Investigation into the effects of lead shielding for fetal dose reduction in CT pulmonary angiography

The effect of contact radiation shielding on breast dose during CT abdomen-pelvis: a phantom study

This study aims to investigate if contact shielding reduces breast radiation dose during computed tomography (CT) abdomen-pelvis examinations using automatic tube current modulation to protect one of the four most radiosensitive organs during CT examinations. Dose measurements were taken with and without contact shielding across the anterior and lateral aspects of the breasts and with and without organ dose modulation (ODM) to quantify achievable dose reductions. Although there are no statistically significant findings, when comparing with and without shielding, the mean breast surface dose was reduced by 0.01 μSv without ODM (1.92-1.91 μSv, p = 0.49) and increased by 0.03 μSv with ODM (1.53-1.56 μSv, p = 0.44). Comparing with and without ODM, the mean breast surface dose was reduced by 0.35 μSv with shielding (1.91-1.56 μSv, p = 0.24) and by 0.39 μSv without shielding (1.92-1.53 μSv, p = 0.17). The addition of contact shielding does not provide significant breast surface radiation dose reduction during CT abdomen-pelvis.

Interventional Radiology and Pregnancy: From Conception through Delivery and Beyond

Interventional radiology (IR) plays a unique and often invaluable role in the care of pregnant patients. Special considerations regarding radiation exposure and medication choice must be taken into account when evaluating a pregnant patient for an interventional procedure. In addition, the physiologic changes that occur during pregnancy can pose special challenges for an interventionalist when treating this patient population and should be appropriately recognized. Still, the majority of standard IR procedures can be safely performed in the pregnant population, often with additional precautions and proper patient education about the risks, benefits, and alternatives. In many cases, interventional radiologists can provide lifesaving and fertility-preserving alternatives to more invasive surgical intervention. The authors summarize radiation exposure effects and guidelines and medication choice during pregnancy. The physiologic changes that occur during pregnancy are discussed, with specific interest in the pathologic consequences that can be treated with IR. The authors also describe a wide variety of minimally invasive image-guided procedures offered by IR in pregnant, peripartum, or postpartum patients. The areas where IR can help in the treatment of pregnant patients include venous access, biopsies, genitourinary and biliary interventions, venous thromboembolism treatments, ectopic pregnancy management, aneurysm intervention, and management of trauma patients. IR is also involved in management during the peripartum or postpartum periods, with roles in treatment of invasive placenta spectrum, postpartum hemorrhage after vaginal delivery, and postcesarean delivery complications. ©RSNA, 2023 Supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Efficiency of tungsten-polymer composite shields on fetal dose reduction in chest CT scans

Given their desirable shielding properties, 5 polymer composite shields reinforced with tungsten were selected and their effects as gamma shields on fetal dose reduction were investigated. According to the results, the selected shields reduce the fetus brain, the fetus lungs, the fetus kidneys, and the total fetus dose almost 34.17%-41.19%, 20.47%-25.08%, 9.27%-12.13%, and 15.39%-18.69%, respectively, at tube voltage of 80 kVp. At the higher tube potentials, the values of dose reduction were smaller. Moreover, it was observed that polymers named PHEMA-WO3 and RS-U-30 had an excellent shielding ability among the other studied composites.

Catheter-Based Interventions for the Management of Valvular Heart Disease During Pregnancy

Pregnancy is associated with a significant increase in hemodynamic burden. These changes can lead to maternal morbidity and mortality as well as unfavorable fetal outcomes in patients with valvular heart disease and limited cardiac reserve. Mechanical interventions may be needed for the management of severe hemodynamic deterioration not responding to medical therapy. Catheter-based percutaneous interventions can provide an alternative therapy to surgery during pregnancy. The purpose of this article is to review indications, potential advantages, and limitations of catheter-based interventions for the management of women with valvular heart disease in pregnancy.

