T2-weighted breathold imaging of the liver: a quantitative and qualitative comparison of fast spin echo and half Fourier single shot fast spin echo imaging

The imaging characteristics of two EPI-hybrid breath-hold sequences, T2-weighted fast spin-echo [FSE, effective echo time (TE_eff) 138ms] and half Fourier single shot turbo spin-echo (HASTE, TE_eff 60 ms), were compared in hepatic imaging. A total of 111 patients with suspected hepatic disease were studied at 1.5 Tesla using a body phase-array coil. The signal-to-noise (S/N) and contrast-to-noise (C/N) ratios for organs and lesions were calculated and quantitatively compared. Organ delineation, visualization of anatomical structures and pathological lesions, artifacts, and total image quality were qualitatively assessed and statistically compared. The final diagnoses were metastases from colorectal, breast, and pancreatic cancer in 23/111, hepatocellular carcinoma in 15/111, cysts in 19/111, hemangiomas in 9/111, several other lesions in 7/111, and no lesions in 38/111 of the cases. A total of 139 lesion in 73% of the patients were seen while 85% of the lesions were at least 1.5 cm in size. Regarding S/Ns HASTE was significantly (P<0.03) superior to FSE with only minor (P>0.05) differences in C/Ns between the two sequences for anatomical and pathological structures. HASTE demonstrated in almost all (97.3%) of the cases no artifacts, while on fast SE imaging moderate to minor artifacts were present in 23.5–51.7% of the cases. The overall image quality and diagnostic confidence was rated significantly higher (good 43.2%, excellent 53.2%) for HASTE than for fast SE imaging (good 44.8%, excellent 17.6%). Providing comparable C/Ns for anatomical and pathological structures, breatheld HASTE imaging proved to be superior to fast SE in T2-weighted imaging of the upper abdomen regarding general image quality, and, with adequate technical prerequisites, may be a suitable substitute of fast T2-imaging techniques.     

Breathhold imaging of the upper abdomen using a circular polarized-array coil: comparison with standard body coil imaging

Current studies emphasize the use of array coils to decrease noise and increase the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). We applied Tl-weighted and T2-weighted standard nonbreathhold spin echo (SE) sequences and Tl-weighted FLASH, TurboFLASH, T2-weighted spin-echo time (TSE), and heavily T2-weighted half Fourier acquisition single-shot TSE (HASTE) sequences during breathhold for abdominal imaging in 15 normal volunteers. The breathhold scans were performed using both a standard coil and a circular polarized array coil. We analyzed the signal intensity (SI), SNR, and CNR of abdominal organs in all sequences. SNRs increased in all cases by an overall factor of 3 due to an 8% increase in overall Sis and a 50% decrease in noise when applying the array coil. Although the array-coil FLASH sequence performed at least as well as the respective SE sequence, the SNRs of the array-coil TurboFLASH, TSE breathhold, and HASTE sequences were generally lower. We conclude that array-coil imaging significantly improves fast imaging of the abdomen.     

Optimization of cardiac cine in the rat on a clinical 1.5-T MR system

Object: the overall goal was to study cardiovascular function in small animals using a clinical 1.5-T MR scanner optimizing a fast gradient-echo cine sequence to obtain high spatial and temporal resolution. Materials and methods: normal rat hearts (n = 9) were imaged using a 1.5-T MR scanner with a spiral fast gradient-echo (fast field echo for Philips scanners) sequence, three Cartesian fast gradient-echo (turbo field echo for Philips scanners) sequences with different in-plane resolution, and with and without flow compensation and half-Fourier acquisition. The hearts of four rats were then excised and left-ventricle mass was weighed. Inter- and intra-observer variability analysis was performed for magnetic resonance imaging (MRI) measurements. Results: half-Fourier acquisition with flow compensation gave the best sequence in terms of image quality, spatial as well as temporal resolution, and suppression of flow artifact. Ejection fraction was 71 ± 4% with less than 5% inter- and intra-observer variability. A good correlation was found between MRI-calculated left-ventricular mass and wet weight. Conclusions: using optimized sequences on a clinical 1.5-T MR scanner can provide accurate quantification of cardiac function in small animals and can promote cardiovascular research on small animals at 1.5-T     

Robust imaging of hippocampal inner structure at 7T: in vivo acquisition protocol and methodological choices

Objective

Motion-robust multi-slab imaging of hippocampal inner structure in vivo at 7T.

