BLADE acquisition method improves T2-weighted MR images of the female pelvis compared with a standard fast spin-echo sequence

Impact of uterine displacement on T2-weighted image quality in the female pelvic MRI

Despite the importance of T2-weighted image in clinical practice, artifacts can significantly degrade image quality and affect diagnosis. This study quantitatively analyzed uterine displacement and surveyed the relationship between the image quality of fast-spin-echo-T2-weighted image of the female pelvis and quantitative value of uterine displacement. Overall, 147 women (mean age, 46.0 ± 12.8 years; age range, 22-84 years) who had undergone pelvic magnetic resonance imaging examination using a 3 T- magnetic resonance imaging scanner were included. Two radiologists performed a visual assessment of the fast-spin-echo-T2-weighted image in the sagittal plane in terms of ghosts and motion blur, and classified the image quality into the following three groups: poor, moderate, and excellent. Uterine displacement on half-Fourier acquisition single-shot turbo spin-echo-cine images was calculated, and the maximum amplitude of uterine displacement and summation of uterine displacement were calculated from the displacement map images. The Kruskal-Wallis and Steel-Dwass tests were performed to compare the maximum amplitude of uterine displacement and summation of uterine displacement among the three groups. Poor, moderate, and excellent image qualities were observed in 48, 71, and 28 patients, respectively. The quality of fast-spin-echo-T2-weighted images degraded statistically significantly with P < 0.01 as the maximum amplitude of uterine displacement increased. The summation of uterine displacement in the poor and moderate groups had greater statistical significance with P < 0.01 than that in the excellent group.

Enhancing repeatability of follicle counting with deep learning reconstruction high-resolution MRI in PCOS patients

Follicle count, a pivotal metric in the adjunct diagnosis of polycystic ovary syndrome (PCOS), is often underestimated when assessed via transvaginal ultrasonography compared to MRI. Nevertheless, the repeatability of follicle counting using traditional MR images is still compromised by motion artifacts or inadequate spatial resolution. In this prospective study involving 22 PCOS patients, we employed periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) and single-shot fast spin-echo (SSFSE) T2-weighted sequences to suppress motion artifacts in high-resolution ovarian MRI. Additionally, deep learning (DL) reconstruction was utilized to compensate noise in SSFSE imaging. We compared the performance of DL reconstruction SSFSE (SSFSE-DL) images with conventional reconstruction SSFSE (SSFSE-C) and PROPELLER images in follicle detection, employing qualitative indices (blurring artifacts, subjective noise, and conspicuity of follicles) and the repeatability of follicle number per ovary (FNPO) assessment. Despite similar subjective noise between SSFSE-DL and PROPELLER as assessed by one observer, SSFSE-DL images outperformed SSFSE-C and PROPELLER images across all three qualitative indices, resulting in enhanced repeatability in FNPO assessment. These results highlighted the potential of DL reconstruction high-resolution SSFSE imaging as a more dependable method for identifying polycystic ovary, thus facilitating more accurate diagnosis of PCOS in future clinical practices.

Feasibility/clinical utility of half-Fourier single-shot turbo spin echo imaging combined with deep learning reconstruction in gynecologic magnetic resonance imaging

BACKGROUND

When antispasmodics are unavailable, the periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER; called BLADE by Siemens Healthineers) or half Fourier single-shot turbo spin echo (HASTE) is clinically used in gynecologic MRI. However, their imaging qualities are limited compared to Turbo Spin Echo (TSE) with antispasmodics. Even with antispasmodics, TSE can be artifact-affected, necessitating a rapid backup sequence.

PURPOSE

This study aimed to investigate the utility of HASTE with deep learning reconstruction and variable flip angle evolution (iHASTE) compared to conventional sequences with and without antispasmodics.

MATERIALS AND METHODS

This retrospective study included MRI scans without antispasmodics for 79 patients who underwent iHASTE, HASTE, and BLADE and MRI scans with antispasmodics for 79 case-control matched patients who underwent TSE. Three radiologists qualitatively evaluated image quality, robustness to artifacts, tissue contrast, and uterine lesion margins. Tissue contrast was also quantitatively evaluated.

