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

Interrelation Between Cerebrospinal Fluid Pressure, Intracranial Morphology and Venous Hemodynamics Studied by 4D Flow MRI.

To quantify the effects of CSF pressure alterations on intracranial venous morphology and hemodynamics in idiopathic intracranial hypertension (IIH) and spontaneous intracranial hypotension (SIH) and assess reversibility when the underlying cause is resolved. We prospectively examined venous volume, intracranial venous blood flow and velocity, including optic nerve sheath diameter (ONSD) as anoninvasive surrogate of CSF pressure changes in 11 patients with IIH, 11 age-matched and sex-matched healthy controls and 9 SIH patients, before and after neurosurgical closure of spinal dural leaks. We applied multiparametric MRI including 4D flow MRI, time-of-flight (TOF) and T2-weighted half-Fourier acquisition single-shot turbo-spin echo (HASTE). Sinus volume overlapped between groups at baseline but decreased after treatment of intracranial hypotension (p = 0.067) along with asignificant increase of ONSD (p = 0.003). Blood flow in the middle and dorsal superior sagittal sinus was remarkably lower in patients with higher CSF pressure (i.e., IIH versus controls and SIH after CSF leak closure) but blood flow velocity was comparable cross-sectionally between groups and longitudinally in SIH. We were able to demonstrate the interaction of CSF pressure, venous volumetry, venous hemodynamics and ONSD using multiparametric brain MRI. Closure of CSF leaks in SIH patients resulted in symptoms suggestive of increased intracranial pressure and caused asubsequent decrease of intracranial venous volume and of blood flow within the superior sagittal sinus while ONSD increased. In contrast, blood flow parameters from 4D flow MRI did not discriminate IIH, SIH and controls as hemodynamics at baseline overlapped at most vessel cross-sections.

Extended and weightbearing wrist 3-T MRI using a novel harness and flexible 24-channel glove coil to evaluate carpal kinematics: a pilot study in 10 volunteers.

Wrist pain in the extended or extended weightbearing positions may be incompletely evaluated using standard magnetic resonance imaging (MRI) with standard rigid clamshell coils in the neutral position. To evaluate a flexible 24-channel glove coil and harness when imaging the wrist in neutral, dorsally extended, and weightbearing positions. Ten wrists in 10 asymptomatic volunteers (mean age = 29 years) were scanned. Participants underwent 3-T MRI using the harness and flexible glove coil, acquiring sagittal turbo spin echo (TSE) and half-Fourier acquisition single-shot turbo spin echo (HASTE) pulse sequences. Static TSE images were obtained in neutral, extended, and weightbearing positions using proton density parameters and independently evaluated by two radiologists for: dorsal radiocarpal ligament thickness; radiocapitate, radiolunate, and capitatolunate angles; palmar translation of the lunate on the radius; angulation of the extensor tendons; and distance from the distal extensor retinaculum to Lister's tubercle. Cine HASTE images were dynamically acquired between neutral-maximum extension to measure the radiocapitate angle. Good reader agreement was observed (r > 0.73) for all measurements except palmar translation in the neutral position (r = 0.27). Significant increases in dorsal radiocarpal ligament thickness; radiocapitate, radiolunate and capitolunate angulation; and extensor tendon angulation were observed between the neutral and extended positions (P < 0.001). A further significant increase in these metrics between extended and weightbearing positions was also seen (P < 0.01). Significant increases in dorsal radiocarpal ligament thickness, articular and tendon angulations occur during wrist extension, that further increase with dorsal weightbearing.

Diagnostic performance of multiparametric magnetic resonance imaging in the differentiation of clear cell renal cell cancer.

This study aimed to evaluate the diagnostic performance of multiparametric magnetic resonance imaging (mpMRI) in the differentiation of renal cell carcinoma (RCC) subtypes. This is a retrospective diagnostic performance study, in which the diagnostic performances of mpMRI features were evaluated to differentiate clear cell RCC (ccRCC) from non-clear cell RCC (non-ccRCC). Adult patients who were evaluated using a 3-Tesla dynamic contrast-enhanced mpMRI before undergoing partial or radical nephrectomy for possible malignant renal tumors were included in the study. Signal intensity change percentages (SICP) between contrast-enhanced phases and pre-administration period for both the tumor and normal renal cortex, and tumor-to-cortex enhancement index (TCEI); tumor apparent diffusion coefficient (ADC) values; tumor-to-cortex ADC ratio; and a scale which was developed according to the tumor signal intensities on the axial fat-suppressed T2-weighted Half-Fourier Acquisition Single-shot Turbo spin Echo (HASTE) images were used in ROC analysis to estimate the presence of ccRCC in the patients. The reference test positivity was the histopathologic examination of the surgical specimens. Ninety-eight tumors from 91 patients were included in the study, and 59 of them were ccRCC, 29 were pRCC, and 10 were chRCC. The mpMRI features that had the three highest sensitivity rates were excretory phase SICP, T2-weighted HASTE scale score, and corticomedullary phase TCEI (93.2%, 91.5%, and 86.4%, respectively). However, those with the three highest specificity rates were nephrographic phase TCEI, excretory phase TCEI, and tumor ADC value (94.9%, 94.9%, and 89.7%, respectively). Several parameters on mpMRI showed an acceptable performance to differentiate ccRCC from non-ccRCC.

