Correlation between image noise and body weight in coronary CTA with 16-row MDCT

RATIONALE AND OBJECTIVES: To evaluate the correlation between image noise and body weight (BW) or body mass index (BMI) in coronary computed tomography angiography (CTA) as a potential parameter for reducing radiation dose in coronary CTA. MATERIALS AND METHODS: Thirty-six patients who underwent electrocardiogram-gated cardiac CT were analyzed in this study. The patients included 26 men and 10 women with a mean age of 60 years (range 43-79 years). All patients were imaged on a 16-row multidetector CT scanner. Mean value of BW and BMI was 83.5 kg and 28.1, respectively. Image noise was defined as standard deviation (SD) of the attenuation values measured by using 1 cm2 circular region of interest in the ascending aorta at the level of the right main pulmonary artery. The SD values were plotted against BW and BMI. The correlations were examined using a linear regression method. A P value of less than .05 was considered significant. RESULTS: The r value of linear regression between noise and BW was 0.90 (P < .001). The r value of linear regression between noise and BMI was 0.74 (P = .015). CONCLUSIONS: Excellent correlation was observed between noise and BW in coronary CTA. These data may be used as potential parameters for customized radiation dose modification to reduce radiation dose in coronary CT examinations.     

Abdominal imaging at 4 T MR system: a preliminary result

In this study, the potential for abdominal MR images at 4 T using a tailored coil was demonstrated using healthy volunteers. These images were compared with those obtained in the same subject at 1.5 T to discuss whether 4 T would be superior to 1.5 T in abdominal imaging. MR images at 4 T were characterized by high contrast and signal-to-noise ratios, more than 2.95 times higher than those at 1.5 T. In conclusion, abdominal MR imaging at 4 T was feasible. Furthermore, abdominal MR imaging at 4 T was superior to that at 1.5 T in qualitative and quantitative analyses.     

Centrically reordered inversion recovery half-Fourier single-shot turbo spin-echo sequence: improvement of the image quality of oxygen-enhanced MRI

PURPOSE: The purpose of the study presented here was to determine the improvement in image quality of oxygen-enhanced magnetic resonance (MR) subtraction imaging obtained with a centrically reordered inversion recovery half-Fourier single-shot turbo spin-echo (c-IR-HASTE) sequence compared with that obtained with a conventional sequentially reordered inversion recovery single-shot HASTE (s-IR-HASTE) sequence for pulmonary imaging. MATERIALS AND METHODS: Oxygen-enhanced MR imaging using a 1.5 T whole body scanner was performed on 12 healthy, non-smoking volunteers. Oxygen-enhanced MR images were obtained with the coronal two-dimensional (2D) c-IR-HASTE sequence and 2D s-IR-HASTE sequence combined with respiratory triggering. For a 256x256 matrix, 132 phase-encoding steps were acquired including four steps for phase correction. Inter-echo spacing for each sequence was 4.0 ms. The effective echo time (TE) for c-IR-HASTE was 4.0 ms, and 16 ms for s-IR-HASTE. The inversion time (TI) was 900 ms. To determine the improvement in oxygen-enhanced MR subtraction imaging by c-IR-HASTE, CNRs of subtraction image, overall image quality, and image degradation of the c-IR-HASTE and s-IR-HASTE techniques were statistically compared. RESULTS: CNR, overall image quality, and image degradation of c-IR-HASTE images showed significant improvement compared to those s-IR-HASTE images (P<0.05). CONCLUSION: Centrically reordered inversion recovery half-Fourier single-shot turbo spin-echo (c-IR-HASTE) sequence enhanced the signal from the lung and improved the image quality of oxygen-enhanced MR subtraction imaging.     

Radiation dose reduction in chest CT: a review

OBJECTIVE: This article aims to summarize the available data on reducing radiation dose exposure in routine chest CT protocols. First, the general aspects of radiation dose in CT and radiation risk are discussed, followed by the effect of changing parameters on image quality. Finally, the results of previous radiation dose reduction studies are reviewed, and important information contributing to radiation dose reduction will be shared. CONCLUSION: A variety of methods and techniques for radiation dose reduction should be used to ensure that radiation exposure is kept as low as is reasonably achievable.     

Fast magnetic resonance imaging of the lung.

The impact of fast MR techniques developed for MR imaging of the lung will soon be recognized as equivalent to the high-resolution technique in chest CT imaging. In this article, the difficulties in MR imaging posed by lung morphology and its physiological motion are briefly introduced. Then, fast MR imaging techniques to overcome the problems of lung imaging and recent applications of the fast MR techniques including pulmonary perfusion and ventilation imaging are discussed. Fast MR imaging opens a new exciting window to multi-functional MR imaging of the lung. We believe that fast MR functional imaging will play an important role in the assessment of pulmonary function and disease process.     

Evaluation of soft palate function with MRI: application to the cleft palate patient.

Magnetic resonance imaging was employed to evaluate soft palate function in four normal volunteers and four patients with surgically repaired cleft palate, using a GE Signa clinical scanner at 1.5 T and a custom designed receive coil with a sensitivity profile encompassing from the nasopharynx to the larynx. Midsagittal images were obtained using spoiled gradient recalled acquisition at steady state while the subject phonated the following sounds: (a) MMM, (b) SSS, (c) DAH, and (d) EEE. An image at rest with normal breathing was also obtained. The soft palate and its relationship to the airway and the posterior pharyngeal wall were clearly visualized in all cases. Phonation of the prescribed sounds demonstrated the normal range of soft palate motion. The images also depicted the ability of the soft palate to divert airflow to the nasopharynx. Interpretation of functional MRI may be of value in evaluation of surgical results, guidance of speech therapy, and surgical planning in the cleft palate patient. This noninvasive alternative to conventional methods of visualization provides advantages in resolution, repeatability, and patient comfort.     

High-resolution magnetic resonance imaging of pulmonary circulation; a prospect

A prospect on high-resolution magnetic resonance imaging of pulmonary circulation is presented, utilizing surface coils, ECG-gating, fast scan technique and breath-holding. A goal for MRI should be the blood-flow-related information, which can not be obtained by CT.