Seven-Tesla MRI of the female pelvis

Objectives

The aim of this study was to investigate the feasibility of 7-T contrast-enhanced MR imaging of the female pelvis.

Methods

Ten healthy female volunteers were examined on a 7-T whole-body MR system utilising a custom-built eight-channel transmit/receive radiofrequency body coil. The examination protocol included (1) T1-weighted fat-saturated 2D spoiled gradient echo (FLASH), (2) dynamic T1-weighted fat-saturated 3D FLASH, and (3) T2-weighted TSE sequences. For qualitative image analysis pelvic anatomy, uterine zonal anatomy and image impairment due to artefacts was assessed using a five-point scale. For quantitative analysis contrast ratios between the junctional zone and myometrium were obtained for T2-weighted MRI.

Results

Two-dimensional FLASH MRI offered the best overall image quality (mean_{contrast-enhanced} 4.9) and highest tissue contrast (mean_{contrast-enhanced} 4.7). T2-weighted TSE imaging provided a moderate to high conspicuity of the uterine zonal anatomy with mean scores ranging from 3.5 for endometrium to 4.65 for myometrium. Overall image impairment was rated strongest for T2-weighted MRI (2.9) and least for 2D FLASH MRI (mean 4.2).

Conclusion

This study demonstrated the feasibility of 7-T T1-weighted MRI of the female pelvis and current constraints associated with T2-weighted MRI.

Key Points

? Dynamic contrast-enhanced female pelvis MR imaging at 7 T is feasible. ? Unenhanced T1-weighted MRI offers inherent hyperintense delineation of pelvic arterial vasculature. ? Two-dimensional FLASH MRI provided best overall image quality and least artefact impairment.     

MR imaging of the knee in patients with medial unicompartmental arthroplasty: comparison among sequences at 1.5 T

Purpose

This study was done to test a series of magnetic resonance (MR) imaging sequences of the knee after medial unicompartmental arthroplasty.

Materials and methods

Four patients who had undergone Oxford III medial unicompartmental arthroplasty underwent 1.5-T MR imaging of the operated knee using coronal sequences: T1-weighted spin-echo (SE), T1-weighted turbo SE (TSE), proton-density (PD)- and T2-weighted TSE, T1-weighted gradient echo (GE), short-tau inversion recovery (STIR), multi echo data image combination (MEDIC), T2*-weighted GE, volumetric interpolated breath-hold examination (VIBE), and dual-echo steady state (DESS). For each sequence, we evaluated the visibility of the anatomical structures of the central pivot, lateral compartment, and anterior compartment using a semiquantitative score (0=total masking; 1=insufficient visibility; 2=sufficient visibility; 3=optimal visibility). The sum of the scores given to each sequence was divided by the maximal sum, obtaining a percentage visibility index. Friedman and sign tests were used for statistical analysis.

Results

MR examination time was 30–32 min. No patients reported pain, heat or other local discomfort. The visibility index ranged between 83% and 89% for the first four sequences without significant differences among them, 58% for STIR and 11%–36% for the last five sequences. Significant differences were found between each of the four first sequences and the remaining sequences (p<0.004) and between STIR and the last five sequences (p<0.008).

Conclusions

MR imaging of the knee after medial unicompartmental arthroplasty was not associated with adverse events. An imaging protocol including SE, TSE and STIR sequences could be used to study the knee with unicompartmental arthroplasty.     

Improved in vivo detection of cortical lesions in multiple sclerosis using double inversion recovery MR imaging at 3 Tesla

Objective

To investigate the impact of a higher magnetic field strength of 3 Tesla (T) on the detection rate of cortical lesions in multiple sclerosis (MS) patients, in particular using a dedicated double inversion recovery (DIR) pulse sequence.

Methods

Thirty-four patients with clinically isolated syndromes or definite MS were included. All patients underwent magnetic resonance imaging (MRI) at 1.5 T and 3 T, including T2-weighted turbo spin echo (TSE), fluid-attenuated inversion recovery (FLAIR) and DIR sequences. All images were analysed for focal lesions categorised according to their anatomical location.

