Validating the safety of low-dose CTPA in pregnancy: results from the OPTICA (Optimised CT Pulmonary Angiography in Pregnancy) Study.

BACKGROUND: Pulmonary embolism (PE) is a leading cause of pregnancy-related mortality. CT pulmonary angiogram (CTPA) is the first-line advanced imaging modality for suspected PE in pregnancy at institutes offering low-dose techniques; however, a protocol balancing safety with low dose remains undefined. The wide range of CTPA doses reported in pregnancy suggests a lack of confidence in implementing low-dose techniques in this group. PURPOSE: To define and validate the safety, radiation dose and image quality of a low-dose CTPA protocol optimised for pregnancy. MATERIALS AND METHODS: The OPTICA study is a prospective observational study. Pregnant study participants with suspected PE underwent the same CTPA protocol between May 2018 and February 2022. The primary outcome, CTPA safety, was judged by the reference standard; the 3-month incidence of venous thromboembolism (VTE) in study participants with a negative index CTPA. Secondary outcomes defined radiation dose and image quality. Absorbed breast, maternal effective and fetal doses were estimated by Monte-Carlo simulation on gestation-matched phantoms. Image quality was assessed by signal-to-noise and contrast-to-noise ratios and a Likert score for pulmonary arterial enhancement. RESULTS: A total of 116 CTPAs were performed in 113 pregnant women of which 16 CTPAs were excluded. PE was diagnosed on 1 CTPA and out-ruled in 99. The incidence of recurrent symptomatic VTE was 0.0% (one-sided 95% CI, 2.66%) at follow-up. The mean absorbed breast dose was 2.9 ± 2.1mGy, uterine/fetal dose was 0.1 ± 0.2mGy and maternal effective dose was 1.4 ± 0.9mSv. Signal-to-noise ratio (SNR) was 11.9 ± 3.7. Contrast-to-noise ratio (CNR) was 10.4 ± 3.5. CONCLUSION: The OPTICA CTPA protocol safely excluded PE in pregnant women across all trimesters, with low fetal and maternal radiation. CLINICAL RELEVANCE: OPTICA (Optimised CT Pulmonary Angiography in Pregnancy) is the first prospective study to define the achievable radiation dose, image-quality and safety of a low-dose CT pulmonary angiogram protocol optimised for pregnancy (NCT04179487). It provides the current benchmark for safe and achievable CT pulmonary angiogram doses in the pregnant population. KEY POINTS: • Despite the increased use of CT pulmonary angiogram in pregnancy, an optimised low-dose protocol has not been defined and reported doses in pregnancy continue to vary widely. • The OPTICA (Optimised CT Pulmonary Angiography in Pregnancy) study prospectively defines the achievable dose, image quality and safety of a low-dose CT pulmonary angiogram protocol using widely available technology. • OPTICA provides a benchmark for safe and achievable CT pulmonary angiogram doses in the pregnant population.

Autonomic instability, arrhythmia and visual impairment in a new presentation of MTFMT-related mitochondrial disease.

Mitochondrial methionyl-tRNA formyltransferase (MTFMT) is required for the initiation of translation in mitochondria. Pathogenic variants in MTFMT have been described in association with clinical presentations with Leigh syndrome, as well with as multisystem involvement (particularly cardiac and ocular involvement). There is a spectrum of severity, but many reported presentations have been milder with a better prognosis than other pathogenic variants associated with Leigh syndrome. We describe the case of a 9-year-old boy homozygous for a pathogenic MTFMT variant (c.626C > T/p.Ser209Leu) who presented with hypertensive crisis on a background of hyperphagia and visual impairment. His clinical course was complicated by supraventricular tachycardia and severe autonomic instability, requiring intensive care unit admission. He also developed seizures, neurogenic bladder and bowel and had a markedly abnormal eye examination with bilateral optic atrophy. Magnetic resonance image brain showed abnormal high T2/fluid-attenuated inversion recovery signal within the dorsal brainstem and in the right globus pallidus with some reduced diffusivity. Despite recovery from the acute neurological and cardiac manifestations, he has ongoing deficits in his gross motor skills and continues to have hyperphagia with rapid weight gain (approx. 20 kg in 2 years). Ophthalmic findings are persistent. This case expands the phenotype associated with MTFMT disease.

Breast Shielding Combined With an Optimized Computed Tomography Pulmonary Angiography Pregnancy Protocol: A Special Use-Case for Shielding?

