Radiation dose comparison between V/P-SPECT and CT-angiography in the diagnosis of pulmonary embolism

Estimation of maternal and foetal risk of radiation-induced cancer from a survey of computed tomography pulmonary angiography and ventilation/perfusion lung scanning for diagnosing pulmonary embolism during pregnancy

INTRODUCTION

While there are many papers on maternal and foetal radiation doses from computed tomography pulmonary angiography (CTPA) and ventilation/perfusion (V/Q) lung scanning examinations for diagnosing pulmonary embolism in pregnant patients, few have used clinical data to examine the patient lifetime attributable risk (LAR) of different cancer types. This paper aims to estimate the cancer risk from maternal radiation doses from CTPA and V/Q examinations and associated foetal doses.

METHODS

Dosimetric data were determined for 267 pregnant patients who received CTPA and/or V/Q examinations over 8 years. Organ and foetal doses were determined using software allowing patient size variations for CTPA and using two different activity-to-organ dose conversion methods for V/Q scans. The LAR of cancer incidence was estimated using International Commission on Radiological Protection (ICRP) modelling including estimates of detriment.

RESULTS

Estimated total cancer incidence was 23 and 22 cases per 100,000 for CTPA and V/Q examinations, respectively, with detriment estimates of 18 and 20 cases. Cancer incidence was evenly divided between lung and breast cancer for CTPA with lung cancer being 80% of all cancer for V/Q. The median foetal doses were 0.03 mSv for CTPA and 0.29 mSv for V/Q. Significant differences in estimated foetal dose for V/Q scans were obtained by the two different methods used. The differences in dose between the modes of CTPA scan acquisition highlight the importance of optimisation.

CONCLUSION

Maternal cancer incidence and detriment were remarkably similar for each examination. Optimisation of examinations is critical for low-dose outcomes, particularly for CTPA examination.

ACR Appropriateness Criteria® Suspected Pulmonary Embolism: 2022 Update

Pulmonary embolism (PE) remains a common and important clinical condition that cannot be accurately diagnosed on the basis of signs, symptoms, and history alone. The diagnosis of PE has been facilitated by technical advancements and multidetector CT pulmonary angiography, which is the major diagnostic modality currently used. Ventilation and perfusion scans remain largely accurate and useful in certain settings. MR angiography can be useful in some clinical scenarios and lower-extremity ultrasound can substitute by demonstrating deep vein thrombosis; however, if negative, further studies to exclude PE are indicated. In all cases, correlation with the clinical status, particularly with risk factors, improves not only the accuracy of diagnostic imaging but also overall utilization. Other diagnostic tests have limited roles. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Venous Thromboembolism During Pregnancy and the Postpartum Period: Risk Factors, Diagnostic Testing, and Treatment

Importance

The risk of venous thromboembolism (VTE) increases during pregnancy and the postpartum period. Deep vein thrombosis is the most common VTE during pregnancy, but pulmonary embolism is typically of greater concern as it contributes to far higher morbidity and mortality. Diagnosis and treatment of VTE during pregnancy differ substantially from the general nonpregnant population.

Objective

This review describes the epidemiology, risk factors, clinical presentation, diagnosis, and treatment of VTE during pregnancy and the postpartum period.

Evidence Acquisition

First, we reviewed the VTE guidelines from professional societies in obstetrics, cardiology, hematology, emergency medicine, pulmonology, and critical care. Second, we examined references from these documents and used PubMed to identify recent articles that cited the guidelines. Finally, we searched PubMed and Google Scholar for articles published since 2018 that included terms for pregnancy and the epidemiology, risk factors, diagnostic imaging, or treatment of VTE.

Results

Venous thromboembolism risk increases throughout pregnancy and peaks shortly after delivery. More than half of pregnancy-related VTE are associated with thrombophilia; other major risks include cesarean delivery, postpartum infection, and the combination of obesity with immobilization. Most VTE can be treated with low molecular weight heparin, but cases of limb- or life-threatening VTE require consideration of thrombolysis and other reperfusion therapies.

Conclusions and Relevance

Venous thromboembolism is far more frequent in antepartum and postpartum women than age-matched controls, and clinical suspicion for VTE in this population should incorporate pregnancy-specific risks. Treatment of limb- or life-threatening antepartum or postpartum VTE requires multispecialty coordination to optimize maternal and fetal outcomes.

