Single Breath-hold Research Articles

Added Value of a Single Fast 20-second Deep-Inspiration Breath-hold Acquisition in FDG PET/CT in the Assessment of Lung Nodules.

Purpose To compare the accuracy of a single 20-second deep-inspiration breath hold (DIBH) in fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) to that with conventional free-breathing (FB) whole-body PET/CT for the assessment, characterization, and quantification of lung lesions in terms of the blurring effect of respiratory motion. Materials and Methods Institutional review board approval was obtained, and the requirement to obtain informed consent was waived. A preclinical study was performed in a test population of 19 patients to evaluate the feasibility and consistency of DIBH techniques compared with phase-based respiratory gating (PBRG). One hundred fifteen patients with lung lesions were then prospectively included and assessed with FB PET/CT followed by 20-second DIBH PET/CT. Maximum standardized uptake value (SUVmax), peak standardized uptake value (SUVpeak), and number and size of nodules were reported for each acquisition and then compared with findings from histopathologic examination and/or clinical-radiologic follow-up. Statistical analysis was performed with the t test, χ2 test, Pearson correlation coefficient, and receiver operating characteristic analysis. Results In the test population, data obtained with DIBH PET and PBRG PET showed close correlation (r = 0.94, P < .001 for SUVmax and r = 0.98, P < .001 for SUVpeak). In the clinical population, both SUVmax and SUVpeak were significantly increased with DIBH compared with FB (5.60 ± 4.20 vs 3.11 ± 1.80 and 2.25 ± 1.75 vs 1.71 ± 0.96, respectively; P < .001). A significantly greater number of lung lesions was detected with DIBH PET/CT compared with FB PET/CT (P < .001), with the detection of 70 additional nodules and more accurate coregistration of 84. According to the area under the receiver operating characteristic curve for SUVpeak, DIBH demonstrated a higher level of accuracy than did FB (P = .039). Conclusion The DIBH PET/CT technique is feasible in routine clinical practice and is more sensitive for quantitative measurements and lesion localization. This technique reduces the blurring effect of respiratory motion, thus improving the diagnostic accuracy for lung nodules. © RSNA, 2017.

Accelerated multicontrast volumetric imaging with isotropic resolution for improved peri-infarct characterization using parallel imaging, low-rank and spatially varying edge-preserving sparse modeling.

To achieve consistent effectiveness in reconstruction of fine image features for cases of varying contrast-to-noise ratio (CNR) to facilitate translating accelerated multicontrast volumetric imaging with isotropic resolution toward clinical utility in peri-infarct characterization. A low-rank and spatially varying edge-preserving constrained compressed sensing parallel imaging reconstruction method (CP-LASER) is developed to effectively preserve contrast of small-scale structures for highly accelerated multicontrast volumetric imaging in CNR-limited scenarios. CP-LASER synergistically integrates parallel imaging, low-rank and spatially varying edge-preserving sparse modeling to achieve high signal-to-noise-ratio efficiency by leveraging prior knowledge about signal properties including coil sensitivity weighting, spatiotemporally correlated signal relaxation, and spatially varying sparsity. In the preclinical study using highly accelerated multicontrast volumetric imaging with an isotropic 1.5-mm resolution, CP-LASER demonstrated robust multicontrast reconstruction of peri-infarct characteristics with excellent correspondence with histopathology. CP-LASER provides better delineation of the peri-infarct border zone with improved sharpness than alternative methods in a clinical demonstration on 1.5T with an isotropic 2.2-mm resolution achieved in a single breath-hold. Accelerated multicontrast volumetric imaging with isotropic resolution using CP-LASER has demonstrated the potential to improve peri-infarct characterization in a clinical setting. Magn Reson Med 79:3018-3031, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Fast and accurate multi‐channel mapping based on the TIAMO technique for 7T UHF body MRI

