The impact of daily shifts on prostate IMRT dose distributions

Nigel P. Orton, Wolfgang A. Tome

Research output: Contribution to journalArticle

48 Citations (Scopus)

Abstract

It is becoming common clinical practice to shift prostate patients daily based on transabdominal ultrasound (US) or imaging of implanted fiducial markers. This paper investigates the dosimetric impact of these shifts by looking at five patients shifted using an optically guided 3D US localization system and treated with IMRT. Treatment plans were generated for each patient for the following 3 cases: (1) the initial preplan, which represents the ideal case in which no shifts are necessary; (2) a postplan incorporating each day's actual shifts; and (3) a postplan in which no shifts were made but the internal organs move by the amounts indicated by daily US imaging. Results show that when daily shifts are made, doses to the target, rectal wall, and bladder wall are nearly identical to those in the preplan. Equivalent uniform dose (EUD) and tumor control probability (TCP) for these plans were also the same as for the preplans. When no shifts were made, however, the dose distributions were degraded, and the computed target EUD and TCP were lower for all five patients. The magnitude of these differences varied: for three patients, the TCP was only 1%-2% lower than for the preplan. For the other two patients, however, the EUD was reduced by more than 10%, resulting in TCP reductions of 6% and 11%. These results indicate that for a symmetric beam arrangement and properly chosen margins, shifting the patient each day and treating without recalculating the dose is unlikely to affect local control or the sparing of normal tissues.

Original languageEnglish (US)
Pages (from-to)2845-2848
Number of pages4
JournalMedical Physics
Volume31
Issue number10
DOIs
StatePublished - Oct 2004
Externally publishedYes

Fingerprint

Prostate
Ultrasonography
Neoplasms
Fiducial Markers
Urinary Bladder

ASJC Scopus subject areas

  • Biophysics

Cite this

The impact of daily shifts on prostate IMRT dose distributions. / Orton, Nigel P.; Tome, Wolfgang A.

In: Medical Physics, Vol. 31, No. 10, 10.2004, p. 2845-2848.

Research output: Contribution to journalArticle

@article{2c1f8f9ac0854f2598f9adb4a2def286,
title = "The impact of daily shifts on prostate IMRT dose distributions",
abstract = "It is becoming common clinical practice to shift prostate patients daily based on transabdominal ultrasound (US) or imaging of implanted fiducial markers. This paper investigates the dosimetric impact of these shifts by looking at five patients shifted using an optically guided 3D US localization system and treated with IMRT. Treatment plans were generated for each patient for the following 3 cases: (1) the initial preplan, which represents the ideal case in which no shifts are necessary; (2) a postplan incorporating each day's actual shifts; and (3) a postplan in which no shifts were made but the internal organs move by the amounts indicated by daily US imaging. Results show that when daily shifts are made, doses to the target, rectal wall, and bladder wall are nearly identical to those in the preplan. Equivalent uniform dose (EUD) and tumor control probability (TCP) for these plans were also the same as for the preplans. When no shifts were made, however, the dose distributions were degraded, and the computed target EUD and TCP were lower for all five patients. The magnitude of these differences varied: for three patients, the TCP was only 1{\%}-2{\%} lower than for the preplan. For the other two patients, however, the EUD was reduced by more than 10{\%}, resulting in TCP reductions of 6{\%} and 11{\%}. These results indicate that for a symmetric beam arrangement and properly chosen margins, shifting the patient each day and treating without recalculating the dose is unlikely to affect local control or the sparing of normal tissues.",
author = "Orton, {Nigel P.} and Tome, {Wolfgang A.}",
year = "2004",
month = "10",
doi = "10.1118/1.1784592",
language = "English (US)",
volume = "31",
pages = "2845--2848",
journal = "Medical Physics",
issn = "0094-2405",
publisher = "AAPM - American Association of Physicists in Medicine",
number = "10",

}

TY - JOUR

T1 - The impact of daily shifts on prostate IMRT dose distributions

AU - Orton, Nigel P.

AU - Tome, Wolfgang A.

PY - 2004/10

Y1 - 2004/10

N2 - It is becoming common clinical practice to shift prostate patients daily based on transabdominal ultrasound (US) or imaging of implanted fiducial markers. This paper investigates the dosimetric impact of these shifts by looking at five patients shifted using an optically guided 3D US localization system and treated with IMRT. Treatment plans were generated for each patient for the following 3 cases: (1) the initial preplan, which represents the ideal case in which no shifts are necessary; (2) a postplan incorporating each day's actual shifts; and (3) a postplan in which no shifts were made but the internal organs move by the amounts indicated by daily US imaging. Results show that when daily shifts are made, doses to the target, rectal wall, and bladder wall are nearly identical to those in the preplan. Equivalent uniform dose (EUD) and tumor control probability (TCP) for these plans were also the same as for the preplans. When no shifts were made, however, the dose distributions were degraded, and the computed target EUD and TCP were lower for all five patients. The magnitude of these differences varied: for three patients, the TCP was only 1%-2% lower than for the preplan. For the other two patients, however, the EUD was reduced by more than 10%, resulting in TCP reductions of 6% and 11%. These results indicate that for a symmetric beam arrangement and properly chosen margins, shifting the patient each day and treating without recalculating the dose is unlikely to affect local control or the sparing of normal tissues.

AB - It is becoming common clinical practice to shift prostate patients daily based on transabdominal ultrasound (US) or imaging of implanted fiducial markers. This paper investigates the dosimetric impact of these shifts by looking at five patients shifted using an optically guided 3D US localization system and treated with IMRT. Treatment plans were generated for each patient for the following 3 cases: (1) the initial preplan, which represents the ideal case in which no shifts are necessary; (2) a postplan incorporating each day's actual shifts; and (3) a postplan in which no shifts were made but the internal organs move by the amounts indicated by daily US imaging. Results show that when daily shifts are made, doses to the target, rectal wall, and bladder wall are nearly identical to those in the preplan. Equivalent uniform dose (EUD) and tumor control probability (TCP) for these plans were also the same as for the preplans. When no shifts were made, however, the dose distributions were degraded, and the computed target EUD and TCP were lower for all five patients. The magnitude of these differences varied: for three patients, the TCP was only 1%-2% lower than for the preplan. For the other two patients, however, the EUD was reduced by more than 10%, resulting in TCP reductions of 6% and 11%. These results indicate that for a symmetric beam arrangement and properly chosen margins, shifting the patient each day and treating without recalculating the dose is unlikely to affect local control or the sparing of normal tissues.

UR - http://www.scopus.com/inward/record.url?scp=7244252932&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=7244252932&partnerID=8YFLogxK

U2 - 10.1118/1.1784592

DO - 10.1118/1.1784592

M3 - Article

C2 - 15543793

AN - SCOPUS:7244252932

VL - 31

SP - 2845

EP - 2848

JO - Medical Physics

JF - Medical Physics

SN - 0094-2405

IS - 10

ER -