Arterial Phase with CAIPIRINHA-Dixon-TWIST (CDT)-Volume-Interpolated Breath-Hold Examination (VIBE) in Detecting Hepatic Metastases.

PURPOSE: To evaluate lesion enhancement performance of Multi-Arterial CAIPIRINHA-Dixon-TWIST-Volume-Interpolated Breath-Hold Examination (MA-CDT-VIBE) for the detection of hepatic metastases. MATERIALS AND METHODS: Thirty-one patients with suspicious hepatic metastases were enrolled in this retrospective study. Two independent radiologists scored visualization of each lesion on a scale of 1 (poor visualization) to 11 (excellent visualization) on 11 sets of images. These included 6 hepatic arterial sub-phases acquired in one breath-hold, 1 series of the mean of 6 hepatic arterial sub-phases, 3 subtracted arterial sub-phases, and 1 portal venous phase. The phases with good (score 8-10) and excellent (score 11) lesion visualization were identified, and the number of lesions seen on each of these phases was compared to the number of lesions that was seen best on the equivalent-to-conventional single arterial phase as well as to those that were see best on the mean of 6 hepatic arterial sub-phases. Inter-reader agreement was also calculated. RESULTS: The MA-CDT-VIBE was successfully acquired in 25 patients with hypervascular metastases (96 lesions) and 6 patients with hypovascular metastases (13 lesions). In case of hypervascular metastases, the 6th/6 arterial sub-phase had excellent lesion visualization (sore of 11) in 56 and 44 lesions for the 2 readers, respectively. Good lesion visualization (score of 8-10) was recorded in 5th/6 arterial subphases, in 81 and 67 lesions for the 2 readers, respectively. In case of hypovascular metastases, the portal venous phase had excellent lesion visualization (sore of 11) in all 13 lesions for the 2 readers. Good lesion visualization (score of 8-10) was recorded in 12 and 13 lesions on the 5th/6 and 6th/6 arterial subphases, respectively. More hypervascular lesions scored good (score of 8-10) and excellent (score of 11) on the 5th/6 and 6th/6 phases of MA-CDT-VIBE compared with the equivalent-to-conventional single arterial phase (3rd/6) and the set with mean of 6 hepatic arterial sub-phases. The results were statistically significant (t test, P<.0001). Inter-reader agreement was good for hypervascular lesions (kappa=0.627, P<.0001) and excellent for hypovascular lesions (kappa=1.0, P<.0001), respectively. CONCLUSIONS: The MA-CDT-VIBE improves lesion conspicuity by providing a wide observation window for hypervascular lesions. For hypovascular lesions, the advantage of multiple arterial sub-phases over the portal venous phase is not apparent.

Improved Detection of Recurrent Hepatocellular Carcinomas in Arterial Phase With CAIPIRINHA-Dixon-TWIST-Volumetric Interpolated Breath-Hold Examination.

PURPOSE: The aim of this study was to assess the detection rate of recurrent hepatocellular carcinoma (HCC) in arterial phase using multiarterial CAIPIRINHA-Dixon-TWIST-VIBE (MA-CDT-VIBE). MATERIALS AND METHODS: Fifty-eight patients with possible recurrence of HCC were retrospectively included in this cohort. Patients were scanned with a prototype dynamic contrast-enhanced breath-hold CDT-VIBE sequence, which included 6 arterial subphases with a temporal resolution of 2.64 seconds on a 3 T scanner. Absence and presence of recurrence was documented by consensus of 2 experienced radiologists using magnetic resonance imaging multiphase imaging and follow-up evaluation. The third of 6 arterial subphases was considered the equivalent-to-conventional single arterial phase from the contrast bolus timing perspective. The detection rate of recurrent HCCs in arterial phase by another 2 independent experienced readers was compared for all 6 arterial subphases of MA-CDT-VIBE and the equivalent-to-conventional single arterial phase. Interreader agreement was also calculated. RESULTS: Of the 55 patients reviewed, 46 patients (201 lesions) had recurrent HCC and 9 patients had no recurrence. There was an excellent interreader agreement for both MA-CDT-VIBE (κ = 1.000, P < 0.0001) and the equivalent-to-conventional single arterial phase (κ = 0.850, P < 0.0001). MA-CDT-VIBE showed the detection rate of 100% for all lesions with the diameter of less than 1 cm, 1 to 2 cm, and more than 2 cm. The equivalent-to-conventional single arterial phase resulted in the detection rate of 81.1% and 83.1% for all recurrent HCCs by the 2 readers, respectively, with 78.7% and 83.6% for lesions measuring less than 1 cm, 79.2% and 81.2% for lesions measuring 1 to 2 cm, and 89.7% and 87.2% for lesions measuring more than 2 cm. CONCLUSIONS: Compared with the equivalent-to-conventional single arterial phase, MA-CDT-VIBE with 6 arterial subphases demonstrated higher detection rate of recurrent HCCs in arterial phase and provided a wider arterial observation window, especially for recurrent HCCs less than 2 cm in diameter.