Current methods for mitigation of transmit field B1+ inhomogeneities at ultrahigh field (UHF) MRI by multi-channel radiofrequency (RF) shimming rely on accurate B1+ mapping. This can be time consuming when many RF channels have to be mapped for in vivo body MRI, where the B1 maps should ideally be acquired within a single breath-hold. Therefore, a new B1+ mapping technique (B1TIAMO) is proposed. The performance of this technique is validated against an established method (DREAM) in phantom measurements for a cylindrical head phantom with an 8-channel transmit/receive (Tx/Rx) array. Furthermore, measurements for a 32-channel Tx/Rx remote array are conducted in a large body phantom and the |B1+| map reliability is validated against simulations of the transmit RF field distribution. Finally, in vivo results of this new mapping technique for human abdomen are presented. For the head phantom (8-channel Tx/Rx coil), the single |B1+| comparison between B1 TIAMO, the direct DREAM measurements, and simulation data showed good agreement with 10-19% difference. For the large body phantom (32-channel Tx/Rx coil), B1TIAMO matched the RF field simulations well. The results demonstrate the potential to acquire 32 accurate single-channel B1+ maps for large field-of-view body imaging within only a single breath-hold of 16 s at 7T UHF MRI. Magn Reson Med 79:2652-2664, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Diagnostic hepatic arterial phase MRI imaging with gadoxetate disodium – stick or TWIST?

Background to the audit: Liver magnetic resonance imaging (MRI) with hepatobiliary contrast agents such as gadoxetate disodium (Primovist) plays a key role in liver lesion characterisation. Transient dyspnoea and resultant artefact with these agents is more frequent with gadoxetate disodium, affecting arterial phase sequences.1,2 To overcome transient severe motion (TSM) artefact, acquiring multiple arterial phases in a single breath hold may help obtain at least one adequate arterial phase sequence.3

Diagnostic accuracy of 256-row multidetector CT coronary angiography with prospective ECG-gating combined with fourth-generation iterative reconstruction algorithm in the assessment of coronary artery bypass: evaluation of dose reduction and image quality.

Effective radiation dose in coronary CT angiography (CTCA) for coronary artery bypass graft (CABG) evaluation is remarkably high because of long scan lengths. Prospective electrocardiographic gating with iterative reconstruction can reduce effective radiation dose. To evaluate the diagnostic performance of low-kV CT angiography protocol with prospective ecg-gating technique and iterative reconstruction (IR) algorithm in follow-up of CABG patients compared with standard retrospective protocol. Seventy-four non-obese patients with known coronary disease treated with artery bypass grafting were prospectively enrolled. All the patients underwent 256 MDCT (Brilliance iCT, Philips) CTCA using low-dose protocol (100kV; 800 mAs; rotation time: 0.275s) combined with prospective ECG-triggering acquisition and fourth-generation IR technique (iDose4; Philips); all the lengths of the bypass graft were included in the evaluation. A control group of 42 similar patients was evaluated with a standard retrospective ECG-gated CTCA (100kV; 800 mAs).On both CT examinations, ROIs were placed to calculate standard deviation of pixel values and intra-vessel density. Diagnostic quality was also evaluated using a 4-point quality scale. Despite the statistically significant reduction of radiation dose evaluated with DLP (study group mean DLP: 274mGycm; control group mean DLP: 1224mGycm; P value<0.001). No statistical differences were found between PGA group and RGH group regarding intra-vessel density absolute values and SNR. Qualitative analysis, evaluated by two radiologists in "double blind", did not reveal any significant difference in diagnostic quality of the two groups. The development of high-speed MDCT scans combined with modern IR allows an accurate evaluation of CABG with prospective ECG-gating protocols in a single breath hold, obtaining a significant reduction in radiation dose.

Variable refocusing flip angle single-shot fast spin echo imaging of liver lesions: increased speed and lesion contrast.

