Coronary artery calcium and cardiovascular disease prediction by scanner type: the multi-ethnic study of atherosclerosis.

AIM: To evaluate the predictive value of coronary artery calcium (CAC) scoring methods across cardiac computed tomography (CT) scanner types. MATERIALS AND METHODS: CAC was measured in participants from the MESA (Multi-Ethnic Study of Atherosclerosis), a prospective cohort study of participants free of baseline cardiovascular disease (CVD), using either EBCT (electron beam CT) or MDCT (multidetector CT). The risks for incident coronary heart disease (CHD) and CVD events were compared for CAC scores per SD using Cox proportional hazards models with multivariable adjustment in 3,362 MESA participants with detectable CAC. RESULTS: Using the Agatston score, the hazard ratio (HR) and 95% confidence interval (CI) for CHD was 1.50 (1.27,1.78) for EBCT and 1.60 (1.37,1.87) for MDCT. Using volume and density scores, the HR for CHD was 2.14 (1.71,2.68) for volume and 0.61 (0.48,0.76) for density on EBCT and 1.73 (1.42,2.11) for volume and 0.88 (0.71,1.10) for density on MDCT. Similar results were seen for CVD risk and in analyses stratified by sex, body mass index (BMI), and age. The volume and density score model demonstrated higher areas under the curve (AUC) for CHD than the Agatston score with EBCT (0.702, 95% CI: 0.666,0.738 versus 0.677, 95% CI: 0.638,0.715, p<0.001) and MDCT (0.669, 95% CI: 0.632,0.705 versus 0.660, 95% CI: 0.622,0.697, p=0.216). CONCLUSION: The CAC volume and density scores provide better risk prediction than the Agatston score for CHD and CVD events, regardless of CT scanner type. CAC density was strongly and inversely associated with CHD risk. Both density and volume score prediction were stronger for EBCT than MDCT.

ICSI does not improve reproductive outcomes in autologous ovarian response cycles with non-male factor subfertility.

