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  • Küçük Resim
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    Effect of region of interest on interobserver variance in apparent diffusion coefficient measures
    (Amer Soc Neuroradiology, 2004) Bilgili, Y; Unal, B
    BACKGROUND AND PURPOSE: Apparent diffusion coefficient (ADC) values derived from diffusion-weighted MR imaging are useful measurements for assessment of cellular alterations in pathologic conditions of the brain. In this study, two radiologists independently quantitated ADCs and region-of interest sizes in prespecified locations of human brain to test interobserver ADC variance and the effect of varying ROI sizes on ADC differences. METHODS: Twenty-seven patients with normal MR findings underwent diffusion-weighted imaging (b value = 1000 s/mm(2)) on a 1.5-T system. Two radiologists independently placed two ROI areas of 22 +/- 5 mm(2) and 62 +/- 6 mm(2) (former area inside the latter area) at different sites of the brain (centrum semiovale, frontal white matter, nucleus caudatus, putamen, thalamus, substantia nigra, red nucleus, and pons) from trace images. Differences in ADC measurement obtained from each region of the brain for each radiologist and the size of each ROI were compared statistically. RESULTS: Mean ADC of prespecified areas of brain ranged between 0.673 and 0.818 mm(2)/s x 10(-3). Interobserver variance was significant in some of the specified areas (centrum semiovale, frontal white matter, pons, substantia nigra, and red nucleus). Varying ROI sizes at the pons, substantia nigra, and red nucleus yielded statistically different ADC values. CONCLUSION. ADC values are found to be unreliable for use in assessing brain disease in some specified areas of the brain owing to interobserver variance and different ROI sizes.
  • Küçük Resim
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    Evaluation of differences between observers and automatic-manual measurements in calculation of Doppler parameters
    (Wiley, 2004) Unal, B; Bagcier, S; Simsir, I; Bilgili, Y; Kara, S
    Objective. We aimed to search for differences between observers and automatic and manual measurements in calculations of Doppler parameters. Methods. The middle cerebral artery (MCA), central retinal artery, ophthalmic artery (OA), common carotid artery (CCA), vertebral artery (VA), popliteal artery (PA), interlobar renal artery (IRA), and arcuate renal artery (ARA) were evaluated in 20 healthy subjects bilaterally Peak systolic velocity (PSV), end-diastolic velocity (EDV), time-averaged maximum velocity (TAMAX), resistive index (RI), and pulsatility index (Pi) were measured from the same spectrum manually by 3 observers and automatically. Results of 4 measurements were compared by analysis of variance and Pearson tests. Results. The comparison of the 4 measurements revealed significant differences for most parameters except TAMAX of the OA, VA, and ARA and PSV EDV and PI of the PA. An automatic calculator yielded lower PSV, RI, and PI values (except the MCA and PA) and higher EDV values compared with manual measurements. The magnitudes of difference were in the range of 1% to 16% for velocities and 4% to 14% for RI and PI. The means of difference were 3.185 cm/s for PSV of the CCA and 0.054 for RI of the IRA. Correlation was high for PSV, EDV, and TAMAX in all arteries (except TAMAX of PA) and relatively low for PI and RI in most of the arteries. Conclusions. Although our study was performed on healthy subjects, our results showed that, in most cases, readers and the automatic approach disagreed on evaluation of Doppler parameters. This may be important in preventing false diagnoses in cases with Doppler values close to upper limits and may necessitate establishment of new limits for each method.