Three-dimensional photon dose distributions with and without lung corrections for tangential breast intact treatments

Journal Article · Fri Dec 01 04:00:00 EST 1989 · International Journal of Radiation Oncology, Biology and Physics; (USA)

DOI:https://doi.org/10.1016/0360-3016(89)90545-2· OSTI ID:7102323

Chin, L M; Cheng, C W; Siddon, R L; Rice, R K; Mijnheer, B J; Harris, J R ^[1]

---

1. Harvard Medical School, Boston, MA (USA)

The influence of lung volume and photon energy on the 3-dimensional dose distribution for patients treated by intact breast irradiation is not well established. To investigate this issue, we studied the 3-dimensional dose distributions calculated for an 'average' breast phantom for 60Co, 4 MV, 6 MV, and 8 MV photon beams. For the homogeneous breast, areas of high dose ('hot spots') lie along the periphery of the breast near the posterior plane and near the apex of the breast. The highest dose occurs at the inferior margin of the breast tissue, and this may exceed 125% of the target dose for lower photon energies. The magnitude of these 'hot spots' decreases for higher energy photons. When lung correction is included in the dose calculation, the doses to areas at the left and right margin of the lung volume increase. The magnitude of the increase depends on energy and the patient anatomy. For the 'average' breast phantom (lung density 0.31 g/cm3), the correction factors are between 1.03 to 1.06 depending on the energy used. Higher energy is associated with lower correction factors. Both the ratio-of-TMR and the Batho lung correction methods can predict these corrections within a few percent. The range of depths of the 100% isodose from the skin surface, measured along the perpendicular to the tangent of the skin surface, were also energy dependent. The range was 0.1-0.4 cm for 60Co and 0.5-1.4 cm for 8 MV. We conclude that the use of higher energy photons in the range used here provides lower value of the 'hot spots' compared to lower energy photons, but this needs to be balanced against a possible disadvantage in decreased dose delivered to the skin and superficial portion of the breast.

• OSTI ID: 7102323
• Journal Information: International Journal of Radiation Oncology, Biology and Physics; (USA), Journal Name: International Journal of Radiation Oncology, Biology and Physics; (USA) Vol. 17:6; ISSN IOBPD; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

550603 -- Medicine-- External Radiation in Therapy-- (1980-)
61 RADIATION PROTECTION AND DOSIMETRY
62 RADIOLOGY AND NUCLEAR MEDICINE
655003* -- Medical Physics-- Dosimetry
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
COBALT 60
COBALT ISOTOPES
CORRECTIONS
DISEASES
ELEMENTARY PARTICLES
GLANDS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MAMMARY GLANDS
MASSLESS PARTICLES
MEDICINE
MINUTES LIVING RADIOISOTOPES
MOCKUP
NEOPLASMS
NUCLEAR MEDICINE
NUCLEI
ODD-ODD NUCLEI
ORGANS
PHANTOMS
PHOTONS
PLANNING
RADIATION DOSE DISTRIBUTIONS
RADIOISOTOPES
RADIOLOGY
RADIOTHERAPY
STRUCTURAL MODELS
THERAPY
YEARS LIVING RADIOISOT