STUDY QUESTION: Does the method of fertilisation improve reproductive outcomes in poor ovarian response (POR) cycles when compared to all other ovarian response categories in the absence of male factor subfertility? SUMMARY ANSWER: ICSI does not confer any benefit in improving the clinical pregnancy or live birth (LB) outcome in autologous ovarian response cycles in the absence of male factor subfertility when compared to IVF. WHAT IS KNOWN ALREADY: ICSI is associated with an improved outcome when compared to IVF in patients with severe male factor subfertility. STUDY DESIGN, SIZE, DURATION: A retrospective study involving 1 376 454 ART cycles, of which 569 605 (41.4%) cycles fulfilled the inclusion and exclusion criteria for all autologous ovarian response categories: 272 433 (47.8%) IVF cycles and 297 172 (52.2%) ICSI cycles. Of these, the POR cohort represented 62 641 stimulated fresh cycles (11.0%): 33 436 (53.4%) IVF cycles and 29 205 (46.6%) ICSI cycles. PARTICIPANTS/MATERIALS, SETTING, METHOD: All cycles recorded on the anonymised Human Fertilisation and Embryology Authority (HFEA) registry database between 1991 and 2016 were analysed. All fresh cycles with normal sperm parameters, performed after 1998 were included: frozen cycles, donor oocyte and sperm usage, intrauterine insemination cycles, preimplantation genetic testing (PGT) for aneuploidies (PGT-A), PGT for monogenic/single gene defects (PGT-M), PGT for chromosomal structural arrangements (PGT-SR) cycles, where the reason for stimulation was for storage and unstimulated cycles were excluded. MAIN RESULTS AND THE ROLE OF CHANCE: ICSI did not confer any benefit in improving the LB outcome when compared to conventional IVF per treatment cycle (PTC), when adjusted for female age, number of previous ART treatment cycles, number of previous live births through ART, oocyte yield, stage of transfer, method of fertilisation and number of embryos transferred in the POR cohort (adjusted odds ratio [a OR] 1.03, 99.5% confidence interval [CI] 0.96-1.11, P = 0.261) and all autologous ovarian response categories (aOR 1.00, 99.5% CI 0.98-1.02, P = 0.900). The mean fertilisation rate was statistically lower for IVF treatment cycles (64.7%) when compared to ICSI treatment cycles (67.2%) in the POR cohort (mean difference -2.5%, 99.5% CI -3.3 to -1.6, P < 0.001). The failed fertilisation rate was marginally higher in IVF treatment cycles (17.3%, 95% binomial exact 16.9 to 17.7%) when compared to ICSI treatment cycles (17.0%, 95% binomial exact 16.6 to 17.4%); however, this did not reach statistical significance (P = 0.199). The results followed a similar trend when analysed for all autologous ovarian response categories with a higher rate of failed fertilisation in IVF treatment cycles (4.8%, 95% binomial exact 4.7 to 4.9%) when compared to ICSI treatment cycles (3.2%, 95% binomial exact 3.1 to 3.3%) (P < 0.001). LIMITATIONS, REASONS FOR CAUTION: The quality of data is reliant on the reporting system. Furthermore, success rates through ART have improved since 1991, with an increased number of blastocyst-stage embryo transfers. The inability to link the treatment cycle to the individual patient meant that we were unable to calculate the cumulative LB outcome per patient. WIDER IMPLICATIONS OF THE FINDINGS: This is the largest study to date which evaluates the impact of method of fertilisation in the POR patient and compares this to all autologous ovarian response categories. The results demonstrate that ICSI does not confer any benefit in improving reproductive outcomes in the absence of male factor subfertility, with no improvement seen in the clinical pregnancy or LB outcomes following a fresh treatment cycle. STUDY FUNDING/COMPETING INTEREST(S): The study received no funding. C.M.B. is a member of the independent data monitoring group for a clinical endometriosis trial by ObsEva. He is on the scientific advisory board for Myovant and medical advisory board for Flo Health. He has received research grants from Bayer AG, MDNA Life Sciences, Volition Rx and Roche Diagnostics as well as from Wellbeing of Women, Medical Research Council UK, the NIH, the UK National Institute for Health Research and the European Union. He is the current Chair of the Endometriosis Guideline Development Group for ESHRE and was a co-opted member of the Endometriosis Guideline Group by the UK National Institute for Health and Care Excellence (NICE). I.G. has received research grants from Bayer AG, Wellbeing of Women, the European Union and Finox. TRIAL REGISTRATION NUMBER: Not applicable.

Secondary sex ratio in assisted reproduction: an analysis of 1 376 454 treatment cycles performed in the UK.