To evaluate acquisition time and clinical image quality of a variable refocusing flip angle (vrf) single-shot fast spin echo (SSFSE) sequence in comparison with a conventional SSFSE sequence for imaging of liver lesions in patients undergoing whole-body PET/MRI for oncologic staging. A vrfSSFSE sequence was acquired in 43 patients with known pancreatic neuroendocrine tumors undergoing 68Ga-DOTA-TOC PET on a simultaneous time-of-flight 3.0T PET/MRI. Liver lesions≥1.5cm with radionucleotide uptake were analyzed. Contrast-to-noise ratios (CNRs) were measured, and four blinded radiologists assessed overall image quality. Differences in repetition time and CNR were assessed using a paired Student's t test with p<0.05 considered statistically significant. Inter-reader variability was assessed with Fleiss' kappa statistic. 53 eligible lesions in 27 patients were included for analysis. vrfSSFSE demonstrated higher mean lesion CNR compared to SSFSE (9.9±4.1 vs. 6.7±4.1, p<0.001). Mean repetition time (TR) was 679±97ms for the vrfSSFSE sequence compared to 1139±106ms for SSFSE (p<0.0001), corresponding to a 1.7-fold decrease in acquisition time. Overall quality of liver lesion and common bile duct images with the vrfSSFSE sequence was graded as superior than or equivalent to the SSFSE sequence for 59% and 67% of patients, respectively. Compared to conventional SSFSE, vrfSSFSE resulted in improved lesion contrast on simultaneous PET/MRI in patients with liver metastases. Due to decreased SAR demands, vrfSSFSE significantly decreased TR, allowing coverage of the entire liver in a single twenty-second breath hold. This may have important clinical implications in the setting of PET/MRI, where scan time is limited by the necessity of whole-body image acquisition in addition to bed specific imaging.

Single-Breath-Hold Whole-heart Unenhanced Coronary MRA Using Multi-shot Gradient Echo EPI at 3T: Comparison with Free-breathing Turbo-field-echo Coronary MRA on Healthy Volunteers.

Purpose:We investigated the feasibility of single breath hold unenhanced coronary MRA using multi-shot gradient echo planar imaging (MSG-EPI) on a 3T-scanner.Methods:Fourteen volunteers underwent single breath hold coronary MRA with a MSG-EPI and free-breathing turbo field echo (TFE) coronary MRA at 3T. The acquisition time, signal to noise ratio (SNR), and the contrast of the sequences were compared with the paired t-test. Readers evaluated the image contrast, noise, sharpness, artifacts, and the overall image quality.Results:The acquisition time was 88.1% shorter for MSG-EPI than TFE (24.7 ± 2.5 vs 206.4 ± 23.1 sec, P < 0.01). The SNR was significantly higher on MSG-EPI than TFE scans (P < 0.01). There was no significant difference in the contrast on MSG-EPI and TFE scans (1.8 ± 0.3 vs 1.9 ± 0.3, P = 0.24). There was no significant difference in image contrast, image sharpness, and overall image quality between two scan techniques. The score of image noise and artifact were significantly higher on MSG-EPI than TFE scans (P < 0.05).Conclusion:The single breath hold MSG-EPI sequence is a promising technique for shortening the scan time and for preserving the image quality of unenhanced whole heart coronary MRA on a 3T scanner.

Simultaneous multislice imaging for native myocardial T1 mapping: Improved spatial coverage in a single breath-hold.

To develop a saturation recovery myocardial T1 mapping method for the simultaneous multislice acquisition of three slices. Saturation pulse-prepared heart rate independent inversion recovery (SAPPHIRE) T1 mapping was implemented with simultaneous multislice imaging using FLASH readouts for faster coverage of the myocardium. Controlled aliasing in parallel imaging (CAIPI) was used to achieve minimal noise amplification in three slices. Multiband reconstruction was performed using three linear reconstruction methods: Slice- and in-plane GRAPPA, CG-SENSE, and Tikhonov-regularized CG-SENSE. Accuracy, spatial variability, and interslice leakage were compared with single-band T1 mapping in a phantom and in six healthy subjects. Multiband phantom T1 times showed good agreement with single-band T1 mapping for all three reconstruction methods (normalized root mean square error <1.0%). The increase in spatial variability compared with single-band imaging was lowest for GRAPPA (1.29-fold), with higher penalties for Tikhonov-regularized CG-SENSE (1.47-fold) and CG-SENSE (1.52-fold). In vivo multiband T1 times showed no significant difference compared with single-band (T1 time ± intersegmental variability: single-band, 1580 ± 119 ms; GRAPPA, 1572 ± 145 ms; CG-SENSE, 1579 ± 159 ms; Tikhonov, 1586 ± 150 ms [analysis of variance; P = 0.86]). Interslice leakage was smallest for GRAPPA (5.4%) and higher for CG-SENSE (6.2%) and Tikhonov-regularized CG-SENSE (7.9%). Multiband accelerated myocardial T1 mapping demonstrated the potential for single-breath-hold T1 quantification in 16 American Heart Association segments over three slices. A 1.2- to 1.4-fold higher in vivo spatial variability was observed, where GRAPPA-based reconstruction showed the highest homogeneity and the least interslice leakage. Magn Reson Med 78:462-471, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