Update on pulmonary embolism in pregnancy and post-partum: The Society of Obstetric Medicine of Australia and New Zealand Position Statement on Pulmonary Embolism in Pregnancy and Post-partum

In this clinical review we highlight aspects of the diagnosis and management of pulmonary embolism (PE) in pregnancy and post-partum and how this may impact on antenatal and postnatal management. Investigation for PE in pregnancy is challenging and includes appropriate patient selection and knowledge of the risks and benefits of pulmonary imaging modalities. The complete Society of Obstetric Medicine of Australia and New Zealand Position Statement on Pulmonary Embolism in Pregnancy and Post-Partum comprehensively reviews all aspects of diagnosis, investigation and management and is accessible at https://www.somanz.org/guidelines.asp. It includes a summary of all recommendations and a guide to developing a management plan for birth in women on anticoagulation.

Novel pregnant model phantoms for measurement of foetal radiation dose in x-ray examinations

This study presents a comparison of novel pregnant model phantoms with a handmade phantom in terms of shape and radiation measurement points to determine which model is more suitable for measuring the foetal radiation dose during x-ray examinations. Novel pregnant model phantoms were constructed using an anthropomorphic phantom in combination with two differently-sized custom-made abdomen phantoms simulating pregnancy, which were constructed from a polyurethane resin. The size and shape of the polyurethane resin were designed based on abdominal sizes and shapes collected from the computed tomography examinations at 18 pregnant patients of one hospital. The handmade pregnant model phantom was constructed using an anthropomorphic phantom and a beach ball containing water. Compared with the handmade phantom, there were additional dose measurement points on the novel pregnant model phantoms. Our model phantoms improved upon the handmade phantom in terms of shape and radiation measurement points. We produced pregnant model phantoms that simulated the shapes and sizes of actual patients for the first time.

The diagnostic accuracy of prospective investigative study of acute pulmonary embolism diagnosis criteria for the detection of acute pulmonary thromboembolism in acutely ill patients

The practical diagnostic performance of Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis (PISAPED) criteria for the detection of acute pulmonary thromboembolism (APTE) in hospitalized patients is not yet well determined. This is the report of the initial results of our recently implemented protocol to employ PISAPED. One hundred and forty-seven pulmonary perfusion scans with 1–3 mCi ^99mTc-MAA of patients of a single pulmonologist were included. Patients with suspicious perfusion defects underwent single-photon emission computed tomography. Interpretations were done by consensus of two nuclear medicine specialists. Comparisons were done with chest X-ray or chest computed tomography when available. The interpreters had access to the clinical records. The scans were reported based on the PISAPED criteria as negative or positive for APTE or indeterminate. Patients were followed up for 6.2 ± 5.3 months when the final diagnosis confirming or excluding APTE was achieved. Patients aged 55.9 (17.2) years; 78 (53.1%) of them were female and 64 (43.8%) had high Wells’ score. The scans were positive, negative, and indeterminate in 17 (11.6%), 126 (85.7%), and 4 (2.7%) patients, respectively. In 6 out of 147 patients, follow-up was not completed and the final diagnosis was not achieved. APTE was finally diagnosed in 21 (14.3%) patients; 12 (57.1%) of them had positive scans. APTE was excluded in 116 (78.9%) patients; 112 (96.5%) of them had negative scans. The accuracy of the test for the diagnosis of APTE was 87.9%. Lung metastasis was the most frequent reason among false-negative cases. The lung perfusion scan using PISAPED criteria could be used with good accuracy in inpatient settings.

Ionizing radiation for maternal medical indications

Ionizing radiation should be considered an avoidable exposure although all pregnant women receive some radiation from their environment. The potential effect of ionizing radiation on the fetus is determined by the dose and the timing of the exposure with growing interest in the potential risks of transgenerational effects of radiation as an epigenetic phenomenon. High dosage exposure is very unlikely in routine situations such as occupational, diagnostic, or therapeutic exposures. Individual diagnostic radiation procedures (fetal dosage <50 mGy), are not associated with any increase in lethality (miscarriage or stillbirth), genetic damage, teratogenicity, growth impairment, mental retardation, or sterility. More recent modeling has suggested that a 10 mGy fetal dose is associated with an excess risk of childhood cancer risk as low as 1 in 4545, well below historical estimates.When the mother's condition necessitates diagnostic radiation it is necessary to balance the risks of the procedure with the benefits to be gained. As almost all diagnostic imaging involves doses below the 50 mGy threshold, clinically indicated investigations should not be withheld because of concerns regarding fetal radiation exposure. Even radiotherapy directed away from the abdomen or pelvis may be considered during pregnancy, if the benefits outweigh the risks and no suitable alternative is available.

