Conventional EPI Research Articles

High resolution diffusion weighted magnetic resonance imaging of the pancreas using reduced field of view single-shot echo-planar imaging at 3 T

Diffusion weighted magnetic resonance imaging (DWI) has been mostly acquired using single-shot echo-planar imaging (ss EPI) to minimize motion induced artifacts. The spatial resolution, however, is inherently limited in ss EPI especially for abdominal imaging, even with the advances in parallel imaging. A novel method of reduced Field of View ss EPI (rFOV ss EPI) has achieved high resolution DWI in human carotid artery, spinal cord with reduced blurring and higher spatial resolution than conventional ss EPI, but it has not been used to pancreas imaging. In the work, comparisons between the full FOV ss-DW EPI and rFOV ss-DW EPI in image qualities and ADC values of pancreatic tumors and normal pancreatic tissues were performed to demonstrate the feasibility of pancreatic high resolution rFOV DWI. There were no significant differences in the mean ADC values between full FOV DWI and rFOV DWI for the 17 subjects using b=600s/mm2 (P=0.962). However, subjective scores of image quality was significantly higher at rFOV ss DWI (P=0.008 and 0.000 for b-value=0s/mm2 and 600s/mm2 respectively). The spatial resolution of DWI for pancreas was increased by a factor of over 2.0 (from almost 3.0mm/pixel to 1.25mm/pixel) using rFOV ss EPI technique. Reduced FOV ss EPI can provide good DW images and is promising to benefit applications for pancreatic diseases.

Whole-head rapid fMRI acquisition using echo-shifted magnetic resonance inverse imaging.

The acquisition time of BOLD contrast functional MRI (fMRI) data with whole-brain coverage typically requires a sampling rate of one volume in 1-3s. Although the volumetric sampling time of a few seconds is adequate for measuring the sluggish hemodynamic response (HDR) to neuronal activation, faster sampling of fMRI might allow for monitoring of rapid physiological fluctuations and detection of subtle neuronal activation timing information embedded in BOLD signals. Previous studies utilizing a highly accelerated volumetric MR inverse imaging (InI) technique have provided a sampling rate of one volume per 100 ms with 5mm spatial resolution. Here, we propose a novel modification of this technique, the echo-shifted InI, which allows TE to be longer than TR, to measure BOLD fMRI at an even faster sampling rate of one volume per 25 ms with whole-brain coverage. Compared with conventional EPI, echo-shifted InI provided an 80-fold speedup with similar spatial resolution and less than 2-fold temporal SNR loss. The capability of echo-shifted InI to detect HDR timing differences was tested empirically. At the group level (n=6), echo-spaced InI was able to detect statistically significant HDR timing differences of as low as 50 ms in visual stimulus presentation. At the level of individual subjects, significant differences in HDR timing were detected for 400 ms stimulus-onset differences. Our results also show that the temporal resolution of 25 ms is necessary for maintaining the temporal detecting capability at this level. With the capabilities of being able to distinguish the timing differences in the millisecond scale, echo-shifted InI could be a useful fMRI tool for obtaining temporal information at a time scale closer to that of neuronal dynamics.

Tracking dynamic resting-state networks at higher frequencies using MR-encephalography

Current resting-state network analysis often looks for coherent spontaneous BOLD signal fluctuations at frequencies below 0.1 Hz in a multiple-minutes scan. However hemodynamic signal variation can occur at a faster rate, causing changes in functional connectivity at a smaller time scale. In this study we proposed to use MREG technique to increase the temporal resolution of resting-state fMRI. A three-dimensional single-shot concentric shells trajectory was used instead of conventional EPI, with a TR of 100 ms and a nominal spatial resolution of 4 × 4 × 4 mm(3). With this high sampling rate we were able to resolve frequency components up to 5 Hz, which prevents major physiological noises from aliasing with the BOLD signal of interest. We used a sliding-window method on signal components at different frequency bands, to look at the non-stationary connectivity maps over the course of each scan session. The aim of the study paradigm was to specifically observe visual and motor resting-state networks. Preliminary results have found corresponding networks at frequencies above 0.1 Hz. These networks at higher frequencies showed better stability in both spatial and temporal dimensions from the sliding-window analysis of the time series, which suggests the potential of using high temporal resolution MREG sequences to track dynamic resting-state networks at sub-minute time scale.

