The use of on-line image verification to estimate the variation in radiation therapy dose delivery

Journal Article · Wed Oct 20 04:00:00 EDT 1993 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/0360-3016(93)90400-P· OSTI ID:54873

Michalski, J M; Wong, J W; Gerber, R L; Yan, Di; Cheng, A; Graham, M V; Renna, M A; Sawyer, P J; Perez, C A ^[1]

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1. Washington Univ. School of Medicine, St. Louis, MO (United States)

On-line radiotherapy imaging systems provide data that allow us to study the geometric nature of treatment variation. It is more clinically relevant to examine the resultant dosimetric variation. In this work, daily beam position as recorded by the on-line images is used to recalculate the treatment plan to show the effect geometric variation has on dose. On-line Image Verification (OLIV) data can differentiate between systematic and random errors in a course of daily radiation therapy. The data emphasize that the type and magnitude of patient set-up errors are unique for individual patients and different clinical situations. Head and neck sites has the least random variation (average 0-100% block overlap isofrequency distribution width = 7 mm) compared to thoracic (average 0-100% block overlap isofrequency distribution width = 12 mm) or pelvic sites (average 0-100% block overlap isofrequency distribution width = 14 mm). When treatment delivery is analyzed case by case, systematic as well as random errors are represented. When the data are pooled by anatomical site, individuality of variations is lost and variation appears random. Recalculated plans demonstrated dosimetric deviations from the original plans. The differences between the two dosimetric distributions were emphasized using a technique of plan subtraction. This allowed quick identification of relative {open_quotes}hot and cold spots{close_quotes} in the recalculated plans. The magnitude and clinical significance of dosimetric variation was unique for each patient. OLIV data are useful to study geometric uncertainties because of the unique nature for individual patients. Dose recalculation is helpful to illustrate the dosimetric consequences of set-up errors. 18 refs., 9 figs., 2 tabs.

• Sponsoring Organization: USDOE
• OSTI ID: 54873
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 3 Vol. 27; ISSN 0360-3016; ISSN IOBPD3
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
56 BIOLOGY AND MEDICINE
APPLIED STUDIES
FIBER OPTICS
HUMAN POPULATIONS
NEOPLASMS
ON-LINE SYSTEMS
RADIATION DOSE DISTRIBUTIONS
RADIATION SCATTERING ANALYSIS
RADIOTHERAPY
VARIATIONS
X-RAY DOSIMETRY
X-RAY RADIOGRAPHY