Generation of portal film charts for 10-MV x rays

Faermann, S.; Krutman, Yanai

doi:10.1118/1.596865

Cited by 6 publications

(4 citation statements)

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“…The Min-R films are highspeed, orthochromatic, high-contrast, single-emulsion x-ray films specifically designed for mammography applications (Kodak 1996a). Because of its high sensitivity (Kodak 1996b), doses of only 1 cGy are adequate compared with 5 cGy usually required in megavoltage portal imaging (Faermann and Krutman 1992). The light ( 700 g), 24 cm × 30 cm, all-plastic moulded Kodak Min-R cassettes provide easy loading of x-ray films for portal imaging.…”

Section: Portal Films With Copper and Aluminium Thin Targetsmentioning

confidence: 99%

A thin target approach for portal imaging in medical accelerators

Tsechanski¹,

Bielajew²,

Faermann³

et al. 1998

Phys. Med. Biol.

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A new thin-target method (patent pending) is described for portal imaging with low-energy (tens of keV) photons from a medical linear accelerator operating in a special mode. Low-energy photons are usually produced in the accelerator target, but are absorbed by the target and flattening filter, both made of medium- or high-Z materials such as Cu or W. Since the main contributor to absorption of the low-energy photons is self-absorption by the thick target through the photoelectric effect, it is proposed to lower the thickness of the portal imaging target to the minimum required to get the maximum low-energy photon fluence on the exit side of the target, and to lower the atomic number of the target so that predominantly photoelectric absorption is reduced. To determine the minimum thickness of the target, EGS4 Monte Carlo calculations were performed. As a result of these calculations, it was concluded that the maximum photon fluence for a 4 MeV electron beam is obtained with a 1.5 mm Cu target. This value is approximately five times less than the thickness of the Cu target routinely used for bremsstrahlung production in radiotherapeutic practice. Two sets of experiments were performed: the first with a 1.5 mm Cu target and the second with a 5 mm Al target (Cu mass equivalent) installed in the linear accelerator. Portal films were taken with a Rando anthropomorphic phantom. To emphasize the low-energy response of the new thin target we used a Kodak Min-R mammographic film and cassette combination, with a strong low-energy response. Because of its high sensitivity, only 1 cGy is required. The new portal images show a remarkable improvement in sharpness and contrast in anatomical detail compared with existing ones. It is also shown that further lowering of the target's atomic number (for example to C or Be) produces no significant improvement.

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Section: Portal Films With Copper and Aluminium Thin Targetsmentioning

confidence: 99%

A thin target approach for portal imaging in medical accelerators

Tsechanski¹,

Bielajew²,

Faermann³

et al. 1998

Phys. Med. Biol.

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“…Megavoltage double‐exposure localization portal images were obtained using a 10‐MV X‐ray beam according to the portal film chart technique, 6 using X‐Omat TL film and X‐Omat TL radiotherapy cassette (Eastman Kodak, New York, USA) for prostate cancer patients treated by whole pelvic irradiation followed by boost, or by arc‐therapy, and in patients treated by small pelvic four‐fields box technique. In both methods, patients’ fixative position was done without an immobilization device.…”

Section: Methodsmentioning

confidence: 99%

Accuracy of prostate radiation therapy using a fiducial point‐pair registration technique based on the computer‐assisted portal imaging quality assurance program PIPSpro

Mermershtain

Cohen

Krutman

2003

Australasian Radiology

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The aim of this study was to assess portal imaging for quality assurance of patient positioning in external beam radiotherapy. We present a retrospective study of the variability of patient position in the treatment of 34 prostate cancer patients who were treated with whole pelvic irradiation followed by arc therapy or boost field (Series I) and 25 patients treated by 'small' pelvic 4-field box technique (Series II). Weekly anteroposterior-posteranterior (AP-PA) and left-lateral portal images were compared to simulation films by using a fiducial point-pair registration technique based on the computer-assisted portal imaging quality assurance program PIPSpro, developed specifically for the verification of treatment positioning in radiation therapy. Series I consisted of 34 patients and 194 portal films (97 AP-PA and 97 left-lateral). Overirradiated (OA) and underirradiated (UA) areas were computed in terms of percentage of the reference field size. For the AP-PA portals, the average OA was 2.75% and average UA was 2.74%. For left-lateral portals, an average OA of 2.49% and UA of 2.78% were measured. Series II consisted of 25 patients and 194 portal films (98 AP-PA and 96 left-lateral). The average OA was 0.88% and average UA was 0.86% in AP-PA portals, and 1.03 and 0.82% for left-lateral portals, respectively. The accuracy of patient positioning in irradiation of prostate cancer in our institution is in the range of 2.69% for whole pelvic fields and 1.0% for small fields. We conclude that PIPSpro is an effective and useful tool for quality assurance in radiotherapy.

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“…Film speed for portal films is defined as the dose required to achieve a reasonable optical density. For portal films this is often taken to be around 1.6 [25,26,28,29]. Speed is important as it determines the use of a particular imaging system.…”

Section: Imaging Mediamentioning

confidence: 99%

“…These exposure conditions depend on the distance between the radiation source and the film, the thickness of the patient and the field size. This necessitates the production of technique charts that give the required exposure as a function of these parameters [25][26][27]. Film speed for portal films is defined as the dose required to achieve a reasonable optical density.…”

Section: Imaging Mediamentioning

confidence: 99%

Portal imaging

Langmack¹

2001

BJR

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Portal imaging is the acquisition of images with a radiotherapy beam. Imaging theory suggests that the quality of portal images could be much higher if the efficiency of the imaging media in detecting radiation could be improved. Introduction of new media (films and electronic portal imaging devices) has confirmed this by markedly increasing the quality of portal images. Images from these devices can then be used to verify a patient's treatment. Geometric verification requires the portal image to be registered with a reference image. Dosimetric verification requires the portal imager to be calibrated for dose. This review gives a brief overview of the current areas of interest in portal imaging: imaging theory; imaging media, film and electronic portal imaging devices; image registration; and dosimetry using these devices.

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Generation of portal film charts for 10-MV x rays

Cited by 6 publications

References 0 publications

A thin target approach for portal imaging in medical accelerators

A thin target approach for portal imaging in medical accelerators

Accuracy of prostate radiation therapy using a fiducial point‐pair registration technique based on the computer‐assisted portal imaging quality assurance program PIPSpro

Portal imaging

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