Challenges and opportunities for proton therapy during pregnancy.

During pregnancy, the use of radiation therapy for cancer treatment is often considered impossible due to the assumed associated fetal risks. However, suboptimal treatment of pregnant cancer patients and unjustifiable delay in radiation therapy until after delivery can be harmful for both patient and child. In non-pregnant patients, proton-radiation therapy is increasingly administered because of its favorable dosimetric properties compared with photon-radiation therapy. Although data on the use of pencil beam scanning proton-radiation therapy during pregnancy are scarce, different case reports and dosimetric studies have indicated a more than 10-fold reduction in fetal radiation exposure compared with photon-radiation therapy. Nonetheless, the implementation of proton-radiation therapy during pregnancy requires complex fetal dosimetry for the neutron-dominated out-of-field radiation dose and faces a lack of clinical guidelines. Further exploration and standardization of proton-radiation therapy during pregnancy will be necessary to improve radiotherapeutic management of pregnant women with cancer and further reduce risks for their offspring.

Radiation oncology department policy development for patients who may become pregnant.

In the context of radiation oncology, radiation exposure from radiation therapy simulation, image guidance, and radiation therapy procedures can have severe adverse biological effects on a developing embryo or fetus. Patients who may be pregnant are screened for the possibility of pregnancy to prevent unnecessary or excessive exposure of radiation in utero. Some radiation therapy patients for whom a pregnancy test is indicated may elect to decline the test. In addition, some patients who are found upon screening to be pregnant may decide, with their attending radiation oncologist, to continue with treatment. A radiation oncology department policy was developed to provide guidelines regarding screening and consent. The policy was designed to prevent unnecessary exposure to patients who may be pregnant, and to limit dose to the embryo or fetus in patients for whom treatment is medically indicated. The policy is presented as an example for physicists intending to develop or revise their own practice's policy regarding patients who may become pregnant.

Fetal radiation dose of four tube voltages in abdominal CT examinations during pregnancy: A phantom study.

This study aimed to compare the dose and noise level of four tube voltages in abdominal computerized tomography (CT) examinations in different abdominal circumference sizes of pregnant women. Fetal radiation doses were measured with two anthropomorphic pregnant phantoms and real-time dosimeters of photoluminescence sensors using four tube voltages for abdominal CT. The noise level was measured at the abdomen of two anthropomorphic pregnant phantoms. In the large pregnant phantom, the mean fetal doses performed using 120 and 135 kV were statistically significantly lower than the lower tube voltages (P < 0.05). In the small pregnant phantom, the mean fetal dose performed by 100, 120, and 135 kV was significantly lower than the lowest tube voltage tested (P < 0.05). The ratios of the peripheral mean dose to the centric mean dose showed that the ratios of 80 kV were the highest and those for 135 kV were the lowest in both pregnant phantoms. The ratios of the peripheral mean dose to the centric mean dose decreased as the tube voltage increased. Compared with low tube voltages, high tube voltages such as 120 and 135 kV could reduce radiation doses to the fetus without compromising the image uniformity in abdominal CT examinations during pregnancy. On low tube voltage protocols, the dose near the maternal skin surface may be increased in large pregnant women because of reduced penetration of the x rays.

Radiation dose reduction at MDCT with iterative reconstruction for prenatal diagnosis of skeletal dysplasia: preliminary study using normal fetal specimens.