Results

The total number of detected lesions was higher at 3 T across all pulse sequences. We observed significantly higher numbers of lesions involving the cortex at 3 T using a DIR sequence. DIR at 3 T showed 192% more pure intracortical (p?<?0.001) and 30% more mixed grey matter-white matter lesions (p?=?0.008). No significant increase in cortical lesions could be detected on the FLAIR and T2-weighted images. Using the T2-weighted and FLAIR sequences, significantly more lesions could be detected at 3 T in the infratentorial, periventricular and juxtacortical white matter.

Conclusion

DIR brain MR imaging at 3 T substantially improves the sensitivity of the detection of cortical lesions compared with the standard magnetic field strength of 1.5 T.     

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

Objective

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.

Methods

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.

Results

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.

Conclusion

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.

Key Points

? 3D T2-weighted MR sequence is equivalent to 2D for cervical carcinoma staging. ? Coronal 3D acquisitions can reduce the examination time. ? SNR and relative tumour conspicuity were significantly higher on 3D sequences. ? Reformatted 3D T2-weighted imaging had limitations in sharpness of tumour margin.     

3-T MRI with phased-array surface coil in the local staging of rectal cancer

Purpose

This study sought to evaluate the diagnostic accuracy of surface-coil 3T magnetic resonance (MR) imaging in the preoperative study of patients with rectal cancer.

Materials and methods

Thirty patients with histologically proven rectal cancer underwent surface-coil 3T MR imaging with sagittal, paracoronal and para-axial T2-weighted turbo spin echo (TSE) sequences. Slice thickness was 3 mm without gap, field of view 24 cm, matrix 400 × 512. Images were assessed for infiltration of the rectal wall, perirectal fat and pelvic structures. Tumours were staged according to the TNM system, and the MR imaging results were correlated with histopathology.

Results

In the patients who underwent MR imaging before and after radiotherapy (group 1), the diagnostic accuracy of 3T MR imaging was 88% for T2, 94% for T3 and 88% for T4 cancers. In those who underwent surgical treatment without preoperative radiotherapy (group 2), the diagnostic accuracy was 90% for T2, 87% for T3 and 87% for T4 cancers.

Conclusions

The high signal-to-noise ratio coupled with a large field of view enables surface-coil 3T MR imaging to achieve high levels of diagnostic accuracy in the local staging of rectal cancer, and in particular in assessing infiltration of mesorectum and mesorectal fascia.     

Diagnostic performance of 64-MDCT and 1.5-T MRI with highresolution sequences in the T staging of gastric cancer: a comparative analysis with histopathology

Purpose

This study was undertaken to compare the accuracy of magnetic resonance (MR) imaging and 64-slice multidetector computed tomography (64-MDCT) in the T staging of gastric carcinoma in comparison with histopathology.

Materials and methods

Forty patients with an endoscopic diagnosis of gastric carcinoma underwent preoperative MR imaging and 64-MDCT, both of which were performed after i.v. injection of scopolamine and water distension of the stomach. In the MR imaging protocol, we acquired T2-weighted turbo spin-echo (TSE) sequences, true fast imaging steady-state free precession (true-FISP) and gadolinium-enhanced T1-weighted volumetric interpolated breath-hold examination (VIBE) 3D sequences. Contrastenhanced CT scans were obtained in the arterial and venous phases. Two groups of radiologists independently reviewed the MR and 64-MDCT images. The results were compared with pathology findings.

Results

In the evaluation of T stage, 64-MDCT had 82.5% and MR imaging had 80% sensitivity. Accuracy of MR imaging was slightly higher than that of 64-MDCT in identifying T1 lesions (50% vs 37.5%), whereas the accuracy of 64-MDCT was higher in differentiating T2 lesions (81.2% vs 68.7%). The accuracy of MR imaging and 64-MDCT did not differ significantly in the evaluation of T3-T4 lesions (p>0.05). Understaging was observed in 20% of cases with MR imaging and in 17.5% with 64-MDCT.

Conclusions

MR imaging and 64-MDCT accuracy levels did not differ in advanced stages of disease, whereas MR imaging was superior in identifying early stages of gastric cancer and can be considered a valid alternative to MDCT in clinical practice.     

