Model-based iterative reconstruction for 320-detector row CT angiography reduces radiation exposure in infants with complex congenital heart disease

PURPOSEWe investigated the impact of model-based iterative reconstruction (MBIR) on 320-detector row computed tomography angiography (CTA) in infants with complex congenital heart disease (CHD).METHODSSeventy infants with complex CHD who underwent 320-detector row CTA (40 boys and 30 girls; age range, 0–22 months; median age, 60 days) were retrospectively evaluated. First, the images were reconstructed by filtered back projection (FBP), hybrid iterative reconstruction (HIR), or MBIR in 20 cases, and variables were compared among the three iterative reconstruction methods (IR test). Second, the variables were compared between 25 cases scanned using HIR and 25 cases scanned using MBIR, with a 20 standard deviation noise level for both. Attenuation values and contrast-to-noise ratios (CNRs) of the great vessels and heart chambers were calculated. Total dose-length products were recorded for all patients (radiation dose: RD test).RESULTSIn the IR test, the mean CNR values were 4.8±1.3 for FBP, 6.9±1.4 for HIR, and 8.2±1.7 for MBIR (P < 0.0001). The best subjective image qualities in the great vessels and heart chambers were obtained with MBIR. In RD testing, no significant differences between HIR and MBIR in image quality (CNR: HIR, 8.4±2.4; MBIR, 8.3±2.4) were observed. The effective dose was significantly lower for MBIR than for HIR (0.7±0.2 vs. 1.1±0.3 mSv; P < 0.001).CONCLUSIONThe MBIR algorithm significantly improved image quality and decreased radiation exposure in 320-row CTA of infants with complex CHD, providing an alternative to FBP or HIR that is both safer and produces better results

Characterization of lung cancer by amide proton transfer (APT) imaging: an in-vivo study in an orthotopic mouse model.

Amide proton transfer (APT) imaging is one of the chemical exchange saturation transfer (CEST) imaging methods which images the exchange between protons of free tissue water and the amide groups (-NH) of endogenous mobile proteins and peptides. Previous work suggested the ability of APT imaging for characterization of the tumoral grade in the brain tumor. In this study, we tested the feasibility of in-vivo APT imaging of lung tumor and investigated whether the method could differentiate the tumoral types on orthotopic tumor xenografts from two malignant lung cancer cell lines. The results revealed that APT imaging is feasible to quantify lung tumors in the moving lung. The measured APT effect was higher in the tumor which exhibited more active proliferation than the other. The present study demonstrates that APT imaging has the potential to provide a characterization test to differentiate types or grade of lung cancer noninvasively, which may eventually reduce the need invasive needle biopsy or resection for lung cancer

Amide Proton Transfer Imaging of Diffuse Gliomas: Effect of Saturation Pulse Length in Parallel Transmission-Based Technique

<div><p>In this study, we evaluated the dependence of saturation pulse length on APT imaging of diffuse gliomas using a parallel transmission-based technique. Twenty-two patients with diffuse gliomas (9 low-grade gliomas, LGGs, and 13 high-grade gliomas, HGGs) were included in the study. APT imaging was conducted at 3T with a 2-channel parallel transmission scheme using three different saturation pulse lengths (0.5 s, 1.0 s, 2.0 s). The 2D fast spin-echo sequence was used for imaging. Z-spectrum was obtained at 25 frequency offsets from -6 to +6 ppm (step 0.5 ppm). A point-by-point B0 correction was performed with a B0 map. Magnetization transfer ratio (MTR_asym) and ΔMTR_asym (contrast between tumor and normal white matter) at 3.5 ppm were compared among different saturation lengths. A significant increase in MTR_asym (3.5 ppm) of HGG was found when the length of saturation pulse became longer (3.09 ± 0.54% at 0.5 s, 3.83 ± 0.67% at 1 s, 4.12 ± 0.97% at 2 s), but MTR_asym (3.5 ppm) was not different among the saturation lengths in LGG. ΔMTR_asym (3.5 ppm) increased with the length of saturation pulse in both LGG (0.48 ± 0.56% at 0.5 s, 1.28 ± 0.56% at 1 s, 1.88 ± 0.56% at 2 s and HGG (1.72 ± 0.54% at 0.5 s, 2.90 ± 0.49% at 1 s, 3.83 ± 0.88% at 2 s). In both LGG and HGG, APT-weighted contrast was enhanced with the use of longer saturation pulses.</p></div

