Prospective Comparison of T1-SPACE and MPRAGE for the Identification of Intrinsic T1 Hyperintensity in Patients with Intracranial Melanoma Metastases.

BACKGROUND AND PURPOSE: Volumetric TSE (3D-TSE) techniques are increasingly replacing volumetric magnetization-prepared gradient recalled-echo (3D-GRE) sequences due to improved metastasis detection. In addition to providing a baseline for assessing postcontrast enhancement, precontrast T1WI also identifies intrinsic T1 hyperintensity, for example, reflecting melanin or blood products. The ability of precontrast 3D-TSE to demonstrate intrinsic T1 hyperintensity is not clear from the literature; thus, this study compares precontrast 3D-TSE and 3D-GRE sequences for identifying intrinsic T1 hyperintensity in patients with metastatic melanoma. MATERIALS AND METHODS: Patients with metastatic melanoma and previously reported intrinsic T1 hyperintensity were identified. MRIs were performed at 3T including both 3D-GRE (MPRAGE) and 3D-TSE T1 sampling perfection with application-optimized contrasts by using different flip angle evolution (T1-SPACE) sequences precontrast. Axial 1-mm slices of both T1WI sequences were independently reviewed by 2 neuroradiologists, comparing the conspicuity of each lesion between the 2 sequences according to a 5-point scale and assessing whether the intrinsic T1 hyperintensity was attributable to melanin, blood products, or both. RESULTS: Twenty examinations were performed, with a total of 214 lesions demonstrating intrinsic T1 hyperintensity. Both readers found that intrinsic T1 hyperintensity was less conspicuous with T1-SPACE compared with MPRAGE for most lesions assessed (81.8%, averaged across both readers), including for lesions with intrinsic T1 hyperintensity attributable to melanin and blood products. Intrinsic T1 hyperintensity was rarely more conspicuous on T1-SPACE (1.4%). CONCLUSIONS: Precontrast intrinsic T1 hyperintensity is more conspicuous with MPRAGE than T1-SPACE. In patients with metastatic melanoma, 3D-GRE should be preferred as the precontrast T1WI sequence when both 3D-TSE and 3D-GRE are performed postcontrast and when not administering IV contrast.

Investigating the role of delayed contrast magnetic resonance imaging (MRI) to differentiate radiation necrosis from tumour recurrence in brain metastases after stereotactic radiosurgery.

INTRODUCTION: The incidence of radionecrosis (RN) after stereotactic radiosurgery (SRS) to brain metastases is increasing. An overlap in the conventional MRI appearances of RN and tumour recurrence (TR) is diagnostically challenging. Delayed contrast MRI compares contrast enhancement over two time periods to create treatment response assessment maps (TRAMs). We aim to assess the utility of TRAMs in brain metastases patients. METHODS: Delayed contrast MRI scans were performed on ten brain metastases patients, previously treated with SRS, who developed equivocal lesion(s) on routine MRI follow-up. T1-weighted images were obtained five minutes and 60-75 min after contrast injection, followed by Brain Lab software analysis to create TRAMs. TRAMs patterns were then compared with the patient's clinical status, subsequent imaging, and histology results. RESULTS: We identified three regions on TRAMs: central, peripheral, and surrounding. Each region could be described either as contrast accumulation (red colour and representing non-tumour tissue) or contrast clearance (blue colour and representing tumour tissue). Our analysis demonstrated similarities in the TRAMs pattern between TR and RN, though to varying degrees. CONCLUSION: In conclusion, the TRAMs appearances of RN and TR overlap. Our findings suggest that the previously-described correlation between contrast clearance and TR is at least partially attributable to more solid initial enhancement, rather than convincingly a difference in the underlying tissue properties, and the additional diagnostic value of TRAMs may be limited. Thus, further research on TRAMs is necessary prior to incorporating it into routine clinical management after SRS for brain metastases.

Prospective comparison of volumetric post-contrast T1-Sampling Perfection with Application optimized Contrasts by using different flip angle Evolutions and Magnetization-Prepared Rapid Acquisition with Gradient Echo in patients with metastatic melanoma.