Placental Area in the Lower Uterine Segment, Cervical Length, and Clinical Outcome in Pregnancies With Complete Placenta Previa.

Complete placenta previa is associated with a higher percentage of adverse clinical outcomes and magnetic resonance imaging (MRI) is widely used in the preoperative examination of patients with placenta previa. To evaluate the effectiveness of the placental area in the lower uterine segment and cervical length in identifying the adverse maternal-fetal outcomes in women with complete placenta previa. Retrospective. A total of 141 pregnant women (median age, 32; age range, 24-40 years) with complete placenta previa were examined by MRI to evaluate the uteroplacental condition. A 3 T with T1 -weighted imaging (T1 WI), T2 -weighted imaging (T2 WI), and half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence. The association of the placental area in the lower uterine segment and cervical length measured using MRI with the risk of massive intraoperative hemorrhage (MIH) and maternal-fetal perinatal outcomes were determined. The adverse neonatal outcomes (preterm delivery, respiratory distress syndrome [RDS], admission to neonatal intensive care unit [NICU]) were analyzed in different groups. The t-test, Mann-Whitney U test, Chi-square, Fisher's exact test, and receiver operating characteristic (ROC) curve were used, and a P < 0.05 indicated a statistically significant difference. The mean operation time, intraoperative blood loss, and intraoperative blood transfusing were significantly higher in patients with large placental area and short cervix than in patients with the small placental area and long cervix, respectively. The incidence of adverse neonatal outcomes was significantly higher in the large placenta area group and short cervix group than in the small placenta group area and long cervix group, respectively, such as preterm delivery, RDS, and NICU. By combining placental area with cervical length sensitivity and specificity increased to 93% and 92%, respectively, for the identification of MIH > 2000 mL with area under the receiver operating curve (AUC) 0.941. Large placental area and short cervical length may be associated with a high risk of MIH and adverse maternal-fetal perinatal outcomes in patients with complete placenta previa. 2.

Evaluation of HASTE T2 weighted image with reduced echo time for detecting focal liver lesions in patients at risk of developing hepatocellular carcinoma

PurposeTo compare the image quality and performance of half-Fourier acquisition single-shot turbo spin echo (HASTE) sequences, using compressed sensing (HASTE-CS) and deep-learning based reconstruction (HASTE-DL) in detecting focal liver lesions (FLLs), to those of T2-weighted image using BLADE sequence (T2WI) in patients at risk of developing hepatocellular carcinoma (HCC). Materials and methodsThis retrospective study included patients at risk of developing HCC who underwent liver MRI including HASTE-DL, HASTE-CS, T2WI and DWI between January and June 2020. Three radiologists independently reviewed the image quality along with FLL detection in the three T2-based sequences and DWI. Reference lesion characterization was done using the complete set of MRI sequences according to the Liver Imaging Reporting and Data System (LI-RADS) v2018. ResultsA total of 227 patients with 88 of whom had FLLs (n = 194, mean size 11.7 ± 10.9 mm) were included. HASTE-DL yielded the highest overall image quality, followed by HASTE-CS and T2WI (3.4 ± 0.5, 3.1 ± 0.6, 2.4 ± 0.5, respectively, P < 0.001 for all). In the detection of FLLs, HASTE-DL showed significantly higher sensitivity than T2WI (51.5 % vs 43.6 %, P = 0.007) whereas HASTE-CS and T2WI bore respectively little difference (P > 0.017) on per-patient basis. For LR-4, -5, -M lesions, HASTE-DL had significantly higher figure of merit than that of T2WI (0.58 vs 0.52, P < 0.001) in per-lesion basis. ConclusionHASTE-DL demonstrated better image quality and higher performance for FLL detection than conventional T2WI in patients at risk of developing HCC.

HASTE MRI sequence findings correlate with loss of deep pain perception in dogs with thoracolumbar disc extrusion.

