast enhancement in the intervertebral disc. The effect of age could not be demonstrated.

Dual-source parallel radiofrequency excitation ACR phantom magnetic resonance imaging at 3 T: Assessment of the effect of image quality on high-contrast spatial resolution, percent signal ghosting, and low-contrast object detectability in comparison with conventional single-source transmission

The purpose of the present study was to assess dual-source parallel radiofrequency (RF) excitation American College of Radiology (ACR) phantom magnetic resonance (MR) imaging at 3T compared with conventional single-source RF transmission and compared with the standard ACR MRI phantom test. We used a 3T MR scanner equipped with dual-source parallel RF excitation and an 8-channel head phased array coil. We employed T1- and T2-weighted fast spin echo (FSE) pulse sequences for an assessment of the impact of image quality on high-contrast spatial resolution, percent signal ghosting and low-contrast object detectability following the ACR MRI quality control (QC) manual. With geometric accuracy and identical slice locations, dual RFs using dual-source parallel RF excitation MR showed an advantage over single RF using dual-source parallel RF excitation MR and conventional MR in terms of high-contrast spatial resolution (p < 0.010), percent signal ghosting (p < 0.010), and low-contrast object detectability (p < 0.010). The quality of the image from the dual-source parallel RF excitation MR equipment was superior to that of the image from conventional MR equipment for the ACR phantom. We need to pursue dual-source parallel RF excitation MR studies involving various clinical cases.

Comparison of Interreader Reproducibility of the Prostate Imaging Reporting and Data System and Likert Scales for Evaluation of Multiparametric Prostate MRI

The objective of our study was to compare interreader reproducibility of the recently proposed "Prostate Imaging Reporting and Data System," or "PI-RADS," scale incorporating fixed criteria and a standard Likert scale based on overall impression for prostate cancer localization using multiparametric MRI. Fifty-five patients who underwent a 3-T prostate MRI examination using a pelvic phased-array coil and incorporating T2-weighted imaging, diffusion-weighted imaging, and dynamic contrast-enhanced imaging were included in the study. Three radiologists (6, 4, and 1 year of experience) independently scored 18 regions (12 in the peripheral zone [PZ] and six in the transition zone [TZ]) using PI-RADS (range, 3-15) and Likert (range, 1-5) scales, which were based on fixed criteria and overall impression, respectively. Interreader reproducibility was evaluated using the concordance correlation coefficient (CCC), which assesses exact agreement between scores (minimal, < 0.2; poor, 0.2-<0.4; moderate, 0.4-<0.6; strong, 0.6-<0.8; almost perfect, ≥ 0.8). Agreement between experienced readers was strong in the PZ and TZ combined and in the PZ for both the PI-RADS and Likert scales (CCC = 0.608-0.677), moderate in the TZ for the Likert scale (CCC = 0.519), and poor in the TZ for PI-RADS (CCC = 0.376). Agreement between experienced and inexperienced readers was moderate to poor in the PZ and TZ combined for PI-RADS (CCC = 0.340-0.477), moderate in the PZ and TZ combined for the Likert scale (CCC = 0.471-0.497), moderate in the PZ for PI-RADS and Likert scales (CCC = 0.472-0.542), minimal to poor in the TZ for PI-RADS (CCC = 0.094-0.283), and poor in the TZ for the Likert scale (CCC = 0.287-0.400). Interreader reproducibility tended to be higher for relatively experienced readers than for less experienced readers and to be higher in the PZ than in the TZ. For the relatively experienced readers, reproducibility was similar for PI-RADS and Likert scales in the PZ but was somewhat higher for the Likert scale than for PI-RADS in the TZ.