Aneurysmal subarachnoid hemorrhage during pregnancy: a comprehensive and systematic review of the literature

Aneurysmal subarachnoid hemorrhage (aSAH) is an emergent condition requiring rapid intervention and prolonged monitoring. There are few recommendations regarding the management of aSAH in pregnancy. We identified all available literature and compiled management decisions as well as reported outcomes through a systematic literature review without meta-analysis to provide recommendations for management of aSAH during pregnancy. We included a total of 23 articles containing 54 cases of pregnancy-related aSAH in our review. From these reports and other literature, we evaluated information on aSAH pathophysiology, diagnosis, and management with respect to pregnancy. Early transfer to an appropriate facility with neurocritical care, a high-risk obstetric service, and a neurosurgery team available is crucial for the management of aSAH in pregnancy. Intensive monitoring and a multidisciplinary approach remain fundamental to ensure maternal and fetal health.

TO USE OR NOT USE PATIENT SHIELDING ON PREGNANT WOMEN UNDERGOING CT PULMONARY ANGIOGRAPHY: A PHANTOM STUDY

Pregnancy increases the risk of pulmonary embolism. Computed tomography pulmonary angiography (CTPA) is used for diagnosis. CT generates ionising radiation, and thus, abdominal shielding may be used. This phantom study investigated the effects of patient shielding and scan length reduction on the fetal and maternal ionising radiation dose from CTPA. The absorbed dose to the fetus was measured using thermoluminescent dosemeters. Estimated effective doses to the pregnant patient were based on the dose-length products. Shielding increased both the effective dose to the patient by 47% and the mean absorbed dose to the fetus (0.10 vs. 0.12 mGy; p < 0.001) compared with unshielded standard CTPA, as it affected the automatic exposure control. Shielded short CTPA marginally lowered only the mean fetal absorbed dose (0.03 vs. 0.02 mGy; p = 0.018). Shortening the scan reduced the fetal absorbed dose most effectively by 70% (0.10 vs. 0.03 mGy; p = 0.006), compared with the standard unshielded scan. Shielding modestly reduces fetal radiation dose but may compromise automatic exposure control, possibly increasing the maternal and fetal radiation dose. Shortening the scan is beneficial, assuming anatomical coverage is secured.

Development of an aperture-type radiation regulator for shielding against secondary radiation from x-ray tubes and collimators in computed tomography

During computed tomography (CT) scans, radiation scatters in all directions, increasing radiation exposure. In this study, an aperture-type radiation regulator was developed to provide shielding against secondary radiation from the x-ray tube and collimator in CT. To evaluate the usefulness of the developed aperture-type radiation regulator, (1) spatial dose distribution within the CT room was measured, (2) dose intensity at 1 m from the isocenter was compared, (3) absorbed dose in the nearby organs was evaluated using a human equivalent phantom, and (4) noise, CNR, and SNR were compared for assessment of image quality. The results showed that the developed aperture-type radiation regulator reduced the intensity of secondary radiation by approximately 25% in front of the gantry and 15% to the rear of the gantry. The maximum dose distribution on 10 μGy was reduced by approximately 18% in front of the gantry and 12% in the rear. In addition, when the neck and head were scanned, the absorbed dose in the chest decreased by 25% and 40%, respectively, and noise was reduced by 3.3%-4.5% for different phantoms. Evaluation of abdominal CT images showed 18% noise reduction, with 27% and 28% increases in the signal-to-noise and contrast-to-noise ratios, respectively. These results confirmed that the proposed aperture-type radiation regulator can reduce radiation exposure without affecting primary radiation that creates medical images. The results also confirmed that the radiation regulator effectively improves the quality of medical images.

Computed tomography pulmonary angiography versus ventilation-perfusion lung scanning for diagnosing pulmonary embolism during pregnancy: a systematic review and meta-analysis

Differences between computed tomography pulmonary angiography and ventilation-perfusion lung scanning in pregnant patients with suspected acute pulmonary embolism are not well-known, leading to ongoing debate on which test to choose. We searched in PubMed, EMBASE, Web of Science and the Cochrane Library databases and identified all relevant articles and abstracts published up to October 1, 2017. We assessed diagnostic efficiency, frequency of non-diagnostic results and maternal and fetal exposure to radiation exposure. We included 13 studies for the diagnostic efficiency analysis, 30 for the analysis of non-diagnostic results and 22 for the radiation exposure analysis. The pooled rate of false negative test results was 0% for both imaging strategies with overlapping confidence intervals. The pooled rates of non-diagnostic results with computed tomography pulmonary angiography and ventilation-perfusion lung scans were 12% (95% confidence interval: 8-17) and 14% (95% confidence interval: 10-18), respectively. Reported maternal and fetal radiation exposure doses were well below the safety threshold, but could not be compared between the two diagnostic methods given the lack of high quality data. Both imaging tests seem equally safe to rule out pulmonary embolism in pregnancy. We found no significant differences in efficiency and radiation exposures between computed tomography pulmonary angiography and ventilation-perfusion lung scanning although direct comparisons were not possible.

