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  • Siebers, J  (5)
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  • 1
    Online Resource
    Online Resource
    TH‐A‐217BCD‐04: Accuracy of Dual‐Energy CT Photon Cross‐Section Mapping Using a Non‐Separable Two Parameter Cross‐Section Model
    Wiley ; 2012
    In:  Medical Physics Vol. 39, No. 6Part29 ( 2012-06), p. 3989-3989
    Details
    In: Medical Physics, Wiley, Vol. 39, No. 6Part29 ( 2012-06), p. 3989-3989
    Abstract: Purpose: To quantify the achievable accuracy in estimating photon radiological quantities in the 20‐1000 keV range from idealized dual‐energy CT measurements using a modified non‐separable two‐parameter cross section model. Methods: The parametric fit model (PFM) [Med Phys 33:4115 2006] is modified based on method of Torikoshi et al [Phys Med Biol 48:673 2003] , yielding a modified parametric fit model (mPFM) to describe attenuation coefficients by the sum of individual interaction cross‐sections. Cross‐sections are estimated as products of power functions of energy (E) and atomic number (Z), the Klein‐Nishina cross section, and slowly varying tables of correction factors to account for residual errors, F(E,Z) and G(E,Z), correcting the photoelectric and scattering processes respectively. For mixtures and compounds, each pair of dual energy measurements yields a pair of non‐separable nonlinear equations in two unknowns, effective atomic number (Z*) and electron density (ρe*) that can be solved iteratively. For mixtures describing the range of biological tissue compositions, the accuracy of the mPFM was compared to a previously described [Med Phys 33:4115 2006] basis vector model (BVM). Results: The mean percent absolute error for mPFM of linear attenuation coefficient, photoelectric interaction coefficient, and energy absorption coefficient of five mixtures and compounds are 0.03%–0.17%, 1.10%–6.03%, and 0.2%– 1.19%, compared to 0.02%–0.15%, 0.44%–11.32%, and 0.11%–1.57% for BVM, compared 0.6%–2.2%, 10.8%–22.4% and 5%–10% for PFM over the 20‐1000 keV range. mPFM reduces maximum errors to 0.15% compared to 4.49% for BVM for fluorine‐based tissue. Conclusions: mPFM improves accuracy of photon cross‐section compared to PFM. BVM shows greater accuracy than mPFM for all tested tissue except for Teflon. mPFM also has the potential to extend DECT to computation of charged particle radiological quantities. Supported by Grant R01‐CA149305 and P01‐CA‐ 11602
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Article
    DOI: 10.1118/1.4736275
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 188780-4
    detail.hit.zdb_id: 1466421-5
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  • 2
    Online Resource
    Online Resource
    TU‐E‐141‐02: Coverage‐Based Treatment Planning to Accommodate Deformable Organ Variations in Prostate Cancer Treatment
    Wiley ; 2013
    In:  Medical Physics Vol. 40, No. 6Part27 ( 2013-06), p. 447-447
    Details
    In: Medical Physics, Wiley, Vol. 40, No. 6Part27 ( 2013-06), p. 447-447
    Abstract: Purpose: To (1) investigate the dosimetric impact of interfraction deformable organ motion for high‐risk prostate cancer treatments and (2) compare two coverage‐based planning (CP) techniques with the fixed margin‐based planning (FM). Methods: 19 patients with 8–13 prostate CT images were used to model interfraction deformable organ changes using principal component analysis (PCA). Displacement vector fields (DVFs) that map from each of the 8–13 images to the reference image were analyzed with PCA to determine the dominant eigenmodes, which were then used to predict the synthetic patient geometries for virtual treatment course simulation. For each patient, an intensity modulated radiation therapy (IMRT) plan with zero PTV margin on target structures (CTVprostate and CTV seminalVesicles ) was created, then evaluated by simulating 1000 30‐fraction virtual treatment courses. Each fraction was prostate centroid aligned. Probabilistic metrics, including 5% and 95% percentile DVHs (pDVH) and TCP/NTCP distributions, were computed. Patients whose D98 failed to achieve 95% coverage probability objective D 98,95 〉 =78Gy (CTV prostate ) or D 98,95 〉 =66Gy (CTV seminalVesicles ) were replanned using (1) FM (PTV prostate = CTV prostate + 5mm, PTV seminalVesicles = CTV seminalVesicles + 8mm), (2) CP OM which optimized uniform margins for CTV prostate and CTV seminalVesicles to meet the CP objective, and (3) CP COP which directly optimized coverage‐based objectives for all structures of interest. Results: For zero‐PTV‐margin plans, 0/19 patients satisfied objective D 98,95 for both CTV prostate and CTV seminalVesicles . The selected margins used in FM failed to ensure target coverage for 8/19 patients. 11 CP OM plans and 8 CP COP plans were favored over the other plans by achieving desirable D98,95 while sparing more normal tissues. Conclusion: The dosimetric impact of deformable organ motions for prostate centroid alignment treatment is not insignificant. Coverage‐based treatment planning techniques can produce better plans than FM, while relative advantages of CP OM and CP COP are patient specific. Supported by NIH P01‐CA‐116602 and Philips Medical Systems. Supported by NIH P01‐CA‐116602 and Philips Medical Systems; NIH P01‐CA‐116602 and Philips Medical Systems
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Article
    DOI: 10.1118/1.4815430
    Language: English
    Publisher: Wiley
    Publication Date: 2013
    detail.hit.zdb_id: 188780-4