Coronary artery angiography and myocardial viability imaging: a 3.0-T contrast-enhanced magnetic resonance coronary artery angiography with Gd-BOPTA

With improving MR sequence, phase-array coil and image quality, cardiac magnetic resonance imaging is becoming a promising method for a comprehensive non-invasive evaluation of coronary artery and myocardial viability. The study aimed to evaluate contrast-enhanced whole-heart coronary MR angiography (CE WH-CMRA) at 3.0-Tesla for the diagnosis of significant stenosis (≥50%) and detection of myocardial infarction (MI) in patients with suspected coronary artery disease (CAD). CE WH-CMRA was performed in consecutive 70 patients with suspected CAD by using a 3.0-T MR system. A respiratory-gated, electrocardiography-triggered, inversion-recovery, segmented fast low angle shot sequence (TI = 200 ms) was used. Data acquisition began 60 s after the slow injection of Gd-BOPTA (0.2 mmol/kg body weight, at an injection rate 0.3 ml/s). At last, breath-hold 2D-PSIR-SSFP sequence was performed. Diagnostic accuracy of CE WH-CMRA in detecting significant stenosis (≥50%) was evaluated using invasive coronary angiography as the referenced standard. The MI region appearing as high signal intensity visualized on CEWH-CMRA and 2D-PSIR-SSFP images were compared and analyzed. CE WH-CMRA correctly identified 42 of 44 patients with significant CAD. The overall sensitivity, specificity, negative predictive value, positive predictive value and accuracy for diagnosing significant CAD was 83.6, 95.8, 96.0, 82.8 and 93.4% respectively. The MI region detected by WH-CMRA and 2D-PSIR-SSFP were consistent in 10 patients and these segments manifested with transmural or subendocardial enhancement patterns. Only one MI patient was judged inconsistent between WH-CMRA and 2D-PSIR-SSFP, who was confirmed by clinical and electrocardiogram results. The enhancement pattern in this patient was spotted and focal in 2D-PSIR-SSFP, but was dismissed by WH-CMRA. It is feasible to obtain information about coronary artery stenosis and myocardial viability in a single CE WH-CMRA with administration of Gd-BOPTA.

The role of apparent diffusion coefficient values in the differential diagnosis of breast lesions in diffusion-weighted MRI

We aimed to determine the apparent diffusion coefficients (ADCs) of focal breast lesions on diffusion-weighted magnetic resonance imaging (DW-MRI) and to evaluate whether ADC measurement can be used to characterize lesions as benign or malignant. Fifty-one patients between the ages of 18-79 years (mean age, 48.5 years) with 51 histopathologically verified breast lesions were included in this study. The patients were examined with a 1.5 Tesla system using a bilateral phased-array breast coil. Spin-echo echo-planar imaging was used. The images were obtained with b values of 50, 400, and 800 s/mm(2). The ADC values were calculated for breast lesions and for normal fibroglandular tissue. Receiver operating characteristics analyses were performed to find the threshold ADC values. The mean ADC was 1.42 ± 0.17 × 10(-3) mm(2)/s for normal fibroglandular tissue, 1.9 ± 0.45 × 10(-3) mm(2)/s for benign lesions, and 0.86 ± 0.26 × 10(-3) mm(2)/s for malignant lesions. The threshold ADC value to differentiate bening and malignant lesions was 1.03 × 10(-3) mm(2)/s (sensitivity, 88.5%; specificity, 100%). With the ADC ratio (lesion to normal fibroglandular tissue), the threshold was 0.8 (sensitivity, 91.4%; specificity, 100%). The ADC value obtained from malignant lesions was statistically different from that of benign lesions (P < 0.001). Diffusion-weighted imaging can be used to differentiate malignant and benign breast lesions.

Role of Endorectal Prostate MRI in Patients with Initial Suspicion of Prostate Cancer

