Pulmonary functional magnetic resonance imaging for paediatric lung disease

Feasibility, tolerability and safety of pediatric hyperpolarized 129Xe magnetic resonance imaging in healthy volunteers and children with cystic fibrosis

BACKGROUND

Hyperpolarized ¹²⁹Xe is a promising contrast agent for MRI of pediatric lung function, but its safety and tolerability in children have not been rigorously assessed.

OBJECTIVE

To assess the feasibility, safety and tolerability of hyperpolarized ¹²⁹Xe gas as an inhaled contrast agent for pediatric pulmonary MRI in healthy control subjects and in children with cystic fibrosis.

MATERIALS AND METHODS

Seventeen healthy control subjects (ages 6-15 years, 11 boys) and 11 children with cystic fibrosis (ages 8-16 years, 4 boys) underwent ¹²⁹Xe MRI, receiving up to three doses of ¹²⁹Xe gas prepared by either a commercially available or a homebuilt ¹²⁹Xe polarizer. Subject heart rate and SpO₂ were monitored for 2 min post inhalation and compared to resting baseline values. Adverse events were reported via follow-up phone call at days 1 and 30 (range ±7 days) post-MRI.

RESULTS

All children tolerated multiple doses of ¹²⁹Xe, and no children withdrew from the study. Relative to baseline, most children who received a full dose of gas for imaging (10 of 12 controls and 8 of 11 children with cystic fibrosis) experienced a nadir in SpO₂ (mean -6.0 ± standard deviation 7.2%, P≤0.001); however within 2 min post inhalation SpO₂ values showed no significant difference from baseline (P=0.11). There was a slight elevation in heart rate (mean +6.6 ± 13.9 beats per minute [bpm], P=0.021), which returned from baseline within 2 min post inhalation (P=0.35). Brief side effects related to the anesthetic properties of xenon were mild and quickly resolved without intervention. No serious or severe adverse events were observed; in total, four minor adverse events (14.3%) were reported following ¹²⁹Xe MRI, but all were deemed unrelated to the study.

CONCLUSION

The feasibility, safety and tolerability of ¹²⁹Xe MRI has been assessed in a small group of children as young as 6 years. SpO₂ changes were consistent with the expected physiological effects of a short anoxic breath-hold, and other mild side effects were consistent with the known anesthetic properties of xenon and with previous safety assessments of ¹²⁹Xe MRI in adults. Hyperpolarized ¹²⁹Xe is a safe and well-tolerated inhaled contrast agent for pulmonary MR imaging in healthy children and in children with cystic fibrosis who have mild to moderate lung disease.

Computed tomography dose optimisation in cystic fibrosis: A review

Cystic fibrosis (CF) is the most common autosomal recessive disease of the Caucasian population worldwide, with respiratory disease remaining the most relevant source of morbidity and mortality. Computed tomography (CT) is frequently used for monitoring disease complications and progression. Over the last fifteen years there has been a six-fold increase in the use of CT, which has lead to a growing concern in relation to cumulative radiation exposure. The challenge to the medical profession is to identify dose reduction strategies that meet acceptable image quality, but fulfil the requirements of a diagnostic quality CT. Dose-optimisation, particularly in CT, is essential as it reduces the chances of patients receiving cumulative radiation doses in excess of 100 mSv, a dose deemed significant by the United Nations Scientific Committee on the Effects of Atomic Radiation. This review article explores the current trends in imaging in CF with particular emphasis on new developments in dose optimisation.