Super-resolution reconstruction to increase the spatial resolution of diffusion weighted images from orthogonal anisotropic acquisitions

Diffusion-weighted imaging (DWI) enables non-invasive investigation and characterization of the white matter but suffers from a relatively poor spatial resolution. Increasing the spatial resolution in DWI is challenging with a single-shot EPI acquisition due to the decreased signal-to-noise ratio and T2(∗) relaxation effect amplified with increased echo time. In this work we propose a super-resolution reconstruction (SRR) technique based on the acquisition of multiple anisotropic orthogonal DWI scans. DWI scans acquired in different planes are not typically closely aligned due to the geometric distortion introduced by magnetic susceptibility differences in each phase-encoding direction. We compensate each scan for geometric distortion by acquisition of a dual echo gradient echo field map, providing an estimate of the field inhomogeneity. We address the problem of patient motion by aligning the volumes in both space and q-space. The SRR is formulated as a maximum a posteriori problem. It relies on a volume acquisition model which describes how the acquired scans are observations of an unknown high-resolution image which we aim to recover. Our model enables the introduction of image priors that exploit spatial homogeneity and enables regularized solutions. We detail our SRR optimization procedure and report experiments including numerical simulations, synthetic SRR and real world SRR. In particular, we demonstrate that combining distortion compensation and SRR provides better results than acquisition of a single isotropic scan for the same acquisition duration time. Importantly, SRR enables DWI with resolution beyond the scanner hardware limitations. This work provides the first evidence that SRR, which employs conventional single shot EPI techniques, enables resolution enhancement in DWI, and may dramatically impact the role of DWI in both neuroscience and clinical applications.

Sinusoidal echo‐planar imaging with parallel acquisition technique for reduced acoustic noise in auditory fMRI

To extend the parameter restrictions of a silent echo-planar imaging (sEPI) sequence using sinusoidal readout (RO) gradients, in particular with increased spatial resolution. The sound pressure level (SPL) of the most feasible configurations is compared to conventional EPI having trapezoidal RO gradients. We enhanced the sEPI sequence by integrating a parallel acquisition technique (PAT) on a 3 T magnetic resonance imaging (MRI) system. The SPL was measured for matrix sizes of 64 × 64 and 128 × 128 pixels, without and with PAT (R = 2). The signal-to-noise ratio (SNR) was examined for both sinusoidal and trapezoidal RO gradients. Compared to EPI PAT, the SPL could be reduced by up to 11.1 dB and 5.1 dB for matrix sizes of 64 × 64 and 128 × 128 pixels, respectively. The SNR of sinusoidal RO gradients is lower by a factor of 0.96 on average compared to trapezoidal RO gradients. The sEPI PAT sequence allows for 1) increased resolution, 2) expanded RO frequency range toward lower frequencies, which is in general beneficial for SPL, or 3) shortened TE, TR, and RO train length. At the same time, it generates lower SPL compared to conventional EPI for a wide range of RO frequencies while having the same imaging parameters.

Highly accelerated PSF-mapping for EPI distortion correction with improved fidelity

This study presents an improved point-spread-function (PSF) mapping-based distortion correction method and accelerated PSF acquisition for distortion correction in EPI without loss of quality or reliability compared to full encoding. To correct geometric distortions accurately, the PSF in the EPI phase-encoding coordinates (EPI-PSF) was measured and used as a kernel for distortion correction. FOV reduction was applied in the PSF mapping dimension for highly accelerated PSF acquisition. A novel approach for fold-over artifact correction in this reduced dimension is introduced. Conventional gradient-echo EPI and corresponding full PSF reference data were acquired in phantoms and in human brain at 7 T. The distortion corrected EPI data with the proposed acceleration were compared to result with full encoding. Previously published interpolation methods based on shift maps, non-uniform Fourier transformation and a b-spline interpolation were compared with the proposed method. The results demonstrate that the proposed method corrects geometric distortions in EPI with high accuracy and quality despite the high acceleration. In contrast to partial parallel imaging acceleration, no noise enhancement is introduced. The proposed EPI-PSF-based distortion correction improves correction of EPI and accelerates PSF reference data acquisition and computation.