Dynamic and steady-state oxygen-dependent lung relaxometry using inversion recovery ultra-fast steady-state free precession imaging at 1.5 T.

To demonstrate the feasibility of oxygen-dependent relaxometry in human lung using an inversion recovery ultra-fast steady-state free precession (IR-ufSSFP) technique. Electrocardiogram-triggered pulmonary relaxometry with IR-ufSSFP was performed in 7 healthy human subjects at 1.5 T. The data were acquired under both normoxic and hyperoxic conditions. In a single breath-hold of less than 9 seconds, 30 transient state IR-ufSSFP images were acquired, yielding longitudinal (T1) and transversal (T2) relaxometry parameter maps using voxel-wise nonlinear fitting. Possible spatial misalignments between consecutive IR-ufSSFP parameter maps were corrected using elastic image registration. Furthermore, dynamic relaxometry oxygen wash-in and wash-out scans were performed in one volunteer. From this, T1 -related wash-in and wash-out time constants (τwi , τwo ) were calculated voxel-wise on registered maps using an exponential fitting model. For healthy lung, observed T1 values were 1399 ± 77 and 1290 ± 76 ms under normoxic and hyperoxic conditions, respectively. Oxygen-related reduction of T1 was statistically significant in every volunteer. No statistically significant change, however, was observed in T2, with normoxic and hyperoxic T2 values of 55 ± 16 and 56 ± 17 ms, respectively. The observed average τwi was 87.0 ± 28.7 seconds, whereas the average τwo was 73.5 ± 21.6 seconds. IR-ufSSFP allows fast, steady-state, and dynamic oxygen-dependent relaxometry of the human lung. Magn Reson Med 79:839-845, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Simultaneous assessment of both lung morphometry and gas exchange function within a single breath-hold by hyperpolarized 129 Xe MRI

During the measurement of hyperpolarized 129 Xe magnetic resonance imaging (MRI), the diffusion-weighted imaging (DWI) technique provides valuable information for the assessment of lung morphometry at the alveolar level, whereas the chemical shift saturation recovery (CSSR) technique can evaluate the gas exchange function of the lungs. To date, the two techniques have only been performed during separate breaths. However, the request for multiple breaths increases the cost and scanning time, limiting clinical application. Moreover, acquisition during separate breath-holds will increase the measurement error, because of the inconsistent physiological status of the lungs. Here, we present a new method, referred to as diffusion-weighted chemical shift saturation recovery (DWCSSR), in order to perform both DWI and CSSR within a single breath-hold. Compared with sequential single-breath schemes (namely the 'CSSR + DWI' scheme and the 'DWI+CSSR' scheme), the DWCSSR scheme is able to significantly shorten the breath-hold time, as well as to obtain high signal-to-noise ratio (SNR) signals in both DWI and CSSR data. This scheme enables comprehensive information on lung morphometry and function to be obtained within a single breath-hold. In vivo experimental results demonstrate that DWCSSR has great potential for the evaluation and diagnosis of pulmonary diseases.

Quantitative single breath-hold renal arterial spin labeling imaging at 7T.

