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Titolo:
A radiographic and tomographic imaging system integrated into a medical linear accelerator for localization of bone and soft-tissue targets
Autore:
Jaffray, DA; Drake, DG; Moreau, M; Martinez, AA; Wong, JW;
Indirizzi:
William Beaumont Hosp, Dept Radiat Oncol, Royal Oak, MI 48073 USA William Beaumont Hosp Royal Oak MI USA 48073 col, Royal Oak, MI 48073 USA Oakland Univ, Dept Phys, Rochester, MI 48063 USA Oakland Univ Rochester MI USA 48063 v, Dept Phys, Rochester, MI 48063 USA
Titolo Testata:
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS
fascicolo: 3, volume: 45, anno: 1999,
pagine: 773 - 789
SICI:
0360-3016(19991001)45:3<773:ARATIS>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
RAY-ENERGY ABSORPTION; RADIATION-THERAPY; MONTE-CARLO; DIAGNOSTIC-QUALITY; PORTAL IMAGES; QUANTUM-NOISE; PROSTATE; RECONSTRUCTION; RADIOTHERAPY; SIMULATION;
Keywords:
portal imaging; conebeam computed tomography; kilovoltage; megavoltage;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Clinical Medicine
Life Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Jaffray, DA William Beaumont Hosp, Dept Radiat Oncol, Royal Oak, MI 48073 USA William Beaumont Hosp Royal Oak MI USA 48073 ak, MI 48073 USA
Citazione:
D.A. Jaffray et al., "A radiographic and tomographic imaging system integrated into a medical linear accelerator for localization of bone and soft-tissue targets", INT J RAD O, 45(3), 1999, pp. 773-789

Abstract

Purpose:Dose escalation in conformal radiation therapy requires accurate field placement. Electronic portal imaging devices are used to verify field placement but are limited by the low subject contrast of bony anatomy at megavoltage (MV) energies, the large imaging dose, and the small size of the radiation fields. In this article, we describe the in-house modification ofa medical linear accelerator to provide radiographic and tomographic localization of bone and soft-tissue targets in the reference frame of the accelerator. This system separates the verification of beam delivery (machine settings, field shaping) from patient and target localization. Materials and Methods: A kilovoltage (kV) x-ray source is mounted on the drum assembly of an Elekta SL-20 medical linear accelerator, maintaining thesame isocenter as the treatment beam with the central axis at 90 degrees to the treatment beam axis. The x-ray tube is powered by a high-frequency generator and can be retracted to the drum-face. Two CCD-based fluoroscopic imaging systems are mounted on the accelerator to collect MV and kV radiographic images. The system is also capable of cone-beam tomographic imaging atboth MV and kV energies. The gain stages of the two imaging systems have been modeled to assess imaging performance. The contrast-resolution of the kV and MV systems was measured using a contrast-detail (C-D) phantom, The dosimetric advantage of using the kV imaging system over the MV system for the detection of bone-like objects is quantified for a specific imaging geometry using a C-D phantom. Accurate guidance of the treatment beam requires registration of the imaging and treatment coordinate systems. The mechanicalcharacteristics of the treatment and imaging gantries are examined to determine a localizing precision assuming an unambiguous object. MV and kV radiographs of patients receiving radiation therapy are acquired to demonstratethe radiographic performance of the system. The tomographic performance isdemonstrated on phantoms using both the MV and the kV imaging system, and the visibility of soft-tissue targets is assessed. Results and Discussion: Characterization of the gains in the two systems demonstrates that the MV system is x-ray quantum noise-limited at very low spatial frequencies; this is not the case for the kV system. The estimates of gain used in the model are validated by measurements of the total gain ineach system. Contrast-detail measurements demonstrate that the MV system is capable of detecting subject contrasts of less than 0.1% (at 6 and 18 MV). A comparison of the kV and MV contrast-detail performance indicates that equivalent bony object detection can be achieved with the kV system at significantly lower doses (factors of 40 and 90 lower than for 6 and 18 MV, respectively). The tomographic performance of the system is promising; soft-tissue visibility is demonstrated at relatively low imaging doses (3 cGy) using four laboratory rats. Conclusions: We have integrated a kV radiographic and tomographic imaging system with a medical linear accelerator to allow localization of bone and soft-tissue structures in the reference frame of the accelerator. Modeling and experiments have demonstrated the feasibility of acquiring high-qualityradiographic and tomographic images at acceptable imaging doses. Full integration of the kV and MV imaging systems with the treatment machine will allow on-line radiographic and tomographic guidance of field placement. (C) 1999 Elsevier Science Inc.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 15/07/20 alle ore 08:44:31