Magnetic resonance-guided radiation therapy (MRgRT) offers advantages for image guidance for radiotherapy treatments as compared to conventional computed tomography (CT)-based modalities. The superior soft tissue contrast of magnetic resonance (MR) enables an improved visualization of the gross tumor and adjacent normal tissues in the treatment of abdominal and thoracic malignancies. Online adaptive capabilities, coupled with advanced motion management of real-time tracking of the tumor, directly allow for high-precision inter-/intrafraction localization. The primary aim of this case series is to describe MR-based interventions for localizing targets not well-visualized with conventional image-guided technologies. The abdominal and thoracic sites of the lung, kidney, liver, and gastric targets are described to illustrate the technological advancement of MR-guidance in radiotherapy.

Rationale and Objectives Pulmonary hypertension (PH) is a complex and fatal disease that is difficult to diagnose non-invasively. This study evaluated previously published CT-based vessel measurement criteria and investigated the predictive power and diagnostic ability of the main pulmonary artery diameter (MPAD) and the ratio of MPAD to aorta diameter (rPA). Materials and Methods The database for this study consisted of 175 PH patients (for whom mean pulmonary artery pressure (mPAP) was known), 16 patients without PH but with known mPAP (non-PH patients), and 114 “normal” patients without known mPAP. The performance of previously published criteria, MPAD > 29 mm and rPA > 1, was determined. The relationship between vessel measurements and mPAP was evaluated through correlation and linear regression analysis. The ability of these measurements to discriminate between patients with and without PH was determined by receiver operating characteristic analysis. Results For discriminating between PH and “normal” patients, the sensitivity and specificity of the criterion MPAD>29mm were 0.89 (0.84-0.93) and 0.83 (0.76-0.90), respectively, and the sensitivity and specificity of the criterion rPA>1 were 0.89 (0.85-0.94) and 0.82 (0.74-0.89), respectively. At a specificity of 0.95 in the task of separating PH and “normal” patients, the sensitivity of MPAD was 0.81 (0.72-0.90) and the sensitivity of rPA was 0.76 (0.66-0.85), but the specificity for both decreased when non-PH patients were included. For the combined PH and non-PH patient groups, the correlation between the vessel measurements and mPAP was significant but low, and the ability of the vessel measurements to predict mPAP was limited. Conclusion This study found that the sensitivity of previously published vessel criteria for identifying PH patients is high but the specificity may not be high enough for routine use in a clinical patient population.

Radiative lifetimes from laser-induced fluorescence measurements, accurate to $AE5%, are reported for 41 oddparity levels of Hf ii. The lifetimes are combined with branching fractions measured using Fourier transform spectrometry to determine transition probabilities for 150 lines of Hf ii. Approximately half of these new transition probabilities overlap with recent independent measurements using a similar approach. The two sets of measurements are found to be in good agreement for lines in common. Our new laboratory data are applied to refine the hafnium photospheric solar abundance and to determine hafnium abundances in 10 metal-poor giant stars with enhanced r-process abundances. For the Sun we derive log "(Hf) ¼ 0:88 AE 0:08 from four lines; the uncertainty is dominated by the weakness of the lines and their blending by other spectral features. Within the uncertainties of our analysis, the r-processYrich stars possess constant Hf /La and Hf /Eu abundance ratios, log "(Hf /La) ¼ À0:13 AE 0:02 (¼ 0:06) and log "(Hf / Eu) ¼ þ0:04 AE 0:02 (¼ 0:06). The observed average stellar abundance ratio of Hf /Eu and La /Eu is larger than previous estimates of the solar system r-processYonly value, suggesting a somewhat larger contribution from the r-process to the production of Hf and La. The newly determined Hf values could be employed as part of the chronometer pair, Th / Hf, to determine radioactive stellar ages.

No abstract

No abstract