A Case of Solid-Appearing Struma Ovarii: Pitfall in the Assessment Using Ovarian-Adnexal Reporting and Data System Magnetic Resonance Imaging Score.

Struma ovarii is a monodermal teratoma characterized by the presence of >50% thyroid tissue. It is mostly benign; therefore, preoperative diagnosis is important. It usually manifests as a multilocular cystic mass but rarely as a predominantly solid mass. On magnetic resonance imaging (MRI), solid-appearing struma ovarii showed early signal intensity enhancement on dynamic gadolinium-enhanced T1-weighted images, which histopathologically indicates the presence of thyroid tissue with abundant blood vessels. The Ovarian-Adnexal Reporting and Data System (O-RADS) MRI score is a validated classification worldwide for characterizing adnexal lesions. Based on the morphology, signal intensity, and enhancement of any solid tissue on the MRI, the scoring system can be used to classify adnexal lesions into five categories from score one (no adnexal mass) to score five (high risk of malignancy). An adnexal solid mass with a higher signal intensity than that of the myometrium 30-40 seconds after gadolinium (Gd) injection on non-dynamic contrast-enhanced (non-DCE) MRI was assigned a score of 5 (high risk of malignancy).  We present a case of solid-appearing struma ovarii with a higher signal intensity than that of the myometrium 30 seconds after Gd injection on non-DCE MRI, and it was classified as score five preoperatively. Therefore, a total abdominal hysterectomy with bilateral salpingo-oophorectomy was performed despite the presence of a benign ovarian mass. When an adnexal mass with a higher signal intensity than that of the myometrium 30-40 seconds after Gd injection on non-DCE MRI is encountered, struma ovarii should be included in the differential diagnosis, despite the O-RADS MRI score of five and management of the situation should be discussed.

Diffusion imaging of reversible and irreversible microstructural changes within the corticospinal tract in idiopathic normal pressure hydrocephalus.

The symptoms of idiopathic normal pressure hydrocephalus (iNPH) can be improved by shunt surgery, but prediction of treatment outcome is not established. We investigated changes of the corticospinal tract (CST) in iNPH before and after shunt surgery by using diffusion microstructural imaging, which infers more specific tissue properties than conventional diffusion tensor imaging. Two biophysical models were used: neurite orientation dispersion and density imaging (NODDI) and white matter tract integrity (WMTI). In both methods, the orientational coherence within the CSTs was higher in patients than in controls, and some normalization occurred after the surgery in patients, indicating axon stretching and recovery. The estimated axon density was lower in patients than in controls but remained unchanged after the surgery, suggesting its potential as a marker for irreversible neuronal damage. In a Monte-Carlo simulation that represented model axons as undulating cylinders, both NODDI and WMTI separated the effects of axon density and undulation. Thus, diffusion MRI may distinguish between reversible and irreversible microstructural changes in iNPH. Our findings constitute a step towards a quantitative image biomarker that reflects pathological process and treatment outcomes of iNPH.

Assessment of arteriovenous malformations with 3-Tesla time-resolved, contrast-enhanced, three-dimensional magnetic resonance angiography.

OBJECT: Although conventional catheter angiography is commonly used in the evaluation of intracranial arteriovenous malformations (AVMs), less invasive tools are more suitable for screening or follow-up. Older MR angiography techniques cannot provide high enough temporal and spatial resolution for assessing AVMs. Threetesla time-resolved imaging of contrast kinetics (TRICKS)-a time-resolved, contrast-enhanced 3D MR angiography technique-achieves subsecond time resolution without sacrificing spatial resolution. The purpose of this study was to assess the accuracy of TRICKS at 3 T in the evaluation of AVMs. METHODS: Between November 2006 and November 2007, 31 patients who were known to have AVMs underwent evaluation in a 3-T unit with the TRICKS technique. The TRICKS images were then evaluated independently by 2 radiologists for nidus detection, early venous filling detection, and Spetzler-Martin classification, and these results were compared with the results of catheter angiography. RESULTS: Time-resolved imaging of contrast kinetics achieved 96% sensitivity and 100% specificity both in nidus detection and early venous filling detection. The Spetzler-Martin grades also showed excellent correlation with catheter angiography findings (kappa= 0.89). CONCLUSIONS: Although this is a preliminary study, the authors' results indicate that time-resolved contrast-enhanced 3D MR angiography at 3 T is a good tool to assess AVMs, and has the potential to replace catheter angiography in screening or follow-up examinations of patients with AVMs.

Utilization of low-field MR scanners.

The evident advantage of high-field MR (magnetic resonance) scanners is their higher signal-to-noise ratio, which results in improved imaging. While no reliable efficacy studies exist that compare the diagnostic capabilities of low- versus high-field scanners, the adoption and acceptance of low-field MRI (magnetic resonance imaging) is subject to biases. On the other hand, the cost savings associated with low-field MRI hardware are obvious. The running costs of a non-superconductive low-field scanner show even greater differences in favor of low-field scanners. Patient anxiety and safety issues also reflect the advantages of low-field scanners. Recent technological developments in the realm of low-field MR scanners will lead to higher image quality, shorter scan times, and refined imaging protocols. Interventional and intraoperative use also supports the installation of low-field MR scanners. Utilization of low-field systems has the potential to enhance overall cost reductions with little or no loss of diagnostic performance.

Two-dimensional magnetic resonance digital subtraction angiography using array spatial sensitivity encoding techniques in the assessment of intracranial hemodynamics.

OBJECTIVE: Array spatial sensitivity encoding techniques (ASSET) were employed to improve the temporal resolution of two-dimensional (2D) thick-slice contrast-enhanced magnetic resonance digital subtraction angiography (MRDSA). METHODS: 2D MRDSA using ASSET was performed in 28 patients via fast spoiled gradient-echo sequence (TR/TE 5.4/1.5 ms; FA 60; FOV 24x24 cm; matrix size 256x256; slicethickness 50-70 mm), followed by a bolus injection of gadolinium chelate and subsequent saline flush, for 40 seconds on a sagittal plane. Images were evaluated for visualization of normal intracranial vessels and brain lesions utilizing a three-point scale; additionally, in 10 of the 28 patients, results were compared with those of conventional 2D MRDSA. RESULTS: 2D MRDSA using ASSET, which improved temporal resolution from 1.45 to 0.77 seconds, displayed image quality comparable to that of conventional 2D MRDSA. Moreover, this technique afforded superior detectability with respect to early venous filling in patients with arteriovenous malformations (AVMs). CONCLUSION: ASSET improves the temporal resolution of 2D MRDSA without compromising spatial resolution.