Irreversible electroporation (IRE) ablation uses brief electric pulses to kill a volume of tissue without damaging the structures contraindicated for surgical resection or thermal ablation, including blood vessels and ureters. IRE offers a targeted nephron-sparing approach for treating kidney tumors, but the relevant organ-specific electrical properties and cellular susceptibility to IRE electric pulses remain to be characterized. Here, a pulse protocol of 100 electric pulses, each 100 μs long, is delivered at 1 pulse/s to canine kidneys at three different voltage-to-distance ratios while measuring intrapulse current, completed 6 h before humane euthanasia. Numerical models were correlated with lesions and electrical measurements to determine electrical conductivity behavior and lethal electric field threshold. Three methods for modeling tissue response to the pulses were investigated (static, linear dynamic, and asymmetrical sigmoid dynamic), where the asymmetrical sigmoid dynamic conductivity function most accurately and precisely matched lesion dimensions, with a lethal electric field threshold of 575 ± 67 V/cm for the protocols used. The linear dynamic model also attains accurate predictions with a simpler function. These findings can aid renal IRE treatment planning under varying electrode geometries and pulse strengths. Histology showed a wholly necrotic core lesion at the highest electric fields, surrounded by a transitional perimeter of differential tissue viability dependent on renal structure.

Introduction: Health professionals in paediatric medical imaging are routinely required to communicate radiation risks to carers and patients. Effective dose alone cannot be used to specify and communicate the radiation risk for an individual as risks are dependent on many factors including age and patient sex. In this study, we estimated typical effective doses for 20 commonly performed paediatric general radiography examinations using the weight-based imaging protocols employed at a major Australian specialist paediatric hospital. Effective doses were used to estimate and categorise associated age-based stochastic risks with commonly used risk terminology to facilitate communication of risk. Methods: Paediatric protocols for common general radiography examinations and World Health Organization 50th percentile weight-for-age data for females and males aged up to 18 years were used to estimate typical effective doses using Monte Carlo software and lifetime risk of cancer incidence using published data. Results were used to determine standardised levels of risk using the Calman risk model. Results: Effective doses, corresponding lifetime risk of cancer incidence and level of risk category from 20 general radiography examinations for paediatric patients were calculated and presented for ease of communication. Doses ranged from <0.001 mSv (negligible risk) to 1.6 mSv (low risk). Conclusion: Typical effective doses from common paediatric general radiography examinations, the associated lifetime risk of cancer incidence and level of risk have been established for our institution. This can be used to convey risks to health professionals, patients and carers in ways that are easy to understand and compare with other everyday risks.

Introduction: Effective dose alone cannot be used to specify and communicate the radiation risk for an individual as risks are dependent on many factors including age and gender. There are limited published data regarding agespecific effective doses and the associated lifetime risk of developing cancers for paediatrics. In this study, we have estimated the typical effective doses for six commonly performed paediatric nuclear medicine and positron emission tomography (PET) studies at the Royal Children's Hospital, Melbourne, Australia. Effective doses were used to estimate and categorise associated stochastic risks with commonly used risk terminology. Methods: Paediatric protocols for common nuclear medicine and PET studies and the World Health Organization (WHO) 50th percentile weight-for-age data for females and males aged up to 18 years were used to estimate typical organ and effective doses using ICRP dosimetric tables for radiopharmaceuticals and lifetime risk of cancer incidence using BEIR VII Phase 2 report data. Results were used to determine standardised levels of risk. Results: Organ doses, effective doses, corresponding lifetime risk of cancer incidence and level of risk category from six common nuclear medicine and PET studies for paediatric patients were calculated and presented for ease of communication. Conclusion: Typical effective doses from common paediatric nuclear medicine and PET studies and the associated lifetime risk of cancer incidence and level of risk have been established for our institution. This can be used to convey risks to health professionals, patients and carers in ways that are easy to understand and compare with other everyday risks.

Introduction: To compare the radiation dose exposure and diagnostic efficiency of computed tomographic pulmonary angiography (CTPA) and ventilation/perfusion imaging (V/Q) for clinically suspected pulmonary embolism (PE) in pregnant and postpartum women in a tertiary hospital setting. Methods: A retrospective cohort study of 473 pregnant and postpartum women referred for CTPA or V/Q for clinically suspected PE between January 2013 and December 2018 at a tertiary hospital. Maternal effective radiation dose, breast-absorbed radiation dose and fetal-absorbed dose estimates were calculated. Diagnostic yield was evaluated from radiological findings. Results: Computed tomographic pulmonary angiography (CTPA) was more commonly used for the imaging of suspected PE in pregnant and postpartum populations (51.9% vs. 48.1% and 77.1% vs. 22.9%, respectively). CTPA was associated with higher maternal effective and breast-absorbed doses (maternal effective CTPA 4.7 (AE2.9) mSv (millisievert), V/Q 1.7(AE0.8) mSv (mean difference 2.93 mSv P < 0.001), and breast-absorbed CTPA 8.0 (AE5.2) mGy (milligray), V/Q 0.3 (AE0.1) (mean difference 7.67 mGy P < 0.001), respectively). Fetal radiation dose exposure was low. The incidence of positive PE was 5.5%. Indeterminate rates of CTPA and V/Q were 3.0% and 5.5% (P = 0.176), respectively. Conclusions: Compared to V/Q, CTPA is associated with higher maternal and breast radiation dose; however, modern CT scanners achieve lower radiation doses than historically described. Fetal radiation dose was comparably low. The diagnostic yield of the imaging modalities in pregnant and postpartum women is similar. Revision of guidelines should occur with the advances in CT technology.