The use of out-of-plane high Z patient shielding for fetal dose reduction in computed tomography: Literature review and comparison with Monte-Carlo calculations of an alternative optimisation technique

When performing CT examinations on pregnant patients, great effort should be dedicated towards optimising the exposure of the mother and the conceptus. For this purpose, many radiology departments use high-Z garments to be wrapped around the patient's lower abdomen for out-of-plane organ shielding to protect the fetus. To assess their current protection efficiency, we performed a literature review and compared the efficiencies mentioned in the literature to Monte-Carlo calculations of CT protocols for which the overall scan length was reduced. We found 11 relevant articles, all of them reporting uterus exposure due to CT imaging performed for exclusion of pulmonary embolism, one of the leading causes of peripartum deaths in western countries. Uterus doses ranged between 60 and 660 µGy per examination, and relative dose reductions to the uterus due to high-Z garments were between 20 and 56%. Calculations showed that reducing the scan length by one to three centimetres could potentially reduce uterus dose up to 24% for chest imaging, and even 47% for upper abdominal imaging. These dose reductions were in the order of those achieved by high-Z garments. However, using the latter may negatively influence the diagnostic image quality and even interfere with the automatic exposure control system thus increasing patient dose if positioned in the primary beam, for example in the overranging length in helical acquisition. We conclude that efforts should be concentrated on positioning the patient correctly in the gantry and optimising protocol parameters, rather than using high-Z garments for out-of-plane uterus shielding.

Imaging of Cardiovascular Disease in Pregnancy and the Peripartum Period

OPINION STATEMENT

Cardiovascular disease is an important cause of morbidity and mortality during pregnancy and the postpartum period. During pregnancy, the cardiovascular system undergoes extensive hemodynamic, hormonal, and microstructural changes which may exacerbate a preexisting underlying cardiovascular condition or predispose to cardiovascular complications not typically seen in young healthy women. Such conditions include spontaneous coronary artery dissection, atherosclerotic coronary artery disease, and peripartum cardiomyopathy. When evaluating this patient population, the diagnostic strategy should be tailored to specifically assess this distinct disease spectrum. The choice of imaging techniques must also consider potential risks to both the mother and child; a unique challenge of diagnostic imaging during pregnancy. The risk of radiation from radiography, computed tomography, and nuclear medicine imaging; iodinated and gadolinium-based contrast media for computed tomography and magnetic resonance imaging respectively; and heat deposition from sonography are of special importance during pregnancy. A thorough understanding of pregnancy-specific cardiovascular complications and the capabilities and risks of available diagnostic imaging modalities is crucial to appropriately manage the pregnant patient.

A Phantom Study on Fetal Dose Reducing Factors in Pregnant Patients with Breast Cancer during Radiotherapy Treatment

PURPOSE

This study aims to investigate the factors that reduce fetal dose in pregnant patients with breast cancer throughout their radiation treatment. Two main factors in a standard radiation oncology center are considered as the treatment planning systems (TPSs) and simple shielding for intensity modulated radiation therapy technique.

MATERIALS AND METHODS

TPS factor was evaluated with two different planning algorithms: Anisotropic analytical algorithm and Acuros XB (external beam). To evaluate the shielding factor, a standard radiological purpose lead apron was chosen. For both studies, thermoluminescence dosimeters were used to measure the point dose, and an Alderson RANDO-phantom was used to simulate a female pregnant patient in this study. Thirteen measurement points were chosen in the 32nd slice of the phantom to cover all possible locations of a fetus up to 8th week of gestation.

RESULTS

The results show that both of the TPS algorithms are incapable of calculating the fetal doses, therefore, unable to reduce them at the planning stage. Shielding with a standard lead apron, however, showed a slight radiation protection (about 4.7%) to the fetus decreasing the mean fetal dose from 84.8 mGy to 80.8 mGy, which cannot be disregarded in case of fetal irradiation.