Functional neuroimaging of the oculomotor brainstem network in humans

The cortical systems involved in eye movement control in humans have been investigated extensively using fMRI. In contrast, there is virtually no data concerning the functional status of the human oculomotor brainstem nuclei. This lack of evidence has usually been explained by technical constraints of EPI based imaging and anatomical characteristics of the brainstem. Against this assumption, we successfully localised nuclei of the oculomotor system using high-resolution fMRI based on standard EPI sequences in a group of healthy subjects executing reflexive horizontal saccades. A random-effects group analysis revealed task-related BOLD increases in the superior colliculus, the oculomotor nucleus, the abducens nucleus and in the paramedian pontine reticular formation. This group analysis was complemented by individual positive findings in up to 94% of single subject analyses. A visual control paradigm led to increased signal levels in the superior colliculus consistent with its visual properties but no corresponding signal changes in other brainstem nuclei. These results are consistent with findings in animal studies and demonstrate the feasibility to detect BOLD signal increases associated with oculomotor tasks even in the human brainstem using conventional EPI imaging techniques.

An improved PSF mapping method for EPI distortion correction in human brain at ultra high field (7T)

To further improve the quality and robustness of the point-spread function (PSF) mapping method for fully automatic and accurate correction of geometric distortions in EPI at ultra high field such as 7Tesla with high fidelity. Conventional gradient-echo EPI and corresponding PSF reference data in phantoms and in in vivo measurements of the human brain were acquired at 7Tesla. To accurately determine and correct geometric distortions, i.e., in peripheral areas, the method calculates the local shift in the distorted phase-encoding dimension instead of the non-distorted spin-wrap encoding dimension. The results of the proposed method are compared with those originally demonstrated (Zaitsev etal. Magn Reson Med (2004) 52:1156-1166). The results show that the proposed method allows measurement and correction of the geometric distortions in EPI with high accuracy, and reduction of residual blurring. In addition, this method prevents errors in the shift map induced by PSF-ghost artifacts. More precise mapping and correction of pixel shifts and blurring is accomplished with the proposed improvements. Errors in the shift map that are caused by PSF-ghost artifacts in the multi-shot PSF acquisition, e.g., from small motion during the reference scan, do not affect the improved shift estimation method.

Comparison of SNR efficiencies and strain for cine DENSE using conventional EPI, flyback EPI and spiral k-space trajectories

The original implementation of 2D cine DENSE (displacement encoding with stimulated echoes) employed a conventional EPI k-space trajectory for rapid data sampling. Follow-up studies used flyback EPI to reduce image artifacts. More recently a spiral k-space trajectory was utilized for improved SNR.

Ultrasensitive and High-Throughput Fluorescence Analysis of Droplet Contents with Orthogonal Line Confocal Excitation

This paper describes a simple modification to traditional confocal fluorescence detection that greatly improves signal-to-noise (s/n) for the high-speed analysis of droplet streams. Rather than using the conventional epi geometry, illumination of the droplet was in the form of a line that is orthogonal to both the direction of flow and the light-collection objective. In contrast to the epi geometry where we observed high levels of scattering background from the droplets, we detected more than 10-fold less background (depending on the laser power used) when orthogonal-line-confocal illumination was used. We characterized this improvement using a standard microfluidic platform over a range of analyte concentrations and observed an improvement in limits of detection of greater than 10. Using this method, we were able to analyze picomolar concentrations of analytes contained within picoliter-volume droplets at a rate of greater than 350 droplets per second.

Halving imaging time of whole brain diffusion spectrum imaging and diffusion tractography using simultaneous image refocusing in EPI

To increase the efficiency of densely encoded diffusion imaging of the brain, such as diffusion spectrum imaging (DSI), we time-multiplex multiple slices within the same readout using simultaneous image refocusing echo-planar imaging (SIR-EPI). Inefficiency in total scan time results from the long time of diffusion encoding gradient pulses which must be repeated for each and every image. We present a highly efficient multiplexing method, simultaneous image refocusing (SIR), for reducing the total scan time of diffusion imaging by nearly one-half. SIR DSI is performed in 10 minutes rather than 21 minutes, acceptable for routine clinical application. Two identical studies were completed, comparing conventional single-slice EPI DSI and SIR-EPI DSI, showing equal signal-to-noise ratio (SNR) and contrast and small differences in registration, likely due to typical subject motion. Comparison of DSI and DTI tractographs showed matching quality and detection of white matter tracts. The net reduction to nearly half the number of diffusion encoding gradient pulses in SIR-EPI significantly reduces acquisition times of DSI and DTI.

