T2-weighted T2-weighted Turbo Spin-echo Research Articles

Technical note: Enhanced radiosurgical planning for cavernous sinus tumors using T1 SPACE sequences with Motion-Sensitized Driven Equilibrium (MSDE).

Radiosurgery can serve as a primary, adjuvant, or salvage treatment modality for cavernous sinus tumors (CST), providing high tumor control. However, particularly with cavernous sinus expansion, there may be insufficient distance from the optic apparatus to perform radiosurgery safely. The internal carotid artery adjacent to the distal dural ring (ICAddr), when enhancing similarly to the CST, can be difficult to delineate, and can lead to over-contouring of target volume near the optic nerve and therefore increasing the risk of radiation-induced optic toxicity. To evaluate the efficacy and safety of 3D T1-weighted Turbo Spin-Echo (TSE) MR sequence with the Motion-Sensitized Driven Equilibrium (MSDE) technique in accurately delineating the internal carotid artery adjacent to the distal dural ring (ICAddr) to minimize the risk of radiation-induced optic toxicity during radiosurgery for cavernous sinus tumors (CST). Nine patients were treated for CST with Gamma Knife radiosurgery from 2021 to 2023, utilizing a 3D T1-weighted Turbo Spin-Echo (TSE) MR sequence with the Motion-Sensitized Driven Equilibrium (MSDE) technique. Improved delineation of the ICAddr from the lesion facilitated precise dosimetry near the optic nerve. At a median follow-up of 15 months, all patients demonstrated stable disease with no reported tumor progression. The use of the T1-weighted TSE MR sequence with MSDE significantly improved the delineation of the ICAddr from the cavernous sinus tumors. Only one patient experienced a transient episode of diplopia. No additional visual deficits were reported. The use of T1 SPACE sequence has enhanced the radiosurgical planning process for CST, allowing for more precise contouring of the lesion near the ICAddr and optic nerve and reducing radiation dose to the ipsilateral optic nerve. Integration of these techniques into standard practice may offer significant benefits for the radiosurgical management of CST.

(005) MRI TECHNIQUES FOR IMAGING BIOMARKERS OF RADIATION-INDUCED DAMAGE TO FEMALE ERECTILE TISSUES AND OTHER GENITOPELVIC ORGANS

Abstract Introduction Difficulties with arousal and orgasm are common in female patients after pelvic radiation. Yet, current classifications of toxicity and normal tissues in radiation oncology account poorly for the anatomy and critical function of female erectile tissues (arousal and orgasm) with respect to patients’ capacities to continue to engage in pleasurable sexual behaviors after cancer treatment. MRI imaging biomarkers of dose-volume dependent radiation damage can provide objective measures of the impact of interventions, help predict sexual dysfunction, and allow for re-optimization of therapy for early mitigation of radiation damage to female erectile tissues. Objective The aim of this project is to develop and optimize MRI imaging techniques for female erectile tissues and other genitopelvic organs. Optimization of this MRI protocol will allow us to establish quantitative and qualitative indices of radiation damage to specific sexual organs, providing mechanistic insights into how to measure radiation damage of current and future therapies. Methods This prospective study includes two female-identifying volunteers with healthy female pelvic anatomy who underwent MRI scans using a 3.0T MRI (Prisma, Siemens Healthcare) scanner. The protocol (Table 1) included 2D T2-weighted turbo spin-echo (TSE) sequences in the axial (spatial resolution 0.5x0.5x2mm), coronal (spatial resolution 0.5x0.5x3mm), and sagittal planes (spatial resolution 0.3x0.3x2mm), T2-weighted with fat saturation in the axial plane (spatial resolution: 0.8x0.8x4mm) diffusion-weighted tensor imaging (DTI, axial plane with 30 diffusion directions and b-values 0s/mm2 and 400s/mm2, TR/TE: 3000/57ms, spatial resolution 1.3x1.3x5mm). Protocol optimization in healthy volunteers consisted of imaging without gadolinium contrast, while future imaging in patients will also include dynamic contrast-enhanced MRI (3D T1-weighted radial acquisition in the axial plane, with 4.7s temporal resolution, 20 slices, spatial resolution 0.8x0.8x2mm) and T1 mapping (axial plane variable flip angle, B1-corrected acquisition with 5 flip angles: 5, 10, 15, 20, 30 degrees, TR/TE: 5.9/2.4ms, with 0.8x0.8x2mm spatial resolution). The sexual regions of interest (ROIs) included the female external genitalia, vagina, bulboclitoris (clitoris and vestibular bulbs), pelvic neurovasculature, and pelvic floor muscles which were visualized and contoured per standard protocols. Results The axial T2-weighted TSE sequences in 2mm slices provided clear visualization of the female erectile tissues for contouring the bulboclitoris, vaginal canal, and external genitalia (Figure 1). The T2-weighted sequences with fat saturation allows us to conduct MR neurography to evaluate the three-dimensional visibility of the nerves (plexus, pudendal and cavernous), enabling us to localize and characterize nerve abnormalities with dose-dependent radiation damage (Figure 2). Perfusion time intensity curves created with the T1 DCE scans can assess changes in vasculature, and the initial areas under the time to signal intensity curve (IAUC) will act as biomarkers for erectile tissue perfusion and permeability. Additional biomarkers include ROI intensity and volume/thickness for both erectile tissues and the vagina wall, as well as fractional anisotropy for the vagina alone. Lastly, we explore the clinical applications of DTI with fiber tractography to evaluate pelvic floor musculature. Conclusions These MRI techniques will be the first to validate normal tissue toxicity imaging biomarkers for radiation damage, allowing us to objectively measure dose-dependent inflammatory, fibrotic and vasculogenic effects of radiotherapy. Disclosure No.