Differentiation between hepatic haemangiomas and cysts with an inversion recovery single-shot turbo spin-echo (SSTSE) sequence using the TI nulling value of hepatic haemangioma with sensitivity encoding

Objective

To evaluate the additional value of inversion recovery (IR) single-shot turbo spin-echo (SSTSE) imaging with sensitivity encoding (SENSE) using the inversion time (TI) value of hepatic haemangioma as a supplement to conventional T2-weighted turbo spin-echo (TSE) imaging for the discrimination of hepatic haemangiomas and cysts.

Methods

A total of 134 lesions (77 hepatic haemangiomas, 57 hepatic cysts) in 59 patients were evaluated. Three readers evaluated these images and used a five-point scale to evaluate the lesion status. A receiver operating characteristic (ROC) analysis and 2?×?2 table analysis were used.

Results

The ROC analysis for all the readers and all the cases revealed a significantly higher area under the curve (AUC) for the combination of moderately and heavily T2-weighted TSE with IR-SSTSE images (0.945) than for moderately and heavily T2-weighted TSE images alone (0.894) (P?<?0.001). For the combination of T2-weighted TSE with IR-SSTSE versus T2-weighted TSE alone, the 2?×?2 table analysis revealed a higher true-positive rate; this difference was statistically significant (P?<?0.0001).

Conclusion

The introduction of IR-SSTSE with SENSE sequences significantly improves the diagnostic accuracy of the differentiation of hepatic haemangioma and cysts while increasing the time required for routine abdominal imaging by only 20 s.     

First-pass contrast-enhanced renal MRA at 7 Tesla: initial results

Objective

The aim of this study was to assess the feasibility of first-pass contrast-enhanced renal MR angiography (MRA) at 7 T.

Methods

In vivo first-pass contrast-enhanced high-field examinations were obtained in eight healthy subjects on a 7-T whole-body MRI. A custom-built body transmit/receive radiofrequency (RF) coil and RF system suitable for RF shimming were used for image acquisition. For dynamic imaging, gadobutrol was injected intravenously and coronal unenhanced, arterial and venous data sets using a T1-weighted spoiled gradient-echo sequence were obtained. Qualitative image analysis and assessment of artefact impairment were performed by two senior radiologists using a five-point scale (5 = excellent, 1 = non-diagnostic). SNR and CNR of the perirenal abdominal aorta and both main renal arteries were assessed.

Results

Qualitative image evaluation revealed overall high-quality delineation of all assessed segments of the unenhanced arterial vasculature (mean_unenhanced 4.13). Nevertheless, the application of contrast agent revealed an improvement in vessel delineation of all the vessel segments assessed, confirmed by qualitative (mean_unenhanced 4.13 to mean_{contrast-enhanced} 4.85) and quantitative analysis (SNR mean_unenhanced 64.3 to mean_{contrast-enhanced} 98.4).

Conclusion

This study demonstrates the feasibility and current constraints of ultra-high-field contrast-enhanced renal MRA relative to unenhanced MRA.

Key Points

? First-pass contrast-enhanced renal MRA at 7 T is technically feasible. ? Unenhanced renal MRA offers inherent hyperintense delineation of renal arterial vasculature. ? Contrast media application improves vessel assessment of renal arteries at 7 T.     

Accuracy of Postcontrast 3D Turbo Spin-Echo MR Sequence for the Detection of Enhanced Inflammatory Lesions in Patients with Multiple Sclerosis