RESULTS

Quantitative evaluations revealed that iHASTE exhibited significantly superior tissue contrast to HASTE and BLADE. Qualitative evaluations indicated that iHASTE outperformed HASTE in overall quality. Two of three radiologists judged iHASTE to be significantly superior to BLADE, while two of three judged TSE to be significantly superior to iHASTE. iHASTE demonstrated greater robustness to artifacts than both BLADE and TSE. Lesion margins in iHASTE had lower scores than BLADE and TSE.

CONCLUSION

iHASTE is a viable clinical option in patients undergoing gynecologic MRI with anti-spasmodics. iHASTE may also be considered as a useful add-on sequence in patients undergoing MRI with antispasmodics.

[Evaluation of the Latest Motion Correction Techniques in Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) Imaging across Different Vendors]

PURPOSE

To evaluate the robustness of the latest periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technology from each vendor against head movements and to investigate their characteristics for effective clinical use.

METHODS

Using a phantom simulating the T2-weighted image of the human brain, images were acquired with devices from CANON MEDICAL SYSTEMS (Tochigi, Japan; hereinafter "Canon"), GE HealthCare (Chicago, IL, USA; hereinafter "GE"), Philips (Amsterdam, Netherlands), and Siemens Healthineers (Forchheim, Germany; hereinafter "SIEMENS"). The head motion patterns were divided into rotation angle dependency (single rotation and multiple rotations) and rotation frequency dependency and evaluated using structural similarity (SSIM).

RESULTS

For rotation angle dependency, Canon was robust against small rotation angles and fine movements. Despite the rotation angle, GE was robust against movements, with deep learning reconstruction (DLR) improving correction functionality. Philips could be used with compressed sensitivity encoding (CS), and robustness varied with blade width. SIEMENS was robust against large movements. For rotation frequency dependency, results were similar across the 4 vendors.

CONCLUSION

The rotation angle and rotation frequency dependencies of the PROPELLER technology from the 4 vendors were quantitatively evaluated. Understanding the characteristics of PROPELLER allows for the possibility of providing diagnostic-quality images even for patients who move during head MRI exams by appropriately using PROPELLER.

A Feasibility Study on Deep Learning Reconstruction to Improve Image Quality With PROPELLER Acquisition in the Setting of T2-Weighted Gynecologic Pelvic Magnetic Resonance Imaging

OBJECTIVES

Evaluate deep learning (DL) to improve the image quality of the PROPELLER (Periodically Rotated Overlapping Parallel Lines with Enhanced Reconstruction technique) for 3 T magnetic resonance imaging of the female pelvis.

METHODS

Three radiologists prospectively and independently compared non-DL and DL PROPELLER sequences from 20 patients with a history of gynecologic malignancy. Sequences with different noise reduction factors (DL 25%, DL 50%, and DL 75%) were blindly reviewed and scored based on artifacts, noise, relative sharpness, and overall image quality. The generalized estimating equation method was used to assess the effect of methods on the Likert scales. Quantitatively, the contrast-to-noise ratio and signal-to-noise ratio (SNR) of the iliac muscle were calculated, and pairwise comparisons were performed based on a linear mixed model. P values were adjusted using the Dunnett method. Interobserver agreement was assessed using the κ statistic. P value was considered statistically significant at less than 0.05.

RESULTS

Qualitatively, DL 50 and DL 75 were ranked as the best sequences in 86% of cases. Images generated by the DL method were significantly better than non-DL images ( P < 0.0001). Iliacus muscle SNR on DL 50 and DL 75 was significantly better than non-DL images ( P < 0.0001). There was no difference in contrast-to-noise ratio between the DL and non-DL techniques in the iliac muscle. There was a high percent agreement (97.1%) in terms of DL sequences' superior image quality (97.1%) and sharpness (100%) relative to non-DL images.

CONCLUSION

The utilization of DL reconstruction improves the image quality of PROPELLER sequences with improved SNR quantitatively.