Thoracolumbar intervertebral disc extrusion (TL IVDE) is a common reason for the veterinary hospital admission. Various imaging factors including degree and length of compression have been tested for correlation with clinical severity, but no reliable correlation has been found. Half-Fourier acquisition single-shot turbo spin echo (HASTE) magnetic resonance imaging (MRI) sequences highlight the dorsal and ventral cerebrospinal fluid (CSF) columns and have been used to demonstrate spinal cord swelling in dogs with TL IVDE. This has been used as a predictor of progressive ascending-descending myelomalacia but has not been correlated with neurological grade. This study aims to investigate the correlation between the attenuation of CSF HASTE signal and clinical severity in dogs suffering from TL disc extrusions. Dogs less than 15kg who were non-ambulatory due to suspected TL IVDE were prospectively recruited for a study into conservative management. MRI studies were undertaken under sedation including HASTE sequences. The ratio of the length of CSF attenuation to the length of the L2 vertebra was calculated and correlated with clinical severity. Twenty dogs met the inclusion criteria. No statistically significant difference was demonstrated between the mean CSF attenuation and neurological grade (p= 0.17 but there was a significant difference in the mean CSF attenuation in those who retained deep pain perception and those who did not (p= 0.02). Time to loss of ambulation was also found to not be correlated with CSF attenuation (p= 0.95). In conclusion, the length of CSF attenuation of HASTE MRI sequences in dogs less than 15kg suffering from IVDEs may be correlated with a loss of deep pain perception.

Susceptibility-weighted imaging to evaluate normal and abnormal vertebrae in fetuses: A preliminary study.

To evaluate the performance of susceptibility-weighted imaging (SWI) in visualizing normal and abnormal fetal vertebrae in vivo and in utero. Ninety-seven women with normal fetal vertebrae and 127 women suspected fetal vertebral anomalies on ultrasound were included in our study. SWI, true fast imaging with steady state precession (TrueFISP), and half-Fourier acquisition single-shot turbo spin-echo (HASTE) of the fetal spine were performed on 1.5-T magnetic resonance imaging. The image quality and diagnostic performance between HASTE/TrueFISP and SWI were compared. Pearson correlations to correlate the L1 centrum ossification center (COC) measurements with gestational age (GA) were performed. The visibility of the fetal vertebral structures on the SWI images (3.58±0.69) was significantly greater than those on the HASTE (1.98±0.51, p<0.001) and TrueFISP (2.63±0.52, p<0.001). The diagnostic accuracy of SWI (89.0%) was superior to HASTE/TrueFISP (48.0%) (p<0.001) and the area under the curve for SWI was 0.909 (p<0.001). The height, transverse, sagittal diameter, and area of L1 COC were linearly correlated with GA (all p<0.001). SWI proved to be a reliable method for depicting fetal vertebral structure and growth, which can significantly improve the diagnostic performance of vertebral anomalies in fetuses.

Radiomics analysis of T2 -weighted images for differentiating invasive placentas in women at high risks.

To develop and validate an MRI-based radiomics model for differentiating invasive placentas in patients with high risks. A total of 181 pregnant women suspected of placenta accreta spectrum (PAS) disorders and who underwent MRI for placenta evaluation were retrospectively enrolled. The data set was randomly divided into the training (n=125; invasive=63, noninvasive=62) and test (n=56; invasive=28, noninvasive=28) groups. Radiomics features were extracted from half-Fourier acquisition single-shot turbo spin echo (HASTE) and sagittal true fast imaging in steady-state precession (TRUFISP) sequences independently and mainly selected based on their correlations with invasive placentas to construct two radiomics signatures including HASTE-Radscore and TRUFISP-Radscore. Then, the predictive performance of radiomic signatures, clinical features, radiographic features, and their combination were evaluated. The model with the best predictive performance was validated with its discrimination ability, calibration, and clinical usefulness. Five radiomics features from HASTE and three radiomics features from TRUFISP were retained, respectively, for predicting invasive placentas. The combination of radiomics signatures and clinical features including prior cesarean delivery, placenta previa, and radiographic feature, the placental thickness resulted in the best discrimination ability, with area under the curve of 0.898 (95% confidence interval [CI] 0.844-0.9522) and 0.858 (95% confidence interval 0.7514-0.9655) in the training and test cohort, respectively. The combined model showed a significantly better area under the curve performance and clinical usefulness than independent clinical or radiographic model according to DeLong test (p < .05), net reclassification improvement and integrated discrimination improvement analysis (positive improvement) and decision curve analysis (higher net benefit). The T2 -weighted imaging MRI radiomics model could serve as a potential prenatal diagnosis tool for identifying invasive placentas in patients with high risks.

