Submillimeter three-dimensional coronary MR angiography with real-time navigator correction: comparison of navigator locations.

Three-dimensional free-breathing coronary magnetic resonance angiography was performed in eight healthy volunteers with use of real-time navigator technology. Images acquired with the navigator localized at the right hemidiaphragm and at the left ventricle were objectively compared. The diaphragmatic navigator was found to be superior for vessel delineation of middle to distal portions of the coronary arteries.     

Inversion recovery radial MRI with interleaved projection sets.

The radial trajectory has found applications in cardiac imaging because of its resilience to undersampling and motion artifacts. Recent work has shown that interleaved and weighted radial imaging can produce images with multiple contrasts from a single data set. This feature was investigated for inversion recovery imaging of scar using a radial technique. The 2D radial imaging method was modified to acquire quadruply interleaved projection sets within each acquisition window of the cardiac cycle. These data were reconstructed using k-space weightings that used a smaller segment of the acquisition window for the central k-space data, the determinant of image contrast. This method generates four images with different T1 weightings. The novel approach was compared with noninterleaved radial imaging, interleaved radial without weightings, and Cartesian imaging in simulations, phantoms, and seven subjects with clinical myocardial infarction. The results show that during a typical acquisition window after an inversion pulse, magnetization changes rapidly. The interleaved acquisition provided better image quality than the noninterleaved radial acquisition. Interleaving with weighting provided better quality when the inversion time (TI) was shorter than optimal; otherwise, interleaving without weighting was superior. These methods enable a radial trajectory to be employed in conjunction with preparation pulses for viability imaging.     

Noncontrast SSFP pulmonary vein magnetic resonance angiography: impact of off-resonance and flow

Purpose

To investigate pulmonary vein (PV) off‐resonance and blood flow as causes of signal void artifacts in noncontrast steady‐state‐free‐precession (SSFP) PV magnetic resonance angiography (MRA).

Materials and Methods

PV blood off‐resonance was measured on 11 healthy adult subjects and 10 atrial fibrillation (AF) patients. Noncontrast PV MRA was performed using a 3D slab‐selective SSFP sequence at 1.5T on seven healthy subjects with signal profile shifts of 0–125 Hz. The time‐resolved blood flow velocity of the PVs was measured on five healthy subjects. The impact of flow was studied on six healthy subjects, on whom SSFP PV MRA was acquired twice with the electrocardiogram (ECG) trigger delay corresponding to low and high flow, respectively.

Results

The PV off‐resonances were 97 ± 27 Hz, 65 ± 20 Hz, 74 ± 25 Hz, and 52 ± 17 Hz for right inferior, left inferior, right superior, and left superior PVs, respectively, on healthy subjects, and 74 ± 20 Hz, 38 ± 9 Hz, 51 ± 20 Hz, and 28 ± 11 Hz on AF patients (P<0.01 for all). The off‐resonance caused severe signal voids in the PVs. Signal acquired during mid‐diastole with high PV flow caused additional signal voids in the left atrium, which was reduced by setting the ECG trigger delay to late‐diastole.

Conclusion

PV off‐resonance and flow causes signal void artifacts in noncontrast 3D slab‐selective SSFP PV MRA. J. Magn. Reson. Imaging 2010;32:1255–1261. © 2010 Wiley‐Liss, Inc.     

Contrast‐enhanced whole‐heart coronary MRI with bolus infusion of gadobenate dimeglumine at 1.5 T