OBJECTIVE: The purpose of this study was to investigate to what degree the radiation dose can be reduced without affecting the ability to evaluate normal fetal bones at MDCT with iterative reconstruction. MATERIALS AND METHODS: Fifteen normal fetal specimens immersed in containers (30- and 35-cm diameter) were scanned with a 64-MDCT scanner, with tube voltage of 100 kVp and tube current of 600, 300, 150, 100, and 50 mA. Images were subjected to adaptive statistical iterative reconstruction (ASIR). The fetal dose was measured using glass dosimeters. We calculated the relative ratio of the dose at 600 mA. Image quality was evaluated on maximum-intensity-projection and volume-rendering images. Two radiologists recorded the visualization scores of five regions. Images at 600 mA were considered to be standard. RESULTS: With the 30-cm-diameter container, the fetal dose was 10.15 mGy (relative ratio, 100%) at a tube current of 600, 51% at 300, 25% at 150, 17% at 100, and 9% at 50 mA. With the 35-cm-diameter container the fetal dose was 10.01 mGy (relative ratio, 100%) at 600, 47% at 300, 24% at 150, 17% at 100, and 8% at 50 mA. Visual evaluation showed that in both containers, with ASIR 90%, there was a statistically significant difference between 50-and 600-mA images (p<0.01) but not between 600-mA images and those acquired at 100, 150, and 300 mA (p=0.08-1.00). CONCLUSION: The fetal radiation dose for the evaluation of normal fetal bones can be reduced by 83% with ASIR 90%.

Medical Imaging in Pregnancy: Safety, Appropriate Utilization, and Alternative Modalities for Imaging Pregnant Patients.

This article reviews the existing literature on diagnostic and medical imaging of pregnant women, the risks and safety measures of different medical imaging modalities, and alternative modalities for imaging pregnant patients. Different medical imaging modalities such as MRI, CT scan, ultrasound, nuclear medicine, and X-ray imaging help to evaluate women with recognized or unrecognized pregnancies and identify any underlying complications among pregnant patients. Fetuses are more sensitive to radiation and the effects of medical imaging as compared to adults since they have a rapidly developing cell system. During cell proliferation, migration, and differentiation, fetuses suffer greatly from imaging radiation since they are developing under a dynamic system. To ensure safety, pregnant women should discuss the benefits and risks of medical imaging with their physicians. In addition, radiologists should not perform any medical imaging procedure without the patient's consent, unless the patient cannot make any sound decision. Fetal risks of medical imaging include slow growth and development of the fetus, abortion, malformations, impaired brain function, abnormal childhood growth, and neurological development. Diagnostic imaging procedures are necessary when a condition that needs medical evaluation arises during pregnancy such as appendicitis.

Three-dimensional helical computed tomography in prenatal diagnosis of fetal skeletal dysplasia.

OBJECTIVES: (1) To study the use and diagnostic value, as a complement to ultrasound, of helical computed tomography (helical CT) to differentiate normal fetuses from cases of skeletal dysplasia; (2) to define the most relevant indications for helical CT; and (3) to evaluate its diagnostic performance with respect to radiological criteria considered discriminatory. METHODS: This was a retrospective study from 2005 to 2008 in 67 pregnant women who underwent helical CT after 26 weeks of gestation for suspected fetal skeletal dysplasia due to fetal shortened long bones on ultrasound (≤ 10(th) percentile), either alone or associated with other bone abnormalities. The results were compared with pediatric examinations in 41 cases and with fetal autopsy findings after elective termination of pregnancy in the others. RESULTS: Helical CT had a sensitivity of 82%, specificity of 91% and positive and negative predictive values of 90% and 83%, respectively, for diagnosis of fetal skeletal dysplasia. An etiological diagnosis that had not been suspected at ultrasound was specified in 15% of cases and diagnoses suspected at ultrasound were confirmed in 24% and discounted in 43% of cases. The prevalence of skeletal dysplasia was increased in cases of micromelia < 3(rd) percentile or if there was a combination of bone signs. Helical CT showed 69% sensitivity in identifying individual predefined pathological bone signs which were confirmed on fetal autopsy findings. CONCLUSION: Helical CT is a key examination, in combination with ultrasound, in the diagnosis of fetal skeletal dysplasia from 26 weeks of gestation. It should be reserved for cases with severe micromelia below the 3(rd) percentile and for those with micromelia ≤ 10(th) percentile associated with another bone sign. A checklist of discriminatory signs is proposed.