Abbreviated non-enhanced magnetic resonance imaging in patients with acute necrotizing pancreatitis.

To investigate the performance of T2-weighted abbreviated magnetic resonance imaging (T2W-AMRI) protocol in evaluating patients with acute necrotizing pancreatitis (ANP). A retrospective analysis of consecutive hospitalized patients with ANP who underwent MRI (contrast-enhanced, CE or non-contrast, NC) between January 2017 and November 2020was performed. The T2W-AMRI and complete MRI (cMRI) sequences were anonymized, and subsequently, two separate sets of data (AMRI and cMRI) were created for presentation to the radiologists involved in reading the data. The T2W-AMRI was based on a single-axial T2 half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence. The pancreatic and extrapancreatic findings were recorded and tabulated independently by two radiologists on T2W-AMRI and cMRI. In addition, the interobserver agreement and association of findings between T2W-AMRI and cMRI were analyzed. Twenty-eight patients (mean age 31.7 ± 12.2years, 17 females) were included. Thirteen patients had CE-cMRI, while the rest underwent NC-cMRI. There was no significant difference in the identification of pancreatic necrosis on T2W-AMRI vs. cMRI (p = 1.00). However, T2W-AMRI underestimated necrosis in one patient. Collections were accurately detected in all patients on T2W-AMRI. The mean size of the collection was larger on cMRI (6.5 ± 3.7cm) than T2W-AMRI (6 ± 3.7cm) with p = 0.006. cMRI detected more patients with disrupted pancreatic duct (n = 9) than T2W-AMRI (n = 6). However, the difference was not statistically significant (p = 0.375). There was a good to an excellent interobserver agreement between the readers for T2W-AMRI (k = 0.62-1). T2W-AMRI may offer a suitable alternative to cMRI in ANP, especially severe disease, as it can be acquired rapidly without the need for contrast injection.

Diagnostic accuracy of a fast MRI T2-sequence for the diagnosis of internal herniation after Roux-and-Y gastric bypass during pregnancy: A retrospective single center study

PurposeThe objective of this retrospective study was to evaluate the diagnostic accuracy of a fast sequence Magnetic Resonance Imaging (MRI) sequence, T2- half-Fourier acquisition single-shot turbo spin echo (HASTE) for the diagnosis of internal herniation (IH) in pregnant patients with a history of Roux-en-Y gastric bypass (RYGB). MethodsAbdominal MRI studies, performed for the clinical suspicion of IH of pregnant patients with a history of RYGB, were analyzed by two abdominal radiologists. Thirty-one cases were included and for each case both readers independently evaluated the T2 HASTE sequence in different planes (axial, coronal and sagittal) to determine the presence or absence of IH. Diagnostic performance of T2 HASTE MRI was evaluated by calculating sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy compared to the clinical diagnosis of IH as the gold standard. IH was diagnosed as the presence of herniated bowel through the mesenteric defect at the time of surgical exploration. IH was deemed absent if the surgical exploration showed no herniated bowel or if patients had no subsequent clinical symptoms of IH after 90 days of clinical follow-up. ResultsThe results in this study, with 16 patients with IH and 15 patients without IH, portray a high accuracy for the detection of IH, ranging from 87.9% to 90.3%. This fast T2 sequence shows a high NPV (86.7% - 100.0% 87.7), sensitivity (88.9% - 100.0%) and specificity (80.0% - 86.7%). This study also portrayed a substantial interobserver agreement (0.741) for the evaluation of IH. ConclusionT2 HASTE MRI shows an excellent sensitivity and NPV for the detection of IH in pregnant patients. The fast acquisition time makes this sequence useful in the emergency setting, and it can be used for the diagnosis or exclusion of IH in pregnant patients.

Impact of rescanning and repositioning on radiomic features employing a multi-object phantom in magnetic resonance imaging