We sought to investigate the T₁ kinetics of blood and myocardium after three infusion schemes of gadobenate dimeglumine (Gd‐BOPTA) and subsequently compared contrast‐enhanced whole‐heart coronary MRI after a bolus Gd‐BOPTA infusion with nonenhanced coronary MRI at 1.5 T. Blood and myocardium T₁ was measured in seven healthy adults, after each underwent three Gd‐BOPTA infusion schemes (bolus: 0.2 mmol/kg at 2 mL/sec, hybrid: 0.1 mmol/kg at 2 mL/sec followed by 0.1 mmol/kg at 0.1 mL/sec, and slow: 0.2 mmol/kg at 0.3 mL/sec). Fourteen additional subjects underwent contrast‐enhanced coronary MRI with an inversion‐recovery steady‐state free precession sequence after bolus Gd‐BOPTA infusion. Images were compared with nonenhanced T₂‐prepared steady‐state free precision whole‐heart coronary MRI in signal‐to‐noise ratio, contrast‐to‐noise ratio, depicted vessel length, vessel sharpness, and subjective image quality. Bolus and slow infusion schemes resulted in similar T₁ during coronary MRI, whereas the hybrid infusion method yielded higher T₁ values. A bolus infusion of Gd‐BOPTA significantly improved signal‐to‐noise ratio, contrast‐to‐noise ratio, depicted coronary artery length, and subjective image quality, when all segments were collectively compared but not when compared segment by segment. In conclusion, whole‐heart steady‐state free precision coronary MRI at 1.5 T can benefit from a bolus infusion of 0.2 mmol/kg Gd‐BOPTA. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.     

Direct comparison of 3D spiral vs. Cartesian gradient-echo coronary magnetic resonance angiography.

While 3D thin-slab coronary magnetic resonance angiography (MRA) has traditionally been performed using a Cartesian acquisition scheme, spiral k-space data acquisition offers several potential advantages. However, these strategies have not been directly compared in the same subjects using similar methodologies. Thus, in the present study a comparison was made between 3D coronary MRA using Cartesian segmented k-space gradient-echo and spiral k-space data acquisition schemes. In both approaches the same spatial resolution was used and data were acquired during free breathing using navigator gating and prospective slice tracking. Magnetization preparation (T(2) preparation and fat suppression) was applied to increase the contrast. For spiral imaging two different examinations were performed, using one or two spiral interleaves, during each R-R interval. Spiral acquisitions were found to be superior to the Cartesian scheme with respect to the signal-to-noise ratio (SNR) and contrast-to-noise-ratio (CNR) (both P < 0.001) and image quality. The single spiral per R-R interval acquisition had the same total scan duration as the Cartesian acquisition, but the single spiral had the best image quality and a 2.6-fold increase in SNR. The double-interleaf spiral approach showed a 50% reduction in scanning time, a 1.8-fold increase in SNR, and similar image quality when compared to the standard Cartesian approach. Spiral 3D coronary MRA appears to be preferable to the Cartesian scheme. The increase in SNR may be "traded" for either shorter scanning times using multiple consecutive spiral interleaves, or for enhanced spatial resolution.     

Non‐contrast‐enhanced pulmonary vein MRI with a spatially selective slab inversion preparation sequence

We propose a non‐contrast‐enhanced, three‐dimensional, free‐breathing, electrocardiogram‐gated, gradient recalled echo sequence with a slab‐selective inversion for pulmonary vein (PV) MRI. A sagittal inversion slab was applied prior to data acquisition to suppress structures adjacent to the left atrium (LA) and PVs, thereby improving the conspicuity of the PV and LA. Compared with other MR angiography methods using an inversion pulse, the proposed method does not require signal subtraction and the inversion slab is not parallel to the imaging slab. The feasibility of the proposed method was demonstrated in healthy subjects. The inversion slab thickness and inversion time were optimized to be 60 mm and 500 ms, respectively. Compared to conventional gradient recalled echo imaging without inversion, the proposed technique significantly increased the contrast‐to‐noise ratios between the LA and the right atrium by 20‐fold (P < 0.01), increased the contrast‐to‐noise ratios between the PVs and right atrium by 10‐fold (P < 0.03), and increased the contrast‐to‐noise ratios between the PVs, LA and pulmonary artery by 4‐fold (P < 0.01 for both). The signal‐to‐noise ratios of the PVs and the LA were similar with and without the inversion slab (P > 0.3). The proposed technique greatly enhances the conspicuity of the PVs and LA without significant loss of signal‐to‐noise ratio. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Free‐Breathing 3D Cardiac MRI Using Iterative Image‐Based Respiratory Motion Correction

