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OBJECTIVE. The purpose of our study was to evaluate image quality in a 3D spoiled gradient-recalled echo (SPGR) sequence that was modified to incorporate respiratory navigation to limit the deleterious effects of respiratory motion and to compare it with conventional scanning during breath-holding and free breathing.CONCLUSION. Respiratory navigation of 3D SPGR sequences is technically feasible, and image quality is modestly improved over free breathing acquisitions using conventional 3D SPGR sequences. This may represent a promising imaging alternative for patients who cannot hold their breath.

Our objective was to compare the sensitivity of non-breath-hold T2-weighted fast spin-echo with and without fat suppression, breath-hold T2-weighted fast spin-echo without fat suppression, and spoiled gradient-recalled echo (GRE) MR imaging for detecting hepatic tumors using surgical findings as the standard of reference.Eighteen patients with 36 surgically proven hepatic tumors had non-breath-hold T2-weighted fast spin-echo (6000/117 [TR/effective TE; echo train length, 16) MR imaging with and without fat suppression, breath-hold T2-weighted fast spin-echo MR imaging (2700/105; echo train length, 20), and spoiled GRE images (10.1/1.9; flip angle, 30 degrees) obtained before and after injection of a gadolinium chelate. Images were analyzed separately by two independent readers, with disagreements resolved by consensus reading.Non-breath-hold T2-weighted fast spin-echo MR imaging with and without fat suppression depicted 22 (61%; 95% confidence interval [CI], 43-77%) and 20 (56%; 95% CI, 37-72%) of 36 hepatic tumors, respectively. Breath-hold T2-weighted fast spin-echo imaging allowed detection of 19 (53%; 95% CI, 35-69%) of 36 hepatic tumors. Unenhanced and gadolinium chelate-enhanced spoiled GRE images allowed depiction of 18 (50%; 95% CI, 33-67%) and 29 (81%; 95% CI, 63-91%) of 36 hepatic tumors, respectively. Gadolinium chelate-enhanced spoiled GRE images allowed depiction of significantly more hepatic tumors than any of the other pulse sequences.Gadolinium chelate-enhanced spoiled GRE imaging is more sensitive than T2-weighted MR imaging obtained with a breath-hold or a non-breath-hold technique.

Axial gradient-recalled-echo (GRE) MR images of the shoulder obtained with the arm in external rotation may show a curvilinear or circular low-signal-intensity focus in the superior portion of the glenohumeral joint space that is thought to represent gas within the joint (vacuum phenomenon). This study was performed to determine the prevalence of this finding on GRE MR images of the shoulder to confirm that it represents gas in the joint, and to establish criteria to distinguish it from a true abnormality.We reviewed all external-rotation GRE images of 45 consecutive patients and 10 volunteers for the presence of low-signal-intensity foci and joint effusion. These findings were correlated with findings on corresponding spin-echo and GRE images of the shoulder with the arm in neutral position. MR findings also were correlated with findings on plain radiographs (37 patients) and shoulder CT scans (three patients and five volunteers) and with results of arthroscopy (19 patients).In nine (20%) of 44 patients and in five (50%) of 10 volunteers, axial external-rotation GRE images showed curvilinear or circular low-signal-intensity foci interposed between the opposing glenohumeral articular surfaces at the superior aspect of the glenohumeral joint that were not seen on MR images obtained with the arm in neutral position. In two of three patients and in all five volunteer subjects, CT scans of the shoulder showed a small focus of gas within the joint, corresponding in location to the intraarticular low-signal-intensity focus seen on MR images. Joint effusions were seen on MR images of 15 patients, and none of these images showed intraarticular gas.Circular or linear areas of low signal intensity are frequently seen on GRE MR images of the shoulder obtained with external rotation of the arm and represent small foci of intraarticular gas (vacuum phenomenon). Awareness of this potential pitfall and an understanding of the characteristic appearance and location of this collection of intraarticular gas may help prevent misdiagnosis of intraarticular loose bodies or chondrocalcinosis.

MR imaging is the imaging technique of choice for evaluating ankle tendons and ligaments. Although reformation of three-dimensional Fourier transform (3DFT) gradient-recalled echo (GRE) MR images on an independent console has been evaluated in other joints, little attention has been given to use of this technique for evaluation of the ankle. In this essay, we illustrate the spectrum of normal appearances of the posterior tibial tendon (PTT), flexor digitorum longus tendon, flexor hallucis longus tendon, and plantar calcaneonavicular ligament (PCNL) on 3DFT GRE images. Also, we describe the advantages of evaluating these structures with 3DFT GRE vs spin-echo (SE) MR images, demonstrate the spectrum of abnormal findings seen in these structures on 3DFT GRE MR images in a large clinical series, and show the relationship of the accessory navicular bone to PTT abnormalities.