To evaluate the role of conventional endorectal prostate MRI in patients with initial suspicion of prostate cancer. Ethics board approval was received for this retrospective study of 87 men who underwent 1.5-Tesla conventional prostate MRI with a combination of endorectal and body phased-array coils for suspected prostate cancer before their first systematic 12-core TRUS-guided biopsy. Three radiologists independently analyzed the images, dividing the prostate into 12 regions corresponding to the biopsy scheme and scoring each region for the presence of prostate cancer on a 5-point scale. Results were analyzed by prostate region. ROC analysis was done and descriptive statistics were calculated. The negative predictive value, specificity, sensitivity and positive predictive value were calculated using dichotomized scores (benign tissue = scores of 1 and 2; malignant tissues = scores of 3, 4, and 5). Biopsy revealed cancer in 47/87 patients (26 low-grade [Gleason score 6]; 21 high-grade [Gleason score ≥ 3 + 4]), and 184/1044 cores (77 low-grade and 107 high-grade) with a median of 3 positive cores per cancer patient (range 1 - 12). The areas under ROC curves were 0.65 - 0.67 for cancer detection by region overall and 0.75 - 0.76 for the detection of high-grade cancer by region. Statistic figures for the detection of all cancers/high-grade cancers by region were as follows: negative predictive value, 87.4 - 88.2 %/92.6 - 93.1 %; specificity, 72.3 - 79.4 %/71.5 - 79.8 %; sensitivity, 49.5 - 54.8 %/62.6 - 69.2 %; and positive predictive value, 29.3 - 34.0 %/29.4 - 34.7 %. In patients with suspected prostate cancer, negative MRI findings indicate the absence of high-grade prostate cancer on subsequent TRUS-guided 12-core biopsy with high probability. However, agreement between conventional 1.5-T endorectal prostate MRI and systematic 12-core TRUS-guided biopsy for the detection of prostate cancer appears to be moderate.

Correlation between MRI and double-balloon urethrography findings in the diagnosis of female periurethral lesions

This study aims to evaluate the correlation of MRI findings with double-balloon urethrography (DBU) in diagnosing female urethral diverticula and other periurethral lesions.In this retrospective study, females with clinically suspected periurethral lesions who underwent both MRI and DBU between 2008 and 2012 were evaluated. MRI was performed on a 1.5Tesla unit using a pelvic phased array coil. Protocol included small FOV pelvic images, multiplanar T2-w, T1-w with and without contrast injection. DBU was performed by a dedicated catheter. Images were evaluated in consensus by two readers. Diverticula were evaluated by, size, number, complexity, location and connection to urethra, and other periurethral lesions were evaluated by size, location and connection. Supplement clinical and surgical data were retrieved from medical records and telephone interviews.Seventeen females (mean age 44 years, range 20–69) were included in the study. Diverticula were diagnosed by both modalities (9 cases), by neither (6 cases, 88% correlation) by MRI alone (1 case) and by DBU alone (1 case). Among diverticula, correlation of number, complexity, location and demonstration of connection to urethra was 89%, 67%, 67%, and 56%, respectively. Alternative diagnosis solely by MRI included vaginal wall cysts (3 cases), endometriosis (1 case) and ectopic ureter (1 case). No periurethral lesion was found by either modality in 2 cases.The correlation between MRI and DBU in diagnosing female periurethral lesions is very good for anatomical delineation of diverticula. MRI, which does not involve radiation, may also indicate alternative diagnoses that can contribute to proper patient management.

Impact of different coils on biochemical T2 and T2* relaxation time mapping of articular patella cartilage

The purpose of our study was to assess T2 and T2* relaxation time values of patella cartilage in healthy volunteers using three different coils at 3.0 Tesla MRI and their influence on the quantitative values. Fifteen volunteers were examined on the same 3-Tesla MR unit using three different coils: (i) a dedicated eight-channel knee phased-array coil; (ii) an eight-channel multi-purpose coil, and (iii) a one-channel 1H surface coil. T2 and T2* relaxation time measurements were prepared by a multi-echo spinecho respectively a gradient-echo sequence. A semi-automatic region-of-interest analysis was performed for patella cartilage. To allow stratification, a subregional analysis was carried out (deep-superficial cartilage layer). Statistical analysis-of-variance was performed. The mean quantitative T2 values showed statistically significant differences in all comparison combinations. The differences between the mean quantitative T2* values were slightly less pronounced than the T2 evaluation and only the comparison between (i) and (ii) showed a significant difference. The results of T2 and T2* values showed, independent of the used coil, higher values in the superficial zone compared to the deep zone (p < 0.05). Looking at the signal alterations, all coils showed clearly higher values (and thus more signal alterations as a sign of noise) in the deep layer. The validation of the reliability showed a high intra-class correlation coefficient and hence a very high plausibility (ICC was between 0.870 and 0.905 for T2 mapping and between 0.879 and 0.888 for T2* mapping). The present results demonstrate that biochemical T2 and T2* mapping is significantly dependent on the utilized coil.

