Low-dose T1W DCE-MRI for early time points perfusion measurement in patients with intracranial tumors: A pilot study applying the microsphere model to measure absolute cerebral blood flow.

BACKGROUND: Previous studies have measured cerebral blood flow (CBF) with DSC-MRI using an "early time points" (ET) method based on microsphere theory. PURPOSE: To develop and assess a new ET method for absolute CBF estimation using low-dose high-temporal (LDHT) T1W-DCE-MRI. STUDY TYPE: Retrospective cohort study. SUBJECTS: Seven patients with sporadic vestibular schwannoma (VS) who underwent test-retest imaging; one patient with glioblastoma multiforme (GBM) imaged pretreatment; and 12 neurofibromatosis type 2 (NF2) patients undergoing bevacizumab treatment, imaged pre- and 90 days posttreatment. FIELD STRENGTH/SEQUENCE: LDHT-DCE-MRI was performed at 1.5 and 3.0T, using 3D spoiled gradient echo with phase cycling. DSC-MRI performed in one patient, using 3D echo-shifted multi-shot echo-planar imaging (PRESTO) at 3T. ASSESSMENT: Through Monte Carlo simulations, CBF estimation using three newly developed average contrast agent concentration (AC) -based methods (ACrPK, ACrMG, ACcomb), was compared against conventional maximum gradient (MG) approaches, at varying Rician noise levels. Reproducibility and applicability of the ACcomb method was assessed in our sporadic-VS/GBM/NF2 patient cohort, respectively. STATISTICAL TESTS: Reproducibility was measured using test-retest coefficient of variation (CoV). Pre- and posttreatment CBF values were compared using paired t-test with Bonferroni correction. RESULTS: Monte Carlo stimulations demonstrated that AC-based methods, particularly ACcomb, offered superior accuracy to conventional MG approaches. Overall test-retest CoV using the ACcomb method was 5.76 in normal-appearing white matter (NAWM). The new ACcomb method produced gray matter/white matter CBF estimates in the NF2 patient cohort of 55.9 ± 13.9/25.8 ± 3.5 on day 0; compared with 155.6 ± 17.2/128.4 ± 29.1 for the classical MG method. There was a moderate (10% using ACcomb and ACrPK) increase in CBF of NAWM 90 days post therapy (P = 0.03 and 0.005). DATA CONCLUSION: Our new AC-based method of CBF estimation offers excellent reproducibility, and displays more accuracy in both Monte Carlo analysis and clinical data application, than conventional MG-based approaches. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 4 J. MAGN. RESON. IMAGING 2018;48:543-557.

Ultrasound assessment of peripheral nerve pathology in neurofibromatosis type 1 and 2.

OBJECTIVE: The neurofibromatoses (NF) type 1 and 2 are hereditary tumor predisposition syndromes caused by germline mutations in the NF1 and NF2 tumor suppressor genes. In NF1 and 2, peripheral nerve tumors occur regularly. For further characterizing nerve ultrasound was performed in patients with NF1 and 2. METHODS: Patients with established diagnosis of NF1 (n=27) and NF2 (n=10) were included. Ultrasound of peripheral nerves and cervical roots was performed during routine follow-up visits. Healthy volunteers were studied for comparison. RESULTS: In patients with NF1, median cross-sectional area (CSA) of most nerves was significantly increased compared to controls and to NF2 due to generalized plexiform tumors, which arose out of multiple fascicles in 23 of 27 patients (85%). These were often accompanied by cutaneous or subcutaneous neurofibromas. In NF2, the overall aspect of peripheral nerves consisted of localized schwannomas (80%) and, apart from that, normal nerve segments. CONCLUSION: Nerve ultrasound is able to visualize different nerve pathologies in NF1 and NF2. It is a precise and inexpensive screening method for peripheral nerve manifestation in neurofibromatosis and should be considered as the first choice screening imaging modality for all peripheral nerves within reach of non-invasive ultrasound techniques. SIGNIFICANCE: Ultrasound patterns of peripheral nerve pathologies are described for the first time in a large cohort of patients with NF1 and NF2. It is a suitable screening tool and enables targeted MRI analysis.