Functional Image-guided Radiotherapy Planning for Normal Lung Avoidance.

For patients with lung cancer undergoing curative intent radiotherapy, functional lung imaging can be incorporated into treatment planning to modify the dose distribution within non-target volume lung by differentiation of lung regions that are functionally defective or viable. This concept of functional image-guided lung avoidance treatment planning has been investigated with several imaging modalities, primarily single photon emission computed tomography (SPECT), but also hyperpolarised gas magnetic resonance (MR) imaging, positron emission tomography (PET) and computed tomography (CT)-based measures of lung biomechanics. Here, we review the application of each of these modalities, review practical issues of lung avoidance implementation, including image registration and the role of both ventilation and perfusion imaging, and provide guidelines for reporting of future lung avoidance planning studies.

Lung ventilation volumetry with same-breath acquisition of hyperpolarized gas and proton MRI.

The purpose of this work was to assess the reproducibility of percentage of ventilated lung volume (PV) measured from hyperpolarized (HP) (3)He and (1)H anatomical images acquired in the same breath-hold when compared with PV measured from (3)He and (1)H images from separate breath-holds. Volumetric (3)He ventilation and (1)H anatomical images of the same resolution were acquired during the same breath-hold. To assess reproducibility, this procedure was performed twice with a short gap between acquisitions. In addition, (1)H images were also acquired in a separate breath for comparison. PV ((3)He ventilated volume divided by (1)H total lung volume) was calculated using the single-breath-hold images (PV(single)) and the separate-breath-hold images (PV(separate)). Short-term reproducibility of PV measurement was assessed for both single- and separate-breath acquisitions. Dice similarity coefficients (DSCs) were calculated to quantify spatial overlap between (3)He and (1)H segmentations for the single- and separate-breath-hold acquisitions. The efficacy of using the separate-breath method combined with image registration was also assessed. The mean magnitude difference between the two sets of PV values (±standard deviation) was 1.49 ± 1.32% for PV(single) and 4.19 ± 4.10% for PV(separate), with a significant difference (p < 0.01). The mean magnitude difference between the two PV values for the registered separate-breath technique (PV(sep-registered)) was 2.27 ± 2.23%. Bland-Altman analysis showed that PV measured with single-breath acquisitions was more repeatable than PV measured with separate-breath acquisitions, regardless of image registration. DSC values were significantly greater (p < 0.01) for single-breath acquisition than for separate-breath acquisition. Acquisition of HP gas ventilation and (1)H anatomical images in a single breath-hold provides a more reproducible means of percentage lung ventilation volume measurement than the previously used separate-breath-hold scan approach, and reduces errors.

Digitally tunable, wide-band amplitude, phase, and frequency detection for atomic-resolution scanning force microscopy.

Frequency-modulation atomic force microscopy (FM-AFM) relies on an accurate tracking of the resonance frequency of a scanning probe. It is now used in environments ranging from ultrahigh vacuum to aqueous solutions, for slow and for fast imaging, with probes resonating from a few kilohertz up to several megahertz. Here we present a versatile experimental setup that detects amplitude, phase, and frequency of AFM probes for resonance frequencies up to 15 MHz and with >70 kHz maximum bandwidth for amplitude/phase detection. We provide generic parameter settings for variable-bandwidth frequency detection and test these using our setup. The signal-to-noise ratio of the frequency detector is sufficiently high to record atomic-resolution images of mica by FM-AFM in aqueous solution.