Materials and methods

Motion is a crucial issue for ultra-high resolution imaging, such as can be achieved with 7T MRI. An acquisition protocol was designed for imaging hippocampal inner structure at 7T. It relies on a compromise between anatomical details visibility and robustness to motion. In order to reduce acquisition time and motion artifacts, the full slab covering the hippocampus was split into separate slabs with lower acquisition time. A robust registration approach was implemented to combine the acquired slabs within a final 3D-consistent high-resolution slab covering the whole hippocampus. Evaluation was performed on 50 subjects overall, made of three groups of subjects acquired using three acquisition settings; it focused on three issues: visibility of hippocampal inner structure, robustness to motion artifacts and registration procedure performance.

Results

Overall, T2-weighted acquisitions with interleaved slabs proved robust. Multi-slab registration yielded high quality datasets in 96 % of the subjects, thus compatible with further analyses of hippocampal inner structure.

Conclusion

Multi-slab acquisition and registration setting is efficient for reducing acquisition time and consequently motion artifacts for ultra-high resolution imaging of the inner structure of the hippocampus.

     

MR imaging of focal liver lesions: comparison between turbo spin-echo and conventional spin-echo pulse sequences

The aim of this study was to compare conventional spin-echo (CSE)T ₂-weighted (T2W) images with turbo spin-echo (TSE) T2W pulse sequences in their ability to detect focal liver lesions. Seventy-eight consecutive patients with focal liver lesions were entered into this study. All patients were imaged using the gradient-echo (GE) sequence with the breath-hold technique forT ₁-weighted (T1W) images, and CSE and TSE sequences for T2W images. Qualitative evaluation included lesion detection (number of lesions detected) and conspicuity (extent of visualization of lesional borders); quantitative evaluation included the signal-to-noise (S/N) ratio and the contrast-to-noise (C/N) ratio. TSE showed the best performance in terms of lesion detection; however, the difference between TSE and CSE was significant only in the case of benign cysts (p<0.01). Conspicuity was higher with TSE and CSE, and lower with GE. The S/N and C/N ratios of the two T2W sequences were also comparable, and better than those of GE. However, the combined use of GE and TSE resulted in improved lesion detection. The results show that, because the acquisition time is greatly reduced with TSE sequences, these should be considered as first-line approach to magnetic resonance imaging of the liver for the study of focal lesions.     

Measurement of activation-related changes in cerebral blood volume: VASO with single-shot HASTE acquisition

Object The recently developed vascular space occupancy (VASO) fMRI technique is gaining popularity as it facilitates the measurement of cerebral blood volume (CBV) changes concomitant with brain activation, without the use of contrast agents. Thus far, VASO fMRI has only been used in conjunction with a GE-EPI (gradient-echo echo planar imaging) sequence, which is proceeded by an inversion recovery (IR) experiment to selectively null the blood signal. The use of GE-EPI has potential disadvantages: (a) the non-zero TE may lead to BOLD contamination and (b) images suffer from the EPI-typical inhomogeneity artefacts. Materials and methods Here, we propose the use of VASO based on an IR-HASTE (inversion recovery half-Fourier acquisition single-shot turbo spin echo) sequence. Results Results from a visual stimulation study (n = 8) show a 43% higher functional contrast-to-noise (CNR) of HASTE compared to EPI, with a strongly increased count of active voxels at the same significance threshold. Sensitivity to inflow effects was investigated and found to be similar for both methods. Conclusion As HASTE VASO yields essentially artefact-free images, it appears to be the method of choice for measuring relative CBV changes with VASO.     

Cranial fixation plates in cerebral magnetic resonance imaging: a 3 and 7 Tesla in vivo image quality study

Objective

This study assesses and quantifies impairment of postoperative magnetic resonance imaging (MRI) at 7 Tesla (T) after implantation of titanium cranial fixation plates (CFPs) for neurosurgical bone flap fixation.

Materials and methods

The study group comprised five patients who were intra-individually examined with 3 and 7 T MRI preoperatively and postoperatively (within 72 h/3 months) after implantation of CFPs. Acquired sequences included T₁-weighted magnetization-prepared rapid-acquisition gradient-echo (MPRAGE), T₂-weighted turbo-spin-echo (TSE) imaging, and susceptibility-weighted imaging (SWI). Two experienced neurosurgeons and a neuroradiologist rated image quality and the presence of artifacts in consensus reading.