Quantitative assessment of iteratively denoised 3D SPACE with inner-volume excitation and simultaneous multi-slice BLADE for optimizing female pelvis magnetic resonance imaging at 1.5 T

RATIONALE AND OBJECTIVES

High-resolution T2-weighted magnetic resonance imaging (MRI) of the pelvis is the main technique used for diagnosing benign and malignant uterine diseases. However, the procedure may be time-consuming and requires training and experience. Therefore, this study was performed to compare the image quality of standard clinical BLADE (stBLADE) with a prototypical accelerated simultaneous multi-slice (SMS) BLADE procedure with either improved temporal resolution (tr) at the same slice thickness (SL) or improved spatial resolution (sr) with the same examination time and a prototypical isotropic 3D SPACE procedure with inner-volume excitation and iterative denoising.

MATERIALS AND METHODS

Patients who underwent clinically indicated MRI of the uterus were included in this prospective study and underwent stBLADE (acquisition time, 2 min 59 s; SL, 4 mm) and SMS BLADE (tr) with the same SL (4 mm) but reduced examination time (1 min 20 s) as well as SMS BLADE (sr) with thinner slices (3 mm) and comparable examination time (3 min 16 s). In addition, 3D SPACE was acquired in a sagittal orientation (5 min 36 s). The short axis of the cervix and the long axis of the corpus uteri were reconstructed in 1-mm and 3-mm SLs, retrospectively. Subjective overall image impression, delineation of anatomy/organs, lesion demarcation, and motion artifacts were assessed using a 5-point Likert scale and compared among the different techniques. The preferred sequence was then selected by three independent assessors.

RESULTS

The analysis was based on 38 women (mean age, 44 ± 15 years). The overall image impression was similar for stBLADE, SMS BLADE (sr), and SMS BLADE (tr) but was significantly lower for 3D SPACE than stBLADE (p = 0.01). SMS BLADE (sr) was considered the preferred sequence because of slightly better performance in terms of overall image impression, organ delineation, and lesion demarcation, but without statistical significance. Both SMS BLADE (tr) and (sr) produced significantly fewer motion artifacts than stBLADE (p < 0.01 and p = 0.01), with no significant difference between SMS BLADE (tr) and (sr), while 3D SPACE had a significantly lower rating than stBLADE (p < 0.01). Image quality was rated as the least diagnostic criterion in all sequences and all cases.

CONCLUSION

SMS BLADE (sr) was the preferred sequence for MRI of the female pelvis, with higher sr than stBLADE. SMS BLADE (tr) may also be used to reduce the acquisition time without compromising image quality. Despite its lower image quality, 3D SPACE can also reduce the examination time and improve the workflow because of the possibility of retrospective multiplanar reconstructions.

Impact of Deep Learning Reconstruction Combined With a Sharpening Filter on Single-Shot Fast Spin-Echo T2-Weighted Magnetic Resonance Imaging of the Uterus

OBJECTIVE

This study aimed to evaluate the effects of deep learning (DL) reconstruction and a postprocessing sharpening filter on the image quality of single-shot fast spin-echo (SSFSE) T2-weighted imaging (T2WI) of the uterus.

MATERIALS AND METHODS

Fifty consecutive patients who underwent pelvic magnetic resonance imaging were included. Parasagittal T2WI with a slice thickness of 4 mm was obtained with the periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) and SSFSE sequences (mean scan time, 204 and 22 seconds, respectively). The following 3 types of SSFSE images were reconstructed, and the signal-to-noise ratio (SNR) and tissue contrast were assessed: conventional reconstruction (SSFSE-C), DL reconstruction (SSFSE-DL), and DL with a sharpening filter (SSFSE-DLF). Three radiologists independently assessed image quality, and area under the visual grading characteristics curve (AUCVGC) analysis was performed to compare the SSFSE and PROPELLER images.

RESULTS

Compared with that of the PROPELLER images, the SNR of the SSFSE-C, SSFSE-DL, and SSFSE-DLF images was significantly lower (P < 0.05), significantly higher (P < 0.05), and equivalent, respectively. The SSFSE-DL images exhibited significantly lower contrast between the junctional zone and myometrium than those obtained with the other sequences (P < 0.05). In qualitative comparisons with the PROPELLER images, all 3 SSFSE sequences, SSFSE-DL, and SSFSE-DLF demonstrated significantly higher scores for artifacts, noise, and sharpness, respectively (P < 0.01). The overall image quality of SSFSE-C (mean AUCVGC, 0.03; P < 0.01) and SSFSE-DL (mean AUCVGC, 0.23; P < 0.01) was rated as significantly inferior, whereas that of SSFSE-DLF (mean AUCVGC, 0.69) was equivalent or significantly higher (P < 0.01).