CONCLUSIONS

Using a lead apron for shielding the abdominal region of a pregnant patient during breast irradiation showed a minor advantage; however, its possible side effects (i.e., increased scattered radiation and skin dose) should also be investigated further to solidify its benefits.

The Management of Lymphoma in the Setting of Pregnancy

The diagnosis of lymphoma in pregnant patients poses a therapeutic challenge necessitating consideration of the developing fetus without compromise of therapy with curative potential for the mother. The decision to initiate therapy during pregnancy is heavily influenced by fetal, maternal, and disease-related factors, of which the most influential are the trimester at diagnosis, the stage, and aggressiveness of the disease and the presence of life-threatening symptoms. Recent data suggest that deferral of therapy until after the first trimester is desirable if it is perceived that postponement of therapy will not compromise maternal outcome. For some patients, delay of therapy to the postpartum period is feasible.

Diagnosing venous thromboembolism in pregnancy

OBJECTIVE

We report the imaging outcomes of all pregnant patients referred for suspected thromboembolism over a 43-month period.

METHODS

We identified 168 patients who underwent ventilation/perfusion (VQ) single-photon emission CT (SPECT), CT pulmonary angiography (CTPA) or a Doppler ultrasound scan of the lower legs, as well as a control group of 89 non-pregnant age- and sex-matched patients who underwent VQ SPECT during the same period. Imaging outcomes were recorded, and radiation doses were calculated for individual patients.

RESULTS

VQ SPECT and CTPA were equally likely to diagnose pulmonary embolism (PE) in about one patient out of every seven patients investigated. One in three CTPA scans was of suboptimal quality. A Doppler ultrasound examination of the legs will find deep venous thrombosis much less often, in about 1 patient out of every 15 patients investigated. The prevalence of PE in pregnant patients (as diagnosed by VQ SPECT) was similar to that in the non-pregnant, age- and sex-matched control group. The effective dose and the absorbed radiation dose to the maternal breast were lower with VQ SPECT. The foetal dose is comparable for both VQ SPECT and CTPA.

CONCLUSION

VQ SPECT and CTPA provide a similar diagnostic yield for diagnosing PE during pregnancy, but VQ SPECT does so with a lower radiation dose to the mother (effective dose and breast dose).

ADVANCES IN KNOWLEDGE

Ours is the first report of the diagnostic performance of VQ SPECT, rather than planar VQ scans, in pregnancy in a routine clinical setting.

A model-based approach of scatter dose contributions and efficiency of apron shielding for radiation protection in CT

Given the contribution of scattered radiations to patient dose in CT, apron shielding is often used for radiation protection. In this study the efficiency of apron was assessed with a model-based approach of the contributions of the four scatter sources in CT, i.e. external scattered radiations from the tube and table, internal scatter from the patient and backscatter from the shielding. For this purpose, CTDI phantoms filled with thermoluminescent dosimeters were scanned without apron, and then with an apron at 0, 2.5 and 5 cm from the primary field. Scatter from the tube was measured separately in air. The scatter contributions were separated and mathematically modelled. The protective efficiency of the apron was low, only 1.5% in scatter dose reduction on average. The apron at 0 cm from the beam lowered the dose by 7.5% at the phantom bottom but increased the dose by 2% at the top (backscatter) and did not affect the centre. When the apron was placed at 2.5 or 5 cm, the results were intermediate to the one obtained with the shielding at 0 cm and without shielding. The apron effectiveness is finally limited to the small fraction of external scattered radiation.

Fetal shielding combined with state of the art CT dose reduction strategies during maternal chest CT

PURPOSE

Custom bismuth-antimony shields were previously shown to reduce fetal dose by 53% on an 8DR (detector row) CT scanner without dynamic adaptive section collimation (DASC), automatic tube current modulation (ATCM) or adaptive statistical iterative reconstruction (ASiR). The purpose of this study is to compare the effective maternal and average fetal organ dose reduction both with and without bismuth-antimony shields on a 64DR CT scanner using DASC, ATCM and ASiR during maternal CTPA.