Patient-specific fetal radiation dosimetry for pregnant patients undergoing abdominal and pelvic CT imaging.

BACKGROUND: Accurate estimation of fetal radiation dose is crucial for risk-benefit analysis of radiological imaging, while the radiation dosimetry studies based on individual pregnant patient are highly desired. PURPOSE: To use Monte Carlo calculations for estimation of fetal radiation dose from abdominal and pelvic computed tomography (CT) examinations for a population of patients with a range of variations in patients' anatomy, abdominal circumference, gestational age (GA), fetal depth (FD), and fetal development. METHODS: Forty-four patient-specific pregnant female models were constructed based on CT imaging data of pregnant patients, with gestational ages ranging from 8 to 35 weeks. The simulation of abdominal and pelvic helical CT examinations was performed on three validated commercial scanner systems to calculate organ-level fetal radiation dose. RESULTS: The absorbed radiation dose to the fetus ranged between 0.97 and 2.24 mGy, with an average of 1.63 ± 0.33 mGy. The CTDIvol -normalized fetal dose ranged between 0.56 and 1.30, with an average of 0.94 ± 0.25. The normalized fetal organ dose showed significant correlations with gestational age, maternal abdominal circumference (MAC), and fetal depth. The use of ATCM technique increased the fetal radiation dose in some patients. CONCLUSION: A technique enabling the calculation of organ-level radiation dose to the fetus was developed from models of actual anatomy representing a range of gestational age, maternal size, and fetal position. The developed maternal and fetal models provide a basis for reliable and accurate radiation dose estimation to fetal organs.

Comparison of estimated and calculated fetal radiation dose for a pregnant woman who underwent computed tomography and conventional X-ray examinations based on a phantom study.

This study aimed to determine the mean fetal doses for patients who underwent computed tomography (CT) and/or conventional X-ray (CXR) examinations. In addition to developing an approach to estimate the fetal dose based on data registered in the picture archive and communication system (PACS), the radiation doses for pregnant women and their fetuses were estimated using the VirtualDoseCT and VirtualDoseIR softwares. To verify the data, the fetal dose was measured using thermoluminescent dosimeters (TLDs) implanted at different uterus sites of an anthropomorphic pregnant phantom. Calculated fetal dose values were estimated in relation to the dose-area product (DAP) and volume CT dose index (CTDIvol). DAP and CTDIvol were obtained from data registered in the PACS. The fetal doses varied between < 0.001 and 3.9 mGy and between 0.26 and 16.21 mGy for the CXR and CT examinations, respectively. These values were similar to those of previous studies on both imaging modalities. The conversion factors obtained to calculate fetal doses for CXR examinations were between 0.01 and 0.73 mGy/Gy cm2, whereas they varied between 0.02 and 0.61 mGy/mGy for CT examinations. Overall, the fetal dose conversion factors based on DAP and CTDIvol values can be used for fast fetal dose estimations in common CXR and CT examinations.

Performance of Low-Dose Perfusion Scintigraphy and CT Pulmonary Angiography for Pulmonary Embolism in Pregnancy.