CONCLUSION

Using a combination of DL and a sharpening filter markedly increases the image quality of SSFSE of the uterus to the level of the PROPELLER sequence.

Evaluation of Iterative Denoising 3-Dimensional T2-Weighted Turbo Spin Echo for the Diagnosis of Deep Infiltrating Endometriosis

OBJECTIVES

The primary end point of this study was to evaluate the image quality and reliability of a highly accelerated 3-dimensional T2 turbo spin echo (3D-T2-TSE) sequence with prototype iterative denoising (ID) reconstruction compared with conventional 2D T2 sequences for the diagnosis of deep infiltrating endometriosis (DIE). The secondary end point was to demonstrate the 3D-T2-TSE sequence image quality improvement using ID reconstruction.

MATERIAL AND METHODS

Patients were prospectively enrolled to our institution for pelvis magnetic resonance imaging because of a suspicion of endometriosis over a 4-month period. Both conventional 2D-T2 (sagittal, axial, coronal T2 oblique to the cervix) and 3D-T2-TSE sequences were performed with a scan time of 7 minutes 43 seconds and 4 minutes 58 seconds, respectively. Reconstructions with prototype ID (3D-T2-denoised) and without prototype ID (3D-T2) were generated inline at the end of the acquisition. Two radiologists independently evaluated the image quality of 3D-T2, 3D-T2-denoised, and 2D-T2 sequences. Diagnosis confidence of DIE was evaluated for both 3D-T2-denoised and 2D-T2 sequences. Intraobserver and interobserver agreements were calculated using Cohen κ coefficient.

RESULTS

Ninety female patients were included. Both readers found that the ID algorithm significantly improved the image quality and decreased the artifacts of 3D-T2-denoised compared with 3D-T2 sequences (P < 0.001). A significant image quality improvement was found by 1 radiologist for 3D-T2-denoised compared with 2D-T2 sequences (P = 0.002), whereas the other reader evidenced no significant difference. The interobserver agreement of 3D-T2-denoised and 2D-T2 sequences was 0.84 (0.73-0.95) and 0.78 (0.65-0.9), respectively, for the diagnosis of DIE. Intraobserver agreement for readers 1 and 2 was 0.86 (0.79-1) and 0.83 (0.76-1), respectively. For all localization of DIE, interobserver and intraobserver agreements were either almost perfect or substantial for both 3D-T2-denoised and 2D-T2 sequences.

CONCLUSIONS

Three-dimensional T2-denoised imaging is a promising tool to replace conventional 2D-T2 sequences, offering a significant scan time reduction without compromising image quality or diagnosis information for the assessment of DIE.

A feasibility study of hyoscine butylbromide (buscopan) to improve image quality of cone beam computed tomography during abdominal/pelvic Stereotactic Ablative Radiotherapy

OBJECTIVES

Cone beam computed tomography (CBCT) is used for image guidance of stereotactic ablative radiotherapy (SABR), but it is susceptible to bowel motion artefacts. This trial evaluated the impact of hyoscine butylbromide (buscopan) on CBCT image quality and its feasibility within a radiotherapy workflow.

METHODS

A single-centre feasibility trial (ISRCTN24362767) was performed in patients treated with SABR for abdominal/pelvic oligorecurrence. Buscopan was administered to separate cohorts by intramuscular (IM) or intravenous (i.v.) injection on alternate fractions, providing within-patient control data. 4-point Likert scales were used to assess overall image quality (ranging from excellent to impossible to use) and bowel motion artefact (ranging from none to severe). Feasibility was determined by patient/radiographer questionnaires and toxicity assessment. Descriptive statistics are presented.