Integrated Shimming Improves Lesion Detection in Whole-Body Diffusion-Weighted Examinations of Patients With Plasma Disorder at 3 T.

OBJECTIVE: The purpose of this study was to evaluate the feasibility of using integrated slice-by-slice shimming (iShim) for improving the image quality of whole-body diffusion-weighted imaging (WBDWI) in patients with plasma disorder at 3 T by comparing to WBDWI using a conventional shimming (3-dimensional [3D] shim) adjustment of each body station. MATERIALS AND METHODS: After approval by the local institutional review board, 2 healthy volunteers and 29 suspected patients with plasma disorder participated in this cross-sectional study. All participants were scanned by the same WBDWI protocol with iShim and 3D shim, consecutively. Body region-dependent signal-to-noise ratio (SNR) between iShim and 3D shim was compared in 2 volunteer scans. Body region-dependent shimming parameters, image quality, the number of suspicious lesions, and the agreement of apparent diffusion coefficient values were compared in 29 suspected patients with plasma disorder. Signal integrity between images acquired at adjacent bed positions, in sagittal reformats, which may be impaired by susceptibility effects, was assessed using an image quality score between 1 (worst) and 4 (best). Spatial displacement of diffusion-weighted images was calculated using a 3D turbo spin-echo acquisition as a reference. RESULTS: For the SNR comparison in 2 volunteers, the iShim technique yielded 8-fold and 15-fold SNR improvements in the neck region (P < 0.05), while keeping a comparable SNR (ratio, 1 ± 0.2) performance in other body regions (P > 0.05). In the patient group, the mean score of image quality for iShim WBDWI was 3.69, and 76% of the cases showed unimpaired whole-body signal integrity, while in 3D shim WBDWI images, the mean image quality score was 1.93, and only 7% of the cases showed unimpaired whole-body signal integrity. The spatial displacement of diffusion-weighted images was on average reduced from 7.21 mm (3D shim) to 3.89 mm by using the iShim technique.Twenty-four of 72 suspicious lesions visible in iShim images of the neck region were missed on 3D shim images due to signal loss, while the number of focal lesions in the other body regions was comparable. With the 2 different shimming techniques, the agreement of apparent diffusion coefficient values of lesion and muscle in the head, thorax, abdomen, and pelvis regions was excellent (r > 0.75; P > 0.05), but there was a significant difference in the neck region (P < 0.05). CONCLUSIONS: The iShim technique is an effective method to reduce the negative impact of susceptibility effects at 3 T on whole-body diffusion imaging, as supported by the apparent improvement in signal integrity and spatial alignment, as well as improved SNR in the neck region. Compared with the 3D shim technique, the iShim technique showed improved conspicuous lesion findings in the neck region.

Towards Routine Clinical Use of Radial Stack-of-Stars 3D Gradient-Echo Sequences for Reducing Motion Sensitivity

PURPOSE: To describe how a robust implementation of a radial 3D gradient-echo sequence with stack-of-stars sampling can be achieved, to review the imaging properties of radial acquisitions, and to share the experience from more than 5000 clinical patient scans. MATERIALS AND METHODS: A radial stack-of-stars sequence was implemented and installed on 9 clinical MR systems operating at 1.5 and 3 Tesla. Protocols were designed for various applications in which motion artifacts frequently pose a problem with conventional Cartesian techniques. Radial scans were added to routine examinations without selection of specific patient cohorts. RESULTS: Radial acquisitions show significantly lower sensitivity to motion and allow examinations during free breathing. Elimination of breath-holding reduces failure rates for non-compliant patients and enables imaging at higher resolution. Residual artifacts appear as streaks, which are easy to identify and rarely obscure diagnostic information. The improved robustness comes at the expense of longer scan durations, the requirement for fat suppression, and the nonexistence of a time-to-center value. Care needs to be taken during the configuration of receive coils. CONCLUSION: Routine clinical use of radial stack-of-stars sequences is feasible with current MR systems and may serve as substitute for conventional fat-suppressed T1-weighted protocols in applications where motion is likely to degrade the image quality.