Fetal dose from radiotherapy with photon beams: Report of AAPM Radiation Therapy Committee Task Group No. 36

Stovall, Marilyn; Blackwell, C. Robert; Cundiff, Jackson; Novack, Devorah H.; Palta, Jatinder; Wagner, Louis K.; Webster, Edward W.; Shalek, Robert J.

doi:10.1118/1.597525

Cited by 353 publications

(366 citation statements)

References 21 publications

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“…Intuitively, it would be expected that wedged PD distributions would be approximately four times larger than open field distributions due to an increase in leakage radiation which is related to increased MUs. Furthermore, it is expected that these differences would be observed at longer distances from the field edge, where the leakage radiation dominates 2 . Data presented here supports this expectation.…”

Section: Discussionsupporting

confidence: 82%

“…Premeasured PD distributions can be used in the planning of radiation therapy treatments for such patients and to determine the need for additional shielding 2 . The AAPM TG‐36 data is often used in these situations.…”

Section: Discussionmentioning

confidence: 99%

“…For all measurements, the ionization chamber was placed at the level of isocenter plane at a depth of 10.0 cm in the phantom (midplane). Due to small PD depth dependence, 1 , 2 , 5 – 7 PD distributions were evaluated only at that depth. The number of monitor units was adjusted to maintain the ionization reading precision at 1%.…”

Section: Methodsmentioning

confidence: 99%

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Peripheral dose distributions for a linear accelerator equipped with a secondary multileaf collimator and universal wedge

Mutic

Esthappan

Klein

2002

J Applied Clin Med Phys

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The American Association of Physicists in Medicine Task Group 36 (AAPM TG‐36) data can be used to estimate peripheral dose (PD) distributions outside the primary radiation field. However, the report data does not apply to linear accelerators equipped with a multileaf collimator (MLC) and universal wedge (UW). Tertiary multileaf collimators have been shown to significantly affect PD distributions and TG‐36 reported data. Measurements were performed to evaluate PD distributions for a linear accelerator equipped with a secondary MLC, backup diaphragms, and UW. This data can be used to compliment the TG‐36 report for estimation of doses to critical structures outside primary radiation fields. For the evaluated linear accelerator, an MLC is incorporated in the upper secondary collimator jaws. Backup shielding diaphragms are located underneath the MLC. At the nominal collimator position, the MLC and the backup diaphragm provide collimation primarily in the transverse direction. Conventional, solid tungsten‐alloy jaws, located underneath the backup diaphragms, provide secondary collimation in the longitudinal direction. The universal wedge provides dose modulation in the direction of the conventional jaws. Measurements were made with an ionization chamber inserted into a 20×40×120cm3 water‐equivalent plastic phantom with the secondary collimator and MLC settings of 5×5,10×10,15×15, and 25×25cm2 with and without UW. Data was acquired along the machine's longitudinal axis for 6, 10, and 18 MV photons. Peripheral dose distributions were measured with the collimator rotated to 0° and 270° for open field measurements and to 0°, 180°, and 270° for wedged fields (IEC 1217). This allowed evaluation of peripheral dose distributions as a function of collimator rotation. Wedged fields were normalized to deliver the same dose at the depth of maximum dose on the central axis as open fields. The measured PD distributions were generally comparable to data reported by TG‐36. At distances close to the field edge (less than 30 or 40 cm), the measured PD distributions were lower when the measurement point was shielded by solid jaws than with MLC and backup diaphragm. At longer distances, this trend reversed for all energies and evaluated field sizes. However, the difference in PD distribution with collimator rotation was not large enough to warrant strategic positioning of the collimator to reduce dose to critical structures outside the primary radiation field. Because internal scatter dominates close to the field edge, wedged PD distributions were comparable to open field doses at distances closer than 30 cm. However, at distances larger than 30 cm from the field edge, wedged PD distributions were significantly grater than those for open fields due to increased contribution of leakage radiation. Increased leakage radiation is due to the increase in wedged field monitor units, which is related to a small wedge factor (0.27 to 0.29).PACS number(s): 87.53.–j, 87.66.–a

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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Peripheral dose distributions for a linear accelerator equipped with a secondary multileaf collimator and universal wedge