Added Value of [18F]PSMA-1007 PET/CT and PET/MRI in Patients With Biochemically Recurrent Prostate Cancer: Impact on Detection Rates and Clinical Management.

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) can change management in a large fraction of patients with biochemically recurrent prostate cancer (BCR). To investigate the added value of PET to MRI and CT for this patient group, and to explore whether the choice of the PET paired modality (PET/MRI vs. PET/CT) impacts detection rates and clinical management. Retrospective. 41 patients with BCR (median age [range]: 68 [55-78]). 3T, including T1-weighted gradient echo (GRE), T2-weighted turbo spin echo (TSE) and dynamic contrast-enhanced GRE sequences, diffusion-weighted echo-planar imaging, and a T1-weighted TSE spine sequence. In addition to MRI, [18F]PSMA-1007 PET and low-dose CT were acquired on the same day. Images were reported using a five-point Likert scale by two teams each consisting of a radiologist and a nuclear medicine physician. The radiologist performed a reading using CT and MRI data and a joint reading between radiologist and nuclear medicine physician was performed using MRI, CT, and PET from either PET/MRI or PET/CT. Findings were presented to an oncologist to create intended treatment plans. Intrareader and interreader agreement analysis was performed. McNemar test, Cohen's κ, and intraclass correlation coefficients. A P-value <0.05 was considered significant. 7 patients had positive findings on MRI and CT, 22 patients on joint reading with PET/CT, and 18 patients joint reading with PET/MRI. For overall positivity, interreader agreement was poor for MR and CT (κ = 0.36) and almost perfect with addition of PET (PET/CT κ = 0.85, PET/MRI κ = 0.85). The addition of PET from PET/CT and PET/MRI changed intended treatment in 20 and 18 patients, respectively. Between joint readings, intended treatment was different for eight patients. The addition of [18F]PSMA-1007 PET/MRI or PET/CT to MRI and CT may increase detection rates, could reduce interreader variability, and may change intended treatment in half of patients with BCR. 3 TECHNICAL EFFICACY: Stage 3.

Deep Learning Super-Resolution Reconstruction for Fast and Motion-Robust T2-weighted Prostate MRI.

Background Deep learning (DL) reconstructions can enhance image quality while decreasing MRI acquisition time. However, DL reconstruction methods combined with compressed sensing for prostate MRI have not been well studied. Purpose To use an industry-developed DL algorithm to reconstruct low-resolution T2-weighted turbo spin-echo (TSE) prostate MRI scans and compare these with standard sequences. Materials and Methods In this prospective study, participants with suspected prostate cancer underwent prostate MRI with a Cartesian standard-resolution T2-weighted TSE sequence (T2C) and non-Cartesian standard-resolution T2-weighted TSE sequence (T2NC) between August and November 2022. Additionally, a low-resolution Cartesian DL-reconstructed T2-weighted TSE sequence (T2DL) with compressed sensing DL denoising and resolution upscaling reconstruction was acquired. Image sharpness was assessed qualitatively by two readers using a five-point Likert scale (from 1 = nondiagnostic to 5 = excellent) and quantitatively by calculating edge rise distance. The Friedman test and one-way analysis of variance with post hoc Bonferroni and Tukey tests, respectively, were used for group comparisons. Prostate Imaging Reporting and Data System (PI-RADS) score agreement between sequences was compared by using Cohen κ. Results This study included 109 male participants (mean age, 68 years ± 8 [SD]). Acquisition time of T2DL was 36% and 29% lower compared with that of T2C and T2NC (mean duration, 164 seconds ± 20 vs 257 seconds ± 32 and 230 seconds ± 28; P < .001 for both). T2DL showed improved image sharpness compared with standard sequences using both qualitative (median score, 5 [IQR, 4-5] vs 4 [IQR, 3-4] for T2C and 4 [IQR, 3-4] for T2NC; P < .001 for both) and quantitative (mean edge rise distance, 0.75 mm ± 0.39 vs 1.15 mm ± 0.68 for T2C and 0.98 mm ± 0.65 for T2NC; P < .001 and P = .01) methods. PI-RADS score agreement between T2NC and T2DL was excellent (κ range, 0.92-0.94 [95% CI: 0.87, 0.98]). Conclusion DL reconstruction of low-resolution T2-weighted TSE sequences enabled accelerated acquisition times and improved image quality compared with standard acquisitions while showing excellent agreement with conventional sequences for PI-RADS ratings. Clinical trial registration no. NCT05820113 © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Turkbey in this issue.

