Evaluation of a beam‐spot camera for megavoltage x rays

Lutz, Wendell R.; Maleki, Nasser; Bjärngard, Bengt E.

doi:10.1118/1.596214

Cited by 32 publications

(38 citation statements)

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“…The focal spot or source size is an important consideration in small fields (2). There are various methods to measure source size (47)(48)(49)(50), however it is beyond the scope of most clinical physicists. In such situation question lies as how sensitive is source size with respect to kΩ of a detector.…”

Section: Discussionmentioning

confidence: 99%

Small field dosimetry: What have we learnt?

Das

Morales

Francescon

2016

AIP Conference Proceedings

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Section: Discussionmentioning

confidence: 99%

Small field dosimetry: What have we learnt?

Das

Morales

Francescon

2016

AIP Conference Proceedings

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“…electron window or carbon insert. This method effectively simulated the experimental technique of Lutz to determine the spot size of radiotherapy linacs (Lutz et al 1988). …”

Section: -Origin Of Photons In Low Z Linacmentioning

confidence: 99%

A lowZlinac and flat panel imager: comparison with the conventional imaging approach

et al. 2008

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Experimental and Monte Carlo simulations were conducted of an Elekta Ltd Precise Treatment System Linac fitted with a low Z insert of sufficient thickness to remove all primary electrons. A variety of amorphous silicon based panels employing different scintillators were modelled to determine their response to a variety of x-ray spectra and produce an optimised portal imaging system. This study has shown that in a low Z configuration the vast majority of x-rays are produced in the nickel electron window and with a combination of a carbon insert and caesium iodide based XVI-panel, significant improvement in the object contrast was achieved. For thin, head and neck type geometries, contrast is 4.62 times greater for 1.6cm bone in 5.8cm water than the standard 6MV/iViewGT system. For thicker, pelvis type geometries contrast increases by a factor of 1.3 for 1.6cm bone in 25.8cm water. To obtain images with the same signal to noise ratio as the 6MV/iViewGT system, dose reductions of a factor of 15 and 4.2 are possible for 5.8cm and 25.8cm phantoms respectively. This design has the advantage of being easily implemented on a standard linac and provides a portal image directly from the therapy beam aperture.

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“…The measured penumbra is slightly larger in the leaf side direction than the leaf end direction, however, and this can be partially explained by differences in geometric penumbra caused by the source characteristics of the Phillips SL 75/5 accelerator. The source distribution for the SL 75/5 accelerator has been measured using a parallel slit camera [16,17]. Fig.…”

Section: Penumbramentioning

confidence: 99%

Clinical Dosimetry Considerations for a Doubled-Focused Miniature Multileaf Collimator

Meeks¹,

Bova²,

Buatti³

et al. 1999

Radiosurgery 1999

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Conventional multileaf collimators (MLCs) have been commercially available and used clinically for both conventional field shaping and conformal therapy for a number of years. Consequently, the dosimetric characteristics of these devices have been thoroughly investigated and reported in the literature [1][2][3][4][5][6][7][8]. Miniature multileaf collimators (mMLCs) are currently being developed and manufactured. These devices, which project leaf widths of 1.6-5 mm at isocenter [9], are expected to minimize the beam scalloping effects caused by conventional MLCs and facilitate conformal treatment planning and delivery for stereotactic radiosurgery and radiotherapy [9][10][11].While it is likely that mMLCs will improve informal treatment delivery, especially for small lesions, their effect on basic dosimetry parameters requires investigation. It is uncertain whether or not current dosimetry formalisms will be adequate to accurately predict the output of the highly irregular small fields that are produced with this new generation of treatment delivery equipment. The purpose of this study is to investigate basic dosimetry parameters such as field size dependence, percent depth dose, collimator transmission, and penumbra of fields shaped by a double-focused mMLC. These parameters will be compared to the basic dosimetry parameters of fields shaped using Lippowitz metal blocks. Further, the applicability of the equivalent square formalism to the prediction of beam output for mMLC-shaped fields will be investigated.

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Evaluation of a beam‐spot camera for megavoltage x rays

Cited by 32 publications

References 0 publications

Small field dosimetry: What have we learnt?

Small field dosimetry: What have we learnt?

A lowZlinac and flat panel imager: comparison with the conventional imaging approach

Clinical Dosimetry Considerations for a Doubled-Focused Miniature Multileaf Collimator

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