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  • 1
    Online Resource
    Online Resource
    Megavoltage CT in Helical Tomotherapy — Clinical Advantages and Limitations of Special Physical Characteristics
    SAGE Publications ; 2009
    In:  Technology in Cancer Research & Treatment Vol. 8, No. 5 ( 2009-10), p. 343-352
    Details
    In: Technology in Cancer Research & Treatment, SAGE Publications, Vol. 8, No. 5 ( 2009-10), p. 343-352
    Abstract: Helical tomotherapy is a form of image-guided intensity-modulated radiotherapy that introduces the ring gantry concept into radiation oncology. The system is a combination of a therapeutic linear accelerator and a megavoltage CT-scanner. This work describes the clinical experience with megavoltage CT with 456 patients in more than 11000 fractions. It also provides a review of the current literature of the possibilities and limitations of megavoltage CT. Between July 2006 and October 2008 456 patients were treated with helical tomotherapy and a pretreatment megavoltage CT was performed in 98.1% of the 11821 fractions to perform position control and correction. CT image acquisition was done with 3.5 MV x-rays in the helical tomotherapy machine. MVCT was used for dose recalculations to quantify doses distributions in cases of changing geometry, tumor shrinkage or presence of metal implants. Inverse treatment planning for prostate cancer patients with bilateral hip replacements was performed based upon an MVCT. A mean 3D-correction vector of 7.1mm with a considerable variation was detected and immediately corrected. Mean shifts were lateral 0.9mm (sd 5.0mm), mean longitudinal shift 1.0mm (sd 5.1mm) and mean vertical shift 3.2mm (sd 5.2mm). The MVCT enables imaging of anatomical structures in the presence of dental metal or orthopedic implants. Especially in these cases, dose recomputations can increase the precision of dose calculations. Due to a mean 3d correction vector of more than 7mm and a variation of corrections of more than 5mm daily image-guidance is recommended to achieve a precise dose application. The MVCT shows evident advantages in cases with metal implants but has limitations due to a reduced soft tissue contrast. Compared with megavoltage cone-beam-CT the tomotherapy fan beam CT adds less extra dose fore the patient and has a better soft tissue contrast.
    Type of Medium: Online Resource
    ISSN: 1533-0346 , 1533-0338
    URL: Article
    DOI: 10.1177/153303460900800504
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2009
    detail.hit.zdb_id: 2146365-7
    detail.hit.zdb_id: 2220436-2
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  • 2
    Online Resource
    Online Resource
    Binding characteristics of [ 18 F]PI-2620 distinguish the clinically predicted tau isoform in different tauopathies by PET
    SAGE Publications ; 2021
    In:  Journal of Cerebral Blood Flow & Metabolism Vol. 41, No. 11 ( 2021-11), p. 2957-2972
    Details
    In: Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, Vol. 41, No. 11 ( 2021-11), p. 2957-2972
    Abstract: The novel tau-PET tracer [ 18 F]PI-2620 detects the 3/4-repeat-(R)-tauopathy Alzheimer’s disease (AD) and the 4R-tauopathies corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP). We determined whether [ 18 F]PI-2620 binding characteristics deriving from non-invasive reference tissue modelling differentiate 3/4R- and 4R-tauopathies. Ten patients with a 3/4R tauopathy (AD continuum) and 29 patients with a 4R tauopathy (CBS, PSP) were evaluated. [ 18 F]PI-2620 PET scans were acquired 0-60 min p.i. and the distribution volume ratio (DVR) was calculated. [ 18 F]PI-2620-positive clusters (DVR ≥ 2.5 SD vs. 11 healthy controls) were evaluated by non-invasive kinetic modelling. R1 (delivery), k2 & k2a (efflux), DVR, 30-60 min standardized-uptake-value-ratios (SUVR 30-60 ) and the linear slope of post-perfusion phase SUVR (9-60 min p.i.) were compared between 3/4R- and 4R-tauopathies. Cortical clusters of 4R-tau cases indicated higher delivery (R1 SRTM : 0.92 ± 0.21 vs. 0.83 ± 0.10, p = 0.0007), higher efflux (k2 SRTM : 0.17/min ±0.21/min vs. 0.06/min ± 0.07/min, p  〈  0.0001), lower DVR (1.1 ± 0.1 vs. 1.4 ± 0.2, p  〈  0.0001), lower SUVR 30-60 (1.3 ± 0.2 vs. 1.8 ± 0.3, p  〈  0.0001) and flatter slopes of the post-perfusion phase (slope 9-60 : 0.006/min ± 0.007/min vs. 0.016/min ± 0.008/min, p  〈  0.0001) when compared to 3/4R-tau cases. [ 18 F]PI-2620 binding characteristics in cortical regions differentiate 3/4R- and 4R-tauopathies. Higher tracer clearance indicates less stable binding in 4R tauopathies when compared to 3/4R-tauopathies.
    Type of Medium: Online Resource
    ISSN: 0271-678X , 1559-7016
    URL: Article
    DOI: 10.1177/0271678X211018904
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2021
    detail.hit.zdb_id: 2039456-1
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