BACKGROUND: The symptoms of normal pregnancy overlap those of pulmonary embolism (PE). Limited literature suggests that low-dose perfusion scanning (LDQ), which yields lower maternal-fetal radiation exposure than CT pulmonary angiography (CTPA), performs well in excluding PE in pregnant patients. METHODS: We performed a retrospective cohort study of sequential pregnant women who underwent imaging for PE with LDQ or CTPA between 2008 and 2013 at Montefiore Medical Center. Our practice recommends LDQ for patients with negative results on chest radiographs. Patients were categorized according to initial imaging modality, and a subgroup analysis was performed in patients with asthma. The primary outcome was the negative predictive value (NPV) of imaging determined by VTE diagnosis within 90 days. RESULTS: Of 322 pregnant women (mean age, 27.3 ± 6.3 years), initial imaging was positive for PE in 2.7% (6 of 225) of LDQs and 4.1% (4 of 97) of CTPAs, negative in 88.0% (198 of 225) of LDQs and 86.6% (84 of 97) of CTPAs, and indeterminate/nondiagnostic in 9.3% (21 of 225) of LDQs and 9.3% (9 of 97) of CTPAs (P = .79). Ten patients (3.1%) were treated for PE. The NPV was 100% for LDQ and 97.5% for CTPA. Subgroup analysis of patients with asthma (23.9% of this population) revealed a high likelihood of a negative study in the LDQ and CTPA groups (74.1% and 87.0%, respectively) and 100% NPV for both modalities. CONCLUSIONS: PE is an uncommon diagnosis in pregnancy. LDQ and CTPA perform well, with less maternal-fetal radiation exposure with LDQ. Therefore, when available, LDQ is a reasonable first-choice modality for suspected PE in pregnant women with a negative result on chest radiograph.

Assessing Health Implications of the Potential Radiation Exposure in the Community During Pregnancy: A Case Study.

The unintentional radiation exposure can have significant implications. We present a case of a 30-year-old pregnant female who was exposed to a potentially radioactive rock for over a one week period during her 13th week of pregnancy. After an arduous process of obtaining activity measurements, the most conservative estimate of dose, the female was exposed to, was found to fall within the permissible limits. We briefly describe the literature on fetal radiation toxicity levels and discuss logistical issues faced in managing such cases.

Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report.

A 42-year-old woman at 29 weeks gestation via in vitro fertilization who presented with eight metastatic brain lesions received Gamma Knife stereotactic radiosurgery (GKSRS) at our institution. In this study, we report our clinical experience and a general procedure of determining the fetal dose from patient-specific treatment plans and we describe quality assurance measurements to guide the safe practice of multi-target GKSRS of pregnant patients. To estimate fetal dose pre-treatment, peripheral dose-to-focal dose ratios (PFRs) were measured in a phantom at the distance approximating the fundus of uterus. Post-treatment, fetal dose was calculated from the actual patient treatment plan. Quality assurance measurements were carried out via the extrapolation dosimetry method in a head phantom at increasing distances along the longitudinal axis. The measurements were then empirically fitted and the fetal dose was extracted from the curve. The computed and measured fetal dose values were compared with each other and associated radiation risk was estimated. Based on low estimated fetal dose from preliminary phantom measurements, the patient was accepted for GKSRS. Eight brain metastases were treated with prescription doses of 15-19 Gy over 143 min involving all collimator sizes as well as composite sector mixed shots. Direct fetal dose computation based on the actual patient's treatment plan estimated a maximum fetal dose of 0.253 cGy, which was in agreement with surface dose measurements at the level of the patient's uterine fundus during the actual treatment. Later phantom measurements also estimated fetal dose to be in the range of 0.21-0.28 cGy (dose extrapolation curve R2 = 0.998). Using the National Council on Radiation Protection and Measurements (NCRP) population-based model, we estimate the fetal risk of secondary malignancy, which is the primary toxicity after 25 weeks gestation, to be less than 0.01%. Of note, the patient delivered the baby via scheduled cesarean section at 36 weeks without complications attributable to the GKSRS procedure. GKSRS of multiple brain metastases was demonstrated to be safe and feasible during pregnancy. The applicability of a general patient-specific fetal dose determination method was also demonstrated for the first time for such a treatment.

Multiple meningiomas in a woman irradiated in utero.

Meningiomas are a common central nervous system tumour and radiation is a known risk factor for their development. In utero radiation exposure correlates to developmental abnormalities and carcinogenesis in a dose- and gestational age-related manner. Radiation induced meningioma has been reported in detail in the literature in patients who had been irradiated earlier in life. At the time of publication, there was no data on radiation exposure whilst in utero and meningioma. We report on a 42-year-old woman with multiple intracranial meningiomas and no other risk factors except a history of in utero exposure to low dose X-ray radiation at 12weeks gestational age.