MATERIALS AND METHODS

A phantom with gravid prosthesis and a bismuth-antimony shield were used. Thermoluminescent dosimeters (TLDs) measured fetal radiation dose. The average fetal organ dose and effective maternal dose were determined using 100 kVp, scanning from the lung apices to the diaphragm utilizing DASC, ATCM and ASiR on a 64DR CT scanner with and without shielding in the first and third trimester. Isolated assessment of DASC was done via comparing a new 8DR scan without DASC to a similar scan on the 64DR with DASC.

RESULTS

Average third trimester unshielded fetal dose was reduced from 0.22 mGy ± 0.02 on the 8DR to 0.13 mGy ± 0.03 with the conservative 64DR protocol that included 30% ASiR, DASC and ATCM (42% reduction, P<0.01). Use of a shield further reduced average third trimester fetal dose to 0.04 mGy ± 0.01 (69% reduction, P<0.01). The average fetal organ dose reduction attributable to DASC alone was modest (6% reduction from 0.17 mGy ± 0.02 to 0.16 mGy ± 0.02, P=0.014). First trimester fetal organ dose on the 8DR protocol was 0.07 mGy ± 0.03. This was reduced to 0.05 mGy ± 0.03 on the 64DR protocol without shielding (30% reduction, P=0.009). Shields further reduced this dose to below accurately detectable levels. Effective maternal dose was reduced from 4.0 mSv on the 8DR to 2.5 mSv on the 64DR scanner using the conservative protocol (38% dose reduction).

CONCLUSION

ASiR, ATCM and DASC combined significantly reduce effective maternal and fetal organ dose during CTPA. Shields continue to be an effective means of fetal dose reduction.

Cancer in pregnancy: cross-sectional oncologic imaging utilization at a tertiary care center with an algorithmic approach to imaging

PURPOSE

To review utilization of imaging in pregnant patients with malignancies and define an imaging algorithm in this patient population.

METHODS

Pregnant patients with concurrent diagnoses of malignancy from January 2002 to January 2011 were identified using an institutional electronic medical record system. Patients with history of malignancy concurrent with pregnancy who had documented cross-sectional imaging studies were included. Clinical charts were reviewed, and patient demographics, diagnoses, indication for imaging, imaging findings, and oncologic stage were recorded. Descriptive statistics were performed.

RESULTS

Thirty-eight women were identified with malignancy concurrent with pregnancy. Twenty-seven patients had cross-sectional imaging studies during their pregnancy. There were 20 new diagnoses of malignancy and 7 with recurrent tumor. The most common new malignancies were lymphoma (5/27, 19%) and breast cancer (4/27, 15%). Two thirds (18/27, 66%) of the patients underwent at least one imaging study associated with ionizing radiation. CT imaging was utilized in 13 (48%) of 27 patients and MRI was used in 14 (52%) of 27 patients. Fifteen (75%) of the 20 patients with new diagnoses underwent oncologic staging with imaging that meets the standard of care based on National Comprehensive Cancer Network guidelines. An imaging algorithm was created as a guideline for the most common malignancies in pregnancy.

CONCLUSIONS

Cross-sectional oncologic imaging in the pregnant patient involves a variety of imaging modalities including those with ionizing radiation. This imaging largely follows standard of care for the nonpregnant patient and is tailored to specific patient complaints. A generalized algorithm is offered here for imaging pregnant oncology patients.

Imaging of pregnant and lactating patients: part 2, evidence-based review and recommendations

OBJECTIVE

The objectives of this article are to discuss the current evidence-based recommendations regarding the use of diagnostic imaging in the evaluation of pulmonary embolism, appendicitis, urolithiasis, and cholelithiasis during pregnancy.

CONCLUSION

Diagnostic imaging should be performed during pregnancy only with an understanding of the maternal and fetal risks and benefits, the comparative advantages of different modalities, and the unique anatomic and physiologic issues associated with pregnancy.

Organ and effective dose reduction in adult chest CT using abdominal lead shielding

OBJECTIVES

The purpose of this study was to evaluate and compare organ and effective dose savings that could be achieved using conventional lead aprons and a new, custom-designed shield as out-of-plane shielding devices during chest CT scans.

