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10 October 2019, 2:21 pm
Cho, D. Y., Kim, B.- S., Choi, J. H., Park, Y. K., Shin, Y. S.
BACKGROUND AND PURPOSE:

Unruptured intracranial vertebrobasilar dissecting aneurysms with brain stem compression are difficult to treat. In the present study, the clinical and radiologic outcomes of unruptured intracranial vertebrobasilar dissecting aneurysms with brain stem compression based on different treatment modalities were evaluated.

MATERIALS AND METHODS:

This study included 28 patients with unruptured intracranial vertebrobasilar dissecting aneurysms with brain stem compression treated from January 2009 to December 2017. Treatment methods were observation (n = 6), stent-assisted coil embolization (n = 9), parent artery occlusion (n = 6), and flow diversion (n = 7). The data of baseline characteristics, change of aneurysm size, retreatment rate, stroke occurrence, and alteration of the mRS score were obtained from retrospective chart review.

RESULTS:

The initial size of dissecting aneurysms was largest in the flow diversion group (22.5 ± 7.7 mm), followed by parent artery occlusion (20.3 ± 8.4 mm), stent-assisted coil embolization (11.7 ± 2.2 mm), and observation (17.8 ± 5.5 mm; P = .01) groups. The reduction rate of aneurysm size was highest in the parent artery occlusion group (26.7 ± 32.1%), followed by flow diversion (14.1% ± 28.7%), stent-assisted coil embolization (–17.9 ± 30.3%), and observation (–31.5 ± 30.8%; P = .007) groups. Additional treatment was needed in the observation (4/6, 66.7%) and stent-assisted coil embolization (3/9, 33.3%; P = .017) groups. Improvement of the mRS score on follow-up was observed in the flow diversion (6/7, 85.7%) and parent artery occlusion (4/6, 66.7%) groups but not in the stent-assisted coil embolization and observation groups. A worsened mRS score was most common in the observation group (4/6, 66.7%), followed by stent-assisted coil embolization (3/9, 33.3%), parent artery occlusion (2/6, 33.3%), and flow diversion (0/7, 0%) groups.

CONCLUSIONS:

When treating intracranial vertebrobasilar dissecting aneurysms with brain stem compression, parent artery occlusion and flow diversion should be considered to reduce aneurysm size and improve the mRS score.


10 October 2019, 2:21 pm
Jaju, A., Hwang, E. I., Kool, M., Capper, D., Chavez, L., Brabetz, S., Billups, C., Li, Y., Fouladi, M., Packer, R. J., Pfister, S. M., Olson, J. M., Heier, L. A.
BACKGROUND AND PURPOSE:

Supratentorial primitive neuroectodermal tumors and pineoblastomas have traditionally been grouped together for treatment purposes. Molecular profiling of these tumors has revealed a number of distinct entities and has led to the term "CNS-primitive neuroectodermal tumors" being removed from the 2016 World Health Organization classification. The purpose of this study was to describe the MR imaging findings of histologically diagnosed primitive neuroectodermal tumors and pineoblastomas and correlate them with molecular diagnoses and outcomes.

MATERIALS AND METHODS:

Histologically diagnosed primitive neuroectodermal tumors and pineoblastomas were enrolled in this Children’s Oncology Group Phase III trial, and molecular classification was retrospectively completed using DNA methylation profiling. MR imaging features were systematically studied and correlated with molecular diagnoses and survival.

RESULTS:

Of the 85 patients enrolled, 56 met the inclusion criteria, in whom 28 tumors were in pineal and 28 in nonpineal locations. Methylation profiling revealed a variety of diagnoses, including pineoblastomas (n = 27), high-grade gliomas (n = 17), embryonal tumors (n = 7), atypical teratoid/rhabdoid tumors (n = 3), and ependymomas (n = 2). Thus, 39% overall and 71% of nonpineal tumor diagnoses were discrepant with histopathology. Tumor location, size, margins, and edema were predictors of embryonal-versus-nonembryonal tumors. Larger size and ill-defined margins correlated with poor event-free survival, while metastatic disease by MR imaging did not.

CONCLUSIONS:

In nonpineal locations, only a minority of histologically diagnosed primitive neuroectodermal tumors are embryonal tumors; therefore, high-grade glioma or ependymoma should be high on the radiographic differential. An understanding of molecularly defined tumor entities and their relative frequencies and locations will help the radiologist make more accurate predictions of the tumor types.


10 October 2019, 2:21 pm
Flood, T. F., Bhatt, P. R., Jensen, A., Maloney, J. A., Stence, N. V., Mirsky, D. M.
BACKGROUND AND PURPOSE:

Various pathologic and nonpathologic states result in brain parenchymal signal intensity changes on unenhanced T1-weighted MR imaging. However, the absence of quantitative data to characterize typical age-related signal intensity values limits evaluation. We sought to establish a range of age-dependent brain parenchymal signal intensity values on unenhanced T1WI in a sample of individuals (18 years of age or younger) with structurally normal brains.