A New Sign for Detection of Extracapsular Extension of Prostatic Adenocarcinoma: Sum of Positive Sextants per Lobe Combining Interpretation of Magnetic Resonance Imaging and Prostate Biopsy Results

BackgroundThe objective of this study was to assess the possibility of improving the reliability of preoperative detection of extracapsular extension (ECE) in each prostate lobe by using a new sign called sum of positive sextants per lobe (SPS-L), combining interpretation of MRI and prostate biopsy results. Patients and MethodsWe reviewed the charts of 590 patients undergoing radical prostatectomy between 2002 and 2007. All patients were assessed by preoperative 1.5 Tesla MRI using an integrated endorectal and pelvic phased array coil. A sextant was defined as “positive” when tumor infiltration was observed on a biopsy sample or a pathologic image was observed on MRI (0 = absent, 1 = present). A score, called sum of positive sextants per lobe (SPS-L), was defined as the sum of positive sextants on biopsy samples and positive sextants on MRI (MRI-L) for each lobe. A second score taking into account the presence or absence of ECE visualized on MRI (T3 MRI-L + SPS-L) was also tested for the detection of ECE per lobe. ResultsOn multivariate analysis, the SPS-L and T3 MRI-L + SPS-L scores were significantly higher in the presence of ECE and extensive ECE (P < .0001). The areas under receiver operating characteristic (ROC) curves were significantly greater for the T3 MRI-L + SPS-L score than for the positive biopsy result per lobe (PB+/L) rate (P < .0001). ConclusionThe use of indirect signs (SPS-L) associated with direct signs (T3 MRI) allows the preoperative detection of ECE per lobe by endorectal 1.5 Tesla MRI with high sensitivity.

Prostate MRI: Who, when, and how? Report from a UK consensus meeting

The current pathway for men suspected of having prostate cancer [transrectal biopsy, followed in some cases by magnetic resonance imaging (MRI) for staging] results in over-diagnosis of insignificant tumours, and systematically misses disease in the anterior prostate. Multiparametric MRI has the potential to change this pathway, and if performed before biopsy, might enable the exclusion of significant disease in some men without biopsy, targeted biopsy in others, and improvements in the performance of active surveillance. For the potential benefits to be realized, the setting of standards is vital. This article summarizes the outcome of a meeting of UK radiologists, at which a consensus was achieved on (1) the indications for MRI, (2) the conduct of the scan, (3) a method and template for reporting, and (4) minimum standards for radiologists.

Diffusion-weighted MRI of the prostate at 3.0 T: Comparison of endorectal coil (ERC) MRI and phased-array coil (PAC) MRI—The impact of SNR on ADC measurement