Results

Minor artifacts occurred around the CFPs in MPRAGE and T₂ TSE at both field strengths, with no significant differences between 3 and 7 T. In SWI, artifacts were accentuated in the early postoperative scans at both field strengths due to intracranial air and hemorrhagic remnants. After resorption, the brain tissue directly adjacent to skull bone could still be assessed. Image quality after 3 months was equal to the preoperative examinations at 3 and 7 T.

Conclusion

Image quality after CFP implantation was not significantly impaired in 7 T MRI, and artifacts were comparable to those in 3 T MRI.

     

Improved short tau inversion recovery (iSTIR) for increased tumor conspicuity in the abdomen

Object

To develop an improved short tau inversion recovery (iSTIR) technique with simultaneous suppression of fat, blood vessels and fluid to increase tumor conspicuity in the abdomen for cancer screening.

Materials and methods

An adiabatic spectrally selective inversion pulse was used for fat suppression to overcome the reduced signal to noise ratio associated with chemically non-selective inversion pulse of STIR. A motion-sensitizing driven equilibrium was used for blood vessel suppression and a dual-echo single-shot fast spin echo acquisition was used for fluid suppression. The technique was optimized on four normal subjects and later tested on five patients referred for metastatic tumor evaluation.

Results

A velocity encoding of 2 cm/s achieved effective blood suppression even in small vessels. Subtraction of two images (one with 60 ms and the other with 280 ms echo time) acquired in the same echo train achieved excellent fluid suppression (>70 % reduction). Simultaneous suppression of fat, blood vessels and fluid improved the tumor conspicuity compared to corresponding fat-suppressed (STIR) image.

Conclusion

This technique generated two complementary images from a single scan: one that is equivalent to a STIR image and the other that qualitatively resembles a diffusion-weighted image and may have potential for magnetic resonance imaging cancer screening.

     

Turbo spin-echo sequences in magnetic resonance imaging of the brain: Physics and applications

Fast SE imaging provides considerable measure time reduction, high signal-to-noise ratios as well as similar contrast behavior compared to conventional SE sequences. Besides TR and TE_eff, echo train length (ETL), interecho time , and-space trajectory determine image contrast and image quality in fast SE sequences. True proton density contrast (CSF hypointense) and not too strong T2 contrast are essential requirements in routine brain MRI. A Turbo SE sequence with very short echo train length (ETL=3), short TE_eff and short interecho time (17 ms), and TR=2000 ms was selected for proton density contrast; a Turbo SE sequence with ETL=7, TE_eff=90 ms, =22 ms, and TR=3250 ms was selected for T₂-weighted images. Using both single-echo Turbo SE sequences yielded 50% measure time reduction compared to the conventional SE technique. Conventional SE and optimized Turbo SE sequences were compared in 150 patients resulting in very similar signal and contrast behavior. Furthermore, reduced flow artifacts in proton density—and especially in T₂-weighted Turbo SE images—and better contrast of high-intensity lesions in proton density-weighted Turbo SE images were found. Slightly reduced edge sharpness—mainly in T₂-weighted Turbo SE images—did not reduce diagnostic reliability. Differences between conventional and Turbo SE images concerning image contrast and quality are explained regarding special features of fast SE technique.Address for correspondence: Institut für Röntgendiagnostik, Klinikum der Universität Regensburg, Franz-Josef-Strauß-Allee 11, 93042 Regensburg, Germany. Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Venn Plaza, New York, NY 10119.     

High-resolution MR imaging appearance of colonic tissue in rabbits using an endoluminal coil

Purpose: This study assessed the value of high-resolution magnetic resonance imaging (MRI) of the distal colon by means of a dedicated endoluminal magnetic resonance receiver coil on a 1.5-T clinical scanner. Materials and Methods: To this end, single-loop, receive-only radio-frequency coils, housed in 18 F sheaths, were built. A 1.5-T clinical imager was used. A 18 French diameter internal MRI receiver coil was inserted into the distal colon in 15 New Zealand rabbits to obtain high-resolution magnetic resonance images by using T1-weighted Flash sequences with and without Fat Saturation (FS), T2-weighted True-Fisp, turbo spin-echo, and T1-weighted Flash FS after contrast media injection. Images were compared to histological sections. Results: An adequate image quality was obtained in all specimens without significant artefacts. Based on histological reports, a five-layer structure of the wall was considered normal. On different MR sequences, only two layers were identified on the images of all rabbits specimens. The nearest layer to the mucosal surface was usually seen as a hyper intense layer and likely corresponds to the mucosa. The highest difference of signal value between internal and external layers was performed on 2D Fat saturation T1 weighted gradient echo. Comparison of mean signal value between the internal and external layers was statistically different in for each sequence used in our protocol (P< 0.05). Conclusion: Dedicated endoluminal RF coil provides good spatial resolution at the region of interest. On this prospective study of in vivo rabbit, evaluation of colon walls allowed to provide detailed information.     

