Radiation exposure and associated radiation risks are major concerns for fetal development for pregnant patients who undergo radiation therapy or diagnostic imaging procedures. In order to accurately estimate the radiation dose to the fetus and assess the uncertainty of fetal position and rotation, three hybrid computational fetus phantoms were constructed using magnetic resonance imaging (MRI) for each fetus model as a starting point to construct a complete anatomically accurate fetus, gravid uterus, and placenta. A total of 27 fetal organs were outlined from radiological images via the Velocity Treatment Planning System. The DICOM-Structure set was imported to Rhinoceros software for further reconstruction of 3D fetus phantom model sets. All fetal organ masses were compared with ICRP-89 reference data. Our fetal model series corresponds to 20, 31, and 35 weeks of pregnancy, thus covering the second and third trimester. Fetal positions and locations were carefully adapted to represent the real fetus locations inside the uterus for each trimester of pregnancy. The new series of hybrid computational fetus models together with pregnant female models can be used in evaluating fetal radiation doses in diagnostic imaging and radiotherapy procedures.
After completion of this article, the reader will be able to summarize the various risk prediction strategies, explain the various methods used to identify risk, and describe potential ways to reduce perioperative risk.
Purpose:
To quantify the dosimetric impact of the tandem loading in the treatment of cervical cancer for HDR brachytherapy procedures.
Methods:
Ten patients were evaluated, each of whom received 5 fractions of treatment. Tandem and ovoid sets were inserted into the uterine cavity based on institutional protocols and procedures. Following insertion and stabilization, CT image sets of 1.5mm slice thickness were acquired and sent to the Oncentra V4.3 Treatment Planning System. Critical structures such as the CTV, bladder, rectum, sigmoid, and bowel were contoured and a fractional dose of 5.5Gy was prescribed to Point A for each patient. Six different treatment plans were created for each fraction using varying tandem weightings; from 0.5 to 1.4 times that of the ovoids. Surface dose evaluation of various ovoid diameters, 2.0‐3.5cm, at the vaginal fornices was also investigated.
Results:
Critical structures were evaluated based on varying dose and volume constraints, in particular the 2.0 cc volume recommendation cited by the gynecological GEC‐ESTRO working group. Based on dose volume histogram evaluation, a reduction of dose to the critical structures was most often discovered when the tandem weighting was increased. CTV coverage showed little change as the tandem weighting was varied. Ovoid surface dose decreased by 50‐65% as the tandem weighting increased.
Conclusion:
The advantage of 3D planning with HDR brachytherapy is the dose optimization for each individual treatment plan. This investigation shows that by utilizing large tandem weightings, 1.4 times greater than the ovoid, one can still achieve adequate coverage of the CTV and relatively low doses to the critical structures. In some cases, one would still have to optimize further per individual case. In addition, the ovoid surface dose was greatly decreased when large tandem weighting was utilized; especially for small ovoid diameters.
RESULTS:The majority of the 303 women completing the questionnaire were non-Hispanic white (36%), Asian (34%), or Hispanic (20%). Mean age was 42 years, and mean BMI 27. Most women (90%) reported no pain or discomfort and felt safe (85%) and comfortable (78%) performing selfcollection at home as a first step in cervical cancer screening. For 87% of the women, HPV self-collection was the preferred method.CONCLUSION: As a primary tool for cervical cancer screening, HPV self-collection appears to be highly accepted and the preferred method for HPV collection among Kaiser Permanente Santa Clara patients age 25-65 years requiring cervical cancer screening. Further studies are needed to assess the acceptability, feasibility, and reliability of self-collected HPV specimens in a more demographically diverse population and in the home setting.
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