PurposeTo compare ADC values measured from diffusion-weighted MR (DW-MR) images of the prostate obtained with both endorectal and phased-array coils (ERC+PAC) to those from DW-MRI images obtained with an eight-channel torso phased-array coil (PAC) at 3.0T. MethodsThe institutional review board issued a waiver of informed consent for this HIPAA-compliant study. Twenty-five patients with biopsy-proven prostate cancer underwent standard 3-T MRI using 2 different coil arrangements (ERC+PAC and PAC only) in the same session. DW-MRI at five b-values (0, 600, 1000, 1200, and 1500s/mm2) were acquired using both coil arrangements. On b=0 images, signal-to-noise ratios (SNRs) were measured as the ratio of the mean signal from PZ and TZ ROIs to the standard deviation from the mean signal in an artifact-free ROI in the rectum. Matching regions-of-interest (ROIs) were identified in the peripheral zone and transition zone on ERC-MRI and PAC-MRI. For each ROI, mean ADC values for all zero and non-zero b-value combinations were computed. ResultsMean SNR with ERC-MRI at PZ (66.33±27.07) and TZ (32.69±12.52) was 9.27 and 5.52 times higher than with PAC-MRI ((7.32±2.30) and (6.13±1.56), respectively) (P<0.0001 for both). ADCs from DW-MR images obtained with all b-values in the PZ and TZ were significantly lower with PAC-MRI than with ERC-MRI (P<0.001 for all). ConclusionLower SNR of DW-MR images of the prostate obtained with a PAC can significantly decrease ADC values at higher b-values compared to similar measurements obtained using the ERC. To address these requirements, clinical MR systems should have image processing capabilities which incorporate the noise distribution.

FID modulus: a simple and efficient technique to phase and align MR spectra

The post-processing of MR spectroscopic data requires several steps more or less easy to automate, including the phase correction and the chemical shift assignment. First, since the absolute phase is unknown, one of the difficulties the MR spectroscopist has to face is the determination of the correct phase correction. When only a few spectra have to be processed, this is usually performed manually. However, this correction needs to be automated as soon as a large number of spectra is involved, like in the case of phase coherent averaging or when the signals collected with phased array coils have to be combined. A second post-processing requirement is the frequency axis assignment. In standard mono-voxel MR spectroscopy, this can also be easily performed manually, by simply assigning a frequency value to a well-known resonance (e.g. the water or NAA resonance in the case of brain spectroscopy). However, when the correction of a frequency shift is required before averaging a large amount of spectra (due to B 0 spatial inhomogeneities in chemical shift imaging, or resulting from motion for example), this post-processing definitely needs to be performed automatically. Zero-order phase and frequency shift of a MR spectrum are linked respectively to zero-order and first-order phase variations in the corresponding free induction decay (FID) signal. One of the simplest ways to remove the phase component of a signal is to calculate the modulus of this signal: this approach is the basis of the correction technique presented here. We show that selecting the modulus of the FID allows, under certain conditions that are detailed, to automatically phase correct and frequency align the spectra. This correction technique can be for example applied to the summation of signals acquired from combined phased array coils, to phase coherent averaging and to B 0 shift correction. We demonstrate that working on the modulus of the FID signal is a simple and efficient way to both phase correct and frequency align MR spectra automatically. This approach is particularly well suited to brain proton MR spectroscopy.

Prostate Cancer Localization Using Multiparametric MR Imaging: Comparison of Prostate Imaging Reporting and Data System (PI-RADS) and Likert Scales

To compare the recently proposed Prostate Imaging Reporting and Data System (PI-RADS) scale that incorporates fixed criteria and a standard Likert scale based on overall impression in prostate cancer localization using multiparametric magnetic resonance (MR) imaging. This retrospective study was HIPAA compliant and institutional review board approved. Seventy patients who underwent 3-T pelvic MR imaging, including T2-weighted imaging, diffusion-weighted imaging, and dynamic contrast material-enhanced imaging, with a pelvic phased-array coil before radical prostatectomy were included. Three radiologists, each with 6 years of experience, independently scored 18 regions (12 peripheral zone [PZ], six transition zone [TZ]) using PI-RADS (range, scores 3-15) and Likert (range, scores 1-5) scales. Logistic regression for correlated data was used to compare scales for detection of tumors larger than 3 mm in maximal diameter at prostatectomy. Maximal accuracy was achieved with score thresholds of 8 and higher and of 3 and higher for PI-RADS and Likert scales, respectively. At these thresholds, in the PZ, similar accuracy was achieved with the PI-RADS scale and the Likert scale for radiologist 1 (89.0% vs 88.2%, P = .223) and radiologist 3 (88.5% vs 88.2%, P = .739) and greater accuracy was achieved with the PI-RADS scale than the Likert scale for radiologist 2 (89.6% vs 87.1%, P = .008). In the TZ, accuracy was lower with the PI-RADS scale than with the Likert scale for radiologist 1 (70.0% vs 87.1%, P < .001), radiologist 2 (87.6% vs 92.6%, P = .002), and radiologist 3 (82.9% vs 91.2%, P < .001). For tumors with Gleason score of at least 7, sensitivity was higher with the PI-RADS scale than with the Likert scale for radiologist 1 (88.6% vs 82.6%, P = .032), and sensitivity was similar for radiologist 2 (78.0% vs 76.5, P = .467) and radiologist 3 (77.3% vs 81.1%, P = .125). Radiologists performed well with both PI-RADS and Likert scales for tumor localization, although, in the TZ, performance was better with the Likert scale than the PI-RADS scale. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122233/-/DC1.