Fetal radiation exposure: Is monitoring really needed?

The effect of fetal radiation during endoscopic retrograde cholangiopancreatography (ERCP) on pregnant women is a very interesting topic. Smith et al recently estimated the fetal radiation exposure in pregnant women undergoing ERCPs using thermoluminescent dosimeters (TLDs). The authors concluded that TLDs are unnecessary during ERCP with modified techniques. We believe that an extreme caution is needed in clinical practice before drawing such conclusions when they are not strongly supported by enough experimental evidence. Therefore, we recommend that fetal radiation exposure be monitored in clinical practice by using dosimeters, bearing in mind that all relevant techniques to control and minimize the exposure must be applied.

Sistema on-line para o cálculo de doses fetais de pacientes e trabalhadoras ocupacionalmente expostas em radiologia diagnóstica / On-line software for the estimation of fetal radiation dose to patients and staff members in diagnostic radiology

Neste trabalho descrevemos um sistema on-line, chamado “Dose Fetal Web”, que calcula a dose fetal e os riscos radiológicos devido a exposições clínicas ou ocupacionais de gestantes. O sistema utiliza a metodologia matemática onde são usados coeficientes de conversão de dose uterina para dose fetal, gerados por meio de simulações pelo método de Monte Carlo. Para exposição médica de uma paciente gestante, uma base de dados de informações de operação de equipamentos acompanhados por um programa de garantia de qualidade e parâmetros fetais e maternos coletados durante exames de ultrassonografia obstétrica são incorporados na estimativa da dose fetal. No caso de dose fetal de uma trabalhadora gestante sujeita à exposição ocupacional (IOE),informações de uma base de dados de monitoração pessoal como dose ocupacional e carga de trabalho são usadas nos cálculos. No primeiro caso, considerando-se uma paciente gestante de 26 semanas submetida a um procedimento abdominal AP (tensão aplicada ao tubo de 70 kVp e filtração total de 3 mmAl), a dose fetal calculada pelo sistema foi 4,61 mGy e os riscos radiológicos obtidos foram 5,0·10-4 e 0,14 para a probabilidade de indução de retardamento mental e declínio de pontos de QI, respectivamente. No segundo caso, considerando-se uma IOE gestante, e assumindo-se que ela utilize um avental de proteção de 0,5 mm de equivalência em chumbo durante cada procedimento de radiologia intervencionista, e que a leitura pessoal de um dosímetro TLD portado fora do avental foi de 2 mGy/mês, a dose fetal calculada pelo sistema foi 0,02 mSv/mês.

In this paper we describe an online software, named “Dose Fetal Web”, which calculates the dose of the fetus and the radiological risks from both medical and occupational exposures of pregnant women. The software uses a mathematical methodology where coefficients for converting uterus to fetal dose, NUD, have been calculated by using Monte Carlo simulation. In the fetal dose from diagnostic medical examination of the pregnant patient, database information regarding output and other equipment related parameters from the QA database, maternal and fetal parameters collected by ultrasound procedures were used for the fetal dose estimation. In the case of fetal dose of the pregnant staff member the database information regarding routine individual monitoring dosimetry, such as occupational dose and workload, were used for the estimation. In the first case, suppose a 26 weeks pregnant patient had to undergo a single AP Abdomen procedure (70 kVp peak tube voltage and total filtration 3 mmAl), the fetal dose calculated by the software was 4.61 mGy and the radiological risks would be 5.0·10-4 and 0.14 to the probability of mental retardation induction and decline in the IQ score, respectively. In the second case,considering that the staff member can be pregnant, and assuming that she wore a 0.5 mm lead equivalent apron during every interventional radiology procedure and a personal dosimetry reading of 2 mGyTLD/month measured with the TLDs outside the apron, the fetal dose calculated by the software was 0.02 mSv/month.