BACKGROUND AND PURPOSE:Therapeutic strategies for patients with MS partly rely on contrast-enhanced MR imaging. Our aim was to assess the diagnostic performance of 3D turbo spin-echo MR imaging with variable refocusing flip angles at 3T for the detection of enhanced inflammatory lesions in patients with multiple sclerosis.MATERIALS AND METHODS:Fifty-six patients with MS were prospectively investigated by using postcontrast T1-weighted axial 2D spin-echo and 3D TSE MR images. The order in which both sequences were performed was randomized. Axial reformats from 3D T1 TSE were generated to match the 2D spin-echo images. The reference standard was defined by using clinical data and all MR images available. Three separate sets of MR images (2D spin-echo images, axial reformats, and multiplanar images from 3D TSE sequences) were examined in a blinded fashion by 2 neuroradiologists separately for the detection of enhanced MS lesions. Image artifacts and contrast were evaluated.RESULTS:No artifacts related to vascular pulsation were observed on 3D TSE images, whereas image artifacts were demonstrated on 2D spin-echo images in 41 patients. One hundred twelve enhanced MS lesions were identified in 19 patients. Sixty-four lesions were correctly diagnosed by using 2D spin-echo images; 90, by using 3D TSE axial reformatted views; and 106, by using multiplanar analysis of the 3D TSE sequence. Multiplanar analysis was 94.7% sensitive and 100% specific for the diagnosis of patients with at least 1 enhanced lesion. Contrast of enhanced MS lesions was significantly improved by using the 3D TSE sequence (P < .011).CONCLUSIONS:The 3D TSE sequence with multiplanar analysis is a useful tool for the detection of enhanced MS lesions.

The diagnosis of multiple sclerosis needs to demonstrate dissemination of brain lesions in space and time and to exclude alternative diagnoses. In some circumstances, dissemination of brain lesions in space and time can be established by a single MR imaging.¹ In such patients, dissemination of brain lesions in time is demonstrated by the simultaneous presence of asymptomatic gadolinium-enhancing and nonenhancing lesions at any time.¹ Indeed, therapeutic strategies for patients with MS partly rely on contrast-enhanced MR imaging. Updated recommendations on the use of MR imaging in MS suggest that axial 2D T1-weighted spin-echo (SE) MR imaging should be performed for the detection of enhanced MS lesions,^2,3 whereas T1-weighted 3D gradient recalled-echo (GRE) MR images are reported to be useful for the assessment of brain atrophy.^2–4 As previously reported,⁵ the sensitivity of the 2D T1-weighted SE sequence for the detection of enhanced MS lesions is progressively increased from 5 to 10 minutes after intravenous injection of gadolinium.Recently, a new technique has been introduced to generate 3D T1-weighted images of the brain (BrainView, Philips Healthcare, Best, the Netherlands; Cube, GE Healthcare, Milwaukee, Wisconsin; SPACE, Siemens, Erlangen, Germany). The BrainView sequence is based on a turbo spin-echo acquisition with variable refocusing flip angles and short echo spacing, allowing longer echo-train readouts and reduced signal losses.⁶ Such an approach provides high spatial resolution and signal-to-noise ratio without the blurring commonly associated with long echo-trains. Thinner section images can be acquired, minimizing the partial volume effect between small lesions and surrounding brain parenchyma. The added value of the postcontrast 3D TSE sequence with variable flip angles was recently reported in patients with brain metastasis.^7,8No data are available on the diagnostic performance of the postcontrast 3D T1-weighted TSE sequence for the detection of enhanced inflammatory lesions in patients with MS. Our purpose was to assess the detectable enhanced MS lesions by using the 3D BrainView sequence compared with the conventional axial 2D SE sequence.     

MRT zum Staging des Lungenkarzinoms

Purpose

Overview of magnetic resonance imaging (MRI) in staging of lung cancer.

Material and methods

Currently available methods of imaging lung cancer, lymph node and distant metastases by MRI are explained. At present, MRI is mainly used in the detection of cerebral metastases and assessment of infiltration of the thoracic wall and of the mediastinum. The capabilities of T2-weighted single-shot TSE (HASTE) and T1-weighted 3D gradient echo techniques (VIBE) are demonstrated.

Results

With the advent of new fast sequences like HASTE and VIBE the spatial resolution comes close to that of computed tomography but with an outstanding soft tissue contrast and without radiation exposure. The introduction of lymph node specific contrast media will improve sensitivity and specificity in N staging. Additionally, whole-body MRI is capable of detecting distant metastases, in particular in the organs at risk, i.e. brain, upper abdomen and musculoskeletal system.

Conclusion

MRI is gaining importance as part of a multimodal imaging approach for staging of lung cancer.     