STUDY QUESTION: Does ART impact the secondary sex ratio (SSR) when compared to natural conception? SUMMARY ANSWER: IVF and ICSI as well as the stage of embryo transfer does impact the overall SSR. WHAT IS KNOWN ALREADY: The World Health Organization quotes SSR for natural conception to range between 103 and 110 males per 100 female births. STUDY DESIGN SIZE DURATION: A total of 1 376 454 ART cycles were identified, of which 1 002 698 (72.8%) cycles involved IVF or ICSI. Of these, 863 859 (85.2%) were fresh cycles and 124 654 (12.4%) were frozen cycles. Missing data were identified in 14 185 (1.4%) cycles. PARTICIPANTS/MATERIALS SETTING METHODS: All cycles recorded in the anonymized UK Human Fertilisation and Embryology Authority (HFEA) registry database between 1991 and 2016 were analysed. All singleton live births were included, and multiple births were excluded to avoid duplication. MAIN RESULTS AND THE ROLE OF CHANCE: The overall live birth rate per cycle for all IVF and ICSI treatments was 26.2% (n = 262 961), and the singleton live birth rate per cycle was 17.1% (n = 171 399). The overall SSR for this study was 104.0 males per 100 female births (binomial exact 95% CI: 103.1-105.0) for all IVF and ICSI cycles performed in the UK recorded through the HFEA. This was comparable to the overall SSR for England and Wales at 105.3 males per 100 female births (95% CI: 105.2-105.4) from 1991 to 2016 obtained from the Office of National Statistics database. Male predominance was seen with conventional insemination in fresh IVF treatment cycles (SSR 110.0 males per 100 female births; 95% CI: 108.6-111.5) when compared to micro-injection in fresh ICSI treatment cycles (SSR 97.8 males per 100 female births; 95% CI: 96.5-99.2; odds ratio (OR) 1.16, 95% CI 1.12-1.19, P < 0.0001), as well as with blastocyst stage embryo transfers (SSR 104.8 males per 100 female births; 95% CI: 103.5-106.2) when compared to a cleavage stage embryo transfer (SSR 101.2 males per 100 female births; 95% CI: 99.3-103.1; OR 1.03, 95% CI 1.01-1.06, P = 0.011) for all fertilization methods. LIMITATIONS REASONS FOR CAUTION: The quality of the data relies on the reporting system. Furthermore, success rates through ART have improved since 1991, with an increased number of blastocyst stage embryo transfers. WIDER IMPLICATIONS OF THE FINDINGS: This is the largest study to date evaluating the impact of ART on SSR. The results demonstrate that, overall, ART does have an impact on the SSR when assessed according to the method of fertilization (ICSI increased female births while IVF increased males). However, given the ratio of IVF to ICSI cycles at present with 60% of cycles from IVF and 40% from ICSI, the overall SSR for ART closely reflects the population SSR for, largely, natural conceptions in England and Wales. STUDY FUNDING/COMPETING INTERESTS: The study received no funding. C.M.B. is a member of the independent data monitoring group for a clinical endometriosis trial by ObsEva. He is on the scientific advisory board for Myovant and medical advisory board for Flo Health. He has received research grants from Bayer AG, MDNA Life Sciences, Volition Rx and Roche Diagnostics as well as from Wellbeing of Women, Medical Research Council UK, the NIH, the UK National Institute for Health Research and the European Union. He is the current Chair of the Endometriosis Guideline Development Group for ESHRE and was a co-opted member of the Endometriosis Guideline Group by the UK National Institute for Health and Care Excellence (NICE). I.G. has received research grants from Wellbeing of Women, the European Union and Finox. TRIAL REGISTRATION NUMBER: Not applicable.

Deformable Known Component Model-Based Reconstruction for Coronary CT Angiography.

PURPOSE: Atherosclerosis detection remains challenging in coronary CT angiography for patients with cardiac implants. Pacing electrodes of a pacemaker or lead components of a defibrillator can create substantial blooming and streak artifacts in the heart region, severely hindering the visualization of a plaque of interest. We present a novel reconstruction method that incorporates a deformable model for metal leads to eliminate metal artifacts and improve anatomy visualization even near the boundary of the component. METHODS: The proposed reconstruction method, referred as STF-dKCR, includes a novel parameterization of the component that integrates deformation, a 3D-2D preregistration process that estimates component shape and position, and a polyenergetic forward model for x-ray propagation through the component where the spectral properties are jointly estimated. The methodology was tested on physical data of a cardiac phantom acquired on a CBCT testbench. The phantom included a simulated vessel, a metal wire emulating a pacing lead, and a small Teflon sphere attached to the vessel wall, mimicking a calcified plaque. The proposed method was also compared to the traditional FBP reconstruction and an interpolation-based metal correction method (FBP-MAR). RESULTS: Metal artifacts presented in standard FBP reconstruction were significantly reduced in both FBP-MAR and STF-dKCR, yet only the STF-dKCR approach significantly improved the visibility of the small Teflon target (within 2 mm of the metal wire). The attenuation of the Teflon bead improved to 0.0481 mm-1 with STF-dKCR from 0.0166 mm-1 with FBP and from 0.0301 mm-1 with FBP-MAR - much closer to the expected 0.0414 mm-1. CONCLUSION: The proposed method has the potential to improve plaque visualization in coronary CT angiography in the presence of wire-shaped metal components.

Methodology for image-based reconstruction of ventricular geometry for patient-specific modeling of cardiac electrophysiology.

