MB-guided biopsy using a T2-weighted single-shot zoom imaging sequence (Local Look technique)

The purpose of this study was to demonstrate the utility of a T2-weighted s ingle shot turbo spin-echo technique - the so-called "Local Look" (LoLo) an d more recently renamed "Zoom Imaging" technique - for MB-guided percutaneo us interventions. We performed 28 procedures on 22 patients using a 1.5-T s ystem for MR guidance, All procedures were controlled with the LoLo techniq ue, which acquires Ta-weighted images in 600 msec, This is achieved by usin g a small held of view (250 x 125 mm) along with a maximum echo train lengt h, the so-called "single shot method." To prevent backfolding artifacts, th e 90 degrees and 180 degrees pulses were oriented orthogonally to each othe r. Because signal is created only in the region in which the pulses overlap , no backfolding can occur from outside this area. Half of the biopsies wer e additionally monitored using a fast gradient-echo sequence, which was com pared with the LoLo technique. All of the procedures were technically succe ssful, and there were no procedural complications, The LoLo technique produ ced images that had good contrast between the lesion and the needle artifac t, and the artifact size was smaller than that produced by the gradient-ech o technique. Subjective judgment of the ability to accurately delineate the needle tip indicated that the LoLo technique was either superior to (73%) or equal to (27%) the gradient-echo sequence in all cases. The LoLo techniq ue is an accurate and effective method for PW guidance of percutaneous proc edures, because it shows good lesion contrast and small needle artifacts. T he additional use of a gradient-echo sequence during the procedure planning stage is advisable in more difficult cases, particularly when adjacent blo od vessels are a concern. Monitoring of the needle tip is best performed wi th the LoLo technique.