Comparison of a deep learning-accelerated T2-weighted turbo spin echo sequence and its conventional counterpart for female pelvic MRI: reduced acquisition times and improved image quality

ObjectivesTo investigate the feasibility of a deep learning-accelerated T2-weighted turbo spin echo (TSE) sequence (T2DL) applied to female pelvic MRI, using standard T2-weighted TSE (T2S) as reference.MethodsIn total, 24 volunteers and 48 consecutive patients with benign uterine diseases were enrolled. Patients in the menstrual phase were excluded. T2S and T2DL sequences in three planes were performed for each participant. Quantitative image evaluation was conducted by calculating the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Image geometric distortion was evaluated by measuring the diameters in all three directions of the uterus and lesions. Qualitative image evaluation including overall image quality, artifacts, boundary sharpness of the uterine zonal layers, and lesion conspicuity were assessed by three radiologists using a 5-point Likert scale, with 5 indicating the best quality. Comparative analyses were conducted for the two sequences.ResultsT2DL resulted in a 62.7% timing reduction (1:54 min for T2DL and 5:06 min for T2S in axial, sagittal, and coronal imaging, respectively). Compared to T2S, T2DL had significantly higher SNR (p ≤ 0.001) and CNR (p ≤ 0.007), and without geometric distortion (p = 0.925–0.981). Inter-observer agreement regarding qualitative evaluation was excellent (Kendall’s W > 0.75). T2DL provided superior image quality (all p < 0.001), boundary sharpness of the uterine zonal layers (all p < 0.001), lesion conspicuity (p = 0.002, p < 0.001, and p = 0.021), and fewer artifacts (all p < 0.001) in sagittal, axial, and coronal imaging.ConclusionsCompared with standard TSE, deep learning-accelerated T2-weighted TSE is feasible to reduce acquisition time of female pelvic MRI with significant improvement of image quality.

Accelerated T2-Weighted TSE Imaging of the Prostate Using Deep Learning Image Reconstruction: A Prospective Comparison with Standard T2-Weighted TSE Imaging.

Simple SummaryMultiparametric magnetic resonance imaging (mpMRI) has become an important diagnostic tool in the assessment of clinically significant prostate cancer. The disadvantages of this technique are primarily related to its long examination time and limited availability. This prospective study presents a novel accelerated deep learning image reconstructed T2-weighted turbo spin echo (TSE) sequence providing an acquisition time reduction of more than 60%. The study results show that the acquisition of three imaging planes of the prostate is feasible within 3:50 min, using deep learning image reconstruction, compared to 10:21 min in standard imaging. Additionally, image quality parameters were evaluated to be superior in deep learning imaging.Multiparametric MRI (mpMRI) of the prostate has become the standard of care in prostate cancer evaluation. Recently, deep learning image reconstruction (DLR) methods have been introduced with promising results regarding scan acceleration. Therefore, the aim of this study was to investigate the impact of deep learning image reconstruction (DLR) in a shortened acquisition process of T2-weighted TSE imaging, regarding the image quality and diagnostic confidence, as well as PI-RADS and T2 scoring, as compared to standard T2 TSE imaging. Sixty patients undergoing 3T mpMRI for the evaluation of prostate cancer were prospectively enrolled in this institutional review board-approved study between October 2020 and March 2021. After the acquisition of standard T2 TSE imaging (T2S), the novel T2 TSE sequence with DLR (T2DLR) was applied in three planes. Overall, the acquisition time for T2S resulted in 10:21 min versus 3:50 min for T2DLR. The image evaluation was performed by two radiologists independently using a Likert scale ranging from 1–4 (4 best) applying the following criteria: noise levels, artifacts, overall image quality, diagnostic confidence, and lesion conspicuity. Additionally, T2 and PI-RADS scoring were performed. The mean patient age was 69 ± 9 years (range, 49–85 years). The noise levels and the extent of the artifacts were evaluated to be significantly improved in T2DLR versus T2S by both readers (p < 0.05). Overall image quality was also evaluated to be superior in T2DLR versus T2S in all three acquisition planes (p = 0.005–<0.001). Both readers evaluated the item lesion conspicuity to be superior in T2DLR with a median of 4 versus a median of 3 in T2S (p = 0.001 and <0.001, respectively). T2-weighted TSE imaging of the prostate in three planes with an acquisition time reduction of more than 60% including DLR is feasible with a significant improvement of image quality.

