half-Fourier Acquisition Single-shot Turbo Spin-echo Research Articles

Usefulness of Postcontrast T2-Weighted Images in Shortening the Total Scan Time of a Gadoxectic Acid Enhanced MRI of the Liver: a Comparison between Precontrast and Postcontrast T2-Weighted Images

Purpose: We evaluated the effects of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) on the overall image quality and lesion contrast of T2-weighted images (T2WI). Materials and Methods: We reviewed T2WI before and after Gd-EOB-DTPA enhancement in 50 patients with 41 focal liver lesions. Pre- and post-contrast T2WI were analyzed qualitatively and quantitatively. For the qualitative analysis, two abdominal radiologists, blinded to other findings in the study, retrospectively scored the image quality, lesion conspicuity, and artifacts. The quantitative analysis involved the measurement of the liver signal-to-noise ratio (SNR) and the lesion-to-liver contrast-to-noise ratio (CNR). Results: Image quality and lesion conspicuity were not significantly different among the respiratory-triggered T2-weighted turbo spin-echo sequence (T2TSE), Half-fourier acquisition single-shot turbo spin-echo (HASTE) sequence, and breath-hold T2-weighted gradient recalled-echo (GRE) sequences. However, there was a trend toward improved lesion conspicuity in post-contrast T2TSE. The quantitative analysis indicated that the SNR for post-contrast images was significantly higher than for pre-contrast images on T2TSE (p=0.04). No significant differences were seen in the CNR of focal lesions, but there was a trend towards an increase in the CNR for postcontrast T2WI of hepatocellular carcinoma. Conclusion: Compared to pre-contrast T2WI, post-contrast T2WI showed no handicap in the overall image quality and lesion contrast. Therefore, to shorten the total scan time during Gd-EOB-DTPA enhanced MRI, pre-contrast T2WI can be replaced by post-contrast T2WI.

Half‐fourier‐acquisition single‐shot turbo spin‐echo (HASTE) MRI of the lung at 3 Tesla using parallel imaging with 32‐receiver channel technology

To assess the feasibility of half-Fourier-acquisition single-shot turbo spin-echo (HASTE) of the lung at 3 Tesla (T) using parallel imaging with a prototype of a 32-channel torso array coil, and to determine the optimum acceleration factor for the delineation of intrapulmonary anatomy. Nine volunteers were examined on a 32-channel 3T MRI system using a prototype 32-channel-torso-array-coil. HASTE-MRI of the lung was acquired at both, end-inspiratory and end-expiratory breathhold with parallel imaging (Generalized autocalibrating partially parallel acquisitions = GRAPPA) using acceleration factors ranging between R = 1 (TE = 42 ms) and R = 6 (TE = 16 ms). The image quality of intrapulmonary anatomy and subjectively perceived noise level was analyzed by two radiologists in consensus. In addition quantitative measurements of the signal-to-noise ratio (SNR) of HASTE with different acceleration factors were assessed in phantom measurements. Using an acceleration factor of R = 4 image blurring was substantially reduced compared with lower acceleration factors resulting in sharp delineation of intrapulmonary structures in expiratory scans. For inspiratory scans an acceleration factor of 2 provided the best image quality. Expiratory scans had a higher subjectively perceived SNR than inspiratory scans. Using optimized multi-element coil geometry HASTE-MRI of the lung is feasible at 3T with acceleration factors up to 4. Compared with nonaccelerated acquisitions, shorter echo times and reduced image blurring are achieved. Expiratory scanning may be favorable to compensate for susceptibility associated signal loss at 3T.