Our purpose was to analyze the robustness and reproducibility of magnetic resonance imaging (MRI) radiomic features. We constructed a multi-object fruit phantom to perform MRI acquisition as scan-rescan using a 3 Tesla MRI scanner. We applied T2-weighted (T2w) half-Fourier acquisition single-shot turbo spin-echo (HASTE), T2w turbo spin-echo (TSE), T2w fluid-attenuated inversion recovery (FLAIR), T2 map and T1-weighted (T1w) TSE. Images were resampled to isotropic voxels. Fruits were segmented. The workflow was repeated by a second reader and the first reader after a pause of one month. We applied PyRadiomics to extract 107 radiomic features per fruit and sequence from seven feature classes. We calculated concordance correlation coefficients (CCC) and dynamic range (DR) to obtain measurements of feature robustness. Intraclass correlation coefficient (ICC) was calculated to assess intra- and inter-observer reproducibility. We calculated Gini scores to test the pairwise discriminative power specific for the features and MRI sequences. We depict Bland Altmann plots of features with top discriminative power (Mann–Whitney U test). Shape features were the most robust feature class. T2 map was the most robust imaging technique (robust features (rf), n = 84). HASTE sequence led to the least amount of rf (n = 20). Intra-observer ICC was excellent (≥ 0.75) for nearly all features (max–min; 99.1–97.2%). Deterioration of ICC values was seen in the inter-observer analyses (max–min; 88.7–81.1%). Complete robustness across all sequences was found for 8 features. Shape features and T2 map yielded the highest pairwise discriminative performance. Radiomics validity depends on the MRI sequence and feature class. T2 map seems to be the most promising imaging technique with the highest feature robustness, high intra-/inter-observer reproducibility and most promising discriminative power.

Jasmine tea as a negative oral contrast agent in magnetic resonance cholangiopancreatography (MRCP)

Fluids of gastrointestinal system produce a high signal in 2D T2 Half-Fourier Acquisition Single-shot Turbo Spin Echo (HASTE) thick-slab MRCP which can overlap the biliary system image. This is the first experimental study use jasmine tea as oral contrast agent and aimed to evaluate it in improving the image quality of MRCP. This study was tested by phantom and healthy volunteers. Different types of tea phantom were tested which then calculated its signal-to-noise ratio (SNR) value and analyzed the manganese content. 15 healthy volunteers performed 2D T2 HASTE thick-slab MRCP scanning before and after administration of jasmine tea with a variation of 3 minutes, 6 minutes and 9 minutes scanning time. Qualitative analysis was carried out by MRCP questionnaire which was examined by radiologist and quantitative analysis was conducted by measuring the contrast-to-noise ratio (CNR) values. After jasmine tea administration, the image information was significantly different and CNR MRCP was increased compared to before giving negative oral contrast agent. The most optimal time to start scanning was 3 minutes after administration of jasmine tea with a volume of 300 ml (0.648 mg/dl manganese). Jasmine tea can be used as an alternative safe natural negative oral contrast agent and can improve MRCP image quality and reduce the intensity of gastrointestinal signals.

Development and Evaluation of Deep Learning-Accelerated Single-Breath-Hold Abdominal HASTE at 3 T Using Variable Refocusing Flip Angles.

Deep learning (DL) reconstruction enables substantial acceleration of image acquisition while maintaining diagnostic image quality. The aims of this study were to overcome the drawback of specific absorption rate (SAR)-related limitations at 3 T and to develop a DL-accelerated single-breath-hold half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence for 2-dimesional T2-weighted fat-suppressed magnetic resonance imaging of the abdomen at 3 T using a variable flip angle (FA) evolution for the refocusing radiofrequency pulses, as well as to evaluate its feasibility and image quality in comparison to state-of-the-art T2-weighted fat-suppressed imaging technique (BLADE). First, a suitable FA evolution with low cardiac motion-related signal loss (CRSL) and low SAR was determined through a prospective volunteer study with 11 participants. Image quality and diagnostic confidence with 5 different FA evolutions of a HASTEDL were assessed to identify the most suitable FA evolution. Second, the identified FA evolution was implemented clinically and evaluated in 51 patients undergoing a clinically indicated liver magnetic resonance imaging at 3 T. Two radiologists assessed the HASTEDL and standard sequences regarding overall image quality, noise, contrast, sharpness, artifacts, CRSL, and diagnostic confidence using a Likert scale ranging from 1 to 4, with 4 being the best. Comparative analyses were conducted to assess the differences between HASTEDL (acquisition time, 21 seconds; single breath-hold) and the routinely used T2-weighted BLADE sequence (acquisition time, 4 minutes; respiratory triggering). From the volunteer study, the FA evolution characterized by the control points 130-90-110-130 degrees (HASTEDL) was identified as optimal among the 5 evolutions evaluated and was implemented in our clinical protocol. In all 51 patients, HASTEDL was successfully acquired at 3 T and showed excellent image quality (median, 4; interquartile range, 3-4). Although BLADE was rated significantly higher for overall image quality, noise, contrast, sharpness, artifacts, CRSL, and diagnostic confidence than HASTEDL, no differences were found concerning the number (n = 102) and measured diameter of the detected hepatic lesions between the 2 sequences BLADE and HASTEDL. The proposed single-breath-hold abdominal HASTEDL with variable refocusing FAs is feasible at 3 T within SAR limits and yields high image quality and diagnostic confidence as compared with a standard T2-weighted acquisition technique, at a 10th of the acquisition time.