To evaluate the feasibility of quantitative single breath-hold renal arterial spin labeling (ASL) imaging at 7T. A single-shot fast spin echo FAIR (flow-sensitive alternating inversion recovery) method was used to perform two studies. First, a multi-delay perfusion study was performed to estimate the spin labeling temporal bolus width achievable with a local transceiver array coil at 7T. Second, with a conservatively defined bolus width, a quantitative perfusion study was performed using the single subtraction approach. To address issues of B1+ inhomogeneity/efficiency and excessive short-term specific absorption rates, various strategies were used, such as dynamic radiofrequency shimming and optimization. A conservative temporal bolus width of 600 ms determined from the multi-delay study was applied for single-subtraction imaging to measure the renal blood flow in the cortex and medulla: 303 ± 31.8 and 91.3 ± 15.2 (mL/100 g/min), respectively. The estimated spatial and temporal signal-to-noise ratios of renal perfusion measurements were 3.8 ± 0.7 and 2.4 ± 0.6 for the cortex, and 2.2 ± 0.6 and 1.4 ± 0.2 for the medulla. With proper management of field strength specific challenges, quantitative renal ASL imaging can be achieved at 7T within a single breath-hold. Magn Reson Med 79:815-825, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Clinical evaluation of three‐dimensional late enhancement MRI

To assess the diagnostic value of three-dimensional late enhancement (3D-LGE) for the detection of myocardial necrosis in a routine clinical setting. 3D-LGE has been proposed as a novel magnetic resonance (MR) technique for the accurate detection of myocardial scar in both the ventricles and atria. Its performance in clinical practice has been poorly examined. Fifty-seven patients referred for cardiac MR examination including scar imaging were prospectively enrolled. Gadolinium enhanced single breathhold 3D T1-weighted gradient-echo inversion recovery sequence and a conventional 2D-LGE sequence were performed using a 1.5 Tesla clinical MR imaging system. The presence, pattern and transmurality of LGE, diagnostic accuracy and level of diagnostic confidence as well as image quality (median quality, mean LGE signal intensity, sharpness, virtual scan time) were graded on a 4-point scale. Interpretable images were obtained in 52/57 2D-LGE and in 47/57 3D high-resolution exams. LGE was detected in 10 patients with ischemic pattern, 9 with nonischemic pattern, while it was absent in 28, resulting in a total of 47 complete datasets. The detection of global and segmental LGE as well as its transmural extent were similar for both techniques (P = 0.65, P = 0.305, and P = 0.15, respectively). Image quality (median quality, LGE/ myocardial and LGE/ blood pool sharpness) was similar for both techniques (P = 0.740, P = 0.34, and P = 1.00, respectively), but LGE signal intensity was higher with 2D (P = 0.020). 3D-LGE diagnostic and quality scores were comparable to 2D-LGE in a routine clinical setting. Further technical refinement is required for 3D LGE to offer a reliable alternative for high quality scar imaging. 2 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;45:1675-1683.

Spin-echo Echo-planar Imaging MR Elastography versus Gradient-echo MR Elastography for Assessment of Liver Stiffness in Children and Young Adults Suspected of Having Liver Disease.