BOLD fMRI using a modified HASTE sequence

For more than a decade, turbo spin echo (TSE) pulse sequences have been suggested as an alternative to echo planar imaging (EPI) sequences for fMRI studies. Recent development in parallel imaging has renewed the interest in developing more robust TSE sequences for fMRI. In this study, a modified half Fourier acquisition single-shot TSE (mHASTE) sequence has been developed with a three-fold GRAPPA to improve temporal resolution as well as a preparation time to enhance BOLD sensitivity. Using a classical flashing checkerboard block design, the BOLD signal characteristics of this novel method have been systematically analyzed as a function of several sequence parameters and compared to those of gradient-echo and spin-echo EPI sequences. Experimental studies on visual cortex of five volunteers have provided evidence suggesting that mHASTE can be more sensitive to extra-vascular BOLD effects around microvascular networks, which leads to more accurate function localization. The studies also show that the activation cluster size in mHASTE increases with the refocusing RF flip angle and TE while decreasing with the echo number (ncenter) used to sample the k-space center. Compared to spin-echo EPI, mHASTE incurs an ∼50% reduction in activation cluster size and an ∼20% decrease in BOLD contrast. However a higher signal-to-noise ratio and a spatially more uniform temporal stability have been observed in mHASTE as compared to the EPI sequences when the scan times are held constant. With further refinement and optimization, mHASTE can become a viable alternative for fMRI in situations where the conventional EPI sequences are limited or prohibitive.

Time-efficient fast spin echo imaging at 4.7 T with low refocusing angles

An implementation of fast spin echo at 4.7 T designed for versatile and time-efficient T(2)-weighted imaging of the human brain is presented. Reduced refocusing angles (alpha < 180 degrees) were employed to overcome specific absorption rate (SAR) constraints and their effects on image quality assessed. Image intensity and tissue contrast variations from heterogeneous RF transmit fields and incidental magnetization transfer effects were investigated at reduced refocusing angles. We found that intraslice signal variations are minimized with refocusing angles near 180 degrees, but apparent gray/white matter contrast is independent of refocusing angle. Incidental magnetization transfer effects from multislice acquisitions were shown to attenuate white matter intensity by 25% and gray matter intensity by 15% at 180 degrees; less than 5% attenuation was seen in all tissues at flip angles below 60 degrees. We present multislice images acquired without excess delay time for SAR mitigation using a variety of protocols. Subsecond half Fourier acquisition single-shot turbo spin echo (HASTE) images were obtained with a novel variable refocusing angle echo train (20 degrees < alpha < 58 degrees) and high-resolution scans with a voxel volume of 0.18 mm(3) were acquired in 6.5 min with refocusing angles of 100 degrees.

MR imaging of aortic coarctation

Aortic coarctation accounts for 5%-10% of all congenital heart diseases and represents 7% of critically ill infants with heart disease. Magnetic resonance (MR) imaging allows the study of this disease with several advantages in comparison with conventional angiography, transesophageal echocardiography, and computed tomography. The MR protocol applied at our institution for both diagnosis and follow-up after surgical or endovascular treatment consists of four steps: morphologic study, cine MR study, flow analysis, and MR angiography (MRA). The first three sequences are acquired during breath-hold and with electrocardiographic gating. Anatomy is well depicted with dark-blood half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences. Cine true-fast imaging with steady-state precession (true-FISP) sequences show not only morphologic features but also blood-flow changes inside the aorta. Gradient-echo sequences for phase-velocity mapping allow flow analysis. Application of Bernoulli's equation--here briefly presented and discussed--allows for calculation of the pressure gradient caused by the coarctation. MRA, acquired with a breath-hold three-dimensional T1-weighted gradient-echo sequence and intravenous administration of paramagnetic contrast material, allows for optimal depiction of the aortic lumen, with a panoramic view of the whole aorta, its main branches and possible collateral circulation.

Differentiation of hepatic tumors by use of image contrast with T2-weighted MRI

Differentiation of hepatic tumors is often evaluated in terms of qualitative diagnostic performance. The signal intensity patterns of hepatic masses are known to differ on certain T2-weighted imaging sequences. In this study, we investigated the quantitative analysis of hepatic masses by using an index called the "T2-shine ratio." Fast-spin-echo (FSE), half-Fourier acquisition single-shot turbo spin echo (HASTE), and true-FISP sequences obtained with quick-imaging techniques during a single breath-hold were examined in 74 patients. T2-shine ratios were calculated by use of the signals of regions of interest (ROIs) placed on a tumor and peripheral tissue: the T2-shine ratio is defined as (tumor signal-liver signal)/liver signal. The rate of change in the T2-shine ratio was compared among three sequences of FSE, HASTE, and true-FISP. The T2-shine ratio of FSE deducted from HASTE was significantly higher for hepatic cysts than for other masses. The T2-shine ratio of HASTE deducted from True-FISP was less than zero for hemangioma. For the value that deducted the T2-shine ratio of HASTE from the T2-shine ratio of true-FISP, hemangiomas had a significantly lower value than did cysts and metastases (P < 0.05), but there was no significant difference from hepatocellular carcinomas (HCCs). Although liver cysts, cavernous hemangiomas, and other lesions could be differentiated, it was virtually impossible to distinguish HCCs from metastatic tumors. In conclusion, the quantitative analysis of hepatic tumors was able to differentiate among these lesions by use of the T2-shine ratio.