INTRODUCTION: Volumetric turbo spin echo (3D-TSE) T1-weighted imaging techniques such as T1-SPACE (Sampling Perfection with Application optimized Contrasts by using different flip angle Evolutions) improve detection of intracranial metastases (IM) compared to volumetric magnetisation-prepared gradient recalled echo techniques such as MPRAGE (Magnetization-Prepared Rapid Acquisition with Gradient Echo). However, incomplete vascular suppression can produce false positives when using 3D-TSE. Research into 3D-TSE has generally targeted patients with known or suspected IM, but the clinical implications of false positives are greater in patients with lower likelihood of IM. This study examined additional findings identified by T1-SPACE in patients with metastatic melanoma, targeting patients with a lower incidence of IM. METHODS: Patients with metastatic melanoma and an upcoming brain MRI booking were identified prospectively. Consent for adding post-contrast T1-SPACE to the MRI protocol (which included MPRAGE) was obtained. Imaging was initially assessed without T1-SPACE. Subsequently, T1-SPACE images were examined and additional findings identified were recorded, including their correlation with MPRAGE. RESULTS: One hundred examinations were performed, 24 having evidence of active IM. T1-SPACE allowed identification of additional lesions in five patients, including two with small solitary IM not identified when first assessing MPRAGE. In 18 examinations, T1-SPACE identified additional equivocal findings, confidently attributed to artefact (most commonly normal vessels) following correlation with MPRAGE. CONCLUSION: T1-SPACE improves detection of small lesions in patients without known IM, changing patient management. False positives are common but can be clarified with MPRAGE. Combining T1-SPACE and MPRAGE allows both sensitivity and specificity to be optimised.

T2-SPACE imaging of the cauda equina for the assessment of leptomeningeal metastatic disease.

The diagnosis of leptomeningeal metastatic disease (LMD) is frequently challenging and MRI of the spine is an important part of the diagnostic paradigm. We sought to examine the value of adding 3-dimensional, heavily T2-weighted, Sampling Perfection with Application optimised Contrasts using different flip angle Evolution (T2-SPACE) imaging of the lumbar spine to the MRI protocol for patients with suspected LMD. MRI spine examinations including T2-SPACE imaging of the lumbar spine performed for suspected or known LMD were retrospectively reviewed by a neuroradiologist to determine the additional benefit of the T2-SPACE sequence. The accuracy of T2-SPACE was also compared to contrast-enhanced T1-weighted imaging (ceT1WI) and standard T2-weighted imaging (T2WI). 59 patients with T2-SPACE were identified over a 20-month period, 17 having abnormal appearances on ceT1WI, including 12 with appearances consistent with LMD. In eight of these 12 patients, nodules visible on T2-SPACE were visible on T2WI, though T2-SPACE improved the temporal comparison of slowly progressive cauda equina nodules in two cases. In three patients, T2-SPACE identified nodules which were not readily identifiable on T2WI, though were visible on ceT1WI. In one patient, LMD visible on ceT1WI was not appreciable on T2-SPACE or T2WI due to the lack of a nodular component. In six patients, T2WI showed equivocal nodularity, which could be confidently attributed to facet joint arthropathy or a tortuous vessel. In conclusion, T2-SPACE has high sensitivity and specificity for the detection of nodular lesions of the cauda equina and can confidently characterise equivocal findings on standard T2WI.

Unexpected diagnosis of spinal leptomeningeal metastatic disease on MRI myelography.

We present a case of leptomeningeal metastatic disease to the cauda equina detected on Magnetic Resonance myelography. The heavy T2-weighting and small field-of-view of this MRI technique are designed to detect CSF leaks, but also provide exquisite detail of the cauda equina and any associated nodularity. Magnetic Resonance myelography thus shows promise as an adjunct to the MRI evaluation of patients with suspected leptomeningeal metastatic disease and other tumours affecting the cauda equina.