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4 results

  • 29 - Abdominal Aortic Aneurysms

  • from Section 6 - Gastrointestinal Emergencies
  • Edited by Kaushal Shah, Weill Cornell Medical Center, New York, Jarone Lee, Massachusetts General Hospital, Boston
  • Edited in association with Clark G. Owyang, Weill Cornell Medical Center, New York, Benjamin Christian Renne, Massachusetts General Hospital, Boston
  • Book:
    Practical Emergency Resuscitation and Critical Care
    Published online:
    02 November 2023
    Print publication:
    23 November 2023, pp 270-278

  • Summary

    Abdominal aortic aneurysm (AAA) refers to aortic dilatations of > 3 cm. True AAA is a localized dilatation of the aorta caused by weakening of the aorta wall involving all three layers (intima, media and adventitia). False aneurysms or pseudoaneurysms typically occur at sites of vessel injury that allow blood to leak out from the arterial lumen while remaining enclosed by adventitia or surrounding soft tissue.

  • Dosimetric accuracy of Acuros® XB and AAA algorithms for stereotactic body radiotherapy (SBRT) lung treatments: evaluation with PRIMO Monte Carlo code

  • B. Sarin, B. Bindhu, P. Raghu Kumar, S. Sumeesh, B. Saju
  • Journal:
    Journal of Radiotherapy in Practice / Volume 22 / 2023
    Published online by Cambridge University Press:
    02 December 2022, e65
    • Article
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  • Purpose:

    The study aimed to compare the dosimetric performance of Acuros® XB (AXB) and anisotropic analytical algorithm (AAA) for lung SBRT plans using Monte Carlo (MC) simulations.

    Methods:

    We compared the dose calculation algorithms AAA and either of the dose reporting modes of AXB (dose to medium (AXB-Dm) or dose to water (AXB-Dw)) algorithms implemented in Eclipse® (Varian Medical Systems, Palo Alto, CA) Treatment planning system (TPS) with MC. PRIMO code was used for the MC simulations. The TPS-calculated dose profiles obtained with a multi-slab heterogeneity phantom were compared to MC. A lung phantom with a tumour was used to validate TPS algorithms using different beam delivery techniques. 2D gamma values obtained from Gafchromic film measurements in the tumour isocentre plane were compared with TPS algorithms and MC. Ten VMAT SBRT plans generated in TPS with each algorithm were recalculated with a PRIMO MC system for identical beam parameters for the clinical plan validation. A dose–volume histogram (DVH) based plan comparison and a 3D global gamma analysis were performed.

    Results:

    AXB demonstrated better agreement with MC and film measurements in the lung phantom validation, with good agreement in PDD, profiles and gamma analysis. AAA showed an overestimated PDD, a significant difference in dose profiles and a lower gamma pass rate near the field borders. With AAA, there was a dose overestimation at the periphery of the tumour. For clinical plan validation, AXB demonstrated higher agreement with MC than AAA.

    Conclusions:

    AXB provided better agreement with MC than AAA in the phantom and clinical plan evaluations.

  • A comparison of Monte Carlo, anisotropic analytical algorithm (AAA) and Acuros XB algorithms in assessing dosimetric perturbations during enhanced dynamic wedged radiotherapy deliveries in heterogeneous media

  • Ashfaq Zaman, Muhammad Basim Kakakhel, Amjad Hussain
  • Journal:
    Journal of Radiotherapy in Practice / Volume 18 / Issue 1 / March 2019
    Published online by Cambridge University Press:
    06 August 2018, pp. 75-81
  • Background

    A comparison of anisotropic analytical algorithm (AAA) and Acuros XB (AXB) dose calculation algorithms with Electron Gamma Shower (EGSnrc) Monte Carlo (MC) for modelling lung and bone heterogeneities encountered during enhanced dynamic wedged (EDWs) radiotherapy dose deliveries was carried out.

    Materials and methods

    In three heterogenous slab phantoms: water–bone, lung–bone and bone–lung, wedged percentage depth doses with EGSnrc, AAA and AXB algorithms for 6 MV photons for various field sizes (5×5, 10×10 and 20×20 cm2) and EDW angles (15°, 30°, 45° and 60°) have been scored.

    Results

    For all the scenarios, AAA and AXB results were within ±1% of the MC in the pre-inhomogeneity region. For water–bone AAA and AXB deviated by 6 and 1%, respectively. For lung–bone an underestimation in lung (AAA: 5%, AXB: 2%) and overestimation in bone was observed (AAA: 13%, AXB: 4%). For bone–lung phantom overestimation in bone (AAA: 7%, AXB: 1%), a lung underdosage (AAA: 8%, AXB: 5%) was found. Post bone up to 12% difference in the AAA and MC results was observed as opposed to 6% in case of AXB.

    Conclusion

    This study demonstrated the limitation of the AAA (in certain scenarios) and accuracy of AXB for dose estimation inside and around lung and bone inhomogeneities. The dose perturbation effects were found to be slightly dependent on the field size with no obvious EDW dependence.

  • 2-Photon Characterization of Optical Proteolytic Beacons for Imaging Changes in Matrix-Metalloprotease Activity in a Mouse Model of Aneurysm

  • Darren G. Haskett, David Maestas, Stephen J. Howerton, Tyler Smith, D. Catalina Ardila, Tom Doetschman, Urs Utzinger, Dominic McGrath, J. Oliver McIntyre, Jonathan P. Vande Geest
  • Journal:
    Microscopy and Microanalysis / Volume 22 / Issue 2 / April 2016
    Published online by Cambridge University Press:
    23 February 2016, pp. 349-360
    Print publication:
    April 2016

  • Abdominal aortic aneurysm is a multifactorial disease that is a leading cause of death in developed countries. Matrix-metalloproteases (MMPs) are part of the disease process, however, assessing their role in disease initiation and progression has been difficult and animal models have become essential. Combining Förster resonance energy transfer (FRET) proteolytic beacons activated in the presence of MMPs with 2-photon microscopy allows for a novel method of evaluating MMP activity within the extracellular matrix (ECM). Single and 2-photon spectra for proteolytic beacons were determined in vitro. Ex vivo experiments using the apolipoprotein E knockout angiotensin II-infused mouse model of aneurysm imaged ECM architecture simultaneously with the MMP-activated FRET beacons. 2-photon spectra of the two-color proteolytic beacons showed peaks for the individual fluorophores that enable imaging of MMP activity through proteolytic cleavage. Ex vivo imaging of the beacons within the ECM revealed both microstructure and MMP activity. 2-photon imaging of the beacons in aneurysmal tissue showed an increase in proteolytic cleavage within the ECM (p<0.001), thus indicating an increase in MMP activity. Our data suggest that FRET-based proteolytic beacons show promise in assessing MMP activity within the ECM and will therefore allow future studies to identify the heterogeneous distribution of simultaneous ECM remodeling and protease activity in aneurysmal disease.