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Objectives: To evaluate the diagnostic performance of brain CT images reconstructed with a model-based iterative algorithm performed at usual and reduced dose., Methods: 115 patients with histologically proven lung cancer were prospectively included over 15 months. Patients underwent two CT acquisitions at the initial staging, performed on a 256-slice MDCT, at standard (CTDIvol: 41.4 mGy) and half dose (CTDIvol: 20.7 mGy). Both image datasets were reconstructed with filtered back projection (FBP) and iterative model-based reconstruction (IMR) algorithms. Brain MRI was considered as the reference. Two blinded independent readers analysed the images., Results: Ninety-three patients underwent all examinations. At the standard dose, eight patients presented 17 and 15 lesions on IMR and FBP CT images, respectively. At half-dose, seven patients presented 15 and 13 lesions on IMR and FBP CT images, respectively. The test could not highlight any significant difference between the standard dose IMR and the half-dose FBP techniques (p-value = 0.12). MRI showed 46 metastases on 11 patients. Specificity, negative and positive predictive values were calculated (98.9-100 %, 93.6-94.6 %, 75-100 %, respectively, for all CT techniques)., Conclusion: No significant difference could be demonstrated between the two CT reconstruction techniques., Key Points: • No significant difference between IMR100 and FBP50 was shown. • Compared to FBP, IMR increased the image quality without diagnostic impairment. • A 50 % dose reduction combined with IMR reconstructions could be achieved. • Brain MRI remains the best tool in lung cancer staging.

Objectives: To compare image quality [low contrast (LC) detectability, noise, contrast-to-noise (CNR) and spatial resolution (SR)] of MDCT images reconstructed with an iterative reconstruction (IR) algorithm and a filtered back projection (FBP) algorithm., Methods: The experimental study was performed on a 256-slice MDCT. LC detectability, noise, CNR and SR were measured on a Catphan phantom scanned with decreasing doses (48.8 down to 0.7 mGy) and parameters typical of a chest CT examination. Images were reconstructed with FBP and a model-based IR algorithm. Additionally, human chest cadavers were scanned and reconstructed using the same technical parameters. Images were analyzed to illustrate the phantom results., Results: LC detectability and noise were statistically significantly different between the techniques, supporting model-based IR algorithm (p < 0.0001). At low doses, the noise in FBP images only enabled SR measurements of high contrast objects. The superior CNR of model-based IR algorithm enabled lower dose measurements, which showed that SR was dose and contrast dependent. Cadaver images reconstructed with model-based IR illustrated that visibility and delineation of anatomical structure edges could be deteriorated at low doses., Conclusion: Model-based IR improved LC detectability and enabled dose reduction. At low dose, SR became dose and contrast dependent., Key Points: • Model- based Iterative Reconstruction improves detectability of low contrast object. • With model- based Iterative Reconstruction, spatial resolution is dose and contrast dependent. • Model-based Iterative Reconstruction algorithms enable improved IQ combined with dose-reduction possibilities. • Improvement of SR and LC detectability on the same IMR data set would reduce reconstructions.

Purpose: To evaluate the technical quality and the diagnostic performance of a protocol with use of low volumes of contrast medium (25 mL) at 64-detector spiral computed tomography (CT) in the diagnosis and management of adult, nontraumatic subarachnoid hemorrhage (SAH)., Materials and Methods: This study was performed outside the United States and was approved by the institutional review board. Intracranial CT angiography was performed in 73 consecutive patients with nontraumatic SAH diagnosed at nonenhanced CT. Image quality was evaluated by two observers using two criteria: degree of arterial enhancement and venous contamination. The two independent readers evaluated diagnostic performance (lesion detection and correct therapeutic decision-making process) by using rotational angiographic findings as the standard of reference. Sensitivity, specificity, and positive and negative predictive values were calculated for patients who underwent CT angiography and three-dimensional rotational angiography. The intraclass correlation coefficient was calculated to assess interobserver concordance concerning aneurysm measurements and therapeutic management., Results: All aneurysms were detected, either ruptured or unruptured. Arterial opacification was excellent in 62 cases (85%), and venous contamination was absent or minor in 61 cases (84%). In 95% of cases, CT angiographic findings allowed optimal therapeutic management. The intraclass correlation coefficient ranged between 0.93 and 0.95, indicating excellent interobserver agreement., Conclusion: With only 25 mL of iodinated contrast medium focused on the arterial phase, 64-detector CT angiography allowed satisfactory diagnostic and therapeutic management of nontraumatic SAH., (© RSNA, 2012.)