Evaluation of perianal fistulas with magnetic resonance imaging: Significance of T2-weighted BLADE sequence in disease diagnosis

Introduction: Anatomical details of perianal fistulas can be revealed more clearly by T2-weighted (T2-W) periodically rotated overlapping parallel lines with enhanced reconstruction (BLADE)sequence during magnetic resonance imaging (MRI). This study aimed to compare the efficacy of the T2-W BLADE sequence and the T2-W turbo spin-echo (TSE) sequence in diagnosing perianal fistula, as well as to compare the findings with the results obtained using the dynamic contrast-enhanced (DCE) T1-weighted (T1-W) sequence during routine pelvic MRI examination.&#x0D; Methods: Ninety patients (M/F: 67/23) who had undergone pelvic MRI examination (1.5Tesla) for the prediagnosis of perianal fistula were included in this prospective study.&#x0D; In addition to our routine pelvic MRI protocol, T2-W BLADE sequence imaging and T2-W TSE sequence imaging in the axial, sagittal, and coronal planes were performed. Using a three-stage scoring system, two radiologists independently compared the T2-W BLADE and T2-W TSE sequences with each other and then with the DCE T1-W sequence in terms of perianal fistula imaging. Statistical analysis was performed using a sample t-test and the Cronbach’s α test.&#x0D; Results: Compared with the T2-W TSE sequence, the T2-W BLADE sequence was associated with fewer ghosting artifacts, higher overall image quality, and with clearer visualization of the anatomical details of the perianal fistula (p &lt; 0.05). Images with high anatomic details and contrast resolution were obtained using the T2-W BLADE sequence similar to those obtained using the DCE T1-W sequence (p &lt; 0.05).&#x0D; Conclusion: On the basis of the reduced imaging time and on the higher image resolution, T2-W images can be obtained with the BLADE technique for the diagnosis of perianal fistula.

Morphological and Functional Outcomes &gt;13 Years After Achilles Tendon Rupture Treated Operatively and Non-operatively

Objectives:In patients >13yrs after treatment for acute Achilles tendon rupture (AATR), 1) investigate side-to-side differences in MRI-defined morphological changes in the Achilles tendon and surrounding calf musculature, 2) investigate side-to-side differences in single-limb functional tasks, and 3) compare patients who received operative vs non-operative treatment.Methods:28 patients (11 operative, 17 non-operative) from a previous randomized trial returned 15±1 years post-AATR for testing (age: 57±7 years; BMI: 30±5 kg/m2). Patients underwent bilateral 3T MRI (MAGNETOM Prisma, Siemens) including sagittal and axial T1 and T2-weighted turbo spin echo (TSE), axial T1-weighted inversion recovery, and sagittal T2-weighted 3D isotropic TSE sequences. The maximum anteroposterior Achilles tendon diameter (MAD) and cross-sectional area (CSA), distance from the MAD to the superior margin of the calcaneus, tendon length, gastrocnemius and soleus CSA, and calf circumference were measured using distance and area software tools (Figure 1; AGFA Healthcare). Functional measures included single-legged heel-rise repetitions and maximum vertical jump height. All outcomes were compared between limbs and between groups.Results:Overall, there were significant side-to-side differences in most MRI and functional measures, with the injured limb Achilles tendon typically wider and thicker (MAD often twice as large), calf musculature CSA smaller, number of heel raises lower, and vertical jump height lower (Table 1). The only differences between treatment groups was in MAD and the distance from the MAD to the superior margin of the calcaneus, with a greater side-to-side difference for patients treated operatively (Table 1).Conclusion:Substantial side-to-side differences in tendon diameter, thickness, muscle bulk and functional performance persist beyond a decade after treatment for AATR. There were no differences favoring operative treatment over non-operative treatment.

Analysis of ovarian volume of Korean children and adolescents at magnetic resonance imaging.

Knowledge of ovarian volume is important for diagnostic evaluations; however, normal ovarian volume studies on children and adolescents are lacking. This study aimed to analyze age-specific ovarian volume and identify the diverse factors that contribute to ovarian diagnoses. We retrospectively enrolled 180 patients (0-18years of age) with normal ovaries who underwent magnetic resonance imaging (MRI) between 2010 and 2018. MRI sequences included coronal and axial T2-weighted turbo spin echo (TSE) images and coronal T1-weighted TSE images. Ovarian volume was calculated by the standard ellipsoid formula. Age-specific ovarian volume, height, weight, height-adjusted total ovarian volume and body mass index were obtained. Linear regression analysis was used to predict ovarian volume. Six age groups (infant; early and late child, and early, middle and late adolescent) were described. The early adolescent group (10-12years) had the highest rate of increase. In the middle adolescent period (13-15years), the curve of ovarian volume appeared flat. Our findings provide age-specific references for ovarian volume.