Fast magnetic resonance imaging evaluating of pulmonary progressive massive fibrosis with vibe and HASTE sequences: comparison with computed tomography imaging

The aim of this prospective study was to evaluate the diagnostic utility of volumetric interpolated breath-hold examination (VIBE) and half-Fourier-acquisition single-shot turbo spin-echo (HASTE) fast magnetic resonance imaging (MRI) sequences in the evaluation of pulmonary progressive massive fibrosis (PMF) in comparison with computed tomography (CT) imaging. If fast MRI is proven to be diagnostically significant, this modality can be used for diagnosis and follow-up studies of PMF patients. Twenty-two PMF lesions from 20 coal workers were evaluated. After CT imaging, patients underwent pre-contrast VIBE, contrast-enhanced VIBE, and HASTE MRI studies for detection and evaluation of the PMF lesions. Measurements of the three groups were evaluated with intra-class coefficients. Correlation levels between sizes, image quality, and artifact were evaluated with linear Pearson correlation analysis. There was almost perfect agreement among radiologists for lesion detection with kappa analysis. There was significant agreement between three MRI study groups and gold standard CT images. We found the best agreement values with contrast- enhanced VIBE images for lesion detection and image quality in comparison with CT imaging. Presence of artifact was also lowest with this protocol. With fast MRI sequences in pulmonary imaging, image quality has significantly improved being very close to that of CT studies. In this study, contrast-enhanced VIBE protocol provided the best depiction of PMF lesions. This protocol may be an alternative choice for CT, avoiding the use of iodinated contrast material and minimizing exposure to ionizing radiation for follow-up studies.

Application of magnetic resonance imaging to measure fasting and postprandial volumes in humans

Our aims were to measure the gastric volume response in excess of ingested meal volume (i.e. gastric accommodation), contribution of swallowed air to this excess, day-to-day variability of gastric volumes measured by MRI and their relationship to volumes measured by single-photon-emission computed tomography (SPECT). In 20 healthy volunteers, fasting and postprandial gastric volumes were measured after technetium(99m)-pertechnetate labeling of the gastric mucosa by SPECT and separately by MRI, using 3D gradient echo and 2D half-Fourier acquisition single-shot turbo spin echo (HASTE) sequences. Ten of these subjects had a second MRI exam to assess intra-individual variation. Thereafter, another 10 subjects had two MRI studies during which they ingested the nutrient in 30 or 150 mL aliquots. During MRI, the postprandial gastric volume change exceeded the ingested meal volume by 106 +/- 12 mL (Mean +/- SEM). The HASTE and gradient echo sequences distinguished air from fluid under fasting and postprandial conditions respectively. This postprandial excess mainly comprised air (61 +/- 5 mL), which was not significantly different when ingested as 30 or 150 mL aliquots. Fasting and postprandial gastric volumes measured by MRI were generally reproducible within subjects. During SPECT, postprandial volumes increased by 158 +/- 18 mL; gastric volumes measured by SPECT were higher than MRI. MRI measures gastric volumes with acceptable performance characteristics; the postprandial excess primarily consists of air, which is not affected by the mode of ingestion. Gastric volumes are technique specific and differ between MRI and SPECT.

