Paul Calderon

General Electric, Fairfield, California, United States

Are you Paul Calderon?

Claim your profile

Publications (4)8.13 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To deploy clinically, a combined parallel imaging compressed sensing method with coil compression that achieves a rapid image reconstruction, and assess its clinical performance in contrast-enhanced abdominal pediatric MRI. With Institutional Review Board approval and informed patient consent/assent, 29 consecutive pediatric patients were recruited. Dynamic contrast-enhanced MRI was acquired on a 3 Tesla scanner using a dedicated 32-channel pediatric coil and a three-dimensional SPGR sequence, with pseudo-random undersampling at a high acceleration (R = 7.2). Undersampled data were reconstructed with three methods: a traditional parallel imaging method and a combined parallel imaging compressed sensing method with and without coil compression. The three sets of images were evaluated independently and blindly by two radiologists at one siting, for overall image quality and delineation of anatomical structures. Wilcoxon tests were performed to test the hypothesis that there was no significant difference in the evaluations, and interobserver agreement was analyzed. Fast reconstruction with coil compression did not deteriorate image quality. The mean score of structural delineation of the fast reconstruction was 4.1 on a 5-point scale, significantly better (P < 0.05) than traditional parallel imaging (mean score 3.1). Fair to substantial interobserver agreement was reached in structural delineation assessment. A fast combined parallel imaging compressed sensing method is feasible in a pediatric clinical setting. Preliminary results suggest it may improve structural delineation over parallel imaging.J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 10/2013; · 2.57 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A 16-channel receive-only, closely fitted array coil is described and tested in vivo for bilateral breast imaging at 3 T. The primary purpose of this coil is to provide high signal-to-noise ratio and parallel imaging acceleration in two directions for breast MRI. Circular coil elements (7.5-cm diameter) were placed on a closed "cup-shaped" platform, and nearest neighbor coils were decoupled through geometric overlap. Comparisons were made between the 16-channel custom coil and a commercially available 8-channel coil. SENSitivity Encoding (SENSE) parallel imaging noise amplification (g-factor) was evaluated in phantom scans. In healthy volunteers, we compared signal-to-noise ratio, parallel imaging in one and two directions, Autocalibrating Reconstruction for Cartesian sampling (ARC) g-factor, and high spatial resolution imaging. When compared with a commercially available 8-channel coil, the 16-channel custom coil shows 3.6× higher mean signal-to-noise ratio in the breast and higher quality accelerated images. In patients, the 16-channel custom coil has facilitated high-quality, high-resolution images with bidirectional acceleration of R = 6.3.
    Magnetic Resonance in Medicine 02/2011; 66(1):281-9. · 3.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report metabolic images of (13)C, following injection of a bolus of hyperpolarized [1-(13)C] pyruvate in a live rat. The data were acquired on a clinical scanner, using custom coils for volume transmission and array reception. Proton blocking of all carbon resonators enabled proton anatomic imaging with the system body coil, to allow for registration of anatomic and metabolic images, for which good correlation was achieved, with some anatomic features (kidney and heart) clearly visible in a carbon image, without reference to the corresponding proton image. Parallel imaging with sensitivity encoding was used to increase the spatial resolution in the SI direction of the rat. The signal to noise ratio in was in some instances unexpectedly high in the parallel images; variability of the polarization among different trials, plus partial volume effects, are noted as a possible cause of this.
    Journal of Magnetic Resonance 01/2011; 208(1):171-7. · 2.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Introduction and Background: NMR of low gamma nuclei in prostate has focussed mostly on phosphorus (1, 2); but with the advent of technology for hyperpolarization of isotopically enriched metabolites (3), carbon is now also feasible. We therefore report development of an endo-rectal dual tuned carbon-proton receive-only antenna for human prostate at 3.0 T, intended particularly for studies with hyperpolarization, but also affording in the same exam conventional proton images and spectra of diagnostic quality. The device comprises separate radiofrequency receiver coils for each of its two channels, each coil with an active pin diode circuit for blocking an external transmitter at its own operating frequency, as well a passive block at the operating frequency of its neighbor coil. The mechanical body (cf Figs 1a and 1b) is of solid delrin, for re-usability and to minimize susceptibility effects (4). A novel circuit layout minimizes extraneous losses by placing all matching and decoupling components proximal to the actual receive coils, so that sections of unmatched transmission line are altogether avoided. Aside from the passive parallel trap for protons, the carbon circuit (Figs 1c and 1d) is a conventional receive-only surface coil design, with shunt match and pin-diode activated trap for transmit blocking. The proton circuit on the other hand (Figs 1e and 1f), uses series match with unconventional inductive imbalance, for the purpose of maximizing the value of the active trap inductor, which would be too small with coventional shunt matching. Results: Figure 2 shows network analysis of the device, showing good impedance matching at each frequency, and good isolation (> -22dB) between the channels, despite the parallelism and proximity of the coils. Sample images and spectra (from phantoms) were acquired on GE Signa scanners, and are shown in Figs. 3 and 4; for the proton images, excitation was by means of the normal system body coil; for carbon, a special bore-insertable volume resonator was used for excitation.