Computed diffusion-weighted imaging of the prostate at 3 T: impact on image quality and tumour detection

To investigate the impact of prostate computed diffusion-weighted imaging (DWI) on image quality and tumour detection. Forty-nine patients underwent 3-T magnetic resonance imaging using a pelvic phased-array coil before prostatectomy, including DWI with b values of 50 and 1,000 s/mm(2). Computed DW images with b value 1,500 s/mm(2) were generated from the lower b-value images. Directly acquired b-1,500 DW images were obtained in 39 patients. Two radiologists independently assessed DWI for image quality measures and location of the dominant lesion. A third radiologist measured tumour-to-peripheral-zone (PZ) contrast. Pathological findings from prostatectomy served as the reference standard. Direct and computed b-1,500 DWI showed better suppression of benign prostate tissue than direct b-1,000 DWI for both readers (P ≤ 0.024). However, computed b-1,500 DWI showed less distortion and ghosting than direct b-1,000 and direct b-1,500 DWI for both readers (P ≤ 0.067). Direct and computed b-1,500 images showed better sensitivity and positive predictive value (PPV) for tumour detection than direct b-1,000 images for both readers (P ≤ 0.062), with no difference in sensitivity or PPV between direct and computed b-1,500 images (P ≥ 0.180). Tumour-to-PZ contrast was greater on computed b-1,500 than on either direct DWI set (P < 0.001). Computed DWI of the prostate using b value ≥1,000 s/mm(2) improves image quality and tumour detection compared with acquired standard b-value images. • Diffusion weighted MRI is increasingly used for diagnosing and assessing prostate carcinoma. • Prostate computed DWI can extrapolate high b-value images from lower b values. • Computed DWI provides greater suppression of benign tissue than lower b-value images. • Computed DWI provides less distortion and artefacts than images using same b value. • Computed DWI provides better diagnostic performance than lower b-value images.

TH-A-134-01: Breast Imaging QA

Implementation of a New Breast Tomosynthesis Program: A Clinical Medical Physicist's Experience-W Geiser Digital breast tomosynthesis (DBT) was approved by the FDA as a screening tool for breast cancer in February 2011. Many systems were preinstalled as 2D systems and are now being upgraded for DBT and there is evidence that DBT is helping reduce recall rates while increasing cancer detection rates. As of February 2013 there were approximately 500 systems certified by the FDA for DBT and it is expected that there will be more than 700 certified systems by the third quarter of 2013. Facilities implementing a breast tomosynthesis program need to be aware that there are many hurdles to be overcome before tomosynthesis studies can be performed. The purpose of this lecture is to provide medical physicists assisting facilities that are upgrading 2D systems or installing new DBT systems, the knowledge to assist with facility design, image storage requirements, choice of PACS, and optimization of diagnostic review. New educational requirements for medical physicists to qualify to perform acceptance testing and continued annual testing of DBT systems will also be reviewed. Learning Objectives: 1. Be able to assist with implementation of breast tomosynthesis at their facility. 2. Know the process for accreditation and certification of DBT systems. 3. Understand additional shielding requirements and facility design for a facility installing digital breast tomosynthesis. Breast MR Imaging and Quality Control — D Reeve MR imaging of the breast is an important adjunct to mammography and ultrasound for the detection of breast cancer and for breast biopsy guidance. Diagnostic breast MRI protocols typically include T2-weighted fat saturated images and 3D T1-weighted dynamic contrast enhanced (DCE) multiphase images using a Gadolinium-based contrast agent. The DCE images are used to determine the kinetic signature of enhancing tissues in order to differentiate between benign and malignant lesions. MR spectroscopy and diffusion weighted images (DWI) may also be acquired in order to provide additional diagnostic information. The diagnostic value of breast MRI scans can be improved by choosing acquisition parameters that optimize image quality parameters such as SNR, contrast and spatial resolution. As with any MRI protocol, achieving the desired image quality must balance the need for acceptable scan times. The timing and temporal resolution of the DCE series are important considerations. Breast radiofrequency (RF) coils are phased array coils capable of simultaneous bilateral imaging. A comprehensive breast MRI quality control program is important to assess the performance of the MRI system as well as the breast RF coils. Learning Objectives: 1. Provide an overview of breast MR imaging and MR-guided biopsy procedures. 2. Describe breast MR image quality criteria and protocol optimization. 3. Discuss the components of a breast MRI quality control program.

