Radiation doses in cerebral perfusion computed tomography: patient and phantom study.

The purpose of this study was to investigate radiation doses in cerebral perfusion computed tomography (CT) examination. As a part of routine patient monitoring, data were collected on patients in terms of the skin dose and CT dose index (CTDIvol) and dose-length product (DLP) values. For the estimation of the dose to the lens a phantom study was performed. Dose values for skin and lens were below the threshold for deterministic effects. The results were also compared with already published data. For better comparison, the effective dose was also estimated. The values collected on patients were in the ranges 230-680 mGy for CTDI and 2120-2740 mGy cm for DLP, while the skin dose and estimated effective dose were 340-800 mGy and 4.9-6.3 mSv, respectively. These values measured in the phantom study were similar, while the doses estimated to the lens were 53 and 51 mGy for the right and left lens, respectively.

Analysis of cystic intracranial lesions performed with fluid-attenuated inversion recovery MR imaging.

BACKGROUND AND PURPOSE: T1-, T2-, and proton density (PD)-weighted sequences are used to characterize the content of cystic intracranial lesions. Fluid-attenuated inversion recovery (FLAIR) MR sequences produce T2-weighted images with water signal saturation. Therefore, we attempted to verify whether FLAIR, as compared with conventional techniques, improves the distinction between intracranial cysts with a free water-like content versus those filled with a non-free water-like substance and, consequently, aids in the identification of these lesions as either neoplastic/inflammatory or maldevelopmental/porencephalic. METHODS: Forty-five cystic intracranial lesions were studied using T1-weighted, T2-weighted, FLAIR, and PD-weighted sequences. By means of clustering analysis of the ratio in signal intensity between the cystic intracranial lesions and CSF, the intracranial lesions were classified as filled with a free water-like content or with a non-free water-like substance. The results were compared with their true content as evaluated either histologically or on the basis of clinical, neuroradiologic, and follow-up features (necrotic material, 13 cases; accumulation of intercellular proteinaceous/myxoid material, eight cases; keratin, five cases; CSF, 19 cases). Cystic intracranial lesions were divided into two clinical groups, neoplastic/inflammatory and maldevelopmental/porencephalic, to evaluate the level of accuracy of each MR technique. The difference in absolute value signal intensity between CSF and cystic intracranial lesion content was calculated on FLAIR and PD-weighted images. RESULTS: PD-weighted and FLAIR sequences, unlike T1- and T2-weighted sequences, accurately depicted all cystic intracranial lesions containing necrotic or myxoid/proteinaceous intercellular material (non-free water-like) and most CSF-containing cystic intracranial lesions (free water-like). All imaging techniques inaccurately showed some of the keratin-containing cystic intracranial lesions and pineal cysts. The overall error rate was 22% for T1-weighted, 27% for T2-weighted, 9% for FLAIR, and 13% for PD-weighted sequences. The signal intensity difference between CSF and cystic intracranial lesion content was higher with FLAIR imaging. CONCLUSIONS: FLAIR imaging depicts far more accurately the content of cystic intracranial lesions and better reveals the distinction between maldevelopmental/porencephalic and neoplastic/inflammatory lesions than do conventional sequences. FLAIR has the added advantage of a higher signal intensity difference between cystic intracranial lesions and CSF.

[Fluid attenuated inversion recovery sequences: indications in neuroradiology]. / Indicazioni delle sequenze Fluid Attenuated Inversion Recovery nella neuroradiologia.

The acronym FLAIR refers to fluid attenuation inversion recovery sequences, which are T2-weighted MR pulse sequences with liquor signal saturation by a long TI. They are characterized by long TR and TE and therefore the acquisition time is very long in the conventional mode, while fast imaging (the Turbo mode) reduces acquisition time to less than 2 minutes. Our study was aimed at codifying the use of this type of sequence in neuroradiologic studies. All the exams were performed with an MR unit with a 1-Tesla magnetic field. We carried out 150 neuroradiologic exams with this pulse sequence on patients with cerebral, medullary or orbital conditions. This technique is very useful to study periventricular or cortical lesions in multiple sclerosis and in other multifocal cerebral conditions (e.g., multiple metastases or lacunar infarcts), but we pointed out the following other advantages: better definition of the extent of infiltrative white matter lesions (i.e., gliomatosis cerebri and lymphomas), better differentiation of cystic from necrotic cavities and exact characterization of cortical damage in cerebral ischemic lesions (useful also for the differential diagnosis). Moreover, FLAIR pulse sequences could diagnose some globe conditions, such as amelanotic uveal melanomas and malformations with no need of contrast agent administration. In contrast, they were useless to study deep ischemic areas, solid neoplasms, hemorrhagic lesions, poroencephalic areas, intrinsic medullary lesions and intra-orbital and extra-ocular conditions. In conclusion, the FLAIR technique is a major diagnostic tool in neuroradiologic MR studies because they overcome such limitations of Turbo SE PD sequences as blurring artifacts; moreover, their acquisition time is always very short. In some cases, FLAIR images are decisive for the diagnosis.

[Comparative assessment of conventional spin echo sequences and turbo spin echo in the study with magnetic resonance of the lesions of the spinal cord]. / Valutazione comparativa fra sequenze SE tradizionali e Turbo SE nello studio con Risonanza Magnetica delle lesioni del midollo spinale.

In the last few years, new magnetic resonance (MR) pulse sequences called Fast or Turbo Spin Echo (TSE) sequences have become available. This kind of T2-weighted images is particularly useful for the study of spondylosis and degenerative spinal conditions, because it both reduces involuntary motion artifacts and its acquisition time is shorter than that of conventional SE T2-weighted images. Our study was aimed at assessing the diagnostic gain of this new type of pulse sequences in intrinsic spinal cord conditions. Therefore, we acquired TSE and conventional SE sequences, consequently, in 36 patients with intrinsic spinal cord conditions, which were apparent on T2-weighted images, and then compared the sensitivity, contrast resolution, and depiction of lesion margins and extent in both acquisition techniques. The results of our study follow: even though all lesions were identified with both techniques, contrast resolution was higher with TSE than with conventional SE images. Lesion margins and extent were substantially equally depicted with both techniques. Finally, TSE sequences had the same, and sometimes even higher, diagnostic yield than conventional SE sequences: therefore, TSE can be considered the sequence of choice in the study of intrinsic spinal cord conditions.