Respiratory motion compensation using diaphragmatic navigator gating with a 5 mm gating window is conventionally used for free‐breathing cardiac MRI. Because of the narrow gating window, scan efficiency is low resulting in long scan times, especially for patients with irregular breathing patterns. In this work, a new retrospective motion compensation algorithm is presented to reduce the scan time for free‐breathing cardiac MRI that increasing the gating window to 15 mm without compromising image quality. The proposed algorithm iteratively corrects for respiratory‐induced cardiac motion by optimizing the sharpness of the heart. To evaluate this technique, two coronary MRI datasets with 1.3 mm³ resolution were acquired from 11 healthy subjects (seven females, 25 ± 9 years); one using a navigator with a 5 mm gating window acquired in 12.0 ± 2.0 min and one with a 15 mm gating window acquired in 7.1 ± 1.0 min. The images acquired with a 15 mm gating window were corrected using the proposed algorithm and compared to the uncorrected images acquired with the 5 and 15 mm gating windows. The image quality score, sharpness, and length of the three major coronary arteries were equivalent between the corrected images and the images acquired with a 5 mm gating window (P‐value > 0.05), while the scan time was reduced by a factor of 1.7. Magn Reson Med, 70:1005–1015, 2013. © 2012 Wiley Periodicals, Inc.     

Paraffin-embedded tissue as a source of RNA for gene expression analysis in oral malignancy

OBJECTIVE: To assess the feasibility of using archival oral mucosal tissue to examine gene expression at the ribonucleic acid (RNA) level.
MATERIALS AND METHODS: We describe the isolation of RNA from 8 nm sections of formalin-fixed paraffin-embedded oral mucosal tissue. RNA was reverse transcribed and three candidate genes amplified by polymerase chain reaction (PCR). The ribosomal protein S14 gene is a housekeeping gene which has been used as an internal standard in several quantitative PCR protocols. The thymidine kinase (TK) gene is expressed at low levels in most tissues and, with a well-documented genomic organisation, is a useful tool for discrimination between genomic DNA and cDNA. The RIa gene is reported to be overexpressed in many cancer cell lines, in malignant tissue and in vitro transformed cellS. RESULTS: The S14 gene, the TK gene and the RIα gene of the cAMP-dependent protein kinase (PKA) were amplified successfully from formalin-fixed paraffin-embedded tissue sections. The TK primer pair is a useful additional tool in the unambiguous identification of RNA-derived species.
CONCLUSION: RNA suitable for reverse transcribed (RT)-PCR was extracted from archival oral mucosal tissue. This should permit rapid sequence analysis of transcribed tumor suppressor genes and oncogenes in this material. Furthermore, the RT-PCR approach described may allow quantification of gene expression in oral mucosal archival material processed in a standard fashion.     

Vaginal swabs versus lavage for detection of Trichomonas vaginalis and bacterial vaginosis among HIV-positive women

OBJECTIVES: Cervicovaginal lavage (CVL) is often used for research and may be easier and more accurate than vaginal swabs as a specimen collection method. GOAL: The goal of this study was to compare (CVL) with vaginal swabs for the detection of bacterial vaginosis (BV) and Trichomonas vaginalis (TV). STUDY: CVL and vaginal swabs were collected from 216 HIV-infected women. Clinical assessments were made using wet mount for TV and Amsel's criteria for BV through CVL and swab collection methods. Laboratory gold standards used were Nugent's criteria for BV and InPouch (Biomed Diagnostics, San Jose, CA) culture for TV collected by swab. RESULTS: The prevalence by gold standards for BV was 49.3% and for TV was 25.2%. Sensitivities for direct microscopy versus culture for TV were 72.2 for CVL and 52.8 for vaginal swab (P <0.05). Sensitivities for Amsel's versus Nugent's criteria for BV were 36.2 for CVL and 34.0 for vaginal swab (P <0.80). Kappa scores of agreement between CVL and vaginal swabs for BV and TV were excellent for both. CONCLUSION: CVL was comparable to vaginal swabs as a specimen collection method for these 2 lower genital tract infections and may be superior for the diagnosis of TV.