EANM guideline for ventilation/perfusion single-photon emission computed tomography (SPECT) for diagnosis of pulmonary embolism and beyond

These guidelines update the previous EANM 2009 guidelines on the diagnosis of pulmonary embolism (PE). Relevant new aspects are related to (a) quantification of PE and other ventilation/perfusion defects; (b) follow-up of patients with PE; (c) chronic PE; and (d) description of additional pulmonary physiological changes leading to diagnoses of left ventricular heart failure (HF), chronic obstructive pulmonary disease (COPD) and pneumonia. The diagnosis of PE should be reported when a mismatch of one segment or two subsegments is found. For ventilation, Technegas or krypton gas is preferred over diethylene triamine pentaacetic acid (DTPA) in patients with COPD. Tomographic imaging with V/PSPECT has higher sensitivity and specificity for PE compared with planar imaging. Absence of contraindications makes V/PSPECT an essential method for the diagnosis of PE. When V/PSPECT is combined with a low-dose CT, the specificity of the test can be further improved, especially in patients with other lung diseases. Pitfalls in V/PSPECT interpretation are discussed. In conclusion, V/PSPECT is strongly recommended as it accurately establishes the diagnosis of PE even in the presence of diseases like COPD, HF and pneumonia and has no contraindications.

Estimation of cancer risks during mammography procedure in Saudi Arabia

The aims of the present work were to quantify radiation doses arises from patients' exposure in mammographic X-ray imaging procedures and to estimate the radiation induced cancer risk. Sixty patients were evaluated using a calibrated digital mammography unit at King Khaled Hospital and Prince Sultan Center, Alkharj, Saudi Arabia. The average patient age (years) was 44.4 ± 10 (26-69). The average and range of exposure parameters were 29.1 ± 1.9 (24.0-33.0) and 78.4 ± 17.5 (28.0-173.0) for X-ray tube potential (kVp) and current multiplied by the exposure time (s) (mAs), respectively. The MGD (mGy) per single projection for craniocaudal (CC), Medio lateral oblique (MLO) and lateromedial (LM) was 1.02 ± 0.2 (0.4-1.8), 1.1 ± 0.3 (0.5-1.8), 1.1 ± 0.3 (0.5-1.9) per procedure, in that order. The average cancer risk per projection is 177 per million procedures. The cancer risk is significant during multiple image acquisition. The study revealed that 80% of the procedures with normal findings. However, precise justification is required especially for young patients.

Diagnostic imaging in pregnancy: Making informed decisions

The use of diagnostic imaging involving ionising radiation may be necessary in pregnancy and requires an assessment of the most appropriate and safest imaging modality which will provide the necessary information balanced with the potential risks to the mother and fetus. In most cases, this will involve a potential fetal radiation dose well below 50 mGy. At these doses, there is no risk of lethality, genetic damage/epigenetic change, teratogenicity, growth impairment or sterility. Older epidemiological data indicating a potential increased cancer risk have been contradicted by newer data and better understanding of the biology of low dose radiation. The linear no-threshold rule has been challenged by many and more realistic estimates of oncogenicity risk along with the potential risks of contrast agents are summarised in this review. Imaging in the pregnant population is increasing in both the number of examinations performed and the number of patients being imaged, with the greatest increase being computed tomography scans. Counselling and obtaining informed consent for imaging that involves radiation requires the clinician to communicate with the woman and her family a realistic estimate of the potential radiation dose to herself and her fetus, to describe and quantitate the risks of this estimated dose, to outline the benefits of the imaging procedure and to respond to any questions or concerns. As almost all diagnostic imaging involves doses below the 50 mGy threshold, clinically indicated investigations should not be withheld during pregnancy. All allied staff must also be well informed to ensure the patient receives a consistent message about the risks and benefits of the proposed test.

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.

1st European Congress of Medical Physics September 1-4, 2016; Medical Physics innovation and vision within Europe and beyond

Medical Physics is the scientific healthcare profession concerned with the application of the concepts and methods of physics in medicine. The European Federation of Organisations for Medical Physics (EFOMP) acts as the umbrella organization for European Medical Physics societies. Due to the rapid advancements in related scientific fields, medical physicists must have continuous education through workshops, training courses, conferences, and congresses during their professional life. The latest developments related to this increasingly significant medical speciality were presented during the 1st European Congress of Medical Physics 2016, held in Athens, September 1-4, 2016, organized by EFOMP, hosted by the Hellenic Association of Medical Physicists (HAMP), and summarized in the current volume.