Multimodality imaging of a right saphenous vein graft pseudoaneurysm

A 74-year-old man with a history that was significant for two-vessel coronary artery bypass grafting (CABG) surgery, underwent magnetic resonance cholangiopancreatography for evaluation of chronic pancreatitis. A complex cystic mass, measuring 2 cm × 2 cm was incidentally observed anterior to the right atrium on the axial T2-weighted magnetic resonance cholangiopancreatography half-Fourier acquisition single-shot turbo spin-echo (HASTE) image (Figure 1A). A subsequent transthoracic echocardiography confirmed the cystic mass, extrinsic to the right atrium, with no intracardiac communication following administration of agitated saline contrast (Figure 1B). Multidetector computed tomography identified a pseudoaneurysm of the right saphenous vein graft from previous CABG (Figure 1C). A three-dimensional, volume-rendered multidetector computed tomography image of the graft arising from the aorta and the pseudoaneurysm is shown in Figure 1D. Cardiac catheterization confirmed the presence of a discrete inlet communication into the saphenous vein graft pseudoaneurysm (Figure 1E). The patient underwent successful occlusion of the ostium of the pseudoaneurysm by a covered stent graft (JOSTENT [Abbott Laboratories, USA] 4.00 mm × 8 mm) and disappearance of the jet of contrast (Figure 1F). Figure 1) A A complex cystic mass (arrow) measuring 3 cm × 3 cm × 4 cm was incidentally observed anterior to the right atrium on the axial T2-weighted magnetic resonance cholangiopancreatography half-Fourier acquisition single-shot turbo spin-echo ... Saphenous vein graft pseudoaneurysms are a rare complication following CABG and warrant prompt recognition due to potential fatal complications (1). They are often asymptomatic, discovered as an incidental paracardiac or mediastinal mass using complementary cardiac imaging including echocardiography, computed tomography and cardiac magnetic resonance imaging (2). Although surgery has traditionally been the treatment of choice (3), percutaneous techniques such as coiled embolization or self-expanding stents are emerging alternative options (4).

Fetal MRI of the central nervous system: clinical relevance

Specific conditions of the mother sometimes reduce the quality of ultrasound. In these cases, fetal magnetic resonance imaging (MRI) can be performed after gestational week (GW) 18. Interpretation of subtle disorders or malformations becomes safe not before GW 23. Clinical development of children with central nervous system (CNS) disorders is not predictable with imaging alone. Statistical evidence and personal experience of the medical team are essential in counseling, but optimized imaging is helpful in being more precise. The value of fetal MRI (fMRI) is evaluated. Twenty-five pregnant women (30.5 +/- 4.5 years) were investigated by additional fMRI. Breath-hold technique with T2 half-Fourier acquisition single-shot turbo spin-echo and T1 FLASH-2D images in three dimensions with field of view of 350 x 400 mm. All cases have been correlated with postnatal MRI, ultrasound, and clinical follow-up. In all fetuses, diagnostic MRI was performed 3-10 days after ultrasound between GW 22 and 34 (GW 26.1 +/- 3.6). Sedation was not necessary. In eight cases of suspicious ultrasound, fMRI confirmed ultrasound findings. In 13 cases, additional diagnoses or exclusions of suspected findings could be established. Complete revision of diagnosis was realized in four cases. Findings could be confirmed by postnatal MRI in 11 patients. The clinical course was not predictable in cases with ambivalent prognosis. Prenatal diagnosis of CNS pathologies should result in parental counseling. Sufficient diagnostic information, statistical data, and experience of the involved professionals are essential. These results show that in detecting congenital CNS abnormalities fMRI is superior to ultrasound and should be considered in difficult cases.

Magnetic resonance cholangiopancreatography in the diagnosis of primary sclerosing cholangitis

Magnetic resonance cholangiopancreatography (MRCP) is a less-invasive alternative to endoscopic retrograde cholangiopancreatography (ERCP) for the diagnosis of primary sclerosing cholangitis (PSC). This study evaluated the diagnostic accuracy of MRCP in PSC compared with ERCP, and assessed the diagnostic accuracy of different T2w sequences. 95 patients (69 PSC, 26 controls) were evaluated using both ERCP and MRCP. Exclusion criteria included secondary sclerosing cholangitis and contraindications to MRCP. The diagnosis of PSC was confirmed in 69 patients based on ERCP as the reference gold standard. MRCP was performed using a 1.5 Tesla MR unit, using breath hold, coronal and transverse half-Fourier acquisition single-shot turbo spin-echo (HASTE), coronal-oblique, fat-suppressed half-Fourier rapid acquisition with relaxation enhancement (RARE), and coronal-oblique, fat-suppressed, multisection, thin-section HASTE (TS-HASTE) sequences. The MRCP morphological criteria of PSC were evaluated and compared with ERCP. The sensitivity, specificity, and diagnostic accuracy were 86%, 77%, and 83%, respectively, using the MRCP-RARE sequence, and increased further to 93%, 77%, and 88%, respectively, by the inclusion of follow-up MRCP in 52 patients, performed at 6-12-month intervals. HASTE and TS-HASTE sequences showed significantly lower diagnostic accuracy but provided additional morphologic information. MRCP can diagnose PSC but has difficulties in early PSC and in cirrhosis, and in the differentiation of cholangiocarcinoma, Caroli's disease, and secondary sclerosing cholangitis. A positive MRCP would negate some diagnostic ERCP studies but a negative MRCP would not obviate the need for ERCP.