Optimal Pulse Sequence for Ferumoxides-Enhanced MR Imaging Used in the Detection of Hepatocellular Carcinoma: A Comparative Study Using Seven Pulse Sequences

Objective

To identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs).

Materials and Methods

Sixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 µmol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333 8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TR∞/TE39 and 98), T2*-weighted gradient-recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis.

Results

Quantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others.

Conclusion

T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxides-enhanced MR imaging in the detection of HCCs.     

Diffusion-weighted and T2-weighted MR imaging for colorectal liver metastases detection in a rat model at 7 T: a comparative study using histological examination as reference

Objectives

To compare diffusion-weighted (DW) and T2-weighted MR imaging in detecting colorectal liver metastases in a rat model, using histological examination as a reference method.

Methods

Eighteen rats had four liver injections of colon cancer cells. MR examinations at 7 T included FSE-T2-weighted imaging and SE-DW MR imaging (b?=?0, 20 and 150 s/mm²) and were analysed by two independent readers. Histological examination was performed on 0.4-mm slices. McNemar’s test was used to compare the sensitivities and the Wilcoxon matched pairs test to compare the average number of false-positives per rat.

Results

One hundred and sixty-six liver metastases were identified on histological examination. The sensitivity in detecting liver metastases was significantly higher on DW MR than on T2-weighted images (99/166 (60 %) (reader 1) and 92/166 (55 %) (reader 2) versus 77/166 (46 %), P?≤?0.001), without an increase in false-positives per rat (P?=?0.773/P?=?0.850). After stratification according to metastasis diameter, DW MR imaging had a significantly higher sensitivity than T2-weighted imaging only for metastases with a diameter (0.6–1.2 mm) similar to that of the spatial resolution of MR imaging in the current study.

Conclusions

This MR study with histological correlations shows the higher sensitivity of DW relative to T2-weighted imaging at 7 T for detecting liver metastases, especially small ones.

Key Points

? Diffusion weighted (DW) sequences are increasingly used in magnetic resonance imaging (MRI). ? DW has higher sensitivity for liver metastases than T2-weighted imaging at 7 T. ? This increase in sensitivity is especially marked for small liver metastasis detection. ? This higher sensitivity is confirmed in an animal model with histological correlation. ? DW imaging has the potential for earlier diagnosis of small liver metastases.     

Anatomical and functional evaluation of the myocardium in patients with acute coronary syndrome (NSTEMI) using MR imaging

Purpose

The aim of our study was to evaluate the role of magnetic resonance (MR) imaging in identifying the location and extent of acute ischaemic injury to predict reversibility and distinguish areas of acute from chronic ischaemia in patients with acute coronary syndrome non- ST-elevation myocardial infarction (NSTEMI).

Materials and methods

We evaluated 22 patients with NSTEMI acute coronary syndrome confirmed by coronary angiography (CA). We studied ventricular function indices and segmental changes in wall thickness and kinetics by cine-MR imaging sequences. Subsequently, we evaluated myocardial wall oedema with T2-weighted black-blood short-tau inversion recovery turbo spin echo (T2 BB-STIRTSE) sequences and identified areas of myocardial necrosis using T1-weighted turbo field-echo inversion recovery (T1 TFE-IR) sequences after contrast material administration.

Results

The results obtained with the single sequences were as follows: T2 BB-STIR-TSE: 96.8% sensitivity, 100% specificity, 99.7% negative predictive value, 99.7% positive predictive value; T1 TFE-IR: 45.8% sensitivity, 96.9% specificity, 92.3% negative predictive value, 90.3% positive predictive value; systolic wall thickening: 87.5% sensitivity, 91.8% specificity, 98.7% negative predictive value, 50% positive predictive value, 91.4% accuracy.

Conclusions

Our study suggests that the sequences used for evaluating oedema and assessing viability allow for precise localisation and differentiation of areas of acute and chronic ischaemia by quantifying the possible mismatch between ischaemia and necrosis.     

Evaluation of MR imaging findings differentiating cavernous haemangiomas from schwannomas in the orbit

Objective

It is important to distinguish between orbital cavernous haemangioma and schwannoma because the treatments of choice for the two tumours are different. The aim was to evaluate MR imaging findings distinguishing the two tumours.