Technical note—Approach to myocardial perfusion with echo planar imaging

Purpose: To evaluate the feasibility of MRI-based myocardial first-pass contrast perfusion imaging with a multi-shot echo planar imaging (EPI) technique. Subjects and methods: A non-sequential (ECG-triggered) gradient echo two-shot EPI acquisition strategy capable of covering the entire heart in contiguous 10-mm sections every two cardiac cycles with an in-plane resolution of 1.56 × 1.56 mm was implemented on a 1.5-T Signa Advantage Scanner equipped with prototype hardware for non-resonant EPI in the transverse plane. The heart of a single volunteer was studied prior to and following the intravenous bolus application of a paramagnetic contrast agent (Gd-DOTA, 0.2 mmol/kg). Results: Twelve contiguous transaxial 10-mm EPI images were obtained every two RR intervals for a total of 40 s. The myocardial contrast perfusion study was technically adequate. Contrast caused a signal loss of 87% in the right and 67% in the left ventricle and 59% in the myocardium. Conclusion: First-pass myocardial perfusion imaging with a gradient echo, two-shot echo planar imaging strategy is feasible.This work has been supported in part by SNF grant 32-2549.88 and KWF grant 2194.1.     

Post-processing water-fat imaging technique for fat suppression in a low-field MR imaging system,evaluation in patients with rheumatoid arthritis

Purpose: To evaluate the feasibility of the phase difference-based post-processing water-fat imaging method for fat suppression at low-field in imaging of arthritic joints.Materials and methods: Thirty joints (wrist, 10; elbow, 10; knee, 10) in 30 patients with rheumatoid arthritis were imaged using a 0.23TMRI unit. Contrast-enhanced Tl-weighted (Tlw) three-dimensional (3D) gradient-echo (GRE) images with and without fat suppression along with short inversion time inversion-recovery (STIR) images were evaluated by two radiologists. Contrast-enhanced Tlw 3D GRE images and corresponding post-processed fat-suppressed images were scored for conspicuity and delineation of enhancing synovial hypertrophy. The uniformity of fat suppression was evaluated between Tlw 3D GRE fat-suppressed images and STIR images, and general image quality was estimated for all of the three techniques by consensus. For a quantitative analysis, the enhancing synovial hypertrophy-to-fat contrast-to-noise (CNR) values for the T1W 3D GRE images with and without fat suppression were measured. For comparison, synovial bright signal-to-fat CNR values for the STIR images were measured.Results: The post-processing water-fat imaging technique for fat suppression was successfully applied in all examinations. Conspicuity and delineation of enhancing tissue were superior in fat-suppressed Tlw 3D GRE images compared to non-fat-suppressed images (P < 0.0001). As expected, the enhancing synovial hypertrophy tissue-to-fat CNRs were significantly higher in fat-suppressed Tlw 3D GRE images compared to non-fat-suppressed images (P < 0.0001). General image quality was assessed to be best in non-fat-suppressed images, and the difference was significant compared to fat-suppressed images (P < 0.05) and STIR images (P < 0.05).Conclusion: The phase difference-based post-processing water-fat imaging technique for fat suppression can be successfully used at low-field, and it provides high-quality fat suppression images in imaging of arthritic joints.     

Interaction between grounding pads used for RF ablation therapy and magnetic resonance imaging

Objectives: To characterize artifacts and imaging problems in the presence of conductive grounding pads for RF ablation therapy as well as potential heating problems due to induction of eddy currents in the pads. Strategies for avoidance of those problems are developed. Materials and methods: Underlying principles of interactions between grounding pads and MR imaging are reported. Influential parameters, e.g., orientation in relation to the magnetic field, shape of the grounding pad, sequence type (spin-echo versus gradient echo) and magnetic field strength (0.2 T, 1.5 T, 3 T) were varied in systematic phantom studies. Heating effects due to induced eddy currents were estimated theoretically and measured by infrared imaging in an adapted set-up. Results: MR imaging artifacts are markedly dependent on the orientation and geometrical shape of the grounding pads. Visible signal extinction artifacts were more pronounced using spin-echo techniques than in gradient echo images and increased for higher field strengths. Suitable incisions in the grounding pad reduced eddy currents markedly and minimized image artifacts. Heating problems due to induced eddy currents by the RF transmitted for MR imaging were excluded by phantom measurements. Conclusions: Suitable positioning of the grounding pads and adaptation of their geometry provide clearly reduced artifacts in MR imaging.     

