Purpose: To assess regional differences in quantitative pulmonary perfusion parameters, i.e., pulmonary blood flow (PBF), mean transit time (MTT), and pulmonary blood volume (PBV) in the entire lung on a pixel-by-pixel basis in normal volunteers and pulmonary hypertension patients.
Materials and Methods:Three-dimensional ultrafast dynamic contrast-enhanced MR imaging was performed in 15 normal volunteers and 25 patients with pulmonary hypertension. From the signal intensity-time course curves, PBF, MTT and PBV maps were generated using deconvolution analysis, indicator dilution theories, and the central volume principle, on a pixel-by-pixel basis. From pulmonary perfusion parameter maps of normal volunteers and pulmonary hypertension patients, regional PBF, MTT, and PBV were statistically evaluated.Results: Regional PBF, MTT, and PBV showed significant differences in the gravitational and isogravitational directions (P Ͻ 0.05). The quantitative pulmonary perfusion parameter maps demonstrated significant differences between normal volunteers and pulmonary hypertension patients (P Ͻ 0.05).
Conclusion:Three-dimensional ultrafast dynamic contrast-enhanced MR imaging is feasible for the assessment of regional quantitative pulmonary perfusion parameters in the entire lung on a pixel-by-pixel basis in normal volunteers and pulmonary hypertension patients.
In order to examine phantom length necessary to assess radiation dose delivered to patients in cone-beam CT with an enlarged beamwidth, we measured dose profiles in cylindrical phantoms of sufficient length using a prototype 256-slice CT-scanner developed at our institute. Dose profiles parallel to the rotation axis were measured at the central and peripheral positions in PMMA (polymethylmethacrylate) phantoms of 160 or 320 mm diameter and 900 mm length. For practical application, we joined unit cylinders (150 mm long) together to provide phantoms of 900 mm length. Dose profiles were measured with a pin photodiode sensor having a sensitive region of approximately 2.8 x 2.8 mm2 and 2.7 mm thickness. Beamwidths of the scanner were varied from 20 to 138 mm. Dose profile integrals (DPI) were calculated using the measured dose profiles for various beamwidths and integration ranges. For the body phantom (320-mm-diam phantom), 76% of the DPI was represented for a 20 mm beamwidth and 60% was represented for a 138 mm beamwidth if dose profiles were integrated over a 100 mm range, while more than 90% of the DPI was represented for beamwidths between 20 and 138 mm if integration was carried out over a 300 mm range. The phantom length and integration range for dosimetry of cone-beam CT needed to be more than 300 mm to represent more than 90% of the DPI for the body phantom with the beamwidth of more than 20 mm. Although we reached this conclusion using the prototype 256-slice CT-scanner, it may be applied to other multislice CT-scanners as well.
Purpose: To investigate the usefulness of magnetic particle imaging (MPI) for predicting the therapeutic effect of magnetic hyperthermia (MH). Materials and Methods: First, we performed phantom experiments to investigate the relationship between the MPI value and the temperature rise of magnetic nanoparticles (MNPs) under an alternating magnetic field (AMF). The MPI value was defined as the pixel value of the transverse image reconstructed from the third-harmonic signals. Samples filled with various iron concentrations of MNPs (Resovist ®) were prepared and were imaged using our MPI scanner. These samples were also heated using the AMF, and the specific loss power (SLP) and volume-specific loss power (vSLP) were calculated from the initial slope of the time-dependent temperature rise. Second, we performed animal experiments using tumor-bearing mice, which were divided into untreated (n = 10) and treated groups (n = 20). The tumors in the treated group were injected with Resovist ® at an iron concentration of 250 mM (n = 10) or 500 mM (n = 10), and received MH for 20 min, during which the temperatures in the tumor and rectum were measured. The relative tumor volume growth (RTVG) was calculated from (V 15 − V 0)/V 0 , where V 0 and V 15 represented the tumor volume on day 0 and day 15 after MH, respectively. Results: In phantom experiments, the MPI value had significant correlations with the iron concentration of MNPs (r = 0.997), temperature rise (r = 0.981), and vSLP (r = 0.961). In animal experiments, the MPI value had significant correlations with the temperature rise in the tumor (r = 0.731) and RTVG (r = −0.687). Conclusion: Our preliminary results suggest that MPI is useful for predicting the therapeutic effect of MH.
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