Methods

Magnetic resonance imaging including T1- and T2-weighted imaging and contrast-enhanced MR imaging was performed in 43 patients with cavernous haemangiomas and 16 patients with schwannomas confirmed by pathology. Location, configuration, margins, signal intensity, homogeneity and enhancement pattern of the tumour were retrospectively evaluated.

Results

There was a significant difference between cavernous haemangiomas and schwannomas regarding the location, configuration and margins of the mass, signal intensity and homogeneity on T1- and T2-weighted imaging, the spread pattern of contrast enhancement, the enhancement pattern and the type of time–intensity curve (P?<?0.05). Markedly homogeneous hyperintensity signal on T2-weighted imaging and the spread pattern of the contrast enhancement favoured cavernous haemangioma rather than schwannoma (P?<?0.01).

Conclusion

Cavernous haemangiomas and schwannomas have different MR imaging features that could be helpful in the differentiation between the tumours. The spread pattern of the contrast enhancement on dynamic contrast-enhanced MR imaging is the most reliable finding distinguishing cavernous haemangiomas from schwannomas.     

Breast MRI at 7 Tesla with a bilateral coil and T1-weighted acquisition with robust fat suppression: image evaluation and comparison with 3 Tesla

Objectives

To evaluate the image quality of T1-weighted fat-suppressed breast MRI at 7 T and to compare 7-T and 3-T images.

Methods

Seventeen subjects were imaged using a 7-T bilateral transmit-receive coil and 3D gradient echo sequence with adiabatic inversion-based fat suppression (FS). Images were graded on a five-point scale and quantitatively assessed through signal-to-noise ratio (SNR), fibroglandular/fat contrast and signal uniformity measurements.

Results

Image scores at 7 and 3 T were similar on standard-resolution images (1.1?×?1.1?×?1.1-1.6 mm³), indicating that high-quality breast imaging with clinical parameters can be performed at 7 T. The 7-T SNR advantage was underscored on 0.6-mm isotropic images, where image quality was significantly greater than at 3 T (4.2 versus 3.1, P?≤?0.0001). Fibroglandular/fat contrast was more than two times higher at 7 T than at 3 T, owing to effective adiabatic inversion-based FS and the inherent 7-T signal advantage. Signal uniformity was comparable at 7 and 3 T (P?<?0.05). Similar 7-T image quality was observed in all subjects, indicating robustness against anatomical variation.

Conclusion

The 7-T bilateral transmit-receive coil and adiabatic inversion-based FS technique produce image quality that is as good as or better than at 3 T.

Key Points

? High image quality bilateral breast MRI is achievable with clinical parameters at 7 T. ? 7-T high-resolution imaging improves delineation of subtle soft tissue structures. ? Adiabatic-based fat suppression provides excellent fibroglandular/fat contrast at 7 T. ? 7- and 3-T 3D T1-weighted gradient-echo images have similar signal uniformity. ? The 7-T dual solenoid coil enables bilateral imaging without compromising uniformity.     

Locally advanced rectal cancer: diffusion-weighted MR tumour volumetry and the apparent diffusion coefficient for evaluating complete remission after preoperative chemoradiation therapy

Objective

To evaluate DW MR tumour volumetry and post-CRT ADC in rectal cancer as predicting factors of CR using high b values to eliminate perfusion effects.

Methods

One hundred rectal cancer patients who underwent 1.5-T rectal MR and DW imaging using three b factors (0, 150, and 1,000 s/mm²) were enrolled. The tumour volumes of T2-weighted MR and DW images and pre- and post-CRT ADC_150–1000 were measured. The diagnostic accuracy of post-CRT ADC, T2-weighted MR, and DW tumour volumetry was compared using ROC analysis.

Results

DW MR tumour volumetry was superior to T2-weighted MR volumetry comparing the CR and non-CR groups (P?<?0.001). Post-CRT ADC showed a significant difference between the CR and non-CR groups (P?=?0.001). The accuracy of DW tumour volumetry (A_z?=?0.910) was superior to that of T2-weighed MR tumour volumetry (A_z?=?0.792) and post-CRT ADC (A_z?=?0.705) in determining CR (P?=?0.015). Using a cutoff value for the tumour volume reduction rate of more than 86.8 % on DW MR images, the sensitivity and specificity for predicting CR were 91.4 % and 80 %, respectively.