Congenital anomalies and variations of the bile and pancreatic ducts: magnetic resonance cholangiopancreatography findings, epidemiology and clinical significance

The objective of this paper is to document the magnetic resonance cholangiopancreatography (MRCP) findings and the epidemiology of congenital anomalies and variations of the bile and pancreatic ducts and to discuss their clinical significance. Three-hundred and fifty patients of both sexes (150 females, 200 males, age range 0-76 years, average age 38 years) underwent MRCP for clinically suspected lithiasic, neoplastic or inflammatory disease of the bile and pancreatic ducts. Patients were imaged with a 1.5-T superconductive magnet (Magnetom Vision, Siemens, Erlangen, Germany), a four-channel phased-array body coil, breath-hold technique, with multislice T2-weighted half-Fourier acquisition single-shot turbo spin echo (HASTE), MIP reconstructions, and a single-shot T2-weighted turbo-spin-echo sequence rapid acquisition with relaxation enhancement (RARE) with different slice thicknesses. Studies in oncological patients were completed with fat saturation 3D T1 gradient-echo sequences during the intravenous injection of gadolinium diethylene triamine pentaacetate acid (DTPA) (0.2 ml/kg). MRCP demonstrated recurrent and therefore normal bile and pancreatic ducts in 57% of patients. In the remaining 42.3%, it documented anatomical variants (41%) and congenital anomalies (1.3%). Variants of the intrahepatic bile duct were seen in 21% of cases: crossover anomaly (6.7%), anterior branch of the right hepatic duct draining the IV and VII segments that flow together with the left bile duct (3.1%) and anterior and posterior branches of the right hepatic duct that flow together with the common hepatic duct (3.3%). Variants of the extrahepatic bile ducts were present in 8.8% of patients: low insertion of the cystic duct into the common hepatic duct (4.5%), emptying of the cystic duct into the right hepatic duct (2.7%) and a second-order large branch draining into the cystic duct (1.6%). MRCP identified a double gall bladder in 3% of patients and anatomical variants of the biliopancreatic system in 8.2%: pancreas divisum (5.2%) and a long sphincter of Oddi (3%). Finally, congenital anomalies were diagnosed in 1.3% of cases: bile duct cysts (0.3%), atresia of the bile ducts (0.3%) and multiple biliary hamartomatosis (0.7%). The congenital anomalies and anatomical variants of the bile and pancreatic ducts present a complex spectrum of frequent alterations, which are worthy of attention in both the clinical and surgical settings and are readily identified by MRCP.

Frequency of Common Bile Duct Motion Artifacts Caused by Inferior Vena Cava Pulsation on Magnetic Resonance Cholangiopancreatography

We assessed the frequency of common bile duct (CBD) motion artifacts caused by inferior vena cava (IVC) pulsation on magnetic resonance cholangiopancreatography (MRCP). We retrospectively evaluated CBD motion artifacts in 4 MRCP sequences from each of 115 consecutive patients. We observed 37 (32.2%) ghost artifacts at the ventral and dorsal aspects of the CBD on transaxial, half-Fourier acquisition single-shot turbo spin-echo (HASTE-ax) images; no such artifacts were observed on transaxial T(2)-weighted turbo spin-echo images. In 10 patients, we observed 9 (7.8%) pseudo-defects of the CBD on 3-dimensional T(2)-weighted turbo spin-echo with navigator-triggered prospective acquisition correction technique MRCP and 6 (5.2%) pseudo-defects on single-shot rapid acquisition with relaxation enhancement MRCP. Pseudo-defects were significantly more frequent in patients with ghost artifacts than without (9 of 37 [24.3%] versus one of 78 [1.3%]; P<0.01, McNemar test). Although uncommon, pseudo-defects of the CBD caused by IVC pulsation are observed on MRCP. MRCP interpretation that includes comparison with HASTE-ax images can diminish the potential misinterpretation of such CBD motion artifact as bile duct tumor or biliary stone.