Patient-specific modeling of ventricular electrophysiology requires an interpolated reconstruction of the 3-dimensional (3D) geometry of the patient ventricles from the low-resolution (Lo-res) clinical images. The goal of this study was to implement a processing pipeline for obtaining the interpolated reconstruction, and thoroughly evaluate the efficacy of this pipeline in comparison with alternative methods. The pipeline implemented here involves contouring the epi- and endocardial boundaries in Lo-res images, interpolating the contours using the variational implicit functions method, and merging the interpolation results to obtain the ventricular reconstruction. Five alternative interpolation methods, namely linear, cubic spline, spherical harmonics, cylindrical harmonics, and shape-based interpolation were implemented for comparison. In the thorough evaluation of the processing pipeline, Hi-res magnetic resonance (MR), computed tomography (CT), and diffusion tensor (DT) MR images from numerous hearts were used. Reconstructions obtained from the Hi-res images were compared with the reconstructions computed by each of the interpolation methods from a sparse sample of the Hi-res contours, which mimicked Lo-res clinical images. Qualitative and quantitative comparison of these ventricular geometry reconstructions showed that the variational implicit functions approach performed better than others. Additionally, the outcomes of electrophysiological simulations (sinus rhythm activation maps and pseudo-ECGs) conducted using models based on the various reconstructions were compared. These electrophysiological simulations demonstrated that our implementation of the variational implicit functions-based method had the best accuracy.

Gynaecological endoscopic evaluation of 4% icodextrin solution: a European, multicentre, double-blind, randomized study of the efficacy and safety in the reduction of de novo adhesions after laparoscopic gynaecological surgery.

BACKGROUND: Gynaecological laparoscopic surgery outcomes can be compromised by the formation of de novo adhesions. This randomized, double-blind study was designed to assess the efficacy and safety of 4% icodextrin solution (Adept(®)) in the reduction of de novo adhesion incidence compared to lactated Ringer's solution (LRS). METHODS: Patients undergoing laparoscopic surgery for removal of myomas or endometriotic cysts were treated with randomized solution as an intra-operative irrigant and 1l post-operative instillate. De novo adhesion incidence (number of sites with adhesions), severity and extent were independently scored at a second-look procedure and the efficacy of the two solutions compared. The effect of surgical covariates on adhesion formation was also investigated. Initial exploratory analysis of individual anatomical sites of clinical importance was progressed. RESULTS Of 498 patients randomized, 330 were evaluable (160 LRS--75% myomectomy/25% endometriotic cysts; 170 Adept--79% myomectomy/21% endometriotic cysts). At study completion, 76.2% LRS and 77.6% Adept had ≥ 1 de novo adhesion. The mean (SD) number of de novo adhesions was 2.58 (2.11) for Adept and 2.58 (2.38) for LRS. The treatment effect difference was not significant (P = 0.909). Assessment of surgical covariates identified significant influences on the mean number of de novo adhesions regardless of treatment, including surgery duration (P = 0.048), blood loss in myomectomy patients (P = 0.019), length of uterine incision in myomectomy patients (P < 0.001) and number of suture knots (P < 0.001). There were 15 adverse events considered treatment-related in the LRS patients (7.2%) and 18 in the Adept group (8.3%). Of 17 reported serious adverse events (9 LRS; 8 Adept) none were considered treatment-related. CONCLUSIONS: The study confirmed the safety of Adept in laparoscopic surgery. The proportion of patients with de novo adhesion formation was considerably higher than previous literature suggested. Overall there was no evidence of a clinical effect but various surgical covariates including surgery duration, blood loss, number and size of incisions, suturing and number of knots were found to influence de novo adhesion formation. The study provides direction for future research into adhesion reduction strategies in site specific surgery.

Urological and colorectal complications following surgery for rectovaginal endometriosis.