MRI evaluation of pulmonary lesions and lung tissue changes induced by tuberculosis

ObjectiveTo evaluate the utility of magnetic resonance imaging (MRI) with an advanced motion correction technique in characterizing lung tissue changes and lesions induced by pulmonary tuberculosis (TB). MethodsSixty-three subjects with computed tomography (CT) features of pulmonary TB underwent lung MRI. All subjects with pulmonary TB were confirmed by acid-fast bacillus (AFB) testing or the detection of Mycobacterium tuberculosis. T2-weighted turbo spin echo (TSE) sequence MRI with the MultiVane motion correction technique was used to image the lungs. Routine lung CT images were obtained as reference. MRI and CT images were reviewed by multiple readers independently. The performance of MRI in depicting abnormalities induced by pulmonary TB and their morphological changes were evaluated and compared with the performance of CT. ResultsLung MRI found pulmonary abnormalities in all 63 TB subjects, with satisfactory quality. With the implementation of MultiVane for T2-weighted TSE sequences to reduce the motion correction effect, MRI showed excellent agreement with CT in detecting abnormal imaging features of pulmonary TB (κ=0.88, p<0.001), such as tree-in-bud sign, ground-glass opacity, consolidation, mass, and cavitation. MRI was advantageous in identifying caseation and liquefactive necrosis based on inhomogeneous signal distribution within consolidations and also in identifying mild pleural effusion. The optimized lung MRI was comparable to CT in detecting non-calcified nodules (κ=0.90), with overall sensitivity of 50.0%, 91.1%, and 100% for nodules of size <5 mm, 5–10 mm, and >10 mm, respectively. However, MRI was less effective in identifying lesions with calcification. ConclusionsThe clinical implementation of an optimized MRI protocol with the MultiVane motion correction technique for imaging pulmonary TB is feasible. Lung MRI without ionizing radiation is a promising alternative to the clinical standard CT, especially for pregnant women, children, adolescents, and patients requiring short-term and repeated follow-up observations.

Accuracy of 3-T MRI for Preoperative T Staging of Esophageal Cancer After Neoadjuvant Chemotherapy, With Histopathologic Correlation.

The purpose of this study was to explore the value of 3-T MRI for evaluating the preoperative T staging of esophageal cancer (EC) treated with neoadjuvant chemotherapy (NAC), with histopathologic confirmation. This prospective study enrolled patients for whom endoscopic biopsy showed EC and pretreatment CT showed stage cT1N+M0 or cT2-T4aN0-N3M0. All patients received two cycles of NAC (paclitaxel and nedaplatin protocol) followed by 3-T MRI and surgical resection. Readers assigned a T category on MRI, and postoperative pathologic confirmation was considered the reference standard. Interreader agreement, the diagnostic accuracy of T staging on T2-weighted turbo spin-echo (TSE) BLADE (Siemens Healthcare), contrast-enhanced StarVIBE (Siemens Healthcare), high-resolution delayed phase StarVIBE, and the combination of the three sequences were analyzed and compared with postoperative pathologic T staging. The study included 79 patients. Mean time between NAC and MRI was 23 days. Interreader agreements of T category assignment were excellent for T2-weighted TSE BLADE (κ = 0.810, p < 0.0001), contrast-enhanced StarVIBE (κ = 0.845, p < 0.0001), high-resolution delayed phase StarVIBE (κ = 0.897, p < 0.0001), and the combination of the three sequences (κ = 0.880, p < 0.0001). The highest accuracy for T0, T1, T2, and T4a lesions was on high-resolution delayed phase StarVIBE (96.2%, 92.4%, 91.1%, and 91.1% for reader 1; 94.9%, 89.9%, 91.1%, and 94.9% for reader 2), and the highest accuracy for T3 lesions was on T2-weighted TSE BLADE (92.4% and 94.9% for reader 1 and reader 2, respectively). Diagnostic accuracy of the combination of the three sequences was not improved compared with individual sequences. High-resolution delayed phase StarVIBE had the highest diagnostic accuracy in staging EC after NAC for all T categories except T3, for which T2-weighted TSE BLADE had the highest accuracy. Combining all three sequences did not improve diagnostic accuracy.

Diagnosis of Nerve Root Compromise of the Lumbar Spine: Evaluation of the Performance of Three-dimensional Isotropic T2-weighted Turbo Spin-Echo SPACE Sequence at 3T