Real-time dynamic 3-T MRI assessment of spine kinematics: a feasibility study utilizing three different fast pulse sequences.

Half-Fourier acquisition single-shot turbo spin-echo (HASTE), continuous radial gradient-echo (GRE), and True FISP allow real-time dynamic assessment of the spine. To evaluate the feasibility of adding dynamic sequences to routine spine magnetic resonance imaging (MRI) for assessment of spondylolisthesis. Retrospective review was performed of patients referred for dynamic MRI of the cervical or lumbar spine between January 2017 and 2018 who had flexion-extension radiographs within two months of MRI. Exclusion criteria were: incomplete imaging; spinal hardware; and inability to tolerate dynamic examination. Blinded, independent review by two board-certified musculoskeletal radiologists was performed to assess for spondylolisthesis (>3 mm translation); consensus review of dynamic radiographs served as the gold standard. Cervical spinal cord effacement was assessed. Inter-reader agreement and radiographic concordance was calculated for each sequence. Twenty-one patients were included (8 men, 13 women; mean age 47.9 ± 16.5 years). Five had MRI of the cervical spine and 16 had MRI of the lumbar spine. Mean acquisition time was 18.4 ± 1.7 min with dynamic sequences in the range of 58-77 s. HASTE and True FISP had the highest inter-reader reproducibility (κ = 0.88). Reproducibility was better for the lumbar spine (κ = 0.94) than the cervical spine (κ = 0.28). Sensitivity of sequences for spondylolisthesis was in the range of 68.8%-78.6%. All three sequences had high accuracy levels: ≥90.5% averaged across the cervical and lumbar spine. Cervical cord effacement was observed during dynamic MRI in two cases (100% agreement). Real-time dynamic MRI sequences added to spine MRI protocols provide reliable and accurate assessment of cervical and lumbar spine spondylolisthesis during flexion and extension.

Needle Heating During Interventional Magnetic Resonance Imaging at 1.5- and 3.0-T Field Strengths

The aim of this study was to test the hypothesis that clinically used magnetic resonance (MR)-conditional needles of varying lengths, orientations, locations, and pulse sequences can result in excessive heating during MR imaging (MRI)-guided interventions that can be minimized to physiological ranges with proper selection of the needle length, needle position, and modification of pulse sequence parameters. We simulated a clinical interventional MRI setting with 2 standard American Society for Testing and Materials F2182-11A phantoms and measured temperatures with fiber optic sensors. Temperature profiles were monitored for commercial 10, 15 and 20 cm MR-conditional cobalt-chromium needles in clinically relevant perpendicular, 45-degree oblique, and parallel orientations relative to the static magnetic field (B0) and center, right off-center, and left off-center needle tip locations in the z = 0 plane. Clinically available interventional MRI pulse sequences including turbo spin echo (TSE), fast TSE, slice encoding for metal artifact correction, compressed sensing slice encoding for metal artifact correction, half-Fourier acquisition single-shot TSE (HASTE), HASTE inversion recovery, fluoroscopic steady-state gradient echo (3.0 T only), fast low-angle shot gradient echo, and volumetric interpolated breath-hold examination gradient echo pulse sequences were tested at 1.5 and 3.0 T field strengths. Acquired temperature data were analyzed using Friedman and Wilcoxon signed-rank tests with Bonferroni correction. After 5-minute of continuous MRI, less than 2.5°C heating occurred when needles were oriented perpendicular and 45-degree oblique to B0, regardless of field strengths. Higher temperature rises capable of causing permanent tissue damage were observed when needles were oriented in parallel to B0 (1.5 T: 22°C with 20 cm needles, 3.0 T: 8°C with 10 and 15 cm needles) using higher radiofrequency energy pulse sequences, such as TSE and HASTE. Left off-center location, parallel orientation, and needle lengths close to half of the radiofrequency pulse wavelength were positively associated with higher temperature rises. Under the herein used experimental conditions, clinically used MR-conditional needles can heat to supraphysiologic temperatures during prolonged MRI at 1.5 and 3.0 T field strengths; however, the temperature rise can be balanced to physiological ranges with proper selection of needle length, needle orientation, and pulse sequence parameters. Caution must be exercised when using different MRI systems, as results may not directly translate.

False-Positive Cholesteatomas on Non-Echoplanar Diffusion-Weighted Magnetic Resonance Imaging.