Purpose To compare two-dimensional (2D) gradient-recalled echo (GRE) and 2D spin-echo (SE) echo-planar imaging (EPI) magnetic resonance (MR) elastography for measurement of hepatic stiffness in pediatric and young adult patients suspected of having liver disease. Materials and Methods In this institutional review board-approved, HIPAA-compliant study, 58 patients underwent both 2D GRE and 2D SE-EPI MR elastography at 1.5 T during separate breath holds. Liver stiffness (mean of means; in kilopascals) was measured by five blinded reviewers. Pooled mean liver stiffness and region-of-interest (ROI) size were compared by using paired t tests. Intraclass correlation coefficients (ICCs) were used to assess agreement between techniques. Respiratory motion artifacts were compared across sequences by using the Fisher exact test. Results Mean patient age was 14.7 years ± 5.2 (standard deviation; age range, 0.7-20.5 years), and 55.2% (32 of 58) of patients were male. Mean liver stiffness was 2.92 kPa ± 1.29 measured at GRE MR elastography and 2.76 kPa ± 1.39 at SE-EPI MR elastography (n = 290; P = .15). Mean ROI sizes were 8495 mm2 ± 4482 for 2D GRE MR elastography and 15 176 mm2 ± 7609 for 2D SE-EPI MR elastography (n = 290; P < .001). Agreement was excellent for measured stiffness between five reviewers for both 2D GRE (ICC, 0.97; 95% confidence interval: 0.95, 0.98) and 2D SE-EPI (ICC, 0.98; 95% confidence interval: 0.96, 0.99). Mean ICC (n = 5) for agreement between 2D GRE and 2D SE-EPI MR elastography was 0.93 (range, 0.91-0.95). Moderate or severe breathing artifacts were observed on 27.5% (16 of 58) of 2D GRE images versus 0% 2D SE-EPI images (P < .001). Conclusion There is excellent agreement on measured hepatic stiffness between 2D GRE and 2D SE-EPI MR elastography across multiple reviewers. SE-EPI MR elastography allowed for stiffness measurement across larger areas of the liver and can be performed in a single breath hold. © RSNA, 2016.

Quantitative comparison of lung physiological parameters in single and multiple breathhold with hyperpolarized xenon magnetic resonance

Hyperpolarized (HP) xenon MR has been an important tool for quantifying the pulmonary structure and gaining functional information by measuring the dynamics of xenon in different lung components, e.g., gas exchange between gaseous xenon in the alveoli and dissolved xenon in tissue/plasma and red blood cells. Chemical shift saturation recovery is a commonly used pulse sequence to measure the xenon dynamics in the lung globally. However, the effect of the dissolved xenon signal oscillation caused by the cardiac cycle on the physiological parameters of the lung is still unclear. In this study, both single-breathhold (SB) and multiple-breathhold (MB) measurements were used to evaluate these effects in rats, and the data acquired with the MB measurement, which did not have oscillations, served as a reference. The pulmonary physiological parameters were extracted using the model of xenon exchange. The results showed that the physiological parameters derived from SB and MB measurements were not significantly different. These findings have clarified a previously unknown issue and will further promote the design of faster real-time acquisition sequences to quantify structural and functional information about the lung.

Simultaneous measurement of iron concentration and fat infiltration in the liver with a single-breathhold 16-echo gradient echo sequence

Introduction In the past few years there have been several methods to determine fat infiltration of the liver, some of them being expensive commercial applications for MRI or expensive services provided by some companies to which the MRI data are sent for evaluation. β -Thalassemia patients with liver iron overload and fat infiltration require determination of both. Purpose To develop and certify a method for simultaneous determination of iron overload and fat infiltration of the liver with a 16-echo single breath-hold gradient echo sequence and compare the calculated results of fat infiltration with those determined by Proton MR spectroscopy (MRS) of the liver. Materials and methods 500 patients were examined at 1.5 Tesla (Signa HDxt, GE, Milwaukee, USA) with a 16-echo sequence at two different echo time ranges (a short and a long one for moderate and low iron overload, respectively). A least-squares-fit of the acquired data yielded T2* values and fat fraction. MR spectra from the liver were acquired from 40 patients. Results The agreement for liver fat infiltration determined by the proposed MRI technique and the MRS method was excellent. The gradient echo method is sensitive enough for fat fractions as low as 1%. Fat infiltration results are accurate for iron concentrations as high as 10 mg/g dry tissue. Conclusion The gradient-echo method is quick and accurate and is a reliable alternative to other expensive methods. Furthermore it provides iron overload and fat infiltration determination simultaneously, in a single breath-hold. Disclosure None of the authors has anything to declare.

Single Breath-Hold T1ρ-Mapping of the Heart for Endogenous Assessment of Myocardial Fibrosis.

