UTE-SENCEFUL: first results for 3D high-resolution lung ventilation imaging.

PURPOSE: This study aimed to develop a 3D MRI technique to assess lung ventilation in free-breathing and without the administration of contrast agent. METHODS: A 3D-UTE sequence with a koosh ball trajectory was developed for a 3 Tesla scanner. An oversampled k-space was acquired, and the direct current signal from the k-space center was used as a navigator to sort the acquired data into 8 individual breathing phases. Gradient delays were corrected, and iterative SENSE was used to reconstruct the individual timeframes. Subsequently, the signal changes caused by motion were eliminated using a 3D image registration technique, and ventilation-weighted maps were created by analyzing the signal changes in the lung tissue. Six healthy volunteers and 1 patient with lung cancer were scanned with the new 3D-UTE and the standard 2D technique. Image quality and quantitative ventilation values were compared between both methods. RESULTS: UTE-based self-gated noncontrast-enhanced functional lung (SENCEFUL) MRI provided a time-resolved reconstruction of the breathing motion, with a 49% increase of the SNR. Ventilation quantification for healthy subjects was in statistical agreement with 2D-SENCEFUL and the literature, with a mean value of 0.11 ± 0.08 mL/mL for the whole lung. UTE-SENCEFUL was able to visualize and quantify ventilation deficits in a patient with lung tumor that were not properly depicted by 2D-SENCEFUL. CONCLUSION: UTE-SENCEFUL represents a robust MRI method to assess both morphological and functional information of the lungs in 3D. When compared to the 2D approach, 3D-UTE offered ventilation maps with higher resolution, improved SNR, and reduced ventilation artifacts.

Evaluation of the MOSkin dosimeter for diagnostic X-ray CT beams.

The aim of the present study was to evaluate the response of the MOSkin MOSFET dosimeter for X-ray diagnostic CT beams. Experiments were performed to investigate the sensitivity, energy dependence, reproducibility, fading and angular dependence of the dose response for the device. The dosimeter's performance was evaluated for the standard radiation qualities RQT 8, RQT 9 and RQT 10 in a metrology laboratory. In a CT scanner, the MOSkin was used to assess the air kerma profile and the dose profile in a phantom. The integral of the dose profile was compared to the CPMMA,100 measured with a pencil ionization chamber. The results showed that the MOSkin response was linear and reproducible with doses in the CT range. Energy dependence varied up to a factor of 1.19 among the tested X-ray energies. Angular dependence of the response was not greater than 7.8% within the angle range from 0 to 90 degrees. Signal fading within 3 min was negligible. Additionally, the MOSkin was able to accurately assess the air kerma profile and the integral of the dose profile in a CT scanner. The integral of the dose profile in a phantom was in agreement with the CPMMA,100. The presented results demonstrated the potential of the MOSkin for application in CT dosimetry.