Objective: To compare the effects of metal artefacts and acquisition time among slice encoding for metal artefact correction (SEMAC), SEMAC with dual-source parallel radiofrequency (SEMAC-DSPRF) transmission and fast spin echo (FSE) images using 3.0-T MRI. Methods: The signal-to-noise ratio (SNR) was calculated in a phantom study using a pedicle screw. A total of 16 patients who underwent spinal surgery using pedicle screws were included in the clinical study. T 1 weighted FSE, SEMAC and SEMAC-DSPRF images were obtained. Four imaging findings (visibility of the dural sac, neural foramens, bone-implant interface and overall artefacts) were evaluated by using five-point scales independently by two observers. The mean scan time was recorded. Results: The mean SNR was 71.2, 25.7 and 28.4 for FSE, SEMAC and SEMAC-DSPRF images, respectively. FSE images were ranked lower than SEMAC and SEMAC-DSPRF images, and ranking of SEMAC and SEMAC-DSPRF images did not differ statistically for all four imaging findings. The mean scan time was 9 min 51 s and 6 min 31 s for SEMAC and SEMAC-DSPRF images, respectively. Conclusion: SEMAC can reduce metallic artefacts and improve the visualisation of anatomical structures around metal implants. An additional DSPRF technique can reduce the acquisition time of SEMAC images without the loss of SNR and image quality. Advances in knowledge: This study demonstrates that the use of the DSPRF transmission technique can reduce the acquisition time of SEMAC images without loss of image quality in patients with metal implants.Metal implants are commonly used in surgical procedures to fixate fractures, replace damaged joints or immobilise joints. However, many kinds of local complications associated with metal implants can occur. They include mechanical aseptic loosening, prosthetic or periprosthetic fracture, dislocation, superficial and deep infections, heterotopic bone formation and osteolysis. Such complications are a common source of patient morbidity and often necessitate revision surgery.MRI is a commonly used imaging modality for musculoskeletal imaging because of its good, soft-tissue contrast. However, metal artefacts limit the usefulness of MRI for evaluation of disease in the presence of metal. Artefacts on MR images obtained in patients with metallic implants are produced by large differences between the magnetic properties of human tissues and those of the implanted metals. Differences in the magnetic susceptibilities of adjacent tissues and implants create local magnetic field inhomogeneities, altering the phase and frequency of local spins [1,2].Much less severe artefacts are produced by implants made of titanium alloy than ferromagnetic implants made of stainless steel. In addition, metal artefacts may generally be decreased either by choosing a small voxel size, using a short echo time (T E ) or short interecho interval, or by increasing the sampling bandwidth [3]. Recently, the three-dimensional MRI technique, slice encoding for metal artefact correction (SEMAC), was developed [4]...

Although radiation therapy (RT) plays an important role in the palliation of localized bone metastases, there is no consensus on a reliable method for evaluating treatment response. Therefore, we retrospectively evaluated the potential of magnetic resonance imaging (MRI) using apparent diffusion coefficient (ADC) maps and conventional images in whole-tumor volumetric analysis of texture features for assessing treatment response after RT. For this purpose, 28 patients who received RT for osteolytic bone metastasis and underwent both pre- and post-RT MRI were enrolled. Volumetric ADC histograms and conventional parameters were compared. Cox regression analyses were used to determine whether the change ratio in these parameters was associated with local disease progression-free survival (LDPFS). The ADCmaximum, ADCmean, ADCmedian, ADCSD, maximum diameter, and volume of the target lesions after RT significantly increased. Change ratios of ADCmean < 1.41, tumor diameter ≥ 1.17, and tumor volume ≥ 1.55 were significant predictors of poor LDPFS. Whole-tumor volumetric ADC analysis might be utilized for monitoring patient response to RT and potentially useful in predicting clinical outcomes.

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