ObjectiveTo explore the performance of three-dimensional (3D) isotropic T2-weighted turbo spin-echo (TSE) sampling perfection with application optimized contrasts using different flip angle evolution (SPACE) sequence on a 3T system, for the evaluation of nerve root compromise by disc herniation or stenosis from central to extraforaminal location of the lumbar spine, when used alone or in combination with conventional two-dimensional (2D) TSE sequence.Materials and MethodsThirty-seven patients who had undergone 3T spine MRI including 2D and 3D sequences, and had subsequent spine surgery for nerve root compromise at a total of 39 nerve levels, were analyzed. A total of 78 nerve roots (48 symptomatic and 30 asymptomatic sites) were graded (0 to 3) using different MRI sets of 2D, 3D (axial plus sagittal), 3D (all planes), and combination of 2D and 3D sequences, with respect to the nerve root compromise caused by posterior disc herniations, lateral recess stenoses, neural foraminal stenoses, or extraforaminal disc herniations; grading was done independently by two readers. Diagnostic performance was compared between different imaging sets using the receiver operating characteristics (ROC) curve analysis.ResultsThere were no statistically significant differences (p = 0.203 to > 0.999) in the ROC curve area between the imaging sets for both readers 1 and 2, except for combined 2D and 3D (0.843) vs. 2D (0.802) for reader 1 (p = 0.035), and combined 2D and 3D (0.820) vs. 3D including all planes (0.765) for reader 2 (p = 0.049).ConclusionThe performance of 3D isotropic T2-weighted TSE sequence of the lumbar spine, whether axial plus sagittal images, or all planes of images, was not significantly different from that of 2D TSE sequences, for the evaluation of nerve root compromise of the lumbar spine. Combining 2D and 3D might possibly improve the diagnostic accuracy compared with either one.

Gd-EOB-DTPA-Enhanced MR Imaging of the Liver: The Effect on T2 Relaxation Times and Apparent Diffusion Coefficient (ADC).

SummaryBackgroundTo investigate the effect of gadoxetic acid disodium (Gd-EOB-DTPA) on T2 relaxation times and apparent diffusion coefficient (ADC) values of the liver and focal liver lesions on a 1.5-T system.Material/MethodsMagnetic resonance (MR) studies of 50 patients with 35 liver lesions were retrospectively analyzed. All examinations were performed at 1.5T and included T2-weighted turbo spin-echo (TSE) and diffusion-weighted (DW) images acquired before and after intravenous administration of Gd-EOB-DTPA. To assess the effect of this hepatobiliary contrast agent on T2-weighted TSE images and DW images T2 relaxation times and ADC values of the liver and FLLs were calculated and compared pre- and post-injection.ResultsThe mean T2 relaxation times of the liver and focal hepatic lesions were lower on enhanced than on unenhanced T2-weighted TSE images (decrease of 2.7% and 3.6% respectively), although these differences were not statistically significant. The mean ADC values of the liver showed statistically significant decrease (of 4.6%) on contrast-enhanced DW images, compared to unenhanced images (P>0.05). The mean ADC value of liver lesions was lower on enhanced than on unenhanced DW images, but this difference (of 2.9%) did not reach statistical significance.ConclusionsThe mean T2 relaxation times of the liver and focal liver lesions as well as the mean ADC values of liver lesions were not significantly different before and after administration of Gd-EOB-DTPA. Therefore, acquisition of T2-weighted and DW images between the dynamic contrast-enhanced examination and hepatobiliary phase is feasible and time-saving.

Performance of Whole-Body Integrated 18F-FDG PET/MR in Comparison to PET/CT for Evaluation of Malignant Bone Lesions

Because of its higher soft-tissue contrast, whole-body integrated PET/MR offers potential advantages over PET/CT for evaluation of bone lesions. However, unlike PET/CT, PET/MR ignores the contribution of cortical bone in the attenuation map. Thus, the aims of this study were to evaluate the diagnostic performance of whole-body integrated (18)F-FDG PET/MR specifically for bone lesions and to analyze differences in standardized uptake value (SUV) quantification between PET/MR and PET/CT. One hundred nineteen patients with (18)F-FDG-avid primary malignancies underwent a single-injection, dual-imaging protocol using (18)F-FDG on a PET/CT scanner and a subsequent PET/MR scan with a T1-weighted volumetric interpolated breath-hold examination (VIBE) Dixon sequence for attenuation correction and an unenhanced coronal T1-weighted turbo spin-echo (TSE) sequence for bone analysis. Three sets of images (CT with PET [from PET/CT; set A], T1-weighted VIBE Dixon with PET [set B], and T1-weighted TSE with PET [both from PET/MR; set C]) were analyzed. Two readers rated every lesion using a 4-point scale for lesion conspicuity on PET, a 4-point scale for anatomic allocation of PET-positive lesions, and a 5-point scale for the nature of every lesion based on its appearance on morphologic imaging and uptake on PET. For all lesions and for representative regions of normal bone, SUV analysis was performed for PET/MR and PET/CT. In total, 98 bone lesions were identified in 33 of 119 patients, and 630 regions of normal bone were analyzed. Visual lesion conspicuity on PET was comparable for PET/CT (mean rating, 2.82 ± 0.45) and PET/MR (2.75 ± 0.51; P = 0.3095). Anatomic delineation and allocation of suggestive lesions was significantly superior with T1-weighted TSE MRI (mean rating, 2.84 ± 0.42) compared with CT (2.57 ± 0.54, P = 0.0001) or T1-weighted VIBE Dixon MRI (2.57 ± 0.54, P = 0.0002). No significant difference in correct classification of malignant bone lesions was found among sets A (85/90), B (84/90), and C (86/90). For bone lesions and regions of normal bone, a highly significant correlation existed between the mean SUVs for PET/MR and PET/CT (R = 0.950 and 0.917, respectively, each P < 0.001). However, substantially lower mean SUVs were found for PET/MR than for PET/CT both for bone lesions (12.4% ± 15.5%) and for regions of normal bone (30.1% ± 27.5%). Compared with PET/CT, fully integrated whole-body (18)F-FDG PET/MR is technically and clinically robust for evaluation of bone lesions despite differences in attenuation correction. PET/MR, including diagnostic T1-weighted TSE sequences, was superior to PET/CT for anatomic delineation and allocation of bone lesions. This finding might be of clinical relevance in selected cases--for example, primary bone tumors, early bone marrow infiltration, and tumors with low uptake on PET. Thus, a diagnostic T1-weighted TSE sequence is recommended as a routine protocol for oncologic PET/MR.