To investigate false-positive findings on non-echoplanar (non-EPI) diffusion-weighted magnetic resonance imaging (DWI) in patients under surveillance post-cholesteatoma surgery. A retrospective review was performed on patients diagnosed with cholesteatoma who underwent surgical resection and were then followed by serial non-EPI DWI using half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence. All patients had at least two annual follow-up imaging studies. False-positive findings were identified in four patients. The size of the suspected lesions was 4 to 12 mm. Otoendoscopy was used during all primary cases and Argon laser was used in one case. In all cases, the entire cholesteatoma was removed, and no residual disease was detected at the end of the procedures. One patient underwent revision surgery but only cartilage graft was found in the area of concern. All patients had stable or resolved hyperintense areas in the subsequent HASTE sequences. False positive findings can occur with non-EPI DWI MRI and patients need to be counseled accordingly before revision surgery. Decreasing intensity and dimension of a suspected lesion and a positive finding in an area other than the location of the initial cholesteatoma may favor a false positive. If a false positive finding is suspected when the surgeon is confident of complete resection of the cholesteatoma, an MRI can be repeated in 6 to 12 months to assess changes in the dimension and intensity of the area of concern. Cartilage grafts may cause restricted diffusion on DWI sequences.

Congenital Anomaly of Gall Bladder Assessed Through Magnetic Resonance Cholangiography in Relation to Its Clinical Relevance

AbstractObjective: The overall incidence of Phrygian cap is about 04%. It is an anomaly of gall bladder found congenitally. It can be a misguided pathological diagnosis often seen mimicking a liver mass on imaging of the hepatobiliary tree. Although Phrygian cap is a congenital anomaly, it does not show any pathological significance, In light of this condition, the purpose of this research was to find out the congenital anomalies of the gallbladder through magnetic resonance cholangiopancreatography (MRCP) along with its clinical significance.Methods: A total of 377 patients were selected with a number of 192 females and 185 males, with ages ranging from 16-90 years, with a mean age of 48 years, who had undergone MRCP for diagnosed stone in gallbladder or bile duct on a clinical basis, carcinoma of pancreas and inflammatory changes of pancreatic and/or bile ducts. The patient's imaging was done using a 1.5-T superconductive magnet which was four-channel phase-arrayed body coil and breath-holding technique was utilized, using multi-sliced T2-weighting half-Fourier acquisition single-shot turbo spin-echo (HASTE), MIP reconstruction, and also single-shot T2-weighted turbo-spin-echo sequence rapid acquisition with relaxation enhancement (RARE) having a varying thickness of slices.Results: The MRCP imaging results demonstrated extra hepatic biliary tract anomalies in 94 out of the 377 patients which represented a frequency of 24.93%. However, a Phrygian cap was found to be present in 6 patients with a frequency of 1.6% with 4 females and 2 males.Conclusion: From the results that we achieved, it was made quite apparent that congenital anomalies can be classified as a complex spectrum of variations that have a propensity to occur on a regular basis, emphasizing their value for attention in clinical as well as surgical settings along with the need to be readily identifiable with MRCP.

Diagnostic accuracy of magnetic resonance imaging in the evaluation of pulmonary infections in immunocompromised patients.

PurposeTo evaluate the accuracy of magnetic resonance imaging (MRI) for diagnosing pulmonary infections in immunocompromised adults.Material and methodsComputed tomography (CT) and MRI chest were performed in 35 immuno-compromised patients suspected of pulmonary infection. The MRI sequences that were performed included axial and coronal T2 half-Fourier acquisition single-shot turbo spin-echo (HASTE), spectrally attenuated inversion recovery (SPAIR), true fast imaging with steady-state free precession (TRUFI), and three-dimensional fast low angle shot (3D FLASH) using breath-hold and respiratory triggered BLADE (proprietary name for periodically rotated overlapping parallel lines with enhanced reconstruction). The presence of nodules, consolidations, and ground-glass opacities was evaluated. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for MRI using CT scan as a reference standard.ResultsThe sensitivity of MRI in nodule detection was 50% overall and 75% for nodules measuring more than 5 mm. Consolidation was detected with 100% sensitivity. Sensitivity and PPV for the detection of ground-glass opacities (GGOs) were 77.7% and 53.8%, respectively. T2 HASTE axial had the fewest image artefacts. Respiratory triggered MR pulse sequence did not add any significant diagnostic information as compared to the non-respiratory triggered MR pulse sequences.ConclusionsSensitivity for detecting small nodules and GGOs on MR is poor; CT scan remains the imaging modality of choice for the evaluation of pulmonary infections in immunocompromised patients. However, MRI can be used in the follow-up imaging of these patients.