Background: Tai Chi Chuan is becoming a popular exercise among elders. This study measured the inter-segmental forces and moments at the lower extremity joints during a Tai Chi gait as compared to those during normal walking gait, in both apparently healthy young and elderly Tai Chi Chuan practitioners., Methods: Three-dimensional inter-segmental joint reaction force and moment were computed using the Inverse Dynamic Approach based on the kinematics and ground reaction force measurements in a laboratory setting in six young (two females, mean age 28; SD 6 years) and six elderly (five females, mean age 72; SD 8 years) subjects who had previous training of Yang style Tai Chi Chuan., Findings: The results showed significant gait differences in both age groups, with significantly smaller peak compressive forces, larger peak shear forces in the ankle, knee and hip joints, and larger peak moments in the knee and hip joints during Tai Chi gait as compared to normal gait. Moreover, the peak shear force was oriented more in the medial-lateral direction at the ankle and knee joints, and the peak moment was in the frontal plane at the knee and hip joints. The results also showed significant age differences, with significantly smaller peak shear forces in all three joints in the elderly group than in the young group during Tai Chi gait., Interpretation: Tai Chi gait has an increased shear force and frontal plane torque at lower extremity joints than normal gait. The shear force at all three lower extremity joints during Tai Chi gait is lower in the elderly subjects than young subjects. This data suggest that, in Tai Chi Chuan training, elderly people with degenerative joint diseases in the lower extremity should use caution when practicing Tai Chi Chuan.

This study was to quantitatively characterize the spatial, temporal, and neuromuscular activation patterns of Tai Chi gait (TCG). Ten healthy young subjects were tested. The kinematics of TCG and normal gait (NG) were measured using a marker-based motion analysis system and two biomechanical force plates. Surface electromyography (EMG) was recorded from six left-side muscles: tibialis anterior, soleus, peronaeus longus, rectus femoris, semitendinosus, and tensor fasciae latae. The results showed that TCG had (1) a longer cycle duration (11.9+/-2.4 vs. 1.3+/-0.2 s) and a longer duration of single-leg stance time (1.8+/-0.6 vs. 0.4+/-0.05 s); (2) a larger joint motion in ankle dorsi/plantar flexion (40+/-9 degrees vs. 20+/-8 degrees), knee flexion (82+/-8 degrees vs. 53+/-10 degrees), hip flexion (81+/-7 degrees vs. 24+/-4 degrees), and hip abduction (20+/-8 degrees vs. 0+/-3 degrees); (3) a larger lateral body shift (>25% vs. 5% body height); and (4) significant involvement of ankle dorsiflexors, knee extensors/hip flexors and hip abductors, as indicated by significantly higher peak (88+/-14%, 80+/-18% and 83+/-17% vs. 35+/-10%, 14+/-8% and 28+/-19% peak amplitude, respectively) and root-mean-square values of their EMG (37+/-6%, 32+/-7% and 33+/-7% vs. 23+/-7%, 11+/-8% and 22+/-11% peak amplitude, respectively), longer proportions of action (76+/-19%, 68+/-8% and 65+/-19% vs. 59+/-23%, 16+/-23% and 40+/-32% gait cycle duration, respectively), longer proportions of isometric and eccentric actions, and longer proportions of co-activations. These results demonstrate that the biomechanical characteristics of TCG can be quantified. The quantification of TCC movements is important for understanding its effect on balance, flexibility, strength, and health.

The systemic effect of three beta-blocking eyedrops was compared in a placebo-controlled, double-blind trial in 12 healthy male volunteers. Each subject received successively each treatment in random order at weekly intervals. The eyedrops administered were as follows: 0.5% timolol, 2% carteolol, 0.6% metipranolol, and placebo. We evaluated the intraocular pressure and systemic beta-blockade 3 hours after a single administration of one eyedrop in each eye. The systemic beta-blocking effect was evaluated by the isoproterenol sensitivity test, that is the dose of isoproterenol required to increase resting heart rate by 25 bpm (I25). Each beta-blocking eyedrop antagonized the chronotropic effect of isoproterenol. I25 for placebo was 3.1 +/- 0.5 micrograms, for metipranolol 5.2 +/- 0.9 micrograms (P less than 0.005), for timolol 10.9 +/- 1.9 micrograms (P less than 0.001), and for carteolol 39.6 +/- 5.4 micrograms (P less than 0.0005). Each treatment significantly decreased the intraocular pressure: metipranolol 3.6 +/- 0.4 mm Hg (P less than 0.001), timolol 2.44 +/- 0.4 mm Hg (P less than 0.01), and carteolol 2.38 +/- 0.48 mm Hg (P less than 0.01) compared with placebo. The resting heart rate and blood pressure were not influenced by the treatments. Even though the results might be different in the case of an earlier or a later time of evaluation or chronic administration, we believe that the isoproterenol sensitivity test may be used to evaluate the systemic effect of beta-blocking eyedrops.