Role of apparent diffusion coefficient values in differentiation between malignant and benign solitary thyroid nodules.

BACKGROUND AND PURPOSE: Accurate imaging characterization of a solitary thyroid nodule has been clearly problematic. The purpose of this study was to evaluate the role of the apparent diffusion coefficient (ADC) values in the differentiation between malignant and benign solitary thyroid nodules. MATERIALS AND METHODS: A prospective study was conducted in 67 consecutive patients with solitary thyroid nodules who underwent diffusion MR imaging of the thyroid gland. Diffusion-weighted MR images were acquired with b factors of 0, 250, and 500 s/mm(2) by using single-shot echo-planar imaging. ADC maps were reconstructed. The ADC values of the solitary thyroid nodules were calculated and correlated with the results of histopathologic examination. Statistical analysis was performed. RESULTS: The mean ADC value of malignant solitary thyroid nodules was 0.73 +/- 0.19 x 10(-3) mm(2)/s and of benign nodules was 1.8 +/- 0.27 x 10(-3) mm(2)/s. The mean ADC values of malignant nodules were significantly lower than those of benign ones (P = .0001). There were no significant differences between the mean ADC values of various malignant thyroid nodules, but there were significant differences between the subtypes of benign thyroid nodules (P = .0001). An ADC value of 0.98 x 10(-3) mm(2)/s was proved as a cutoff value differentiating between benign and malignant nodules, with 97.5%, 91.7%, and 98.9% sensitivity, specificity, and accuracy, respectively. CONCLUSION: The ADC value is a new promising noninvasive imaging approach used for differentiating malignant from benign solitary thyroid nodules.

Hepatic lesions: discrimination of nonsolid, benign lesions from solid, malignant lesions with heavily T2-weighted fast spin-echo MR imaging.

PURPOSE: To determine whether the combined use of heavily and moderately T2-weighted fast spin-echo magnetic resonance (MR) images improves differentiation of non-solid, benign hepatic lesions from solid malignancies. MATERIALS AND METHODS: Three radiologists reviewed moderately (n = 133) and heavily (n = 133) T2-weighted and multiphasic dynamic contrast material-enhanced (n = 93) MR images in 133 patients with proved focal hepatic lesions (95 benign, 38 malignant). The radiologists used a five-point scale to rate their confidence in determination of malignancy. RESULTS: All three reviewers were statistically significantly better able to differentiate small (diameter less than 3 cm; n = 84) benignancies from small malignancies with the combination of moderately and heavily T2-weighted images (area under the receiver operating characteristic curve, 0.99 for each reader) than with moderately T2-weighted images alone (area, 0.88-0.90; P < .05). Confident diagnoses were rendered in 69 (82%) patients, with 100% accuracy for the combined use of moderately and heavily T2-weighted images. For larger lesions (diameter 3 cm or larger; n = 49), accurate differentiation was possible with moderately T2-weighted images alone. Additional use of multiphasic images did not improve the sensitivity, specificity, or accuracy of image interpretation. CONCLUSION: The combined use of moderately and heavily T2-weighted fast spin-echo MR images improves differentiation of small benign hepatic lesions from small malignant lesions.

Respiratory and postprandial changes in portal flow rate: assessment by phase contrast MR imaging.

The objective of this study was to investigate the variability of several different phase contrast (PC) magnetic resonance techniques and duplex Doppler imaging (DDI) for measuring portal flow rate (PFR) with different patterns of respiration before and after a standard meal. PFR was measured in nine normal volunteers in both fasting and postprandial states, using both 2D and cine PC MR techniques. Two-dimensional PC technique was performed with and without breath-hold (BH). Four different patterns of BH (relaxed maximal inspiration, expiration, Valsalva maneuver, and Müller or reversed Valsalva) were used. Cine PC technique was performed without BH. DDI measurement of PFR was done in the fasting state with relaxed inspiration. PFR measurements made by means of PC MR techniques varied, depending on BH method, and were systematically less than those obtained by DDI. PFR measured during inspiration was significantly less than that measured during expiration and other respiratory maneuvers (P < .03). PFR increased significantly after a meal for PC and Doppler measurements, with a range of mean increases of 24 to 74%. Two-dimensional PC MR imaging techniques yielded differing measurements of PFR, depending on whether they were done with or without BH, as well as on the pattern of BH. PC mean measures of PFR were consistently less than those of DDI. The physiologic inspiratory decreases and postprandial increases of the PFR were evident from 2D and cine PC MRI techniques, as well as with DDI.

Early hepatocellular carcinoma that develops within macroregenerative nodules: growth rate depicted at serial MR imaging.

PURPOSE: To assess by means of magnetic resonance (MR) imaging the growth rate of early hepatocellular carcinoma (HCC) that develops within macroregenerative nodules. MATERIALS AND METHODS: Serial MR imaging was performed in five patients with six macroregenerative nodules that demonstrated a "nodule-within-nodule" pattern (small intranodular focus). The diameter and volume increases of the internal foci at different time intervals were estimated. Average doubling time (DT) was then calculated. RESULTS: The tiny foci within macroregenerative nodules exhibited rapid growth, with average DTs of 29 weeks for diameter and 9.5 weeks for volume. HCC was proved histopathologically in all five patients. CONCLUSION: HCC, which manifests initially as a small focus within a macroregenerative nodule, has the potential for rapid growth. This growth rate should be considered when plans are formulated for follow-up and/or treatment.