LAUSR

MRI-only detected lesions are still a challenge for the radiologists. These lesions are difficult to identify on second look ultrasound due to the displacement of the lesion with regard to position changes between prone MRI and supine US examinations which frequently cause distortion of the lesion particularly in non mass enhancement findings. The review of Nakashima et al. [1] has a great value in defining the challenges and solutions for these MRI-only detected lesions as well as recognition of MRI/US fusion imaging, otherwise US volume navigation technique (US-VNT) coregistered examination. I have some comments in the quotidian implementation of the system. First, we used VNT in MRI-only detected lesions and showed its effectiveness as a guidance for a 14G core needle biopsy even in cases where a distinct lesion was not detected on MRI/US fusion imaging compared to the studies reviewed by Nakashima et al. [1, 2]. We had 22 patients with 26 lesions (34%) in the study where second look US examination and third look MRI/US fusion imaging did not show any US findings, but some subtle changes that cannot be defined as a finding in nine of the cases. The biopsy of the corresponding location of these MRI only detected lesions without any third look MRI/US fusion imaging findings using 14G cut needle biopsy resulted in 30.8% malignancy detection rate. Our study showed that MRI/US fusion imaging otherwise US-VNT can be used as a guiding method in the absence of any US findings despite the fusion imaging [2]. To our knowledge, it is the only study where MRI/ US fusion imaging was used as a guiding method without any distinct US findings and we believe that it is a reliable alternative method to MRI guided biopsy in such undetectable lesion with US-VNT. Second, MRI/US fusion imaging otherwise US-VNT requires an additional supine contrast enhanced MRI examination as co-registration of a standard prone breast MRI with real time supine US examination is not possible. A novice contrast enhanced supine breast MR imaging is fundamental for this co-registration. The patient has to be positioned in the magnet similar to the position on the US examination bed to obtain a successful fusion imaging. Although it is a short time examination, this additional supine MRI of the breast will necessitate another contrast media administration and occupation of the magnet for the second time. To avoid multiple contrast media administrations and scans we tried to add a supplemental supine breast MRI sequence at the end of the primary standard prone dynamic contrast enhanced MRI (DCE-MRI) examination where the initial lesion was detected [3]. Before the acquisition of this supplemental T1 weighted examination the fiduciary markers that will aid for the co-registration process can be placed on the breast. We have examined 45 lesions of 42 patients and were able to identify 44 of the lesions (97.8%) on the supine MRI images acquired following a standard prone DCE-MRI protocol. This supplemental supine MRI procedure takes no longer than 4 min and acquires sufficient data set for MRI/US fusion imaging without administering further contrast media [3]. We believe that this method can help reduce the repetitive contrast media injections and acquire already on hand images for such fusion techniques and also can improve orientation of the physicians in locating MRI detected lesions.