Conclusion

DW MR tumour volumetry after CRT showed significant superiority in predicting CR compared with T2-weighted MR images and post-CRT ADC.

Key Points

? Diffusion-weighted MR (DWMR) imaging offers new information about rectal cancer. ? DWMR helps to predict complete remission after chemoradiotherapy in patients with advanced rectal cancer. ? DWMR provides more accurate diagnostic information than T2-weighted MRI. ? Apparent diffusion coefficients can predict CR, but they have certain clinical limitations.     

Magnetic resonance imaging of the knee at 3 and 7 Tesla: a comparison using dedicated multi-channel coils and optimised 2D and 3D protocols

Objectives

To show the feasibility and possible superiority of two 7 Tesla knee protocols (“7?T high resolution” and “7?T quick”) using a new 28-channel knee coil compared to an optimised 3?T knee protocol using an 8-channel knee coil.

Methods

The study was approved by the ethics committee. Both 3?T and 7?T MRI of the knee were performed in 10 healthy volunteers (29.6?±?7.9?years), with two 2D sequences (PD-TSE and T1-SE) and three isotropic 3D sequences (TRUFI, FLASH and PD-TSE SPACE). Quantitative contrast-to-noise ratio (CNR) and qualitative evaluations were performed by different readers, and intra- and inter-rater agreement was assessed.

Results

The signal-to-noise ratio (SNR) as well as the CNR values for cartilage–bone, cartilage–fluid, cartilage–menisci and menisci–fluid were, in most cases, higher at 7?T compared to 3?T, and the 7?T quick measurement was slightly superior compared to the 7?T high-resolution measurement. The results of the subjective qualitative analysis were higher for the 7?T measurements compared to the 3?T measurements. Inter- and intra-observer reliability was high (0.884–0.999).

Conclusions

Through higher field strength and an optimal coil, resolution at 7?T can be increased and acquisition time can be reduced, with superior quantitative and comparable qualitative results compared to 3?T.

Key Points

? 7-Tesla MRI using a dedicated 28-channel knee coil provides high quality. ? Isotropic 3D-MR sequences benefit more from ultra-high-field than basic 2D sequences. ? At 7 T high resolution and short MR acquisition are possible. ? Dedicated coils ensure the clinical applicability of musculoskeletal MRI at ultra-high-field.     

Feasibility of high-resolution pituitary MRI at 7.0 tesla

Objectives

Since the pituitary gland measures 3-8 mm, imaging with the highest possible spatial resolution is important for the detection of even smaller lesions such as those seen in Cushing's disease. In the current feasibility study, we tested a multi-sequence MRI protocol to visualize the pituitary gland in high resolution at 7.0 Tesla (7.0 T).

Methods

Ten healthy volunteers were examined with a 7.0 T pituitary gland protocol. The protocol consisted of a T1-weighted magnetization-prepared inversion recovery (MPIR) turbo spin-echo (TSE) sequence and a T2-weighted TSE sequence. Additionally, this protocol was tested in five patients with clinical and biochemical suspicion of a microadenoma.

Results

The dedicated protocol was successful in visualizing normal pituitary anatomy. At 7.0 T compared to 1.5 T, four times as many slices covered the pituitary gland in sagittal and coronal direction. In three patients, a lesion was diagnosed at 7.0 T, and was confirmed by histopathology to be a microadenoma.

Conclusion

Head-to-head comparisons of 7.0 T with 1.5 T and 3.0 T are needed with larger samples of patients and with imaging times feasible for clinical settings. However, the current study suggests that high-resolution 7.0 T MRI of the pituitary gland may provide new perspectives when used as a second-line diagnostic examination in the specific context of Cushing's disease.