A fast volumetric 4D-MRI with sub-second frame rate for abdominal motion monitoring and characterization in MRI-guided radiotherapy.

To propose a fast volumetric 4D-MRI based on 3D pulse sequence acquisition for abdominal motion monitoring and characterization in MRI-guided radiotherapy (MRgRT). A 3D spoiled gradient echo sequence volumetric interpolated breath-hold examination (VIBE) [repetition time/echo time (TR/TE) =0.53/1.57 ms, flip-angle =5°, receiver bandwidth (RBW) =1,400 Hz/voxel] based 4D-MRI acquisition, accelerated by 4-fold controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA), named CAIPIRINHA-VIBE 4D-MRI, was implemented on a 1.5T MRI simulator (MR-sim) and applied for abdominal imaging of nine healthy volunteers under free breathing. One hundred and forty-four dynamics of the entire abdomen volume (56 slices), in total 8,064 (144×56) images with a voxel size of 2.7×2.7×4.0 mm3, were acquired in 89 s for 4D-MRI. This CAIPIRINHA-VIBE 4D-MRI was qualitatively compared with a 2D half-Fourier acquisition single-shot turbo spin-echo (2D-HASTE) based 4D-MRI. The motions of liver dome, kidney and spleen were analyzed using the CAIPIRINHA-VIBE 4D-MRI data. The kidney motion was quantitatively characterized in terms of motion range and the correlations between left and right kidneys. CAIPIRINHA-VIBE 4D-MRI was successfully conducted in all subjects. CAIPIRINHA-VIBE 4D-MRI exhibited much higher effective volumetric temporal resolution (0.615 vs. ~5 s/volume) and better reconstructed volume consistency than 2D-HASTE 4D-MRI. CAIPIRINHA-VIBE 4D-MRI was able to characterize the respiratory motion of abdominal organs simultaneously in three orthogonal directions, and could potentially be used for whole abdomen deformable motion tracking. Renal motion range was most pronounced in superior-inferior (SI) direction (L: 10.03±2.65 mm; R: 10.38±2.80 mm), significantly larger (P<0.001) than that in anterior-posterior (AP) and the least in left-right (LR) directions. Right kidney had significantly larger mobility (4.18±2.19 vs. 2.32±1.34 mm, P=0.045) than left kidney in AP, but not in LR and SI directions. The Pearson correlation coefficients r between left and right kidney motion were 0.5063 (P=0.164), 0.6624 (P=0.052) and 0.5752 (P=0.105) in LR, AP and SI correspondingly. The correlation of renal motion in SI and AP was found significant in right kidney (r=0.843, P=0.004) but not in left kidney (r=0.467, P=0.205). A fast volumetric 4D-MRI was implemented for abdominal motion monitoring in MRgRT. A sub-second volumetric temporal resolution of 0.615 s, covering the entire abdomen, was demonstrated for respiratory motion monitoring and characterization. This technique holds potentials for MRgRT applications.

Growth and Late Detection of Post-Operative Cholesteatoma on Long Term Follow-Up With Diffusion Weighted Magnetic Resonance Imaging (DWI MRI): A Retrospective Analysis From a Single UK Centre.

To evaluate the growth rate and late detection of residual cholesteatoma on long-term follow-up with diffusion weighted magnetic resonance imaging (DWI MRI) in clinically stable ears following definitive surgery, in order to define surveillance imaging protocols. Retrospective case review. Tertiary referral center. Patients who underwent DWI MRI at our institution between February 2007 and May 2013 for postoperative cholesteatoma follow-up. Non-echo planar imaging (non-EPI) Half-Fourier Acquisition Single-shot Turbo spin Echo (HASTE) DWI MRI. Intervals between the definitive surgery and the first and subsequent DWI MRI, the maximum coronal dimension of the lesion on DWI and length of follow-up. The study evaluated 152 postoperative DWI studies performed for 88 patients. In 12 cases, DWI was initially negative but became positive on repeat imaging after a mean interval of 3.8 years from the initial cholesteatoma surgery (median 3.7 years, range 1.6-7.9). Of these, 3/12 had more than one negative/indeterminate DWI before disease was eventually detected on imaging; in this subgroup, the mean interval between surgery and positive DWI was 3.2 years (median 2.6 years, range 2.3-4.2). 39 DWI positive foci with serial imaging demonstrated a mean growth rate of 4 mm/year (median 2 mm, range 0-18). After negative initial DWI, it is proposed that interval imaging should be considered for a minimum of 5 years in stable ears following definitive cholesteatoma surgery. In view of the marked variability in growth rate, an additional interval scan between 2 and 3 years postoperatively is indicated.