OBJECTIVES: To report the short- and medium-term complications of laparoscopic laser excisional surgery for rectovaginal endometriosis. DESIGN: Retrospective cohort study. SETTING: University teaching hospital, UK. POPULATION: A total of 128 women with histologically confirmed rectovaginal endometriosis who underwent laparoscopic laser surgery between May 1999 and September 2006. METHODS: Women were identified from operative database, and a case note review was performed. Data for surgical outcome and surgical complications were collected. MAIN OUTCOME MEASURES: Rates of urinary tract and colorectal complications. RESULTS: A total of 128 women underwent surgery. Of these, 32 required intraoperative closure of a rectal wall defect, including 3 segmental rectosigmoid resections. There were three rectovaginal fistulae and one ureterovaginal fistula. Ureteric damage occurred in two women, and five women suffered postoperative urinary retention. The risk of intraoperative bowel intervention was increased in women who complained of cyclical rectal bleeding. CONCLUSION: Laparoscopic laser excision of rectovaginal endometriosis is a safe procedure with similar, if not lower, complication rates to other published surgical series.

Laparoscopic nerve-sparing complete excision of deep endometriosis: is it feasible?

BACKGROUND: Little is known about the morbidity associated with laparoscopic complete excision of endometriosis in terms of urinary, digestive and sexual function. METHODS: We performed a prospective non-randomized study in 45 patients with laparoscopic complete excision of all detectable foci of endometriosis with segmental bowel resection using a non nerve-sparing technique (control group-group A n=20) and a nerve-sparing technique (case group-group B n=25). At initial gynaecological evaluation, and at follow-up details on dysmenorrhoea, pelvic pain, dyspareunia and dyschezia were evaluated using an interview-based questionnaire (10-point analogue rating scale: 0=absent, 10=unbearable). RESULTS: The mean (+/-SD) follow-up period was 15.3+/-10 months (range, 8.8-23 months) for group A and 3.5+/-2.1 months (range, 0.3-5.2 months) for group B. In the immediate postoperative course, in group A three women required blood transfusion vs seven women in group B (P=0.003). The median time to resume the voiding function was significantly shorter in group B (12.5 vs 3.0 days; P<0.01). At the time of follow-up a higher proportion of patients in group B were 'very satisfied' than those in group A (87.7% vs 59.0%, P=0.013). CONCLUSIONS: Laparoscopic nerve-sparing complete excision of endometriosis seems to be feasible and offers good results in terms of bladder morbidity reduction with apparently higher satisfaction than classical technique. Larger series with longer follow-up are needed to confirm our results.

S5FP: spectrally selective suppression with steady state free precession.

A method is presented that employs the inherent spectral selectivity of the Steady-State Free Precession (SSFP) pulse sequence to provide a spectral band of suppression. At TE = TR/2, SSFP partitions the magnetization into two phase-opposed spectral components. Z-storing one of these components simultaneously further excites the other, which is then suppressed by gradient crushing and RF spoiling. The Spectrally Selective Suppression with SSFP (S(5)FP) method is shown to provide significant attenuation of fat signals, while the water signals are essentially unaffected and provide the normal SSFP contrast. Fat suppression is achieved with relatively little temporal overhead (less than 10% reduction in temporal resolution). S(5)FP was validated using simulations, phantoms, and human studies.

Electromechanics of paced left ventricle simulated by straightforward mathematical model: comparison with experiments.

Intraventricular synchrony of cardiac activation is important for efficient pump function. Ventricular pacing restores the beating frequency but induces more asynchronous depolarization and more inhomogeneous contraction than in the normal heart. We investigated whether the increased inhomogeneity in the left ventricle can be described by a relatively simple mathematical model of cardiac electromechanics, containing normal mechanical and impulse conduction properties. Simulations of a normal heartbeat and of pacing at the right ventricular apex (RVA) were performed. All properties in the two simulations were equal, except for the depolarization sequence. Simulation results of RVA pacing on local depolarization time and systolic midwall circumferential strain were compared with those measured in dogs, using an epicardial sock electrode and MRI tagging, respectively. We used the same methods for data processing for simulation and experiment. Model and experiment agreed in the following aspects. 1) Ventricular pacing decreased systolic pressure and ejection fraction relative to natural sinus rhythm. 2) Shortening during ejection and stroke work declined in early depolarized regions and increased in late depolarized regions. 3) The relation between epicardial depolarization time and systolic midwall circumferential strain was linear and similar for the simulation (slope = -3.80 +/- 0.28 s(-1), R2 = 0.87) and the experiments [slopes for 3 animals -2.62 +/- 0.43 s(-1) (R2 = 0.59), -2.97 +/- 0.38 s(-1) (R2 = 0.69), and -4.44 +/- 0.51 s(-1) (R2 = 0.76)]. We conclude that our model of electromechanics is suitable to simulate ventricular pacing and that the apparently complex events observed during pacing are caused by well-known basic physiological processes.

