Contrast agents and temporal resolution in breast MR imaging

The article summarizes the technique of dynamic Gd-enhanced breast magnetic resonance (MR) imaging and the established clinical indications to this examination. The main features of the four different non-selective Gd-chelates today available for contrast-enhanced MR breast imaging are described. Their typical two-compartment (vascular/interstitial) distribution is related to the temporal resolution used for the MR acquisition; the gain in specificity obtained increasing the temporal resolution during the first phase after the contrast intravenous injection (using both, rapid T1-weighted sequences or ultrafast T2*-weighted perfusion imaging) is discussed. Moreover, a survey of new contrast agents is supplied, including a high T1-relaxivity Gd-chelate, blood pool agents, and lymph node targeted agents. In conclusion, future directions are delineated

Dynamic breast magnetic Resonance imaging : effect of changing the region of interest on early enhancement using 2D and 3D techniques

Objective: To assess the effect of changing the region of interest (ROI) on early enhancement (EE) in dynamic breast magnetic resonance (MR) imaging. Methods: We evaluated retrospectively 102 breast lesions: 54 lesions (33 malignancies and 21 benignancies) studied with 2D and 48 lesions (30 and 18, respectively) with 3D gradient-echo dynamic technique (contrast dose 0.1 mmol/kg). Each lesion was postprocessed using 3 different regions of interest (ROIs): small circular ROI on maximal enhancement (SCR); large circular ROI within the lesion (LCR); and irregular ROI by manual contouring (IRR). EE was classified as benign ( 6450%), uncertain (51-89%), or malignant ( 6590%). Results: With 2D, the uncertain EEs were 17% for both SCR and LCR, 33% for IRR (P = 0.008); with 3D, the uncertain EEs were 4%, 15%, and 13%, respectively (SCR versus LCR, P = 0.063). More uncertain EEs were obtained with 2D (17-33%) than with 3D (4-15%), significantly for SCR (P = 0.043) and IRR (P = 0.013). Considering uncertain EEs as positive, sensitivity was 100% for SCR, 91% for LCR, and 82% for IRR (SCR versus IRR, P = 0.031) with 2D, 100%, 97%, and 87%, respectively, with 3D technique, without significant differences; specificity ranged from 71% to 90% with 2D and 61% to 83% with 3D, without significant differences. Conclusion: The type of ROI influences the EE in dynamic breast MR. Using 3D technique with small ROI located on the area of maximal enhancement gives the best results in terms of certainty of the level of EE together with top levels of sensitivity

Three subsequent single doses of gadolinium chelate for brain MR imaging in multiple sclerosis

BACKGROUND AND PURPOSE: A triple-dose (TD) of gadolinium chelate is highly sensitive approach for detecting lesion activity in multiple sclerosis (MS). However, individual TD injections do not provide data on the severity of the pathologic process in a population of lesions, and its clinical use is limited by the cost-benefit considerations. Our aim was to determine whether the use of three subsequent single doses (SD) of a gadolinium chelate in brain MR imaging is useful in detecting MS lesions with different patterns of enhancement. METHODS: In 10 patients, T1-weighted spin-echo images were acquired before and after three intravenous administrations of 0.1 mmol/kg of gadodiamide. RESULTS: In all patients, SD images showed six enhancing lesions; double-dose (DD) images, 13; and TD images, 22. Differences between SD and TD and between DD and TD were significant (P < .018). Six lesions (27%) enhanced with all the three doses; seven (32%), with both DD and TD; and nine (41%), only TD. Proportions of patients with at least one enhancing lesion were, for SD, 10; DD, seven of 10; and TD, nine of 10. In defining active disease in these nine patients, we needed only 19 SDs versus the 30 SDs that would have been needed if individual TD injections were used. CONCLUSION: With three subsequent SD injections, the number of enhancing lesions progressively increases. This approach allows the distinction of three levels of enhancement, and it reduces the amount of contrast agent needed to distinguish patients with active MS from those with nonactive MS

Gadobenate dimeglumine-enhanced MR imaging breast vascular maps: association between invasive cancer and ipsilateral increased vascularity

Purpose: To retrospectively compare three doses of Gd-BOPTA with a standard dose of Gd-DTPA for MR evaluation of breast vessels and to evaluate the accuracy of one-side increased vascularity as an indicator of ipsilateral breast cancer on Gd-BOPTA-enhanced MR images. Methods and Materials: Ninety-five patients with known or suspected breast cancer were randomized to four groups to receive Gd-BOPTA at doses of .05 (n=24), .1 (n=24), or .2 (n=24) mmol/kg or Gd-DTPA at a dose of .1 mmol/kg (n=23). T1-weighted gradient echo images were acquired before and at 2 minutes after intravenous contrast injection. Subtracted images were used to obtain maximum intensity projections (MIPs). A score between 0 (poor) and 3 (extensive) was assigned to the bilateral MIPs of all groups based on vessel number, length and conspicuity. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of one-side increased vascularity in association with ipsilateral malignancy was determined for 69 histologically-confirmed lesions (reference standard) after Gd-BOPTA. Results: Significantly higher mean scores were assigned to the combined Gd-BOPTA groups than to the Gd-DTPA group (P < .044). In patients studied with Gd-BOPTA, histology revealed malignant lesions in 52 patients (invasive ductal, n=45; invasive lobular, n=4; invasive ductal/lobular, n=3) and benign lesions in 17 patients. Two cases of bilateral invasive cancer with symmetric breast vascular maps were excluded to give overall values for sensitivity, specificity, accuracy, PPV and NPV of 88% (44/50), 82% (14/17), 87% (58/67), 94% (44/47) and 70% (14/20), respectively, for one-side increased vascularity as a finding associated with ipsilateral malignancy. Conclusion: Gd-BOPTA is effective for MR evaluation of breast vessels at doses as low as .05 mmol/kg. One-side increased vascularity is an MR finding frequently associated with ipsilateral invasive breast cancer

MR evaluation of coronary stents with navigator echo and breath-hold cine gradient-echo techniques

The aim of this study was to evaluate coronary artery stents with MR. Thirty-eight patients underwent MR imaging 48.1 +/- 6.6 days (range 38-60 days) after placement of 47 coronary stents of 11 different types, using navigator echo (NE) and cine gradient-echo (GE) techniques. For both sequences the low signal artifact was used to localize the stent, whereas the flow-related high signal before and distal to the stent was considered as a patency sign. Exercise electrocardiographic test (EET) had been performed 1-7 days before MR. No adverse event with possible relation to the MR examination was observed. All the stents were recognized as signal void with GE, and all but one with NE. Of the 2 patients with positive EET, the first one, with a stent on the left anterior descending coronary artery, presented low signal distal to the stent at both MR sequences, suggesting dysfunction [60% stenosis at conventional coronary angiography (CCA)]; the second one, with two sequential stents on the right coronary artery, presented lack of signal distal to the stents at both MR sequences, suggesting occlusion (97% stenosis at CCA). For the 44 remaining stents in 36 patients with negative EET, MR high signal before and distal to the stent suggested patency at both sequences. MR seems to be a safe and promising technique for non-invasive evaluation of coronary stents