In this study, we propose a method to acquire high spatial-resolution T1ρ-maps, which allows bright and black-blood imaging, in a single breath-hold. To validate this innovative method, the reproducibility was tested in phantoms and volunteers. Lastly, the sensitivity and specificity for infarct detection was compared with the criterion standard late gadolinium enhancement (LGE). T1ρ-mapping was performed using a T1ρ-prepared balanced steady-state free precession sequence at 1.5 T and 3 T. Five images with increasing spin-lock preparation times (spin-lock = 0, 10, 20, 30, 40 milliseconds, amplitude = 500 Hz) were acquired with an interval of 3 beats. Black-blood imaging was performed using a double inversion pulse sequence. The method was tested in 2 times 10 healthy volunteers at 1.5 and 3 T and in 9 myocardial infarction patients at 1.5 T. T1ρ-maps, and LGE images were scored for presence and extent of myocardial scarring. Phantom results show that the proposed T1ρ-mapping method gives accurate T1ρ-values. The mean T1ρ-relaxation time of the myocardium in healthy controls was 52.8 ± 1.8 milliseconds at 1.5 T and 46.4 ± 1.8 milliseconds at 3 T. In patients, the T1ρ of infarcted myocardium was (82.4 ± 5.2 milliseconds), and the T1ρ of remote myocardium was (54.2 ± 2.8 milliseconds; P < 0.0001). Sensitivity of infarct detection on a T1ρ-map was 70%, with a specificity of 94%, compared with LGE. In this study, we have investigated a method to acquire high spatial-resolution T1ρ-maps of the heart in a single breath-hold. This method proved to be reproducible and had high specificity compared with LGE and can thus be used for the endogenous detection of myocardial fibrosis in patients with ischemic cardiomyopathy.

Modified Subtraction Coronary CT Angiography Method for Patients Unable to Perform Long Breath-Holds: A Preliminary Study

Severe calcifications of the coronary arteries are still a major challenge in coronary computed tomography (CT) angiography (CCTA). Subtraction CCTA using a 320-detector row CT scanner has recently been introduced for patients with severe calcifications. However, the conventional subtraction CCTA method requires a long breath-holding time of approximately 20-40 seconds. This is a major problem in clinical practice because many patients may not be able to perform such a long breath-hold. We explored a modified subtraction CCTA method with a short breath-holding time to overcome this problem. This study was approved by our institutional review board, and all patients gave written informed consent. A total of 12 patients with a coronary calcium score of >400 were enrolled in this study. All patients were unable to hold their breath for more than 20 seconds. Modified subtraction CCTA was performed using the bolus-tracking method. The acquisition protocol was adjusted so that the mask scan was acquired 10 seconds after the postcontrast scan during a single breath-hold. The subtraction image was obtained by subtracting the mask image data from the postcontrast image data. The breath-holding times were recorded. Enhancement of the coronary arteries in the subtraction images was assessed. Subjective image quality was evaluated in a total of 32 segments using a 4-point scale. The mean breath-holding time was 12.8 ± 0.8 seconds (range, 12-14 seconds). The average CT number in the coronary arteries was 288.6 ± 80.5 Hounsfield units (HU) in the subtraction images. Average image quality was significantly increased from 2.1 ± 0.9 with conventional CCTA to 3.1 ± 0.7 with subtraction CCTA (P < 0.001). With subtraction CCTA, the number of non-diagnostic segments was significantly reduced from 53% to 19% (P = 0.001). This preliminary study has shown that our modified subtraction CCTA method allows the breath-holding time to be shortened to <15 seconds. This may substantially improve the success rate of subtraction CCTA by reducing artifacts and allowing this technique to be applied to patients who are unable to perform a long breath-hold.

Safely prolonging single breath-holds to >5 min in patients with cancer; feasibility and applications for radiotherapy.