Low-field magnetic resonance imaging of the pelvis in patients with anal dynamic graciloplasty: initial experience

The aim of this study was to determine whether low-field magnetic resonance (MR) imaging can safely and accurately depict inflammatory changes in patients with anal dynamic graciloplasty, in whom high-field MR imaging is contraindicated and ultrasonography and computed tomography are inadequate. A 0.2-T field-strength MR examination was performed in six patients with anal dynamic graciloplasty malfunction in whom reoperation was contemplated. The following sequences were applied:T ₂-weighted turbo spinecho with fat saturation,T ₁-weighted conventional spin-echo, and contrastenhancedT ₁-weighted conventional spin-echo with fat saturation. Results indicated that none of the patients experienced relevant discomfort, pacemaker malfunction, or electrode dislocation with low-field MR imaging. Inflammatory pelvic changes were visualized in four patients and atrophy of the transposed gracilis muscle in another. Surgery was thus avoided in the four, who underwent conservative treatment for their pelvic inflammation. It was concluded that these prelininary results demonstrate the feasibility of MR imaging with a low field strength in patients with anal dynamic graciloplasty. In such patients, in whom diagnostic imaging had been problematic, the potential for safe and accurate visualization will be a boon to treatment planning.     

Cardiac activation mapping by MRI

To establish cardiac MRI as a tool for noninvasive evaluation of activation patterns, 10 healthy volunteers were examined by cine segmented turboFLASH imaging sequences. Sequence modifications for low signal blood-pool appearance were applied, i.e., bilateral spatial saturation for segmented turboFLASH imaging. Pixelwise calculation of first-harmonic Fourier phase values (displayed as color-encoded maps) reveal either anterior septal or left ventricular free-wall sites as areas of earliest phase spreading towards posterior paraseptal sites in segmented turboFLASH scans. Phase scatter is lower in unsaturated than spatially presaturated segmented turboFLASH studies. Phase standard deviation in areas of endocardial displacement is higher in basal than apical slice positions in these scans. Early results indicate that first-harmonic Fourier phase analysis of cardiac-segmented turboFLASH MRI cine studies may provide a tool for noninvasive studies of cardiac activation sequence.     

Comparison of 2D simultaneous multi-slice and 3D GRASE readout schemes for pseudo-continuous arterial spin labeling of cerebral perfusion at 3 T

Objective

In this perfusion magnetic resonance imaging study, the performances of different pseudo-continuous arterial spin labeling (PCASL) sequences were compared: two-dimensional (2D) single-shot readout with simultaneous multislice (SMS), 2D single-shot echo-planar imaging (EPI) and multishot three-dimensional (3D) gradient and spin echo (GRASE) sequences combined with a background-suppression (BS) module.

Materials and methods

Whole-brain PCASL images were acquired from seven healthy volunteers. The performance of each protocol was evaluated by extracting regional cerebral blood flow (rCBF) measures using an inline morphometric segmentation prototype. Image data postprocessing and subsequent statistical analyses enabled comparisons at the regional and sub-regional levels.

Results

The main findings were as follows: (i) Mean global CBF obtained across methods was were highly correlated, and these correlations were significantly higher among the same readout sequences. (ii) Temporal signal-to-noise ratio and gray-matter-to-white-matter CBF ratio were found to be equivalent for all 2D variants but lower than those of 3D-GRASE.

Discussion

Our study demonstrates that the accelerated SMS readout can provide increased acquisition efficiency and/or a higher temporal resolution than conventional 2D and 3D readout sequences. Among all of the methods, 3D-GRASE showed the lowest variability in CBF measurements and thus highest robustness against noise.

     

Development and evaluation of a numerical simulation approach to predict metal artifacts from passive implants in MRI

Objective

This study presents the development and evaluation of a numerical approach to simulate artifacts of metallic implants in an MR environment that can be applied to improve the testing procedure for MR image artifacts in medical implants according to ASTM F2119.

Methods

The numerical approach is validated by comparing simulations and measurements of two metallic test objects made of titanium and stainless steel at three different field strengths (1.5T, 3T and 7T). The difference in artifact size and shape between the simulated and measured artifacts were evaluated. A trend analysis of the artifact sizes in relation to the field strength was performed.