Physiological noise modelling for spinal functional magnetic resonance imaging studies

Spinal cord functional imaging allows assessment of activity in primary synaptic connections made by sensory neurons relaying information about the state of the body. However, reported human data based on gradient-echo techniques have been largely inconsistent, with no clear patterns of activation emerging. One reason for this variability is the influence of physiological noise, which is typically not corrected for. By acquiring single-slice resting data from the spinal cord with a conventional gradient-echo EPI pulse sequence at TR = 200 ms (critically sampled) and TR = 3 s (under-sampled), we have characterised various sources of physiological noise. In 8 healthy subjects, the presence of physiologically dependent signal was explored using probabilistic independent component analysis (PICA). Based on the insights provided by PICA, we defined a new physiological noise model (PNM) based on retrospective image correction (RETROICOR), which uses independent physiological measurements taken from the subject to model sources of noise. Statistical significance of individual components included in the PNM was assessed by F-tests, which demonstrated that the optimal PNM included cardiac, respiratory, interaction and low-frequency regressors. In a group of 10 healthy subjects, activation data were acquired from the cervical spinal region (T1 to C5) during painful thermal stimulation of the right and left hands. The improvement obtained when using a PNM in estimating spinal cord activation was reflected in a reduction of false-positive activation (active voxels in the CSF space surrounding the cord), when compared to conventional GLM modelling without a PNM.

Updated 12-year results of a randomized clinical trial comparing standard-dose to high-dose myeloablative chemotherapy in the adjuvant treatment of breast cancer with more than three positive nodes (LN+)

549 Aims: We conducted a multicenter randomized trial comparing sequential adjuvant standard-dose with high-dose chemotherapy in breast cancer patients younger than 60 years, with 4 or more positive nodes. Patients: Following surgery, patients were stratified by number of positive nodes (4–9 or 9), and randomly assigned to either conventional Epi–CMF (3 courses of epirubicin 120 mg/m2, followed by 6 courses of CMF), or high-dose chemotherapy (HDS) with stem cells support (one course of cyclophosphamide 7 g/m2, followed by one course of methotrexate 8 g/m2 with leukovorin rescue, by two courses of epirubicin 120 mg/m2, and by one course of thiotepa 600 mg/m2 plus melphalan 160–180 mg/m2 with stem cell autografting). Tamoxifen (20 mg/d × 5 yr) was also planned regardless of menopausal and receptor status. The study was designed with a power of 80% to detect a 15% increase in progression-free survival at 5 years in the HDS arm. Results: Of the initially enrolled 398 patients, 16 were ineligible, and the remaining 382 patients (Epi–CMF: 197 patients, HDS: 185 patients) were analyzed according to intent-to- treat. One patient treated with HDS (0.5%) died of interstitial pneumonia. With a median follow-up of 136 months, the 12-year progression-free survival rates were 44% and 52% for the Epi–CMF and the HDS groups, respectively, and the overall survival rates were 51% and 60%, respectively. However, among the 68 patients younger than 36 years, and the 189 patients with 4–9 LN+, those in the HDS group showed a trend for a progression-free survival advantage (HR 0.76 and 0.74, respectively). Conclusions: In the intent-to-treat analysis the 9% overall survival advantage associated with the HDS regimen failed to reach statistical significance in a study powered to detect a 15% difference. To reliably define the role of high-dose therapy, meta-analysis of patient data from all relevant randomized trials (such as that planned by the Early Breast Cancer Trialists’ Collaborative Group) is needed. Supported in part by AIRC and Pharmacia & Upjohn, Milano, Italy. No significant financial relationships to disclose.

T1ρ contrast in functional magnetic resonance imaging

The application of T1 in the rotating frame (T1rho) to functional MRI in humans was studied at 3 T. Increases in neural activity increased parenchymal T1rho. Modeling suggested that cerebral blood volume mediated this increase. A pulse sequence named spin-locked echo planar imaging (SLEPI) that produces both T1rho and T2* contrast was developed and used in a visual functional MRI (fMRI)experiment. Spin-locked contrast significantly augments the T2* blood oxygen level-dependent (BOLD) contrast in this sequence. The total functional contrast generated by the SLEPI sequence (1.31%) was 54% larger than the contrast (0.85%) obtained from a conventional gradient-echo EPI sequence using echo times of 30 ms. Analysis of image SNR revealed that the spin-locked preparation period of the sequence produced negligible signal loss from static dephasing effects. The SLEPI sequence appears to be an attractive alternative to conventional BOLD fMRI, particularly when long echo times are undesirable, such as when studying prefrontal cortex or ventral regions, where static susceptibility gradients often degrade T2*-weighted images.