MATERIALS AND METHODS:

A single-center retrospective study was performed. Gadolinium-naïve pediatric patients with structurally normal MR brain imaging examination findings were analyzed (n = 114; 50% female; age range, 68 days to 18 years). ROI signal intensity measurements were obtained from the globus pallidus, thalamus, dentate nucleus, pons, and frontal lobe cortex and subcortical white matter. Multivariable linear regression was used to analyze the relationship between signal intensity values and age.

RESULTS:

Results demonstrated a statistically significant association between signal intensity values and linear age in all neuroanatomic areas tested, except the frontal gray matter, (P < .01). There were no statistically significant differences attributable to patient sex.

CONCLUSIONS:

Age-dependent signal intensity values were determined on unenhanced T1WI in structurally normal pediatric brains. Increased age correlated with increased signal intensity in all brain locations, except the frontal gray matter, irrespective of sex. The biologic mechanisms underlying our results remain unclear and may be related to chronologic changes in myelin density, synaptic density, and water content. Establishing age-dependent signal intensity parameters in the structurally normal pediatric brain will help clarify developmental aberrations and enhance gadolinium-deposition research by providing an improved understanding of the confounding effect of age.


10 October 2019, 2:21 pm
Hara, S., Tanaka, Y., Hayashi, S., Inaji, M., Maehara, T., Hori, M., Aoki, S., Ishii, K., Nariai, T.
BACKGROUND AND PURPOSE:

CBF analysis of DSC perfusion using the singular value decomposition algorithm is not accurate in patients with Moyamoya disease. This study compared the Bayesian estimation of CBF against the criterion standard PET and singular value decomposition methods in patients with Moyamoya disease.

MATERIALS AND METHODS:

Nineteen patients with Moyamoya disease (10 women; 22–52 years of age) were evaluated with both DSC and 15O-gas PET within 60 days. DSC-CBF maps were created using Bayesian analysis and 3 singular value decomposition analyses (standard singular value decomposition, a block-circulant deconvolution method with a fixed noise cutoff, and a block-circulant deconvolution method that adopts an occillating noise cutoff for each voxel according to the strength of noise). Qualitative and quantitative analyses of the Bayesian-CBF and singular value decomposition–CBF methods were performed against 15O-gas PET and compared with each other.

RESULTS:

In qualitative assessments of DSC-CBF maps, Bayesian-CBF maps showed better visualization of decreased CBF on PET (sensitivity = 62.5%, specificity = 100%, positive predictive value = 100%, negative predictive value = 78.6%) than a block-circulant deconvolution method with a fixed noise cutoff and a block-circulant deconvolution method that adopts an oscillating noise cutoff for each voxel according to the strength of noise (P < .03 for all except for specificity). Quantitative analysis of CBF showed that the correlation between Bayesian-CBF and PET-CBF values ( = 0.46, P < .001) was similar among the 3 singular value decomposition methods, and Bayesian analysis overestimated true CBF (mean difference, 47.28 mL/min/100 g). However, the correlation between CBF values normalized to the cerebellum was better in Bayesian analysis ( = 0.56, P < .001) than in the 3 singular value decomposition methods (P < .02).

CONCLUSIONS:

Compared with previously reported singular value decomposition algorithms, Bayesian analysis of DSC perfusion enabled better qualitative and quantitative assessments of CBF in patients with Moyamoya disease.


10 October 2019, 2:21 pm
Raslau, F. D., Escott, E. J., Smiley, J., Adams, C., Feigal, D., Ganesh, H., Wang, C., Zhang, J.
BACKGROUND AND PURPOSE:

Iterative reconstruction has promise in lowering the radiation dose without compromising image quality, but its full potential has not yet been realized. While phantom studies cannot fully approximate the subjective effects on image quality, live animal models afford this assessment. We characterize dose reduction in head CT by applying advanced modeled iterative reconstruction (ADMIRE) in a live ovine model while evaluating preservation of gray-white matter detectability and image texture compared with filtered back-projection.

MATERIALS AND METHODS:

A live sheep was scanned on a Force CT scanner (Siemens) at 12 dose levels (82–982 effective mAs). Images were reconstructed with filtered back-projection and ADMIRE (strengths, 1–5). A total of 72 combinations (12 doses x 6 reconstructions) were evaluated qualitatively for resemblance to the reference image (highest dose with filtered back-projection) using 2 metrics: detectability of gray-white matter differentiation and noise-versus-smoothness in image texture. Quantitative analysis for noise, SNR, and contrast-to-noise was also performed across all dose-strength combinations.

RESULTS:

Both qualitative and quantitative results confirm that gray-white matter differentiation suffers at a lower dose but recovers when complemented by higher iterative reconstruction strength, and image texture acquires excessive smoothness with a higher iterative reconstruction strength but recovers when complemented by dose reduction. Image quality equivalent to the reference image is achieved by a 58% dose reduction with ADMIRE-5.

CONCLUSIONS:

An approximately 60% dose reduction may be possible while preserving diagnostic quality with the appropriate dose-strength combination. This in vivo study can serve as a useful guide for translating the full implementation of iterative reconstruction in clinical practice.


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