Search

Introduction Model-driven registration (MDR) is a general approach to remove patient motion in quantitative imaging. In this study, we investigate whether MDR can effectively correct the motion in free-breathing MR renography (MRR). Materials and methods MDR was generalised to linear tracer-kinetic models and implemented using 2D or 3D free-form deformations (FFD) with multi-resolution and gradient descent optimization. MDR was evaluated using a kidney-mimicking digital reference object (DRO) and free-breathing patient data acquired at high temporal resolution in multi-slice 2D (5 patients) and 3D acquisitions (8 patients). Registration accuracy was assessed using comparison to ground truth DRO, calculating the Hausdorff distance (HD) between ground truth masks with segmentations and visual evaluation of dynamic images, signal-time courses and parametric maps (all data). Results DRO data showed that the bias and precision of parameter maps after MDR are indistinguishable from motion-free data. MDR led to reduction in HD (HDunregistered = 9.98 ± 9.76, HDregistered = 1.63 ± 0.49). Visual inspection showed that MDR effectively removed motion effects in the dynamic data, leading to a clear improvement in anatomical delineation on parametric maps and a reduction in motion-induced oscillations on signal-time courses. Discussion MDR provides effective motion correction of MRR in synthetic and patient data. Future work is needed to compare the performance against other more established methods.

Accurate prediction of early treatment response in patients receiving neoadjuvant chemotherapy for breast cancer is essential to provide patients with the best care. Diffusion-weighted magnetic resonance imaging (DWI) provides a novel approach to distinguishing responders from non-responders. This article aims to review the literature regarding the accuracy of DWI in predicting patients who will respond to neoadjuvant chemotherapy at an early stage within their treatment pathway. The initial search yielded 11,171 articles. After careful review, 19 of these articles were found to adhere to the inclusion criteria. Despite the varied research methods and data analysis across the studies, 16 out of 19 of these studies (84%) demonstrated DWI to be an accurate predictor of neoadjuvant chemotherapy response. These results are promising; however, further multi-centre studies with larger sample sizes, homogenous imaging and treatment parameters and formal assessment of pathological response are required to accurately evaluate the use of DWI as an early predictor of neoadjuvant chemotherapy response in patients with breast cancer.

Background Quantification of physiological parameters, including myocardial blood flow (MBF), by perfusion MRI relies on analysis of data that describes temporal variation of relative contrast agent concentration following bolus administration. At doses required for sufficient SNR, signal enhancement cannot be used directly as the relationship between signal intensity (SI) and the resulting concentrations in blood and myocardium is non-linear. Proposed solutions to this include separation of the AIF and myocardial data acquisition, or model based non-linearity correction.

The introduction of fast clinical imaging techniques enables the dynamic sampling of contrast agent kinetics. The quantity of data generated by such techniques demands the application of automated analysis tools to provide objective assessments of contrast washin/washout characteristics across an entire image. Using a simple compartmental model, the washin/washout characteristics may be defined in terms of a biexponential function. Curve fitting to this nonlinear function may be approached using a nonlinear least squares technique. We demonstrate an alternative technique, simplex minimization, to be more robust in a comparative study using Monte Carlo simulation. The application of the technique is illustrated by pixel-by-pixel analysis of dynamic data obtained from a patient with primary carcinoma of the breast.

The limits of the spatial resolution achievable on a standard GE Signa 1.5-T imaging machine have been explored by interfacing a 12-cm-diameter local gradient set to such a system. Using a range of purpose-built radio-frequency (RF) coils, 3D gradient echo images with a spatial resolution of 100×100×500 µ have been routinely obtained on the finger. Also produced were 100×200×500 µ, resolution angiograms of the finger detailing submillimeter vessels, with a velocity encoding of 6 cm s−1. High-resolution fat/water suppressed images and isotropic data sets with a resolution of 170 µ are also demonstrated. With regard to the investigation of the mechanics of the human finger, isotropic data sets are desirable if accurate segmentation is to be implemented. A preliminary study illustrating the potential for producing a magnetic-resonance-based computer simulation of the mechanics of the human finger shows the distal interphalangeal joint extended and then in flexion.