RESULTS

16 patients were treated (8 by IM and 8 by i.v. buscopan). The percentage of images of excellent quality with/without buscopan was 47 vs 29% for IM buscopan and 65 vs 40% for i.v. buscopan. The percentage of images with no bowel motion artefact with/without buscopan was 24.6 vs 8.9% for IM buscopan and 25.8 vs 7% for i.v. buscopan. Four patients (25%) reported dry mouth. 14 patients (93%) would accept buscopan as routine. 11 radiographers (92%) reported no delay in treatments.

CONCLUSIONS

A trend towards improved image quality/reduced bowel motion artefact was observed with IM/i.v. buscopan. Buscopan was well tolerated with limited impact on workflow.

ADVANCES IN KNOWLEDGE

This is the first trial of buscopan within a radiotherapy workflow. It demonstrated a trend to improved image quality and feasibility of use.

Free-breathing BLADE acquisition method improves T2-weighted cardiac MR image quality compared with conventional breath-hold turbo spin-echo cartesian acquisition

BACKGROUND

Cardiac magnetic resonance (MR) has become an essential diagnostic imaging modality in cardiovascular disease. However, the insufficient image quality of traditional breath-hold (BH) T2-weighted (T2W) imaging may compromise its diagnostic accuracy.

PURPOSE

To assess the efficacy of the BLADE technique to reduce motion artifacts and improve the image quality.

MATERIAL AND METHODS

Free-breathing TSE-T2W imaging sequence with cartesian and BLADE k-space trajectory were acquired in 20 patients. Thirty patients underwent conventional BH turbo spin-echo (TSE) T2W imaging and free-breathing BLADE T2W (FB BLADE-T2W) imaging. Twenty-one patients who had a signal loss of myocardium in BH short-axis T2W turbo inversion recovery (TSE-T2W-TIR) were scanned using free-breathing BLADE T2W turbo inversion recovery (BLADE TSE-T2W-TIR). The overall image quality, blood nulling, and visualization of the heart were scored on a 5-point Likert scale. The signal loss of myocardium, incomplete fat suppression near the myocardium, and the streaking or ghosting artifacts were noted in T2W-TIR sequences additionally.

RESULTS

The overall imaging quality, blood nulling, and the visualization of heart structure of FB BLADE-T2W imaging sequence were significantly better than those of FB T2W imaging with Cartesian k-space trajectory and BH TSE-T2W imaging sequence (P<0.01). The FB BLADE TSE-T2W-TIR reduces the myocardium signal dropout (P<0.05), incomplete fat suppression near myocardium (P<0.05), and the streaking and ghosting artifacts (P<0.05) in comparison with the BH TSE-T2W-TIR.

CONCLUSIONS

FB BLADE T2W imaging provides improved myocardial visibility, less motion sensitivity, and better image quality. It may be applied in patients who have poor breath-holding capability.

Effect of uterine position and intrapelvic motions on the image quality of 3D T2-weighted MRI of the uterus: Can short prescans predict the non-diagnostic image quality?

PURPOSE

To evaluate prescan findings of uterine position and intrapelvic motions that predict the non-diagnostic image quality of three-dimensional T2-weighted MRI (3D-T2WI) of the uterus.

METHODS

This retrospective study included 287 women who underwent pelvic MRI including 3D-T2WI and short prescans consisting of 2D-T2WI and cine imaging. One radiologist classified 3D-T2WI of the uterus as being of diagnostic or non-diagnostic image quality and evaluated the prescans regarding uterine position and intrapelvic motions. Multivariate logistic regression analysis was performed to identify predictors of non-diagnostic 3D-T2WI. The predictive ability of the prescans was verified by two independent MRI technologists.

RESULTS

Non-diagnostic 3D T2WI was found in 42 patients (14.6 %) and was significantly associated with severe motions of urinary flow in the bladder (p < 0.001), small bowel (p = 0.039), and respiration (p < 0.001). In the multivariate analysis of uterine position and intrapelvic motions, risk factors for the non-diagnostic image quality were prominent urinary flow when the uterus contacted the bladder (p < 0.001, adjusted odds ratio = 35.1) and severe respiratory and small bowel motions when the uterus was surrounded by the bowel (p < 0.001, adjusted odds ratio = 68.4). No risk factors were found for the uterus contacting the vertebrae. With these predictors, the prescans demonstrated a sensitivity of 82.9 and 68.3 %, and specificity of 88.2 and 93.9 % for the non-diagnostic 3D-T2WI by the two technologists, respectively.