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  • 3
    Online Resource
    Online Resource
    WE‐D‐BRF‐05: Quantitative Dual‐Energy CT Imaging for Proton Stopping Power Computation
    Wiley ; 2014
    In:  Medical Physics Vol. 41, No. 6Part29 ( 2014-06), p. 496-496
    Details
    In: Medical Physics, Wiley, Vol. 41, No. 6Part29 ( 2014-06), p. 496-496
    Abstract: To extend the two‐parameter separable basis‐vector model (BVM) to estimation of proton stopping power from dual‐energy CT (DECT) imaging. Methods: BVM assumes that the photon cross sections of any unknown material can be represented as a linear combination of the corresponding quantities for two bracketing basis materials. We show that both the electron density (ρe) and mean excitation energy (Iex) can be modeled by BVM, enabling stopping power to be estimated from the Bethe‐Bloch equation. We have implemented an idealized post‐processing dual energy imaging (pDECT) simulation consisting of monogenetic 45 keV and 80 keV scanning beams with polystyrene‐water and water‐CaCl2 solution basis pairs for soft tissues and bony tissues, respectively. The coefficients of 24 standard ICRU tissue compositions were estimated by pDECT. The corresponding ρe, Iex, and stopping power tables were evaluated via BVM and compared to tabulated ICRU 44 reference values. Results: BVM‐based pDECT was found to estimate ρe and Iex with average and maximum errors of 0.5% and 2%, respectively, for the 24 tissues. Proton stopping power values at 175 MeV, show average/maximum errors of 0.8%/1.4%. For adipose, muscle and bone, these errors result range prediction accuracies less than 1%. Conclusion: A new two‐parameter separable DECT model (BVM) for estimating proton stopping power was developed. Compared to competing parametric fit DECT models, BVM has the comparable prediction accuracy without necessitating iterative solution of nonlinear equations or a sample‐dependent empirical relationship between effective atomic number and Iex. Based on the proton BVM, an efficient iterative statistical DECT reconstruction model is under development.
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Article
    DOI: 10.1118/1.4889403
    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 188780-4
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  • 4
    Online Resource
    Online Resource
    MO-E-T-618-01: An Integrated CT-Based Monte Carlo Dose-Evaluation System for Brachytherapy and Its Application to Permanent Prostate Implant Postprocedure Dosimetric Analysis
    Wiley ; 2005
    In:  Medical Physics Vol. 32, No. 6Part14 ( 2005-06), p. 2068-2068
    Details
    In: Medical Physics, Wiley, Vol. 32, No. 6Part14 ( 2005-06), p. 2068-2068
    Type of Medium: Online Resource
    ISSN: 0094-2405
    URL: Article
    DOI: 10.1118/1.1998298
    Language: English
    Publisher: Wiley
    Publication Date: 2005
    detail.hit.zdb_id: 188780-4
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  • 5
    Online Resource
    Online Resource
    TH‐C‐M100F‐08: HDR Brachytherapy and Online Image‐Guided Adaptive IMRT for Dose Escalation in Prostate Cancer: Comparison of Brachytherapy and IMRT Boosts
    Wiley ; 2007
    In:  Medical Physics Vol. 34, No. 6Part23 ( 2007-06), p. 2632-2632
    Details
    In: Medical Physics, Wiley, Vol. 34, No. 6Part23 ( 2007-06), p. 2632-2632
    Abstract: Purpose: A course of one to three large fractions of HDR interstitial brachytherapy (HIB) is an attractive alternative to intensity modulated radiation therapy (IMRT) for delivering boost dose to the prostate in combination with additional external beam irradiation for intermediate risk disease. The purpose of this work is to quantitatively compare single‐fraction HIB boost to biologically equivalent fractionated IMRT, assuming idealized image‐guided delivery (igIMRT) and conventional delivery (cIMRT). Materials & Methods: For 9 prostate patients, both 7‐field IMRT and HIB boosts were planned. The Linear‐Quadratic model (alpha/beta = 3Gy) was used to compute biologically equivalent dose (BED) prescriptions: (a) HIB boost delivered 9Gy in a single fraction, (b) igIMRT boost delivered 20.25Gy to the CTV (prostate gland) in 9 fractions, (c) cIMRT boost delivered 20.25Gy in 9 fractions to the PTV (10mm expansion, 6mm posteriorily). The cIMRT plan was evaluated as a static plan, and with a simulated random and setup errors. The plan evaluation endpoints were: (a) for Tumor Control, the CTV Equivalent Surviving Fraction (ESD index) and (b) for Bladder and Rectum toxicity the Generalized Equivalent Uniform Dose (gEUD) and BED VH parameters. Results: HIB delivery produces outcomes comparable to or better than the idealized igIMRT delivery. On average, the ESD is 16% higher in the HIB delivery than it is in the IMRT delivery. For the HIB, the bladder/rectal gEUD values are strongly influenced by high dose DVH tails. A saturation BED, beyond which no further injury can occur, must be assumed. The gEUD values in HIB delivery are comparable, or better, than those for the IMRT delivery. Modeling of organ motion uncertainties yields mean outcomes similar to static plan outcomes. Conclusion: HIB offers therapeutic gains which exceed even the most optimum igIMRT.
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Article
    DOI: 10.1118/1.2761686
    Language: English
    Publisher: Wiley
    Publication Date: 2007
    detail.hit.zdb_id: 188780-4
    detail.hit.zdb_id: 1466421-5
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