Less severe retinopathy of prematurity induced by surfactant replacement therapy.

To assess the effect of surfactant replacement therapy (SRT) on the prevalence and severity of retinopathy of prematurity (ROP), we compared data from 160 SRT-treated preterm infants with data from 230 historic controls. The prevalence of ROP was 30.6% in the treatment group and 23.4% in the control group. Severe ROP (stages 3-4) was seen in 6.1% of the infants with ROP in the treatment group and 20.3% of the ROP patients in the control group. Surfactant therapy had no influence on the prevalence of ROP (odds ratio 1.4, 95% confidence interval 0.797-2.459, p = 0.242). However, SRT was associated with a decreased risk for severe ROP, compared to mild ROP (odds ratio 0.226, 95% confidence interval 0.056-0.905, p = 0.036). These data suggest that SRT is associated with a decreased risk for severe ROP.

Dosimetric characteristics of a liquid-filled electronic portal imaging device.

PURPOSE: To determine the characteristics of a commercial electronic portal imaging device (EPID), based on a two-dimensional matrix of liquid-filled ionization chambers, for transmission dose measurements during patient treatment. METHODS AND MATERIALS: Electronic portal imaging device measurements were performed in a cobalt-60 beam and two accelerator x-ray beams, and compared with measurements performed with a Farmer-type ionization chamber in air in a miniphantom and in an extended water phantom. RESULTS: The warming up time of the EPID is about 1 h. The long-term stability of the detector is better than 1% under reference conditions for a period of about 3 months. The signal of the ionization chambers follows approximately the square root of the dose rate, although the relation becomes more linear for larger (> 1 Gy/min) dose rates. The signal can be transformed to dose rate with an accuracy of 0.6% (1 SD). The short-term influence of integrated dose on the sensitivity of the ionization chambers is small. The sensitivity increases about 0.5% for all ionization chambers after an absorbed dose of 8 Gy and returns to its original value in less than 5 min after stopping the irradiation. This small increase in sensitivity can be ascribed to the electrode distance of the ionization chambers in commercial EPIDs, which is 0.8 +/- 0.1 mm. The sensitivity increase depends on the electrode distance and is 4% for a 1.4 mm electrode distance. The scattering properties of the EPID ionization chambers were between those of an ionization chamber in a miniphantom and in a water phantom. CONCLUSION: The matrix ionization chamber EPID has characteristics that make it very suitable for dose rate measurements. It is therefore a very promising device for in vivo dosimetry purposes.

Surfactant replacement therapy: a new risk factor in developing retinopathy of prematurity?

We documented the prevalence of retinopathy of prematurity (ROP) in a group of 46 infants suffering from a moderate or severe respiratory distress syndrome and treated with surfactant replacement therapy (SRT) and 61 controls admitted in the year prior to the institution of SRT. Mortality in the treatment group was lower than in the control group (15.5% versus 23.8; P = 0.29). The ROP prevalence in the treatment group was 47.8% and in the control group 27.9%. To analyse the contribution of SRT alone to the prevalence of ROP, multivariate analysis using logistic regression technique was used. The odds ratio for SRT was 5.2 with a 95% confidence interval of 1.3-20.7, P = 0.02. The prevalence of severe ROP in the surfactant treated group was not increased compared to the control group. From our data we conclude that SRT increases the risk of developing ROP but is not associated with more severe forms of ROP.