Mutic

Esthappan

Klein

2002

J Applied Clin Med Phys

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“…However, in the setting of very aggressive malignancies, where chemotherapy or surgical resection alone would not be sufficient to ensure survival of the mother and fetus, radiation therapy may be employed. Indeed, up to 4000 women per year in the US receive radiotherapy during pregnancy (1) . Even though the primary radiation is commonly delivered to a site far away from the fetus position (i.e., for brain tumors), exposure of the fetus to stray radiation is of great concern, since even very low dose of radiation can cause devastating damage.…”

Section: Introductionmentioning

confidence: 99%

“…A detailed summary of the radiation risk to the embryo/fetus can be found in a recent review article of radiation therapy in the pregnant cancer patient (2) and the AAPM Task Group Report Number 36 (TG‐36) (1) . In short, the biological effect of radiation exposure to the fetus may include death, gross malformations, growth retardation, mental retardation, cancer induction, and hereditary defects.…”

Section: Introductionmentioning

confidence: 99%

Spot scanning proton therapy minimizes neutron dose in the setting of radiation therapy administered during pregnancy

Wang

Poenisch

Zhu

et al. 2016

J Applied Clin Med Phys

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This is a real case study to minimize the neutron dose equivalent (H) to a fetus using spot scanning proton beams with favorable beam energies and angles. Minimum neutron dose exposure to the fetus was achieved with iterative planning under the guidance of neutron H measurement. Two highly conformal treatment plans, each with three spot scanning beams, were planned to treat a 25‐year‐old pregnant female with aggressive recurrent chordoma of the base of skull who elected not to proceed with termination. Each plan was scheduled for delivery every other day for robust target coverage. Neutron H to the fetus was measured using a REM500 neutron survey meter placed at the fetus position of a patient simulating phantom. 4.1 and 44.1 44.1 μSv/fraction were measured for the two initial plans. A vertex beam with higher energy and the fetal position closer to its central axis was the cause for the plan that produced an order higher neutron H. Replacing the vertex beam with a lateral beam reduced neutron H to be comparable with the other plan. For a prescription of 70 Gy in 35 fractions, the total neutron H to the fetus was estimated to be 0.35 mSv based on final measurement in single fraction. In comparison, the passive scattering proton plan and photon plan had an estimation of 26 and 70 mSv, respectively, for this case. While radiation therapy in pregnant patients should be avoided if at all possible, our work demonstrated spot scanning beam limited the total neutron H to the fetus an order lower than the suggested 5 mSv regulation threshold. It is far superior than passive scattering beam and careful beam selection with lower energy and keeping fetus further away from beam axis are essential in minimizing the fetus neutron exposure.PACS number(s): 87.53.Bn, 87.55.D‐, 87.55.N‐

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Breast Cancer Following Radiotherapy and Chemotherapy Among Young Women With Hodgkin Disease

Travis¹,

Hill²,

Dores³

et al. 2003

JAMA

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601

480

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REATMENT OF HODGKIN DISease (HD) represents one of the major medical successes of the 20th century. Fifty years ago, the typical patient survived only a few years, 1 whereas the current 5-year relative survival rate is 85%. 2 In the United States alone, approximately 120000 survivors of HD 2 are at risk for the serious late sequelae of curative therapies, including the occurrence of new primary cancers. 3,4 Second malignant neoplasms are now the leading cause of death in longterm survivors of HD, 5,6 with breast cancer representing the most frequent solid tumor among women. 7,8 Estimates of breast cancer risk appear inversely related to age at treat-Author Affiliations are listed at the end of this article.

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Fetal dose from radiotherapy with photon beams: Report of AAPM Radiation Therapy Committee Task Group No. 36

Cited by 353 publications

References 21 publications

Peripheral dose distributions for a linear accelerator equipped with a secondary multileaf collimator and universal wedge

Peripheral dose distributions for a linear accelerator equipped with a secondary multileaf collimator and universal wedge

Spot scanning proton therapy minimizes neutron dose in the setting of radiation therapy administered during pregnancy

Breast Cancer Following Radiotherapy and Chemotherapy Among Young Women With Hodgkin Disease

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