CONCLUSION

Intrapelvic motions have a different effect on the image quality of 3D-T2WI depending on the uterine position, and short prescans may be useful in predicting time-consuming non-diagnostic 3D-T2WI of the uterus.

MRI of Bladder Cancer: Local and Nodal Staging

Accurate staging of bladder cancer (BC) is critical, with local tumor staging directly influencing management decisions and affecting prognosis. However, clinical staging based on clinical examination, including cystoscopy and transurethral resection of bladder tumor (TURBT), often understages patients compared to final pathology at radical cystectomy and lymph node (LN) dissection, mainly due to underestimation of the depth of local invasion and the presence of LN metastasis. MRI has now become established as the modality of choice for the local staging of BC and can be additionally utilized for the assessment of regional LN involvement and tumor spread to the pelvic bones and upper urinary tract (UUT). The recent development of the Vesical Imaging-Reporting and Data System (VI-RADS) recommendations has led to further improvements in bladder MRI, enabling standardization of image acquisition and reporting. Multiparametric magnetic resonance imaging (mpMRI) incorporating morphological and functional imaging has been proven to further improve the accuracy of primary and recurrent tumor detection and local staging, and has shown promise in predicting tumor aggressiveness and monitoring response to therapy. These sequences can also be utilized to perform radiomics, which has shown encouraging initial results in predicting BC grade and local stage. In this article, the current state of evidence supporting MRI in local, regional, and distant staging in patients with BC is reviewed. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 2 J. Magn. Reson. Imaging 2020;52:649-667.

Periodically rotated overlapping parallel lines with enhanced reconstruction acquisition to improve motion-induced artifacts in bladder cancer imaging: Initial findings

Motion-induced artifacts have been a major drawback in bladder cancer imaging. This study is to evaluate the clinical utility of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) acquisition in improving motion-induced artifacts in T2-weighted (T2W) magnetic resonance imaging (MRI) of bladder cancer at 3T.Sixteen patient MRI exams were included. Using a Likert scale, 2 radiologists independently scored T2W data without and with PROPELLER in terms of artifact severity and tumor visualization. Statistical analysis was done to assess the image quality improvement by PROPELLER and inter-observer variability.Without PROPELLER, the median scores of artifact severity and tumor visualization were 1.5 and 1.5 for reviewer 1, and 2.0 and 2.0 for reviewer 2. With PROPELLER, the scores increased to 3 and 3.5 for reviewer 1, and 3.5 and 3.5 for reviewer 2. Despite the inter-observer variability (κ scores < 0.2), both reviewers found significant improvement in artifacts and visualization (all P < .001).PROPELLER acquisition significantly improved the image quality of T2W-MRI. These initial findings indicate that this technique should be utilized in clinical MRI of the bladder.

Protocol optimization of sacroiliac joint MR Imaging at 3 Tesla: Impact of coil design and motion resistant sequences on image quality

PURPOSE

To evaluate the impact of coil design and motion-resistant sequences on the quality of sacroiliac magnetic resonance imaging (MRI) examination in patients with spondyloarthropathy.

PATIENTS AND METHODS

One hundred and twenty-one patients with suspected sacroiliitis and referred for MRI of the sacroiliac joints were retrospectively evaluated with MRI at 3-Tesla. There were 78 women and 43 men with a mean age of 36.7±11.5 (SD) years (range: 15.8-78.4 years). Conventional and motion-resistant fat-saturated fast-spin echo T2-weighted sequences were performed with two different coils. Image quality was subjectively evaluated by two independent readers (R1 and R2) using a four-point scale. Confidence in the identification of bone marrow edema pattern (BMEP) was also evaluated subjectively using a three-point scale.

