The total prevalence of variation in the origin of the LVA was 6.0 % and of the RVA, 3.8 %. The total prevalence of variation in entry level into the TF was 7.0 % for the LVA and 6.2 % for the RVA. Recognition and reporting of these variations is important in interpreting CT angiography to prevent complications during surgery of the aortic arch or lower neck.

We frequently observed VA variations at the C1-2 level and with female predominance. The persistent FIA was most prevalent and sometimes seen bilaterally. Preoperative identification of these variations in VA is necessary to avoid complications during surgery at the craniovertebral junction.

Purpose:To compare normal vertebrae with vertebrae with neoplastic compression fractures by means of opposedphase (OP) and in-phase (IP) gradient-echo (GRE) imaging. Materials and Methods:On OP and IP T1-W GRE images (obtained at 1.5 T with the fast low-angle shot (FLASH) technique) of dual-phase chemical shift sequences, we compared the signal intensity ratios (SIRs) of normal and compression-fractured vertebrae in 108 patients. Dualphase chemical shift sequences were measured in three groups of vertebral bone marrow in terms of the relative SIR in OP and IP images: group 1: normal vertebrae (N ϭ 30 with 90 vertebrae); group 2: non-neoplastic compressionfractured vertebrae (N ϭ 58 with 73 vertebrae); and group 3: neoplastic compression-fractured vertebrae (N ϭ 20 with 27 vertebrae). The presence of compressed vertebrae was ascertained based on the consensus of two experienced radiologists. The mean SIRs among the three groups were compared by means of the Tukey-Kramer test. Results:The mean SIRs of the three groups (group 1: 0.46 Ϯ 0.14; group 2: 0.63 Ϯ 0.21; and group 3: 1.02 Ϯ 0.11) were significantly different according to the TukeyKramer test (P Ͻ 0.01). Conclusion:OP and IP T1-W GRE MRI of vertebral SI abnormalities can help predict the nature of compression fractures.

The overall prevalence of fenestrations of the intracranial VB system was 2.77%. We found associated cerebral aneurysms relatively frequently but rarely at the fenestration.

The prevalence of usual PHA diagnosed by CT angiography was 0.29 %, slightly higher than that reported for angiography and may be due to selection bias in the examined patients. We propose naming usual PHA "type 1 PHA"; PHA originating from the ECA, of which we found three, "type 2 PHA"; and PICA arising from the ECA, of which we found two, "type 2 PHA variant."

The total prevalence of variations of LCCA origin diagnosed by CT angiography was 11.7 %.

Quantitative MRS provides higher specificity than qualitative MRS for differentiating malignant from benign lesions and could be more useful as an additional examination in routine breast MR imaging.

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