Quantitative characterization of tomotherapy MVCT dosimetry

Mingli Chen, Edward Chao, Weiguo Lu

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Megavoltage computed tomography (MVCT) is used as image guidance for patient setup in almost every tomotherapy treatment. Frequent use of ionizing radiation for image guidance has raised concern of imaging dose. The purpose of this work is to quantify and characterize tomotherapy MVCT dosimetry. Our dose calculation was based on a commissioned dose engine, and the calculation result was compared with film measurement. We studied dose profiles, center dose, maximal dose, surface dose, and mean dose on homogeneous cylindrical water phantoms of various diameters for various scanning parameters, including 3 different jaw openings (of nominal value J4, J1, and J0.1) and couch speeds (fine, normal, and coarse). The comparison between calculation and film measurement showed good agreement. In particular, the thread pattern on the film of the helical delivery matched very well with calculation. For the J1 jaw and coarse imaging mode, the maximum difference between calculation and measurement was about 6% of the center dose. Calculation on various sizes of synthesized phantoms showed that the center dose decreases almost linearly as the phantom diameter increases, and that the fine mode (couch speed of 4. mm/rotation) received twice the dose of the normal mode (couch speed of 8. mm/rotation) and 3 times that of the coarse mode (couch speed of 12. mm/rotation) as expected. The maximal dose ranged from 100% to ~200% of the center dose, with increasing ratios for larger phantoms, smaller jaws, and faster couch speed. For all jaw settings and couch speeds, the mean dose and average surface dose vary from 95% to 125% of the center dose with increasing ratios for larger phantoms. We present a quantitative dosimetric characterization of the tomotherapy MVCT in terms of scanning parameters, phantom size, center dose, maximal dose, surface dose, and mean dose. The results can provide an overall picture of dose distribution and a reference data set that enables estimation of CT dose index for the tomotherapy MVCT.

Original languageEnglish (US)
Pages (from-to)280-286
Number of pages7
JournalMedical Dosimetry
Volume38
Issue number3
DOIs
StatePublished - 2013

Fingerprint

Jaw
Tomography
Ionizing Radiation
Water
Therapeutics

Keywords

  • MVCT dose quantification
  • Tomotherapy

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology

Cite this

Quantitative characterization of tomotherapy MVCT dosimetry. / Chen, Mingli; Chao, Edward; Lu, Weiguo.

In: Medical Dosimetry, Vol. 38, No. 3, 2013, p. 280-286.

Research output: Contribution to journalArticle

Chen, Mingli ; Chao, Edward ; Lu, Weiguo. / Quantitative characterization of tomotherapy MVCT dosimetry. In: Medical Dosimetry. 2013 ; Vol. 38, No. 3. pp. 280-286.
@article{6f066eae7c964d2684c1f15adea53c64,
title = "Quantitative characterization of tomotherapy MVCT dosimetry",
abstract = "Megavoltage computed tomography (MVCT) is used as image guidance for patient setup in almost every tomotherapy treatment. Frequent use of ionizing radiation for image guidance has raised concern of imaging dose. The purpose of this work is to quantify and characterize tomotherapy MVCT dosimetry. Our dose calculation was based on a commissioned dose engine, and the calculation result was compared with film measurement. We studied dose profiles, center dose, maximal dose, surface dose, and mean dose on homogeneous cylindrical water phantoms of various diameters for various scanning parameters, including 3 different jaw openings (of nominal value J4, J1, and J0.1) and couch speeds (fine, normal, and coarse). The comparison between calculation and film measurement showed good agreement. In particular, the thread pattern on the film of the helical delivery matched very well with calculation. For the J1 jaw and coarse imaging mode, the maximum difference between calculation and measurement was about 6{\%} of the center dose. Calculation on various sizes of synthesized phantoms showed that the center dose decreases almost linearly as the phantom diameter increases, and that the fine mode (couch speed of 4. mm/rotation) received twice the dose of the normal mode (couch speed of 8. mm/rotation) and 3 times that of the coarse mode (couch speed of 12. mm/rotation) as expected. The maximal dose ranged from 100{\%} to ~200{\%} of the center dose, with increasing ratios for larger phantoms, smaller jaws, and faster couch speed. For all jaw settings and couch speeds, the mean dose and average surface dose vary from 95{\%} to 125{\%} of the center dose with increasing ratios for larger phantoms. We present a quantitative dosimetric characterization of the tomotherapy MVCT in terms of scanning parameters, phantom size, center dose, maximal dose, surface dose, and mean dose. The results can provide an overall picture of dose distribution and a reference data set that enables estimation of CT dose index for the tomotherapy MVCT.",
keywords = "MVCT dose quantification, Tomotherapy",
author = "Mingli Chen and Edward Chao and Weiguo Lu",
year = "2013",
doi = "10.1016/j.meddos.2013.02.009",
language = "English (US)",
volume = "38",
pages = "280--286",
journal = "Medical Dosimetry",
issn = "0958-3947",
publisher = "Elsevier Inc.",
number = "3",