Simultaneous perfusion and blood‐oxygenation‐level‐dependent measurements using single‐shot interleaved z‐shim echo‐planar imaging

Single-shot interleaved z-shim EPI (SSIZS-EPI) was extended to a simultaneous perfusion and blood-oxygenation-level-dependent (BOLD) imaging technique that reduces susceptibility-induced signal loss while preserving rapid image acquisition. Experiments on human brains showed that images acquired with this technique had improved signal-to-noise ratio in the inferior prefrontal, meso-, and lateral-temporal lobes compared with a conventional EPI. Perfusion maps obtained from the SSIZS-EPI images at resting state illustrated substantial signal recovery in these brain areas. Perfusion and BOLD images collected with a sensorimotor paradigm demonstrated the feasibility of the technique to simultaneously measure cerebral blood flow and blood oxygenation signals associated with brain activation. Functional experiments with a neuropsychiatric paradigm showed increased brain activities in the periamygdalar regions in both perfusion and BOLD maps, consistent with a previous H(2) (15)O PET study. The proposed technique, with its advantages of reducing susceptibility artifacts and fast scanning speed, would be useful for obtaining more reliable measurements of functional signals, particularly in the brain regions with field inhomogeneities.

An Investigation of the Value of Spin-Echo-Based fMRI Using a Stroop Color–Word Matching Task and EPI at 3 T

This study examines the value of spin-echo-based fMRI for cognitive studies at the main magnetic field strength of 3 T using a spin-echo EPI (SE-EPI) sequence and a Stroop color–word matching task. SE-EPI has the potential advantage over conventional gradient-echo EPI (GE-EPI) that signal losses caused by dephasing through the slice are not present, and hence although image distortion will be the same as for an equivalent GE-EPI sequence, signal voids will be eliminated. The functional contrast in SE-EPI will be lower than for GE-EPI, as static dephasing effects do not contribute. As an auxiliary experiment interleaved diffusion-weighted and non-diffusion-weighted SE-EPI was performed in the visual cortex to further elucidate the mechanims of functional contrast. In the Stroop experiment activation was detected in all areas previously found using GE-EPI. Additional frontopolar and ventral frontomedian activations were also found, which could not be detected using GE-EPI. The experiments from visual cortex indicated that at 3 T the BOLD signal change has contributions from the extravascular space and larger blood vessels in roughly equal amounts. In comparison with GE-EPI the absence of static dephasing effects would seem to result in a superior intrinsic spatial resolution. In conclusion the sensitivity of SE-EPI at 3 T is sufficient to make it the method of choice for fMR studies that require a high degree of spatial localization or where the requirement is to detect activation in regions affected by strong susceptibility gradients.

Conventional Diffusion Weighted Imaging In Acute Stroke Overestimates Apparent Diffusion Coefficient (ADC): Improved Accuracy of ADC Measurements of Brain Using Fluid-Inversion Prepared Diffusion (FLIPD) Imaging

13 Background: The measurement of ADC of water in brains of stroke patients is used in developing tissue models of reversible from irreversible injury. Cerebrospinal fluid (CSF) has a higher ADC and T2 value than parenchyma and measurement of lesion ADC by conventional EPI methods may be overestimated by the presence of CSF in sulci and perivascular spaces. We investigated whether the suppression of signal from CSF using an inversion recovery MRI method would give different ADC values than with the conventional DWI technique. Methods: Thirteen consecutive patients with stroke onset of less than 6 hours and an acute lesion on conventional DWI were studied. Conventional isotropic DWI was a T2-weighted single shot EPI technique with a b value of 1000 s/mm2. CSF suppression was achieved by the addition of an inversion pulse (TI = 2200 ms) at the beginning of the DWI sequence. The method is termed Fluid-Inversion Prepared Diffusion (FLIPD), and it is a combination of FLAIR and DWI in a single sequence. The region of the acute lesion was identified on the conventional DWI and the ADC of that region was measured in both the conventional and FLIPD ADC images. Results: In all 13 patients, FLIPD ADC was lower than conventional ADC. The mean (SD) of the 13 patients’ lesion ADC was 0.587 (0.075) x 10 -3 mm/s with FLIPD and 0.696 (0.078) x 10 -3 mm/s with conventional DWI (p -3 mm/s for lesions and (SD = 0.151 vs. 0.514 x 10 -3 mm/s for normal brain). The reduced variance in FLIPD ADC improved the diagnostic conspicuity of FLIPD ADC lesions. Conclusions: Suppression of CSF leads to lesion ADC values more homogeneous and greater than 15% lower than with conventional EPI DWI techniques. We suggest that FLIPD ADC measurements are more accurate and give more diagnostically useful images than conventional ADC maps. Because FLIPD measures water diffusion within parenchyma only, it should be more sensitive to ischemic changes.