Feasibility of post mortem cardiac proton density weighted fast field echo imaging in two cases of sudden death

The aim of this work is to investigate and compare cardiac proton density (PD) weighted fast field echo (FFE) post-mortem magnetic resonance (PMMR) imaging with standard cardiac PMMR imaging (T1-weighted and T2-weighted turbo spin-echo (TSE)), postmortem CT (PMCT) as well as autopsy. Two human cadavers sequentially underwent cardiac PMCT and PMMR imaging (PD-weighted FFE, T1-weighted and T2-weighted TSE) and autopsy. The cardiac PMMR images were compared to each other as well as to PMCT and autopsy findings. For the first case, cardiac PMMR exhibited a focal region of low signal in PD-weighted FFE and T2-weighted TSE images, surrounded by a signal intense rim in the T2-weighted images. T1-weighted TSE and PMCT did not appear to identify any focal abnormality. Macroscopic inspection identified a blood clot; histology confirmed this to be a thrombus with an adhering myocardial infarction. In the second case, a myocardial rupture with heart tamponade was identified in all PMMR images, located at the anterior wall of the left ventricle; PMCT excluded additional ruptures. In PD-weighted FFE and T2-weighted TSE images, it occurred hypo-intense, while resulting in small clustered hyper-intense spots in T1-weighted TSE. Autopsy confirmed the PMMR and PMCT findings. Presented initial results have shown PD-weighted FFE to be a valuable imaging sequence in addition to traditional T2-weighted TSE imaging for blood clots and myocardial haemorrhage with clearer contrast between affected and healthy myocardium.

Regularization method for phase-constrained parallel MRI

To implement a regularization method for the phase-constrained generalized partially parallel acquisitions (GRAPPA) algorithm to reduce image artifacts caused by data inconsistencies. Phase-constrained GRAPPA reconstructions are implemented through the use of virtual coils. To that end, synthetic virtual coils are generated by using complex conjugate symmetric signals from the actual coils. Regularization is achieved by applying coefficient-based penalty factors during the GRAPPA calibration procedure. Different penalizing factors are applied for the actual and virtual coils. The method is tested in vivo using T2-weighted turbo spin echo (TSE) images. T2 signal decay perturbs conjugate k-space symmetry and produces artifacts in phase-constrained parallel MRI reconstructions of T2-weighted TSE images. Using the proposed regularization method, artifacts are suppressed at the cost of noise amplification. However, there is still a significant SNR gain compared with conventional GRAPPA. The proposed regularization method is an efficient approach for artifact suppression and maintains the SNR benefit of phase-constrained parallel MRI over conventional parallel MRI.

The value of T2*-weighted gradient-echo MRI for the diagnosis of cerebral venous sinus thrombosis

ObjectivesThe purpose of this study is to compare the various magnetic resonance imaging (MRI) sequences when they are used to visualize and evaluate cerebral venous thrombosis. MethodsEleven patients with cerebral venous thrombosis were retrospectively analyzed using computed tomography, MRI, magnetic resonance angiography (MRA), and conventional angiography. The MR sequence included T1-weighted spin echo (SE) imaging, obtained before and after administration of contrast medium, T2-weighted turbo spin echo (TSE), fluid-attenuated inversion recovery (FLAIR), T2*-weighted conventional gradient-echo (GRE), as well as three-dimensional (3D) venous time-of-flight MRA and conventional angiography. ResultsIn all of our patients, the venous sinus thromboses were most successfully detected during the T2*-weighted GRE sequence. The thrombosis was well visualized with the T1-weighted SE sequence in three of four patients in whom it was in the subacute stage. The T2*-weighted GRE sequence was superior to the T2-weighted TSE, T1-weighted SE, and FLAIR sequences in all patients. Enhanced 3D MR venography showed the thrombosed segment of the venous sinus and well correlated with the conventional angiographic findings. ConclusionsThe T2*-weighted conventional GRE sequences may be the best method for detecting of cerebral venous thrombosis. Therefore, it would seem to be beneficial to integrate a T2*-weighted conventional GRE sequence into the MR protocol to diagnose cerebral venous thrombosis.