Fetal MRI on a multi-element digital coil platform

Fetal MRI has an increasing list of indications and is most commonly employed when anomalies detected by prenatal ultrasonography require further characterization. This may occur when sonography is technically challenging or where specific MRI findings will determine pre- and postnatal management, including critical in utero and/or peripartum interventions. In these circumstances, there are high expectations for MRI to sort out complex diagnostic dilemmas through exquisite anatomical imaging that fetal surgeons and obstetricians can comprehend and relay to their patients. These expectations, in light of evolving clinical innovations, continue to drive advances in fetal imaging. Increasing signal-to-noise ratio (SNR) is fundamental to improving MR image quality, and proper coil selection is a key component of this pursuit. Since the introduction of parallel imaging techniques, the numbers of elements in phased-array coils have been continuously increased to achieve high SNR and shorter scan times. With the invention of a digital coil platform, it is now possible to connect combinations of multiple coil elements to enhance SNR beyond the capabilities of the adult eight-channel torso-coil routinely used in fetal imaging. This paper describes the application of multi-element radiofrequency coils on a digital broadband imaging platform with unique coil combinations to perform dedicated fetal MRI.

259 ASYMMETRICAL SEPTAL HYPERTROPHY IS ASSOCIATED WITH MEAN ARTERIAL BLOOD PRESSURE IN HEALTHY ADULTS: DATA FROM HIGH RESOLUTION 3D CARDIAC MRI

Background Left ventricular hypertrophy (LVH) is the result of complex interactions between genes and environmental factors, and an independent risk factor for all-cause mortality. Clinically, it is important to differentiate ‘physiological’ LVH, such as in hypertension, from pathological LVH as found in hypertrophic cardiomyopathy. Standard methods of cardiac phenotyping such as echocardiography or 2D cardiac magnetic resonance (CMR) provide only macroscopic descriptors of LV mass (LVM) and function. These methods are underpowered for population wide study of regional wall thickness variability. Methods and Results 187 healthy multi-ethnic volunteers (105 female, age range 18–72, mean age 40) were recruited into a sub-study of the UK GenScan project. Exclusion criteria included established history of cardiovascular disease, hypertension, diabetes or hypercholesterolemia. Subjects were phenotyped by CMR using a 1.5T Philips Achieva system with a 32 element cardiac phased-array coil. High resolution 3D cine imaging of the LV was obtained with a voxel size of 2x2x4 mm and 20 cardiac phases. Three blood pressure (BP) measurements were taken and averaged (in mmHg): Mean systolic BP 123 (range 90–186), mean diastolic BP 80.4 (range 47–109). The high resolution 3D images were automatically segmented using training data from 10 healthy volunteers in which the myocardium had been manually labelled at end-diastole and end-systole (Figure 1). The 187 3D segmentations were exactly co-registered with each other so that corresponding points within the myocardium could be accurately compared within the cohort. Mean wall thickness was calculated at each point as the distance between the endocardial and epicardial surfaces. Automated measurements were validated against manual readings using standard clinical software (Philips Extended Workspace). LV end-diastolic volumes and LVM measurements were highly correlated (R 2 =.98 and R 2 =0.93 respectively). Mass univariate analysis was performed on the co-registered 3D models with wall thickness as the dependent variable. Pooling data from all the subjects, we plotted wall thickness at each 3D coordinate as a linear function of Mean Arterial Pressures (MAP) with gender and age held constant. The 3D models showed that blood pressure associated LVH begins asymmetrically within the mid-septum and progressively extends towards the base and apex with rising MAP (Figure 2). The lateral wall and apex are relatively spared. Conclusions Whole-heart high-resolution 3D CMR provides new opportunities for quantitative phenotyping of the heart and understanding the genetic and environmental determinants of heart disease. In this study we used these techniques to show the pattern of progressive asymmetrical septal hypertrophy that is associated with increasing blood pressure even within the general population.