Objective:Multiple, short and deep inspiratory breath-holds with air of approximately 20 s are now used in radiotherapy to reduce the influence of ventilatory motion and damage to healthy tissue. There may be further clinical advantages in delivering each treatment session in only one single, prolonged breath-hold. We have previously developed techniques enabling healthy subjects to breath-hold for 7 min. Here, we demonstrate their successful application in patients with cancer.Methods:15 patients aged 37–74 years undergoing radiotherapy for breast cancer were trained to breath-hold safely with pre-oxygenation and mechanically induced hypocapnia under simulated radiotherapy treatment conditions.Results:The mean breath-hold duration was 5.3 ± 0.2 min. At breakpoint, all patients were normocapnic and normoxic [mean end-tidal partial pressure of carbon dioxide was 36 ± 1 standard error millimetre of mercury, (mmHg) and mean oxygen saturation was 100 ± 0 standard error %]. None were distressed, nor had gasping, dizziness or disturbed breathing in the post-breath-hold period. Mean blood pressure had risen significantly from 125 ± 3 to 166 ± 4 mmHg at breakpoint (without heart rate falling), but normalized within approximately 20 s of the breakpoint. During breath-holding, the mean linear anteroposterior displacement slope of the L breast marker was <2 mm min−1.Conclusion:Patients with cancer can be trained to breath-hold safely and under simulated radiotherapy treatment conditions for longer than the typical beam-on time of a single fraction. We discuss the important applications of this technique for radiotherapy.Advances in knowledge:We demonstrate for the first time a technique enabling patients with cancer to deliver safely a single prolonged breath-hold of >5 min (10 times longer than currently used in radiotherapy practice), under simulated radiotherapy treatment conditions.

Fast Determination of Flip Angle and T1 in Hyperpolarized Gas MRI During a Single Breath-Hold.

MRI of hyperpolarized media, such as 129Xe and 3He, shows great potential for clinical applications. The optimal use of the available spin polarization requires accurate flip angle calibrations and T1 measurements. Traditional flip angle calibration methods are time-consuming and suffer from polarization losses during T1 relaxation. In this paper, we propose a method to simultaneously calibrate flip angles and measure T1 in vivo during a breath-hold time of less than 4 seconds. We demonstrate the accuracy, robustness and repeatability of this method and contrast it with traditional methods. By measuring the T1 of hyperpolarized gas, the oxygen pressure in vivo can be calibrated during the same breath hold. The results of the calibration have been applied in variable flip angle (VFA) scheme to obtain a stable steady-state transverse magnetization. Coupled with this method, the ultra-short TE (UTE) and constant VFA (CVFA) schemes are expected to give rise to new applications of hyperpolarized media.

Magnetic Resonance Spectroscopy in Living-Donor Liver Transplantation

ObjectiveThe purpose of this study is to evaluate the accuracy rate of the one breath-hold single voxel hydrogen-1 magnetic resonance spectroscopy (MRS) in comparison with intraoperative biopsy for liver fat quantification in living-donor liver transplantation. Materials and MethodsA total of 80 living liver donors participated in this study. Each patient underwent both MRS and intraoperative biopsy for evaluation of liver fatty content. MRS was performed using 1.5-T magnetic resonance imaging and placed in segments 2–4, 5–8, and left lateral segment for each donor. Accuracy was assessed through receiver operating characteristic curve analysis. Sensitivity and specificity of MRS fat fractions were also calculated. ResultsEighty living-donor liver transplantation donors were enrolled in this study. There was no fatty liver in 59 subjects (73.8%), 5% to 10% fatty liver in 17 subjects, 11% to 15% fatty liver in 3 subjects, and >16% fatty liver in 1 subject. MRS fat fraction showed excellent parameters to predict between normal liver and fatty liver groups (1.85% ± 0.98, 8.13% ± 3.52, respectively; P < .0001). Linear regression between MRS fat fraction and pathology grading showed high correlation (R2 = 0.7092). Pearson correlation revealed high correlation between MRS and pathology results (r = 0.936), poor correlation between body mass index and pathology results (r = 0.390). The sensitivity and specificity for detection of liver steatosis in MRS fat fraction were 95.2% and 98.3%, respectively. Conclusion1H MRS fat fraction is a highly precise and accurate method in quantification of hepatic steatosis for the living donor and can be finished in a single breath-hold.