MR imaging of omphalopagus conjoined twins with a dandy-walker malformation: prenatal true FISP &amp; HASTE sequences

Conjoined twins are an extremely rare congenital malformation without any known genetic predisposition. Omphalopagus twins are the second most common variety of conjoined twins and usually are joined at the umbilicus. We present omphalopagus conjoined twins demonstrated with true FISP (fast imaging with steady-state procession) and HASTE (half- Fourier acquisition single-shot turbo spin-echo) magnetic resonance imaging (MRI) sequences, which showed Dandy- Walker malformation in one of the pair. To our knowledge, this is the first case of conjoined twins with this malformation, which was diagnosed with ultrafast MRI.

Magnetic resonance imaging examination of the fetal brain

Magnetic resonance imaging examination of the fetal brain

MR imaging of the female pelvis at 3 Tesla: Evaluation of image homogeneity using different dielectric pads

To evaluate improvements in image homogeneity in pelvic MR imaging at 3 Tesla (T) using two different dielectric pads. A total of eight healthy females were scanned using a 3T MR scanner equipped with a body-array coil. Axial and sagittal fast spin-echo T2-weighted images (T2WI) (TR/TE = 3200 msec/94 msec), axial fast spin-echo T1-weighted images (T1WI) (TR/TE = 700 msec/11 msec), and sagittal half-Fourier acquisition single-shot turbo spin-echo (HASTE) images (TR/TE = 3000 msec/100 msec) were performed for pelvic imaging. Sequences were repeated with dielectric pads (consisting of either ultrasound [US] gel or water), and without pads. Three or four regions of interest (ROIs) were placed on fatty tissues and the ratio of minimum to maximum signal intensity (RSI) was calculated as a marker of image homogeneity. RSI was significantly higher on T2WI and T1WI when using dielectric pads than when no pad was used. A similar tendency was observed in RSI on HASTE. No significant difference was found between images with US gel pads and those with water pads. Dielectric pads consisting of either US gel or water are effective in improving image homogeneity of the pelvis on 3T MRI.

Quantitative regional oxygen transfer imaging of the human lung

To demonstrate that the use of nonquantitative methods in oxygen-enhanced (OE) lung imaging can be problematic and to present a new approach for quantitative OE lung imaging, which fulfills the requirements for easy application in clinical practice. A total of 10 healthy volunteers and three non-small-cell lung cancer (NSCLC) patients were examined using a 1.5T scanner. OE imaging was performed using a snapshot fast low-angle shot (FLASH) T(1)-mapping technique (TE = 1.4 msec, TR = 3.5 msec) as well as a series of T(1)-weighted inversion recovery (IR) half- Fourier acquisition single-shot turbo spin-echo (HASTE) (TE(effective) = 43 msec, TE(inter) = 4.2 msec, and inversion time [TI] = 1200 msec) images. Semiquantitative relative signal enhancement ratios (RER) of T(1)-weighted images before and after inhalation of oxygen-enriched gas were compared to the quantitative change in T(1). A hybrid method is proposed that combines the advantages of T(1)-weighted imaging with the quantification provided by T(1)-mapping. To this end, the IR-HASTE images were transformed into quantitative parameter maps. To prevent mismatching and incorrect parameter maps, retrospective image selection was performed using a postprocessing navigator technique. The RER was dependent on the intrinsic values of T(1) in the lung. Quantitative parameters, such as the decrease of T(1) after switching the breathing gas, were more suited to oxygen transfer quantification than to relative signal enhancement. The mean T(1) value during inhalation of room air (T(1,room)) for the volunteers was 1260 msec. This value decreased by about 10% after switching the breathing gas to carbogen. For the patients, the mean T(1,room) value was 1182 msec, which decreased by about 7% when breathing carbogen. The parameter maps generated using the proposed hybrid method deviated, on average, only about 1% from the T(1)-maps. For the purpose of intersubject comparison, OE lung imaging should be performed quantitatively. The proposed hybrid technique produced reliable quantitative results in a short amount of time and, therefore, is suited for clinical use.