Amide Proton Transfer Imaging of Diffuse Gliomas: Effect of Saturation Pulse Length in Parallel Transmission-Based Technique - Fig 1

<p>Z-spectra of LGG <b>(A)</b>, HGG <b>(C)</b>, and corresponding NAWM <b>(B, D)</b>. Z-spectra of tumor was steeper than that of NAWM, presumably because of less MT effect in tumor compared with NAWM. Prolongation of saturation pulses results in larger MT effect and thus wider Z-spectra in both tumor and NAWM.</p

Amide Proton Transfer Imaging of Diffuse Gliomas: Effect of Saturation Pulse Length in Parallel Transmission-Based Technique - Fig 2

<p>MTR_asym of tumor <b>(A)</b> and NAWM <b>(B)</b> and ΔMTR_asym <b>(C)</b> in LGG. MTR_asym (<b>A</b>) of tumor was decreased with the saturation length in lower frequency range (1–2 ppm), but equivalent at 3.5 ppm. MTR_asym of NAWM (<b>B</b>) is decreased with the saturation length in the entire frequency range. ΔMTR_asym (<b>C</b>) was increased with the saturation length at higher frequency offsets (>2 ppm).</p

A case of glioblastoma multiforme (Grade IV, HGG).

<p>The APT-weighted signal of the tumor in the left temporal lobe is increased with the saturation length, and the contrast between tumor and normal brain tissue becomes larger at longer saturation pulses.</p

MTR_asym of tumor and NAWM and ΔMTR_asym in HGG.

<p>MTR_asym of tumor <b>(A)</b> was decreased with the saturation length in lower frequency range (<2 ppm), but was increased at 3.5 ppm. MTR_asym of NAWM <b>(B)</b> was decreased with the saturation length in entire frequency range. ΔMTR_asym <b>(C)</b> was increased with the saturation length at higher frequency (>2 ppm). ΔMTR_asym (3.5 ppm) with the 2 s saturation reached maximum at around 3.5 ppm (specific frequency of amide protons).</p

MTR_asym (3.5 ppm) and ΔMTR_asym (3.5 ppm) of LGG and HGG.

<p>No significant differences were observed in MTR_asym (3.5 ppm) among the three saturation lengths in LGG, while MTR_asym (3.5 ppm) with the 1 s and 2 s saturation was significantly higher than that with the 0.5 s saturation in HGG (<b>A</b>). ΔMTR_asym (3.5 ppm) with the 1 s and 2 s saturation length was significantly higher than that with the 0.5 s saturation in LGG, and ΔMTR_asym (3.5ppm) of HGG significantly increased with the saturation length (<b>B</b>). Both MTR_asym (3.5ppm) and ΔMTR_asym (3.5ppm) were significantly higher in HGG than in LGG at any saturation pulse lengths.</p

A case of diffuse astrocytoma (Grade II, LGG).

<p>The APT-weighted signal of the tumor in the left frontal lobe is almost comparable in all the saturation pulse lengths, but the contrast between tumor and normal brain tissue is slightly increased at longer saturation pulses due to decreased signal in NAWM.</p

Correlating Function and Imaging Measures of the Medial Longitudinal Fasciculus.

OBJECTIVE:To test the validity of diffusion tensor imaging (DTI) measures of tissue injury by examining such measures in a white matter structure with well-defined function, the medial longitudinal fasciculus (MLF). Injury to the MLF underlies internuclear ophthalmoparesis (INO). METHODS:40 MS patients with chronic INO and 15 healthy controls were examined under an IRB-approved protocol. Tissue integrity of the MLF was characterized by DTI parameters: longitudinal diffusivity (LD), transverse diffusivity (TD), mean diffusivity (MD) and fractional anisotropy (FA). Severity of INO was quantified by infrared oculography to measure versional disconjugacy index (VDI). RESULTS:LD was significantly lower in patients than in controls in the medulla-pons region of the MLF (p < 0.03). FA was also lower in patients in the same region (p < 0.0004). LD of the medulla-pons region correlated with VDI (R = -0.28, p < 0.05) as did FA in the midbrain section (R = 0.31, p < 0.02). CONCLUSIONS:This study demonstrates that DTI measures of brain tissue injury can detect injury to a functionally relevant white matter pathway, and that such measures correlate with clinically accepted evaluation indices for INO. The results validate DTI as a useful imaging measure of tissue integrity