Key Points

? 7.0 T MRI enables ultra-high-resolution imaging of the pituitary gland. ? 7.0 T MRI is appropriate to visualize normal pituitary gland anatomy. ? The pituitary protocol consists of a T ₁ -MPIR-TSE and a T ₂ -TSE sequence. ? In four patients, a suspected ACTH-producing microadenoma was visualized at 7.0 T. ? Histopathology confirmed three of four lesions to be ACTH-producing microadenomas.     

Endometrial cancer: preoperative staging using three-dimensional T2-weighted turbo spin-echo and diffusion-weighted MR imaging at 3.0 T: a prospective comparative study

Objectives

To prospectively assess the efficacy of 3-T magnetic resonance (MR) imaging using the three-dimensional turbo spin-echo T2-weighted and diffusion-weighted technique (3D-TSE/DW) compared with that of conventional imaging using the two-dimensional turbo spin-echo T2-weighted and dynamic contrast-enhanced technique (2D-TSE/DCE) for the preoperative staging of endometrial cancer, with pathological analysis as the reference standard.

Methods

Seventy-one women with endometrial cancer underwent MR imaging using 3D-TSE/DW (b?=?1,000 s/mm²) and 2D-TSE/DCE. Two radiologists independently assessed the two imaging sets. Accuracy, sensitivity, and specificity for staging were analysed with the McNemar test; the areas under the receiver operating characteristic curve (Az) were compared with a univariate z-score test.

Results

The results for assessing deep myometrial invasion, accuracy, sensitivity, specificity and Az, respectively, were as follows: 3D-TSE/DW—observer 1, 87 %, 95 %, 85 % and 0.96; observer 2, 92 %, 84 %, 94 % and 0.95; 2D-TSE/DCE—observer 1, 80 %, 79 %, 81 % and 0.89; observer 2, 86 %, 84 %, 87 % and 0.86. Most of the values were higher with 3D-TSE/DW without significant differences (P?>?0.12). For assessing cervical stromal invasion, there were no significant differences in those values for both observers (P?>?0.6).

Conclusions

Accuracy of 3D-TSE/DW was at least equivalent to that of the conventional technique for the preoperative assessment of endometrial cancer.

Key Points

? New techniques in MR imaging help assess patients with endometrial cancer. ? A 3D T2-weighted TSE sequence seems equally as accurate as conventional techniques. ? Three-dimensional TSE/DW imaging does not require intravenous contrast material and is relatively quick. ? Tumour extent of endometrial cancer can be clearly shown on diffusion-weighted images. ? Junctional zone can be visualised well on 3D-TSE T2-weighted images.     

Image quality and cancer visibility of T2-weighted Magnetic Resonance Imaging of the prostate at 7 Tesla

Objectives

To assess the image quality of T2-weighted (T2w) magnetic resonance imaging of the prostate and the visibility of prostate cancer at 7 Tesla (T).

Materials & methods

Seventeen prostate cancer patients underwent T2w imaging at 7T with only an external transmit/receive array coil. Three radiologists independently scored images for image quality, visibility of anatomical structures, and presence of artefacts. Krippendorff’s alpha and weighted kappa statistics were used to assess inter-observer agreement. Visibility of prostate cancer lesions was assessed by directly linking the T2w images to the confirmed location of prostate cancer on histopathology.

Results

T2w imaging at 7T was achievable with ‘satisfactory’ (3/5) to ‘good’ (4/5) quality. Visibility of anatomical structures was predominantly scored as ‘satisfactory’ (3/5) and ‘good’ (4/5). If artefacts were present, they were mostly motion artefacts and, to a lesser extent, aliasing artefacts and noise. Krippendorff’s analysis revealed an α?=?0.44 between three readers for the overall image quality scores. Clinically significant cancer lesions in both peripheral zone and transition zone were visible at 7T.

Conclusion

T2w imaging with satisfactory to good quality can be routinely acquired, and cancer lesions were visible in patients with prostate cancer at 7T using only an external transmit/receive body array coil.

Key Points

? Satisfactory to good T2-weighted image quality of the prostate is achievable at 7T. ? Periprostatic lipids appear hypo-intense compared to healthy peripheral zone tissue at 7T. ? Prostate cancer is visible on T2-weighted MRI at 7T.