title: Topological detector: measuring continuous dosimetric quantities with few-element detector array.
abstract: A prototype topological detector was fabricated and investigated for quality assurance of radiation producing medical devices. Unlike a typical array or flat panel detector, a topological detector, while capable of achieving a very high spatial resolution, consists of only a few elements and therefore is much simpler in construction and more cost effective. The key feature allowing this advancement is a geometry-driven design that is customized for a specific dosimetric application. In the current work, a topological detector of two elements was examined for the positioning verification of the radiation collimating devices (jaws, MLCs, and blades etc). The detector was diagonally segmented from a rectangular thin film strip (2.5 cm  ×  15 cm), giving two contiguous but independent detector elements. The segmented area was the central portion of the strip measuring 5 cm in length. Under irradiation, signals from each detector element were separately digitized using a commercial multichannel data acquisition system. The center and size of an x-ray field, which were uniquely determined by the collimator positions, were shown mathematically to relate to the difference and sum of the two signals. As a proof of concept, experiments were carried out using slit x-ray fields ranging from 2 mm to 20 mm in size. It was demonstrated that, the collimator positions can be accurately measured with sub-millimeter precisions.
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, MA, USA. Harvard Medical School, Boston, MA, USA.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Han
authors.forename: Davide
authors.initials: D
authors.lastname: Brivio
authors.forename: Erno
authors.initials: E
authors.lastname: Sajo
authors.forename: Piotr
authors.initials: P
authors.lastname: Zygmanski
mesh_terms: D006801:Humans; D010315:Particle Accelerators / Q000295:instrumentation*; D011785:Quality Assurance, Health Care / Q000592:standards*; D011874:Radiometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D014965:X-Rays