Uterine cervical carcinoma: a comparison of two- and three-dimensional T2-weighted turbo spin-echo MR imaging at 3.0 T for image quality and local-regional staging

To compare three-dimensional (3D) T2-weighted turbo spin-echo (TSE) with multiplanar two-dimensional (2D) T2-weighted TSE for the evaluation of invasive cervical carcinoma. Seventy-five patients with cervical carcinoma underwent MRI of the pelvis at 3.0 T, using both 5-mm-thick multiplanar 2D (total acquisition time = 12 min 25 s) and 1-mm-thick coronal 3D T2-weighted TSE sequences (7 min 20 s). Quantitative analysis of signal-to-noise ratio (SNR) and qualitative analysis of image quality were performed. Local-regional staging was performed in 45 patients who underwent radical hysterectomy. The estimated SNR of cervical carcinoma and the relative tumour contrast were significantly higher on 3D imaging (P < 0.0001). Tumour conspicuity was better with the 3D sequence, but the sharpness of tumour margin was better with the 2D sequence. No significant difference in overall image quality was noted between the two sequences (P = 0.38). There were no significant differences in terms of the diagnostic accuracy, sensitivity, and specificity of parametrial invasion, vaginal invasion, and lymph node metastases. Multiplanar reconstruction 3D T2-weighted imaging is largely equivalent to 2D T2-weighted imaging for overall image quality and staging accuracy of cervical carcinoma with a shorter MR data acquisition, but has limitations with regard to the sharpness of the tumour margin.

MAGNETIC RESONANCE IMAGING METALLIC ARTIFACT OF COMMONLY ENCOUNTERED SURGICAL IMPLANTS AND FOREIGN MATERIAL

Magnetic resonance imaging (MRI) artifacts secondary to metallic implants and foreign bodies are well described. Herein, we provide quantitative data from veterinary implants including total hip arthroplasty implants, cranial cruciate repair implants, surgical screws, a skin staple, ligation clips, an identification microchip, ameroid constrictor, and potential foreign bodies including air gun and BB projectiles and a sewing needle. The objects were scanned in a gelatin phantom with plastic grid using standardized T2-weighted turbo-spin echo (TSE), T1-weighted spin echo, and T2*-weighted gradient recalled echo (GRE) image acquisitions at 1.5 T. Maximum linear dimensions and areas of signal voiding and grid distortion were calculated using a DICOM workstation for each sequence and object. Artifact severity was similar between the T2-weighted TSE and T1-weighted images, while the T2*-weighted images were most susceptible to artifact. Metal type influenced artifact size with the largest artifacts arising from steel objects followed by surgical stainless steel, titanium, and lead. For animals with metallic surgical implants or foreign bodies, the quantification of the artifact size will help guide clinicians on the viability of MRI.

Correlation Between Vacuum Phenomenon on CT and Fluid on MRI in Degenerative Disks

The purpose of this study is to correlate the presence of intradiscal vacuum phenomenon on CT to that of intradiscal fluid on MRI. In a prospective study, 20 patients with lumbar vacuum phenomenon on CT underwent two MRI examinations. One was performed after mobilization, and the other was performed after 6 hours of bed rest. T2-weighted turbo-spin echo (TSE), STIR, T1-weighted TSE, and four consecutive T2-weighted TSE sequences were performed on a 1.5-T scanner. Ninety-five discal segments were assessed for the presence of intradiscal fluid or hyperintense signal on the T2-weighted MRI examinations and were correlated with the presence of vacuum phenomenon on CT, degenerative endplate abnormalities on CT, and edema on MRI. Sixty-nine of 95 discal segments (72.6%) showed vacuum phenomenon on CT. Sixteen of those 69 discal segments (23.1%) showed intradiscal fluid (n = 12) or hyperintense signal (n = 4) on MRI examinations performed after mobilization. Forty-one of 69 discal segments (59.4%) with vacuum phenomenon showed intradiscal fluid (n = 29) or hyperintense signal (n = 12) on MRI examinations performed after bed rest. Seventeen segments showed only fluid after bed rest. Nine segments showed more fluid after bed rest than after mobilization. Three segments showed an unchanged amount of fluid. There was a significant correlation between the presence of intradiscal fluid and the amount of bone marrow edema on MRI and the presence of degenerative endplate abnormalities on CT, respectively. The replacement of intradiscal vacuum phenomenon by intradiscal fluid is a time- and position-dependent dynamic process and is related to Modic type 1 degenerative disk disease and degenerative endplate changes.