Conventional Diffusion Weighted Imaging In Acute Stroke Overestimates Apparent Diffusion Coefficient (ADC): Improved Accuracy of ADC Measurements of Brain Using Fluid-Inversion Prepared Diffusion (FLIPD) Imaging

13 Background: The measurement of ADC of water in brains of stroke patients is used in developing tissue models of reversible from irreversible injury. Cerebrospinal fluid (CSF) has a higher ADC and T2 value than parenchyma and measurement of lesion ADC by conventional EPI methods may be overestimated by the presence of CSF in sulci and perivascular spaces. We investigated whether the suppression of signal from CSF using an inversion recovery MRI method would give different ADC values than with the conventional DWI technique. Methods: Thirteen consecutive patients with stroke onset of less than 6 hours and an acute lesion on conventional DWI were studied. Conventional isotropic DWI was a T2-weighted single shot EPI technique with a b value of 1000 s/mm2. CSF suppression was achieved by the addition of an inversion pulse (TI = 2200 ms) at the beginning of the DWI sequence. The method is termed Fluid-Inversion Prepared Diffusion (FLIPD), and it is a combination of FLAIR and DWI in a single sequence. The region of the acute lesion was identified on the conventional DWI and the ADC of that region was measured in both the conventional and FLIPD ADC images. Results: In all 13 patients, FLIPD ADC was lower than conventional ADC. The mean (SD) of the 13 patients’ lesion ADC was 0.587 (0.075) x 10 -3 mm/s with FLIPD and 0.696 (0.078) x 10 -3 mm/s with conventional DWI (p < 0.0001). The distribution of ADC values in all voxels pooled across all subjects indicated a narrower distribution of for FLIPD ADC (SD = 0.128 vs. 0.220 x 10 -3 mm/s for lesions and (SD = 0.151 vs. 0.514 x 10 -3 mm/s for normal brain). The reduced variance in FLIPD ADC improved the diagnostic conspicuity of FLIPD ADC lesions. Conclusions: Suppression of CSF leads to lesion ADC values more homogeneous and greater than 15% lower than with conventional EPI DWI techniques. We suggest that FLIPD ADC measurements are more accurate and give more diagnostically useful images than conventional ADC maps. Because FLIPD measures water diffusion within parenchyma only, it should be more sensitive to ischemic changes.

Alternate k-space sampling in EPI: compensation for T2* and adjustable T2 weighting.

In this work, preliminary results are described for a modification of the MBEST sampling scheme such that image resolution can be increased while preserving image contrast. In this new approach, a single spin-echo is used in sampling k-space. The basic idea relies on acquiring a conventional EPI image from the center of k-space and applying a pi pulse to permit the acquisition of the two outer edges of k-space. Using this new approach, it is possible to obtain an enhancement in EPI image resolution, while reducing the extent of T2* weighting. As a result, the resulting images possess reduced T2* contrast and suffer less signal loss from T2* effects such as spatial variations in susceptibility and field inhomogeneity.

Surface planarity and microstructure of low temperature silicon SEG and ELO

Surface planarity and epi/SiO2 interface characteristics of selective epitaxial growth (SEG) and epitaxial lateral overgrowth (ELO), deposited at 800–950 °C/10 or 25 Torr, have been studied for micron-sized structures. SEG at 860 °C showed superior planarity and reduced ratio of facet width to epi thickness, compared to higher deposition temperatures. Data showed that epi/SiO2 interface defects are greatly reduced for structures parallel to (100) and/or by adding HCl to the source gas, compared to interfaces positioned at standard orientation (110) on a (100) substrate. The transition from SEG to ELO in view of the facet orientations will be discussed. To correlate structural with electrical data, n+/p diodes were fabricated on as-grown and polish planarized SEG. Leakage current values of approximately 100 nA/cm2 could be measured. These are comparable to similar n+/p junctions fabricated on conventional epi.