Extended coverage first-pass perfusion imaging using slice-interleaved TSENSE.

Parallel imaging applied to first-pass, contrast-enhanced cardiac MR can yield greater spatial coverage for a fixed temporal resolution. The method combines rate R=2 acceleration using TSENSE with shot-to-shot interleaving of two slices. The square root R SNR loss is largely compensated for by a longer effective repetition time (TR) and increased flip angle associated with slice interleaving. In this manner, increased spatial coverage is achieved while comparable or better image quality is maintained. Single-heartbeat temporal resolution was accomplished with spatial coverage of eight slices at heart rates up to 71 bpm, six slices up to 95 bpm, and four slices up to 143 bpm. Experiments in normal subjects (N=6) were performed to assess signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values.

Routine use of r-hFSH follitropin alfa filled-by-mass for follicular development for IVF: a large multicentre observational study in the UK.

The technical advance of recombinant biotechnology to manufacture FSH has resulted in a biochemically pure FSH preparation with high batch-to-batch consistency. The protein content of recombinant human FSH (r-hFSH) can be reliably quantified in mass units by size exclusion high performance liquid chromatography (SE-HPLC) enabling r-hFSH follitropin alfa (Gonal-F) to be filled and released in the vial on the basis of mass with dose variability of only +/-2% [filled-by-mass (FbM)]. Observational studies have merit in addressing the effectiveness of a new product in routine clinical practice. This non-interventional study assessed r-hFSH follitropin alfa FbM for the multifollicular stimulation of patients undergoing assisted reproduction. A total of 1427 patients were recruited in 21 centres in the UK and the mean age was 34.3 years (+/-4.48, range 18-48). Of those who started treatment, 1388 (97.3%) received human chorionic gonadotrophin and 1330 (93.2%) underwent oocyte retrieval. A total of 1213 (85%) patients had embryo transfer and in the majority of recorded cases, most embryos replaced were graded as 1 or 2 (74.6%). The ongoing clinical pregnancy rate was 29.2% per cycle and 34.4% per embryo transfer. The routine use of r-hFSH follitropin alfa FbM in normal clinical practice in IVF has been demonstrated to be effective, safe and well received by patients.

Economic implications of assisted reproductive techniques: a systematic review.

BACKGROUND: Approximately one in six couples experiences problems with their fertility at some point in their reproductive lives. The economic implications of the use of assisted reproductive techniques require consideration. Herein, the health economics research in this area are critically appraised. METHODS: Multiple strategies were used to identify relevant studies. Each title and abstract was independently reviewed by two members of the study team and categorized according to perceived relevance. The selected papers were then assessed for quality and data were extracted, converted to UK pounds sterling at 1999/2000 prices, tabulated and critically appraised. RESULTS: A total of 2547 papers was identified through the searches; this resulted in 30 economic evaluations, 22 cost studies and five economic benefit studies that met the selection criteria. The quality of these studies was mixed; many failed to disaggregate costs, discount future costs or conduct sensitivity analyses. Consistent findings included the following: initiating treatment with intrauterine insemination appeared to be more cost-effective than IVF; vasectomy reversal appeared to be more cost-effective than ICSI; factors associated with poor prognosis decreased the cost-effectiveness of interventions. CONCLUSIONS: The cost-effectiveness of different interventions should be considered when making decisions about treatment. Future economic appraisals of assisted reproductive techniques would benefit from more robust methodology than is evident in much of the published literature to date.

A comparison of prospective and retrospective respiratory navigator gating in 3D MR coronary angiography.