090 HIGH RESOLUTION 3D CINE IMAGING: A NOVEL APPROACH FOR AUTOMATED RIGHT VENTRICULAR PHENOTYPING

<h3>Background</h3> Despite technological advances in cardiac imaging, accurate phenotyping of the right ventricle (RV) remains challenging. Current cardiac magnetic resonance (CMR) methods have poor through-plane resolution limiting the accuracy of modelling the complex RV shape and dynamics. RV function and mass are increasingly recognised as pivotal in guiding treatment and establishing prognosis in cardiomyopathies and pulmonary hypertension. Here we acquire high resolution 3D cine imaging of the RV and exploit the advantages of this approach with automated segmentation. <h3>Methods</h3> We used a 1.5 T Philips Achieva system with a 32 element cardiac phased-array coil. 26 healthy volunteers from the GenScan (Genetic Studies of the Heart and Circulation) study were imaged. Short axis SSFP images were acquired: 2D: voxel size 2.0×2.2×8 mm, 12 sections, two sections per breath-hold, slice thickness 8 mm with 2 mm gap, 30 cardiac phases. 3D: single breath-hold 3D b-SSFP volumes: voxel size 2×2×4 mm (reconstructed to 2×2×2 mm), 48 sections, 20 cardiac phases, SENSE factor 4. Right ventricular 2D volumes were measured using CMRtools software. For the creation of the atlas each voxel in the 3D cine sequences obtained from five volunteers was manually labelled using ITKsnap software. Datasets from 21 other volunteers were non-rigidly registered to the 3D atlas. Images were segmented automatically using multi-atlas simultaneous segmentation and registration. <h3>Results</h3> Presentation is confined to RV end-diastolic volumes (RVEDV) here. Data were log-transformed due to positive skewing (Normal plots, Shapiro-Wilk). 3D automated volumes were correlated with 2D manual volumes (rs=0.83, p&lt;.001, figure&nbsp;1A). RVEDV (geometric means and 95% CIs) was greater when measured by 2D manual techniques (157, 144–172 ml) than by 3D automated techniques (144, 131–160 ml). One sample t test demonstrated a small, but statistically significant difference between transformed values (mean difference=−0.037, t=−4.256, p=.0004). As a percentage of the mean absolute value, 3D volumes were 8% smaller than 2D manual volumes. <h3>Discussion</h3> The 8% underestimation of RVEDV compared to manual volumetry represents a volume of 13 ml which we believe is of limited clinical significance. Furthermore visual assessment of 3D and 2D models derived from source data (figure&nbsp;2) suggests that our approach tracks regional variations more accurately, which may indicate indicate clinically significant subtypes in RV disease. We conclude that near-isotropic, whole heart, single breath-hold 3D cine imaging is a feasible approach for parametric modelling of the RV. This method is robust, quantitative and automated and suited to high-throughput population studies.