RESULTS

Phased array body coil yielded improved image quality compared to surface coil (14.1 to 30.4% for R1 and 14.6 to 25.7% for R2; P<0.0001). The impact of the sequence type on quality was also statistically significant (P=0.0046). BMEP was identified in 40 patients and best inter-reader agreement was obtained using the combination of phased-array body coil with motion-resistant T2-weighted sequence (kappa 0.990). The smallest number of indeterminate BMEP zones was seen on MRI set acquired with the phased-array body coil and motion-resistant T2-weighted sequence.

CONCLUSION

Phased array body coil and motion-resistant T2-weighted sequences perform better than surface coil and conventional T2-weighted sequences for the evaluation of sacroiliac joints, increasing confidence in the identification of BMEP.

MRI of the lung using the PROPELLER technique: Artifact reduction, better image quality and improved nodule detection

PURPOSE

To evaluate the benefit of the PROPELLER technique (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction, MultiVane, MV) for MR imaging of the lung.

MATERIALS AND METHODS

30 Participants of a lung cancer screening program were recruited for the comparison of T2-MV and T2-Fast Spin Echo (FSE) sequences at 1.5T. Two readers evaluated artifacts, image quality, and pulmonary lesions. Artifacts and image quality were rated using a four-point scale. Lesion detection was correlated to low-dose computed tomography (CT). Wilcoxon rank-test for ratings of artifacts and image quality, sensitivity and specificity values for lesion detection, and Cohen's kappa for inter-rater agreement were used.

RESULTS

The MV sequence showed less pulsation and motion artifacts, and higher image quality (p=0.001 for R1, p=0.002 for R2) than FSE (p<0.001 for both readers, R1 and R2). Inter-rater agreement was excellent for lesion detection (0.84-0.95) and good to excellent for artifacts and image quality (0.66-0.84). 17 patients had lesions <8mm, and 7 had lesions >8mm as seen on CT. For R1 and R2, the MV sequence allowed for higher detection rates of pulmonary lesions <8mm with a sensitivity of 56% (R1) and 59% (R2); the FSE sequence achieved 50% (R1) and 53% (R2). Specificity was also higher for MV with 94% (R1) and 83% (R2) compared to 78% (R1) and 76% (R2). Lesions >8mm were detected with a sensitivity of 100% by both readers on both MV and FSE images. For both readers, specificity for larger lesions was higher on MV images with 100% compared to 96%.

CONCLUSION

The superior image quality and the very robust artifact reduction make MV a promising technique for MRI of the lung compared to FSE, especially since it is not requiring breathholds. Moreover, MV allows for improved lesion detection.

Advances in T1-weighted and T2-weighted imaging in the abdomen and pelvis

Utilization of abdominopelvic MR imaging continues to increase in volume and gain widespread clinical acceptance. Many factors such as diaphragmatic respiratory motion, bulk patient motion, and the need for large volumetric coverage while maintaining clinically feasible scan times have proven challenging for body applications of MRI. However, many advances in MR acquisition, including non-Cartesian T1-weighted and T2-weighted acquisitions, advanced Dixon sequences, and 3-dimensional volumetric T2-weighted imaging have helped to mitigate some of the issues which have hampered abdominopelvic MR. This article will summarize these advances in T1-weighted and T2-weighted imaging, with an emphasis on clinical applications and implementation.

Advanced MRI in malignant neoplasms of the uterus

Conventional magnetic resonance imaging (MRI) such as T1-weighted and T2-weighted images of the female pelvis provide morphological information with excellent tissue contrast, which reflects the pathology of malignant diseases of the uterus. Owing to the recent improvement in hardware and software, in combination with extensive research in imaging techniques, not only MRI at higher magnetic field was facilitated, but also insight into tumor pathophysiology was provided. These methods include diffusion-weighted imaging (DWI), dynamic contrast-enhanced MRI (DCE-MRI) with pharmacokinetic analysis, and MR spectroscopy (MRS). The application of these techniques is expanding from the brain to the body because information on the tissue microenvironment and cytoarchitecture is helpful for lesion characterization, evaluation of treatment response after chemotherapy or radiation, differentiating posttherapeutic changes from residual active tumor, and for detecting recurrent cancer. These techniques may provide clues to optimize the treatment of patients with malignant diseases of the uterus. In the first half of this article we provide an overview of the technical aspects of MRI of the female pelvis, especially focusing on the state-of-the-art techniques such as 3 T MRI, DCE-MRI, DWI, etc. For the latter half we review the clinical aspects of these newly developed techniques, focusing on how these techniques are applicable, what has been revealed with respect to clinical impact, and the remaining problems.