“MR Cholangiopancreatography Using HASTE (Half-Fourier Acquisition Single-Shot Turbo Spin-Echo) Sequences”—A Commentary

Each month the American Journal of Roentgenology will republish online one of the 100 most-cited articles from its first century. A corresponding commentary in the print journal by a contemporary radiologist will provide a current perspective. For a full list of these articles, see page 3 of the January 2006 issue of the AJR or go to www.ajronline.org. Centennial article series Guest Editor: Liem T. Bui-Mansfield, ARRS Figley Fellow 2004.

MRI of the female pelvis at 3T compared to 1.5T: Evaluation on high‐resolution T2‐weighted and HASTE images

To evaluate the feasibility of MRI of the female pelvis using high-resolution T2-weighted imaging (T2WI) and the half-Fourier acquisition single-shot turbo spin-echo (HASTE) technique at 3 Tesla (T) compared to 1.5T, while focusing on the uterine body and cervical anatomy. A total of 19 healthy women underwent pelvic MR scans on 3T and 1.5T scanners. Axial and sagittal T2W (voxel size of 0.6 x 0.8 x 2 mm) and sagittal HASTE images were obtained. The images were evaluated qualitatively for overall image quality, contrast in the uterine zonal appearance and cervical structure, image inhomogeneity, and artifacts. A quantitative evaluation was performed regarding zonal contrast and image inhomogeneity. On T2WI, the image contrast in the uterine cervix and vagina were significantly higher at 3T than at 1.5T, although there was no significant difference in the overall image quality or contrast in the uterine zonal appearance. Image inhomogeneity was more prominent at 3T, and motion artifact was more severe at 1.5T. Our results suggest that MRI of the female pelvis at 3T may potentially provide excellent images of the uterine cervix on high-resolution T2WI. New techniques to reduce inhomogeneity are thus called for.

Small hepatic lesions found on single‐phase helical CT in patients with malignancy: Diagnostic capability of breath‐hold, multisection fluid‐attenuated inversion‐recovery (FLAIR) MR imaging using a half‐fourier acquisition single‐shot turbo spin‐echo (HASTE) sequence

To evaluate the diagnostic capability of breath-hold, multisection fluid-attenuated inversion-recovery (FLAIR) imaging using a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence in combination with T2-weighted fast spin-echo (FSE) magnetic resonance (MR) sequences for small hepatic lesions found on CT in patients with malignancy. This study included 48 patients with extrahepatic malignancy who underwent both CT and MR examinations. There were a total of 112 small hepatic lesions (73 cysts and 39 liver metastases, <2 cm in diameter) that showed low attenuation on enhanced CT. Three radiologists independently reviewed the CT and MR (FLAIR-HASTE and T2-weighted FSE) images and assigned a confidence level to their evaluation (cyst or metastasis) on a five-point scale. All three reviewers were significantly better able (P < 0.05) to differentiate small hepatic cyst from liver metastasis with combined FLAIR-HASTE and T2-weighted FSE images (Az values = 0.997-0.999) than with CT (0.917-0.932). The mean values of sensitivity, specificity, and accuracy were significantly higher (P < 0.001) for T2-weighted FSE with FLAIR-HASTE (96.6%, 96.8%, and 96.7%, respectively) than for CT (76.9%, 61.6%, and 67.3%, respectively). A confident diagnosis was rendered in 12 of 112 lesions (10.7%) on the basis of CT, and this rate increased to 83 of 112 (74.1%) on the basis of T2-weighted FSE and FLAIR-HASTE imaging. FLAIR-HASTE is considered to be an effective sequence for differentiating hepatic cysts from liver metastases without the use of a contrast agent. With FLAIR-HASTE one can confidently diagnose small hepatic lesions found on CT in patients with a malignancy.