A comparison between the prospective and retrospective respiratory navigator gating in MR coronary angiography was performed with eight normal subjects. A three-dimensional (3D) ECG-gated fast gradient echo pulse sequence was used for image data acquisition. The results show that the MR coronary angiography obtained using retrospective gating retains a considerable amount of motion artifacts. In this study, the images acquired using prospective navigator gating demonstrated significantly reduced motion artifacts (p = 0.009), improved vessel visibility (p = 0.021) with reduced imaging time (p = 0.013) compared to the images obtained using retrospective navigator gating.

Techniques for fast stereoscopic MRI.

Stereoscopic MRI can impart 3D perception with only two image acquisitions. This economy over standard multiplanar 3D volume renderings allows faster frame rates, which are needed for real-time imaging applications. Real-time 3D perception may enhance the appreciation of complex anatomical structures, and may improve hand-eye coordination while manipulating a medical device during an image-guided interventional procedure. To this goal, a system is being developed to acquire and display stereoscopic MR images in real-time. A clinically used, fast gradient-recalled echo-train sequence has been modified to produce stereo image pairs. Features have been added for depth cueing, view sharing, and bulk signal suppression. A workstation was attached to a clinical MR scanner for fast data extraction, image reconstruction and stereoscopic image display.

Ghost artifact cancellation using phased array processing.

In this article, a method for phased array combining is formulated which may be used to cancel ghosts caused by a variety of distortion mechanisms, including space variant distortions such as local flow or off-resonance. This method is based on a constrained optimization, which optimizes SNR subject to the constraint of nulling ghost artifacts at known locations. The resultant technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation it is applied to full field-of-view (FOV) images. The method is applied to multishot EPI with noninterleaved phase encode acquisition. A number of benefits, as compared to the conventional interleaved approach, are reduced distortion due to off-resonance, in-plane flow, and EPI delay misalignment, as well as eliminating the need for echo-shifting. Experimental results demonstrate the cancellation for both phantom as well as cardiac imaging examples.

Myocardial wall tagging with undersampled projection reconstruction.

Azimuthally undersampled projection reconstruction (PR) acquisition is investigated for use in myocardial wall tagging with MR using grid tags to provide increased temporal and spatial resolution. PR can provide the high-resolution images required for tagging with very few projections, at the expense of artifact. Insight is provided into the PR undersampling artifact, in the context of measuring myocardial motion with tags. For Fourier transform imaging, at least 112 phase-encodings must be collected to image tagging grids spaced 7 pixels apart. PR requires about 80 projections, a 1.4-fold reduction in scan time. Magn Reson Med 45:562-567, 2001. Published 2001 Wiley-Liss, Inc.

Adaptive sensitivity encoding incorporating temporal filtering (TSENSE).

A number of different methods have been demonstrated which increase the speed of MR acquisition by decreasing the number of sequential phase encodes. The UNFOLD technique is based on time interleaving of k-space lines in sequential images and exploits the property that the outer portion of the field-of-view is relatively static. The differences in spatial sensitivity of multiple receiver coils may be exploited using SENSE or SMASH techniques to eliminate the aliased component that results from undersampling k-space. In this article, an adaptive method of sensitivity encoding is presented which incorporates both spatial and temporal filtering. Temporal filtering and spatial encoding may be combined by acquiring phase encodes in an interleaved manner. In this way the aliased components are alternating phase. The SENSE formulation is not altered by the phase of the alias artifact; however, for imperfect estimates of coil sensitivities the residual artifact will have alternating phase using this approach. This is the essence of combining temporal filtering (UNFOLD) with spatial sensitivity encoding (SENSE). Any residual artifact will be temporally frequency-shifted to the band edge and thus may be further suppressed by temporal low-pass filtering. By combining both temporal and spatial filtering a high degree of alias artifact rejection may be achieved with less stringent requirements on accuracy of coil sensitivity estimates and temporal low-pass filter selectivity than would be required using each method individually. Experimental results that demonstrate the adaptive spatiotemporal filtering method (adaptive TSENSE) with acceleration factor R = 2, for real-time nonbreath-held cardiac MR imaging during exercise induced stress are presented.