Results

The numerical simulation approach shows high similarity (between 75% and 84%) of simulated and measured artifact sizes of metallic implants. Simulated and measured artifact sizes in relation to the field strength resulted in a calculation guideline to determine and predict the artifact size at one field strength (e.g., 3T or 7T) based on a measurement that was obtained at another field strength only (e.g. 1.5T).

Conclusion

This work presents a novel tool to improve the MR image artifact testing procedure of passive medical implants. With the help of this tool detailed artifact investigations can be performed, which would otherwise only be possible with substantial measurement effort on different MRI systems and field strengths.

     

Measurements of T1 and T2 relaxation times of colon cancer metastases in rat liver at 7 T

The purpose of this study was to investigate the magnetic resonance imaging (MRI) characteristics of colon cancer metastases in rat liver at 7 T. A dedicated RF microstrip coil of novel design was built in order to increase the signal-to-noise ratio and, in combination with respiratory triggering, to minimize motion artifacts. T₁- and T₂-weighted MR imaging was performed to follow tumor growth. T₁-weighted images provided a good anatomical delineation of the liver structure, while the best contrast between metastases and normal liver tissue was achieved with T₂-weighted images.Measurements of T₁ and T₂ relaxation times were performed with inversion recovery FLASH and Carr–Purcell–Meiboom–Gill and inversion recovery FLASH imaging sequences, respectively, for quantitative MR characterization of metastases. Both the T₁ and T₂ of the metastases were significantly higher than those of normal liver tissue. Further, an increase in the T₁ relaxation time of the metastases was observed with tumor growth. These findings suggest that quantitative in vivo MR characterization provides information on tumor development and possibly response to therapy, though additional studies are needed to elucidate the correlation between the changes in relaxation times and tumor microenvironment.     

Small-animal MRI: signal-to-noise ratio comparison at 7 and 1.5 T with multiple-animal acquisition strategies

Objective: The purpose of this study was to compare the signal-to-noise ratio (SNR) of phantom and rat brain images performed at 1.5 T on a clinical MR system and at 7 T on a small-animal experimental system. Comparison was carried out by taking into account SNR values based on a single sample acquisition at 1.5 and 7 T as well as on simultaneous imaging of multiple samples at 1.5 T. Methods: SNR was experimentally assessed on a phantom and rat brains at 1.5 and 7 T using 25 mm surface coils and compared to theoretical SNR gain estimations. The feasibility of multiple-animal imaging, using the hardware capabilities available on the 1.5 T system, was demonstrated. Finally, rat brain images obtained on a single animal at 7 T and on multiple animals acquired simultaneously at 1.5 T were compared. Results: Experimentally determined SNR at 7 T was far below theoretical estimations. Taking into account chemical shift, susceptibility artifacts and modifications of T1 and T2 relaxation times at higher field, a 7-T system holds limited advantage over a 1.5-T system. Instead, a multiple-animal acquisition methodology was demonstrated on a clinical 1.5-T scanner. This acquisition method significantly increases imaging efficiency and competes with single animal acquisitions at higher field. Conclusion: Multiple-animal imaging using a standard clinical scanner has a great potential as a high-throughput acquisition method for small animals.     

Fast spin echo sequences for BOLD functional MRI

At higher field strengths, spin echo (SE) functional MRI (fMRI) is an attractive alternative to gradient echo (GE) as the increased weighting towards the microvasculature results in intrinsically better localization of the BOLD signal. Images are free of signal voids but the commonly used echo planar imaging (EPI) sampling scheme causes geometric distortions, and T ₂* effects often contribute considerably to the signal changes measured upon brain activation. Multiply refocused SE sequences such as fast spin echo (FSE) are essentially artifact free but their application to fast fMRI is usually hindered due to high energy deposition, and long sampling times. In the work presented here, a combination of parallel imaging and partial Fourier acquisition is used to shorten FSE acquisition times to near those of conventional SE-EPI, permitting sampling of eight slices (matrix 64 × 64) per second. Signal acquisition is preceded by a preparation experiment that aims at increasing the relative contribution of extravascular dynamic averaging to the BOLD signal. Comparisons are made with conventional SE-EPI using a visual stimulation paradigm. While the observed signal changes are approximately 30% lower, most likely due to the absence of T ₂* contamination, activation size and t-scores are comparable for both methods, suggesting that HASTE fMRI is a viable alternative, particularly if distortion free images are required. Our data also indicate that the BOLD post-stimulus undershoot is most probably attributable to persistent elevated oxygen metabolism rather than to delayed vascular compliance.