Silicon Diodes as an Alternative to Diamond Detectors for Depth Dose Curves and Profile Measurements of Photon and Electron Radiation

Scherf, Christian; Peter, Claudia; Moog, Jussi; Licher, Jörg; Kara, E.; Zink, Klemens; Rödel, Claus; Ramm, U.

doi:10.1007/s00066-009-2004-x

Cited by 12 publications

(8 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There have been several studies comparing different detector types for measurements including the buildup region . The scintillator Exradin W1 was shown to produce depth dose curves in water in close agreement to Monte Carlo calculated curves .…”

Section: Introductionmentioning

confidence: 71%

“…In a more recent work, the same author recommended the microDiamond for requiring depth dose corrections k Ω (0, z, PDD) < 1% at all depths in all studied rectangular fields from 7.6 × 7.7 to 115 × 100.1 mm 2 with a CyberKnife 6 MV system. Scherf et al recommended the natural Diamond detector PTW 60003 for measurements both in the buildup region and the fall‐off region of small photon beams. The studied shielded and unshielded diode and a PTW 233642 thimble chamber (0.125 cm 3 volume) showed restrictions in at least one of the regions.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Detector response in the buildup region of small MV fields

2020

View full text Add to dashboard Cite

Purpose The model used to calculate dose distributions in a radiotherapy treatment plan relies on the data entered during beam commissioning. The quality of these data heavily depends on the detector choice made, especially in small fields and in the buildup region. Therefore, it is necessary to identify suitable detectors for measurements in the buildup region of small fields. To aid the understanding of a detector's limitations, several factors that influence the detector signal are to be analyzed, for example, the volume effect due to the detector size, the response to electron contamination, the signal dependence on the polarity used, and the effective point of measurement chosen. Methods We tested the suitability of different small field detectors for measurements of depth dose curves with a special focus on the surface‐near area of dose buildup for fields sized between 10 × 10 and 0.6 × 0.6 cm2. Depth dose curves were measured with 14 different detectors including plane‐parallel chambers, thimble chambers of different types and sizes, shielded and unshielded diodes as well as a diamond detector. Those curves were compared with depth dose curves acquired on Gafchromic film. Additionally, the magnitude of geometric volume corrections was estimated from film profiles in different depths. Furthermore, a lead foil was inserted into the beam to reduce contaminating electrons and to study the resulting changes of the detector response. The role of the effective point of measurement was investigated by quantifying the changes occurring when shifting depth dose curves. Last, measurements for the small ionization chambers taken at opposing biasing voltages were compared to study polarity effects. Results Depth‐dependent correction factors for relative depth dose curves with different detectors were derived. Film, the Farmer chamber FC23, a 0.13 cm3 scanning chamber CC13 and a plane‐parallel chamber PPC05 agree very well in fields sized 4 × 4 and 10 × 10 cm2. For most detectors and in smaller fields, depth dose curves differ from the film. In general, shielded diodes require larger corrections than unshielded diodes. Neither the geometric volume effect nor the electron contamination can account for the detector differences. The biggest uncertainty arises from the positioning of a detector with respect to the water surface and from the choice of the detector's effective point of measurement. Depth dose curves acquired with small ionization chambers differ by over 15% in the buildup region depending on sign of the biasing voltage used. Conclusions A scanning chamber or a PPC40 chamber is suitable for fields larger than 4 × 4 cm2. Below that field size, the microDiamond or small ionization chambers perform best requiring the smallest corrections at depth as well as in the buildup region. Diode response changes considerably between the different types of detectors. The position of the effective point of measurement has a huge effect on the resulting curves, therefore detector specific rather than general shifts of half th...

show abstract

Section: Introductionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Detector response in the buildup region of small MV fields

2020

View full text Add to dashboard Cite

show abstract

“…Radiation was given with four (prone, supine, two lateral) equally weighted fields. Real-time dose measurement using ion chambers helped to observe a homogenous dose distribution [9,11]. In case of a TBI dose exceeding 8 Gy, shielding blocks in the lateral fields were placed at the side of the thorax to reduce the lung dose to 8 Gy.…”

Section: Methodsmentioning

confidence: 99%

Retrospective, Monocentric Analysis of Late Effects after Total Body Irradiation (TBI) in Adults

et al. 2011

View full text Add to dashboard Cite

show abstract

“…110 Scherf intercompared the surface dose from a nonenergy compensated diode and a diamond detector and found a 6%-9% difference, increasing with field size, for a 6 MV beam and about 3% for 25 MV irrespective of field size. 111 A noncommercial MOSFET was used for surface dose measurements compared to TLD and an Attix parallel plate chamber. Photons (6 and 18 MV) and a range of electrons were measured and the MOSFET doses were in agreement (within 3%) with the other detectors.…”

Section: B2 Detectors Used For Measurement Of Surface Dose and Bumentioning

confidence: 99%

Dosimetric effects caused by couch tops and immobilization devices: Report of AAPM Task Group 176

et al. 2014

View full text Add to dashboard Cite

The dosimetric impact from devices external to the patient is a complex combination of increased skin dose, reduced tumor dose, and altered dose distribution. Although small monitor unit or dose corrections are routinely made for blocking trays, ion chamber correction factors, e.g., accounting for temperature and pressure, or tissue inhomogeneities, the dose perturbation of the treatment couch top or immobilization devices is often overlooked. These devices also increase skin dose, an effect which is also often ignored or underestimated. These concerns have grown recently due to the increased use of monolithic carbon fiber couch tops which are optimal for imaging for patient position verification but cause attenuation and increased skin dose compared to the "tennis racket" style couch top they often replace. Also, arc delivery techniques have replaced stationary gantry techniques which cause a greater fraction of the dose to be delivered from posterior angles. A host of immobilization devices are available and used to increase patient positioning reproducibility, and these also have attenuation and skin dose implications which are often ignored. This report of Task Group 176 serves to present a survey of published data that illustrates the magnitude of the dosimetric effects of a wide range of devices external to the patient. The report also provides methods for modeling couch tops in treatment planning systems so the physicist can accurately compute the dosimetric effects for indexed patient treatments. Both photon and proton beams are considered. A discussion on avoidance of high density structures during beam planning is also provided. An important aspect of this report are the recommendations the authors make to clinical physicists, treatment planning system vendors, and device vendors on how to make measurements of surface dose and attenuation and how to report these values. For the vendors, an appeal is made to work together to provide accurate couch top models in planning systems.

show abstract

Silicon Diodes as an Alternative to Diamond Detectors for Depth Dose Curves and Profile Measurements of Photon and Electron Radiation

Abstract: Relative dose profiles obtained with the two silicon diodes have the same degree of accuracy as with the diamond detector.

Cited by 12 publications

References 25 publications

Detector response in the buildup region of small MV fields

Detector response in the buildup region of small MV fields

Retrospective, Monocentric Analysis of Late Effects after Total Body Irradiation (TBI) in Adults

Dosimetric effects caused by couch tops and immobilization devices: Report of AAPM Task Group 176

Contact Info

Product

Resources

About