Chest MR imaging in the follow-up of pulmonary alterations in paediatric patients with middle lobe syndrome: comparison with chest X-ray

PURPOSE

The authors evaluated the role of magnetic resonance (MR) imaging of the chest in comparison with chest X-ray in the follow-up of pulmonary abnormalities detected by computed tomography (CT) in paediatric patients with middle lobe syndrome.

MATERIALS AND METHODS

Seventeen patients with middle lobe syndrome (mean age 6.2 years) underwent chest CT at the time of diagnosis (100 kV, CARE dose with quality reference of 70 mAs; collimation 24×1.2 mm; rotation time 0.33 s; scan time 5 s); at follow-up after a mean of 15.3 months, all patients were evaluated with chest MR imaging with a respiratory-triggered T2-weighted BLADE sequence (TR 2,000; TE 27 ms; FOV 400 mm; flip angle 150°; slice thickness 5 mm) and chest X-ray. Images from each modality were assessed for the presence of pulmonary consolidations, bronchiectases, bronchial wall thickening and mucous plugging. Hilar and mediastinal lymphadenopathies were assessed on CT and MR images.

RESULTS

Baseline CT detected consolidations in 100% of patients, bronchiectases in 35%, bronchial wall thickening in 53% and mucous plugging in 35%. MR imaging and chest X-ray identified consolidations in 65% and 35%, bronchiectases in 35% and 29%, bronchial wall thickening in 59% and 6% and mucous plugging in 25% and 0%, respectively. Lymphadenopathy was seen in 64% of patients at CT and in 47% at MR imaging.

CONCLUSIONS

Patients with middle lobe syndrome show a wide range of parenchymal and bronchial abnormalities at diagnosis. Compared with MR imaging, chest X-ray seems to underestimate these changes. Chest MR imaging might represent a feasible and radiation-free option for an overall assessment of the lung in the follow-up of patients with middle lobe syndrome.

Should less motion sensitive T2-weighted BLADE TSE replace Cartesian TSE for female pelvic MRI?

Objectives

To prospectively compare the diagnostic performance of a non-Cartesian k-space sampling T2-weighted TSE BLADE sequence with a conventional T2-weighted TSE sequence in female pelvic organs.

Methods

Forty-seven patients with sonographically indeterminate adnexal masses or uterine lesions underwent sagittal BLADE and conventional TSE at 1.5 T after glucagon administration. Two radiologists independently determined their preferred sequence by rating: overall image diagnostic quality, conspicuity of the zonal anatomy and delineation of pathologies of the uterus and cervix, presence of artefacts, and of fluid in the pouch of Douglas (Wilcoxon signed rank test). Signal-to noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were measured for the myometrium versus the rectus abdominis muscle (Student’s t-test).

Results

BLADE significantly (p < 0.0001) reduced motion and ghosting artefacts and showed improved conspicuity (p = 0.3/0.24), but overall image quality did not differ significantly (inter-observer agreement BLADE κ = 0.89; TSE κ = 0.84). In the majority of cases (53.2 % vs 59.6 %, respectively, κ = 0.82) radiologists preferred conventional TSE due to better image contrast (p < 0.0001) and visibility of free pelvic fluid (p ≤ 0.0001). SNR (TSE 57.5 ± 37.7; BLADE 16.6 ± 12.2) and CNR (TSE 40.4 ± 33.5; BLADE 7.2 ± 8.8) were significantly higher on conventional TSE (p < 0.0001).

Conclusions

Although BLADE reduces motion artefacts and provides a clearer delineation of uterine zonal anatomy compared with conventional TSE, this comes at the expense of overall contrast.

Main Messages

• Use of BLADE may reduce T2 contrast and thus visibility of free pelvic fluid or cystic structures

• Non-Cartesian sampling of k-space such as BLADE is beneficial due to less motion sensitivity

• BLADE provides clearer delineation and conspicuity of uterine zonal anatomy on pelvic MRIs