246 research outputs found
A Simple Penalty that Encourages Local Invertibility and Considers Sliding Effects for Respiratory Motion
Nonrigid image registration is a key tool in medical imaging. Because of high degrees of freedom in nonrigid transforms,
there have been many efforts to regularize the deformation based on some reasonable assumptions. Especially, motion
invertibility and local tissue rigidity have been investigated as reasonable priors in image registration. There have been
several papers on exploiting each constraint separately.
These constraints are reasonable in respiratory motion estimation because breathing motion is invertible and there are
some rigid structures such as bones. Using both constraints seems very attractive in respiratory motion registration since
using invertibility prior alone usually causes bone warping in ribs. Using rigidity prior seems natural and straightforward.
However, the “sliding effect” near the interface between rib cage and diaphragm makes problem harder because it is not
locally invertible. In this area, invertibility and rigidity priors have opposite forces.
Recently, we proposed a simple piecewise quadratic penalty that encourages the local invertibility of motions. In this
work we relax this penalty function by using a Geman-type function that allows the deformation to be piecewise smooth
instead of globally smooth. This allows the deformation to be discontinuous in the area of the interface between rib
cage and diaphragm. With some small sacrifice of regularity, we could achieve more realistic discontinuous motion near
diaphragm, better data fitting error as well as less bone warping. We applied this Geman-type function penalty only to the
x- and y-direction partial derivatives of the z-direction deformation to address the sliding effect. 192 × 128 × 128 3D CT
inhale and exhale images of a real patient were used to show the benefits of this new penalty method.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85922/1/Fessler238.pd
Use and uncertainties of mutual information for computed tomography/magnetic resonance (CT/MR) registration post permanent implant of the prostate
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134844/1/mp1920.pd
Dose reconstruction in deforming lung anatomy: Dose grid size effects and clinical implications
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135133/1/mp9749.pd
How extensive of a 4D dataset is needed to estimate cumulative dose distribution plan evaluation metrics in conformal lung therapy?a)
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134757/1/mp0624.pd
Monte Carlo-based lung cancer treatment planning incorporating PET-defined target volumes
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135172/1/acm20065.pd
Dust in an extremely metal-poor galaxy: mid-infrared observations of SBS 0335-052
The metal deficient (Z = Z_sun/41) Blue Compact Dwarf Galaxy (BCD) SBS
0335-052 was observed with ISOCAM between 5 and 17 mic. With a L_12mic/L_B
ratio of 2.15, the galaxy is unexpectedly bright in the mid-infrared for such a
low-metallicity object. The mid-infrared spectrum shows no sign of the
Unidentified Infrared Bands, which we interpret as an effect of the destruction
of their carriers by the very high UV energy density in SBS 0335-052. The
spectral energy distribution (SED) is dominated by a very strong continuum
which makes the ionic lines of [SIV] and [NeIII] very weak. From 5 to 17 mic,
the SED can be fitted with a grey-body spectrum, modified by an extinction law
similar to that observed toward the Galactic Center, with an optical depth of
A_V~19-21 mag. Such a large optical depth implies that a large fraction (as
much as ~ 75%) of the current star-formation activity in SBS 0335-052 is hidden
by dust with a mass between 3x10^3 M_sun and 5x10^5 M_sun. Silicate grains are
present as silicate extinction bands at 9.7 and 18 mic can account for the
unusual shape of the MIR spectrum of SBS 0335-052. It is remarkable that such a
nearly primordial environment contains as much dust as galaxies which are 10
times more metal-rich. If the hidden star formation in SBS 0335-052 is typical
of young galaxies at high redshifts, then the cosmic star formation rate
derived from UV/optical fluxes would be underestimated.Comment: 13 pages, 4 figures, requires aaspp4.sty, accepted in Ap
Stereotactic Body Radiation Therapy for Primary and Metastatic Liver Tumors
AbstractOBJECTIVES: The full potential of stereotactic body radiation therapy (SBRT), in the treatment of unresectable intrahepatic malignancies, has yet to be realized as our experience is still limited. Thus, we evaluated SBRT outcomes for primary and metastatic liver tumors, with the goal of identifying factors that may aid in optimization of therapy. METHODS: From2005 to 2010, 62 patients with 106 primary and metastatic liver tumors were treated with SBRT to a median biologic effective dose (BED) of 100 Gy (42.6-180). The majority of patients received either three (47%) or five fractions (48%). Median gross tumor volume (GTV) was 8.8 cm3 (0.2-222.4). RESULTS: With a median followup of 18 months (0.46-46.8), freedom from local progression (FFLP) was observed in 97 of 106 treated tumors, with 1- and 2-year FFLP rates of 93% and 82%. Median overall survival (OS) for all patients was 25.2 months, with 1- and 2-year OS of 81%and 52%. Neither BED nor GTV significantly predicted for FFLP. Local failure was associated with a higher risk of death [hazard ratio (HR) = 5.1, P = .0007]. One Child-Pugh Class B patient developed radiationinduced liver disease. There were no other significant toxicities. CONCLUSIONS: SBRT provides excellent local control for both primary and metastatic liver lesions with minimal toxicity. Future studies should focus on appropriate selection of patients and on careful assessment of liver function to maximize both the safety and efficacy of treatment
SafetyNet: streamlining and automating QA in radiotherapy
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135420/1/acm20387-sup-0002.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135420/2/acm20387.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135420/3/acm20387-sup-0003.pd
Evaluation des besoins et des activités. Problématique de leur localisation. Critères, méthodes et applications pour la révision des plans de secteur. Problématique pour la mise en oeuvre des zones d'aménagement différé
Rapport final de la subvention 2001, Cinquième Volum
Community-based in situ simulation: bringing simulation to the masses
Simulation-based methods are regularly used to train inter-professional groups of healthcare providers at academic medical centers (AMC). These techniques are used less frequently in community hospitals. Bringing in-situ simulation (ISS) from AMCs to community sites is an approach that holds promise for addressing this disparity. This type of programming allows academic center faculty to freely share their expertise with community site providers. By creating meaningful partnerships community-based ISS facilitates the communication of best practices, distribution of up to date policies, and education/training. It also provides an opportunity for system testing at the community sites. In this article, we illustrate the process of implementing an outreach ISS program at community sites by presenting four exemplar programs. Using these exemplars as a springboard for discussion, we outline key lessons learned discuss barriers we encountered, and provide a framework that can be used to create similar simulation programs and partnerships. It is our hope that this discussion will serve as a foundation for those wishing to implement community-based, outreach ISS
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