}

TY - JOUR

T1 - Quantitative characterization of tomotherapy MVCT dosimetry

AU - Chen, Mingli

AU - Chao, Edward

AU - Lu, Weiguo

PY - 2013

Y1 - 2013

N2 - Megavoltage computed tomography (MVCT) is used as image guidance for patient setup in almost every tomotherapy treatment. Frequent use of ionizing radiation for image guidance has raised concern of imaging dose. The purpose of this work is to quantify and characterize tomotherapy MVCT dosimetry. Our dose calculation was based on a commissioned dose engine, and the calculation result was compared with film measurement. We studied dose profiles, center dose, maximal dose, surface dose, and mean dose on homogeneous cylindrical water phantoms of various diameters for various scanning parameters, including 3 different jaw openings (of nominal value J4, J1, and J0.1) and couch speeds (fine, normal, and coarse). The comparison between calculation and film measurement showed good agreement. In particular, the thread pattern on the film of the helical delivery matched very well with calculation. For the J1 jaw and coarse imaging mode, the maximum difference between calculation and measurement was about 6% of the center dose. Calculation on various sizes of synthesized phantoms showed that the center dose decreases almost linearly as the phantom diameter increases, and that the fine mode (couch speed of 4. mm/rotation) received twice the dose of the normal mode (couch speed of 8. mm/rotation) and 3 times that of the coarse mode (couch speed of 12. mm/rotation) as expected. The maximal dose ranged from 100% to ~200% of the center dose, with increasing ratios for larger phantoms, smaller jaws, and faster couch speed. For all jaw settings and couch speeds, the mean dose and average surface dose vary from 95% to 125% of the center dose with increasing ratios for larger phantoms. We present a quantitative dosimetric characterization of the tomotherapy MVCT in terms of scanning parameters, phantom size, center dose, maximal dose, surface dose, and mean dose. The results can provide an overall picture of dose distribution and a reference data set that enables estimation of CT dose index for the tomotherapy MVCT.

AB - Megavoltage computed tomography (MVCT) is used as image guidance for patient setup in almost every tomotherapy treatment. Frequent use of ionizing radiation for image guidance has raised concern of imaging dose. The purpose of this work is to quantify and characterize tomotherapy MVCT dosimetry. Our dose calculation was based on a commissioned dose engine, and the calculation result was compared with film measurement. We studied dose profiles, center dose, maximal dose, surface dose, and mean dose on homogeneous cylindrical water phantoms of various diameters for various scanning parameters, including 3 different jaw openings (of nominal value J4, J1, and J0.1) and couch speeds (fine, normal, and coarse). The comparison between calculation and film measurement showed good agreement. In particular, the thread pattern on the film of the helical delivery matched very well with calculation. For the J1 jaw and coarse imaging mode, the maximum difference between calculation and measurement was about 6% of the center dose. Calculation on various sizes of synthesized phantoms showed that the center dose decreases almost linearly as the phantom diameter increases, and that the fine mode (couch speed of 4. mm/rotation) received twice the dose of the normal mode (couch speed of 8. mm/rotation) and 3 times that of the coarse mode (couch speed of 12. mm/rotation) as expected. The maximal dose ranged from 100% to ~200% of the center dose, with increasing ratios for larger phantoms, smaller jaws, and faster couch speed. For all jaw settings and couch speeds, the mean dose and average surface dose vary from 95% to 125% of the center dose with increasing ratios for larger phantoms. We present a quantitative dosimetric characterization of the tomotherapy MVCT in terms of scanning parameters, phantom size, center dose, maximal dose, surface dose, and mean dose. The results can provide an overall picture of dose distribution and a reference data set that enables estimation of CT dose index for the tomotherapy MVCT.

KW - MVCT dose quantification

KW - Tomotherapy

UR - http://www.scopus.com/inward/record.url?scp=84881085972&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84881085972&partnerID=8YFLogxK

U2 - 10.1016/j.meddos.2013.02.009

DO - 10.1016/j.meddos.2013.02.009

M3 - Article

C2 - 23558147

AN - SCOPUS:84881085972

VL - 38

SP - 280

EP - 286

JO - Medical Dosimetry

JF - Medical Dosimetry

SN - 0958-3947

IS - 3

ER -