OBJECTIVES: To determine the impact of breast shields on breast dose and image quality when combined with a low-dose computed tomography pulmonary angiography (CTPA) protocol for pregnancy. METHODS: A low-dose CTPA protocol, with and without breast shields, was evaluated by anthropomorphic phantom and 20 prospectively recruited pregnant participants from January to October 2019. Thermoluminescent dosimeters measured surface and absorbed breast dose in the phantom and surface breast dose in participants. The Monte-Carlo method estimated the absorbed breast dose in participants. Image quality was assessed quantitatively by regions of interest analysis and subjectively by the Likert scale. Doses and image quality for CTPA alone were compared with CTPA with breast shields. RESULTS: Mean surface and absorbed breast dose for CTPA alone were 1.3±0.4 and 2.8±1.5 mGy in participants, and 1.5±0.7 and 1.6±0.6 mGy in the phantom. Shielding reduced surface breast dose to 0.5±0.3 and 0.7±0.2 mGy in the phantom (66%) and study participants (48%), respectively. Absorbed breast dose reduced to 0.9±0.5 mGy (46%) in the phantom.Noise increased with breast shields at lower kV settings (80 to 100 kV) in the phantom; however, in study participants there was no significant difference between shield and no-shield groups for main pulmonary artery noise (no-shield: 34±9.8, shield: 36.3±7.2, P =0.56), SNR (no-shield: 11.2±3.7, shield: 10.8±2.6, P =0.74) or contrast-to-noise ratio (no-shield: 10.0±3.3, shield: 9.3±2.4, P =0.6). Median subjective image quality scores were comparable (no-shield: 4.0, interquartile range: 3.5 to 4.4, shield: 4.3, interquartile range: 4.0 to 4.5). CONCLUSION: Combining low-dose CTPA with breast shields confers additional breast-dose savings without impacting image quality and yields breast doses approaching those of low-dose scintigraphy, suggesting breast shields play a role in protocol optimization for select groups.

Increased incidence of acute calculous cholecystitis observed during COVID-19 social restrictions.

PURPOSE: In response to the outbreak of COVID-19 in Ireland, the government implemented a nationwide stay-at-home order, with the closure of all non-essential businesses. During this period, there was a significant increase in supermarket expenditure. It has been shown that stress, anxiety and boredom are triggers for unhealthy eating habits. Fat consumption is a risk factor for both the development of gallstones and, additionally, the development of acute calculous cholecystitis. The aim of this study was to assess the incidence of acute calculous cholecystitis during the nationwide lockdown and compare it to the same period one year prior. METHODS: A retrospective review of all emergency abdominal imaging performed during the first 5 weeks of the lockdown was completed using the hospital PACS (picture archiving and communication system). All cases of acute calculous cholecystitis were identified and compared with the same period 1 year prior. RESULTS: Eighteen cases of acute calculous cholecystitis were identified from 24 March to 27 April 2020. Eleven cases were identified during the same period in 2019. This represented an increase of 63%. Non-COVID-19-related emergency presentations decreased during this period, and imaging of emergency presentations decreased by 24%. The rate of scans positive for acute cholecystitis more than doubled (p < 0.037). CONCLUSION: A statistically significant increase in cases of acute calculous cholecystitis was observed during a nationwide lockdown during the COVID-19 pandemic. It is hypothesised that this is due to increased consumption of fatty foods during this period due to stress, anxiety and boredom.

The OPTICA study (Optimised Computed Tomography Pulmonary Angiography in Pregnancy Quality and Safety study): Rationale and design of a prospective trial assessing the quality and safety of an optimised CTPA protocol in pregnancy.

BACKGROUND: CTPA is the gold standard investigation for evaluating suspected pulmonary embolism (PE) in the general population however is sometimes considered second line in pregnant and post-partum patients with a normal CXR due to its higher breast dose and the increased radio-sensitivity of breast tissue during this period. Guidelines advocating for scintigraphy over CTPA, however, quote significantly higher breast doses than those achievable with optimised low dose strategies. Defining the radiation dose achievable with a specific low-dose CTPA protocol is therefore imperative. As decreasing dose is associated with increased image noise, demonstrating the image quality and validity of a negative low-dose CTPA in out-ruling PE in this population is necessary. METHODS: The OPTICA study is a prospective multicentre observational study aiming to validate the clinical utility and safety of an optimised low-dose CTPA protocol in pregnancy. An optimised low-dose CTPA protocol has been agreed across all study sites with equivalent CT capabilities. Pregnant women undergoing CTPA for suspected PE will be included. Independent review of CTPAs by two radiology consultants, image data analysis and 3-month patient follow up will be performed. The primary outcome is the 3-month incidence of VTE in pregnant patients in whom PE was excluded at baseline CTPA. Secondary outcomes will confirm the associated radiation dose and image quality of this protocol. The radiation dose will be calculated using the Monte Carlo method and will include maternal effective, breast and foetal doses. Image quality will be assessed objectively by measuring opacification of the main pulmonary trunk, signal-to-noise and contrast-to-noise ratios and subjectively using a grading scale and inter-reader variability of CTPA results. CONCLUSION: The OPTICA study is the first prospective trial of a low-dose CTPA protocol in the pregnant population. It will provide high-quality evidence defining the achievable dose, image quality and safety of an optimised CTPA for this population. It will assist other institutes with similar CT capabilities in achieving comparable low doses for its patients and provide an evidence base upon which modern CTPA protocols can be appropriately compared to scintigraphy in the pregnant population.