METHODS

Thermoluminescent dosimeters were used to measure doses throughout the abdomen and pelvis during CT scans of the chest of a RANDO phantom. Dose measurements were made with no shielding, with lead aprons and with the new shield around the abdomen and pelvis in order to quantify the achievable organ and effective dose reductions.

RESULTS

Average dose savings in the 10 phantom sections ranged from 5% to 78% with the highest point dose saving of 93% being found in the mid-pelvis. When shielding was used, the maximum measured organ dose reduction was a 72% dose saving to the testes. Significant dose savings were found throughout the abdomen and pelvis, which contributed to an effective dose saving of 4% that was achieved over and above the dose savings obtained through conventional optimisation strategies. This could yield significant population dose savings and reductions in collective radiation risk.

CONCLUSION

In this study significant organ and effective dose reductions have been achieved through the use of abdominal shielding during chest CT examinations and it is therefore recommended that out-of-plane patient shielding devices should be used for all chest CT scans and potentially for every CT scan, irrespective of body part.

Cancer and pregnancy: a comprehensive review

BACKGROUND

Pregnancy complicated by cancer is relatively rare but, as women in western societies tend to delay childbearing to the third and fourth decade of life, this phenomenon is going to be encountered more often in the future.

MATERIAL AND METHODS

Review of the literature and description of the different diagnostic and therapeutic approaches which are required to diagnose and treat pregnant mothers with cancer.

RESULTS

As in non-pregnant patients, every effort should be made to provide the maximal benefit and best prognosis to the pregnant patient. In most cases, in order to avoid any harm to the fetus, different diagnostic approach should be incorporated and treatment should be tailored to each pregnant woman. Cooperation of multidisciplinary teams, incorporating medical and radiation oncologists, surgeons, obstetricians, neonatologists and experienced nursing staff, is required to provide optimal care for the patient. The benefits from use of surgery, chemotherapy and/or radiotherapy as well as the mother's wishes and beliefs need to be factored into recommendations and treatment planning.

CONCLUSIONS

With the experience gained, the developments in clinical and radiation oncology and the cooperation of multidisciplinary teams, treatment of cancer during pregnancy with normal fetal outcome is feasible.

Imaging for suspected pulmonary embolism in pregnancy-what about the fetal dose? A comprehensive review of the literature

OBJECTIVE: To give a comprehensive overview of fetal doses reported in the literature when imaging the pregnant woman with suspected pulmonary embolism (PE). METHODS: A comprehensive literature search in the PubMed, MEDLINE and EMBASE databases yielded a total of 1,687 papers that were included in the analysis and have been analysed with regard to fetal dose in suspected PE radiological imaging strategies. RESULTS: Fetal dose in chest computed tomography (CT) ranges between 0.013 and 0.026 mGy in early and 0.06-0.1 mGy in late pregnancy compared with 99mTc-MAA perfusion scintigraphy with a fetal dose of 0.1-0.6 mGy in early and 0.6-0.8 mGy in late pregnancy. (99m)Tc-aerosol ventilation scintigraphy results in 0.1-0.3 mGy. However, there is concern about female breast irradiation in CT, which is higher than in scintigraphy. CT radiation risks for breast tissue remain unclear. CONCLUSION: Knowledge of dosimetry and radiation risks is crucial in the radiological work-up of suspected PE in pregnancy. It is reasonable to reserve scintigraphy for pregnant patients with normal chest radiography findings and no history of asthma or chronic lung disease. Performing CT applying dose reduction instead of scintigraphy will minimise fetal radiation dose and maximise the diagnostic value.

Cancer presenting during pregnancy: radiological perspectives

Malignancy presenting during pregnancy is rare. When it does, there are important considerations and challenges for the radiologist. The physiological changes of pregnancy may mask signs and symptoms of malignancy leading to delayed presentation. Endocrine and physiological changes during pregnancy can interact with tumour biology to alter the behaviour and patterns of growth of certain tumours. The timing and choice of imaging technique pose potential risks to the foetus, but this must be weighed against the risks to both mother and foetus of inadequate investigation or misdiagnosis. This review outlines the general principles and approach to imaging the pregnant patient with suspected malignancy, following which there is a more detailed discussion of the effects of pregnancy on tumour biology and presentation of specific tumours. Imaging strategies are discussed for the different entities, and where possible, evidence-based imaging recommendations are made.