Impact of iterative reconstruction on image quality and radiation dose in multidetector CT of large body size adults

Objective

To compare image quality and radiation dose using Adaptive Statistical Iterative Reconstruction (ASiR) and Filtered Back Projection (FBP) in patients weighing ≥91?kg.

Methods

In this Institution Review Board-approved retrospective study, single-phase contrast-enhanced abdominopelvic CT examinations of 100 adults weighing ≥91?kg (mean body weight: 107.6?±?17.4?kg range: 91–181.9?kg) with (1) ASiR and (2) FBP were reviewed by two readers in a blinded fashion for subjective measures of image quality (using a subjective standardized numerical scale and objective noise) and for radiation exposure. Imaging parameters and radiation dose results of the two techniques were compared within weight and BMI sub-categories.

Results

All examinations were found to be of adequate quality. Both subjective (mean?=?1.4?±?0.5 vs. 1.6?±?0.6, P?P?P?Conclusion In obese individuals, abdominal CT images reconstructed using ASiR provide diagnostic images with reduced image noise at lower radiation dose.

Key Points

? CT images in obese adults are noisy, even with high radiation dose. ? Newer iterative reconstruction techniques have theoretical advantages in obese patients. ? Adaptive statistical iterative reconstruction should reduce image noise and radiation dose. ? This has been proven in abdominopelvic CT images of obese patients.     

Management implications of fluorodeoxyglucose positron emission tomography/magnetic resonance in untreated intrahepatic cholangiocarcinoma

European Journal of Nuclear Medicine and Molecular Imaging - Intrahepatic cholangiocarcinoma (ICC) is associated with a poor prognosis with surgical resection offering the best chance for long-term...     

Evaluation of high-resolution CT and MR cisternography in the diagnosis of cerebrospinal fluid fistula.

PURPOSEWe undertook this study to determine the accuracy of MR cisternography and plain high-resolution CT as a noninvasive alternative to CT cisternography in the diagnosis of CSF fistula in patients with clinically suspected CSF rhinorrhea.METHODSForty-five consecutive patients with clinically suspected CSF rhinorrhea were examined prospectively for CSF fistula with MR cisternography and plain high-resolution CT. Twenty-one patients also underwent CT cisternography. The MR imaging technique included 3-mm thin-section T1-weighted coronal sequences and fast spin-echo T2-weighted coronal, axial, and sagittal sequences in the supine position. The plain high-resolution CT study included 3-mm and sometimes 1- to 1.5-mm thin coronal sections in the prone position. Similar sequences were used after injecting nonionic contrast material intrathecally via lumbar puncture for the CT cisternographic study. The plain high-resolution CT and MR cisternographic studies were compared with results of CT cisternography; surgical findings were used as the standard of reference.RESULTSPlain high-resolution CT successfully depicted the presence or absence of CSF fistula in 42 of 45 patients, whereas MR cisternography was correct in 40 patients. MR cisternography or plain high-resolution CT correctly showed the site(s) of CSF fistula leakage in 36 of the 38 cases proved surgically. The combined techniques also correctly indicated the absence of CSF leakage in seven cases, six of which were confirmed at CT cisternography. Both MR cisternography and high-resolution CT failed to definitively locate the CSF fistula in two patients. High-resolution CT was accurate in 93% of patients, whereas MR cisternography was accurate in 89% of patients. The combination of high-resolution CT and MR cisternography was accurate in 96% of patients.CONCLUSIONIn the presence of clinically diagnosed CSF leakage, the combination of MR cisternography and plain high-resolution CT is highly accurate in locating the site and extent of CSF fistula and should be considered a viable noninvasive alternative to CT cisternography.     

Implicit knowledge of visual uncertainty guides decisions with asymmetric outcomes

Perception is an "inverse problem," in which the state of the world must be inferred from the sensory neural activity that results. However, this inference is both ill-posed (Helmholtz, 1856; Marr, 1982) and corrupted by noise (Green & Swets, 1989), requiring the brain to compute perceptual beliefs under conditions of uncertainty. Here we show that human observers performing a simple visual choice task under an externally imposed loss function approach the optimal strategy, as defined by Bayesian probability and decision theory (Berger, 1985; Cox, 1961). In concert with earlier work, this suggests that observers possess a model of their internal uncertainty and can utilize this model in the neural computations that underlie their behavior (Knill & Pouget, 2004). In our experiment, optimal behavior requires that observers integrate the loss function with an estimate of their internal uncertainty rather than simply requiring that they use a modal estimate of the uncertain stimulus. Crucially, they approach optimal behavior even when denied the opportunity to learn adaptive decision strategies based on immediate feedback. Our data thus support the idea that flexible representations of uncertainty are pre-existing, widespread, and can be propagated to decision-making areas of the brain.     

Cholesterol crystal embolization presenting as either solid or cystic pancreatic lesion

Cholesterol crystal embolization (CCE) can result in end-organ ischemia. Retrospective review of clinicopathologic data. The first patient was anticoagulated with coumadin for chronic atrial fibrillation and presented subacutely with a solid mass. The second patient suffered from coronary artery disease post-angioplasty/stenting and presented with acute pancreatitis and pancreatic cystification. CCE should be considered in patients with significant vascular disease, arrhythmias or vascular manipulation who present with a pancreatic mass.     

Comparison of enhancement, image quality, cost, and adverse reactions using 2 different contrast medium concentrations for routine chest CT on 16-slice MDCT

OBJECTIVE: To evaluate the degree of enhancement and image quality of chest computed tomographic (CT) examinations on 16-slice multidetector CT using low-concentration [300 milligrams of iodine per milliliter (mg I/mL)] and high-concentration (370 mg I/mL) contrast media; to assess the impact on cost and adverse reactions of the use of high-iodine concentration contrast medium. MATERIALS AND METHODS: A total of 100 patients scheduled for routine chest CT examinations were administered nonionic contrast medium of 2 strengths: low-iodine concentration contrast medium (300 mg I/mL) [group A: n = 50; male-female ratio, 28:22; mean age, 58.4 years] and high-iodine concentration contrast medium (370 mg I/mL) (group B: n = 50; male-female ratio, 18:32; mean age, 57.6 years) with a constant amount of iodine (400 mg) injected per kilogram of body weight. Contrast media were injected using a dual injector at 2.5 mL/s followed by a 30-mL saline at 2.5 mL/s. The degree of enhancement was quantified by measuring Hounsfield unit values in different arteries and veins and was also rated on a 5-point scale for qualitative assessment. We also evaluated perivenous contrast-related artifacts. The data were compared using Mann-Whitney U test for both qualitative and quantitative enhancement ratings. A value of less than 0.05 was considered statistically significant. The value was adjusted using Bonferroni correction for statistical significance when multiple comparisons were performed. The difference in cost and the incidence of adverse reactions in both groups were calculated. RESULTS: The mean enhancement values in group B were significantly greater (P < 0.05) than those in group A. The mean Hounsfield units and standard deviation in groups A and B were aorta = 153 +/- 4, 216 +/- 20; pulmonary artery = 147 +/- 10, 208 +/- 20; superior vena cava = 155 +/- 27, 299 +/- 72; and pulmonary vein = 134 +/- 10, 215 +/- 30, respectively. The mean enhancement on a 5-point scale was greater in group B (4.2) than in group A (3.3) (P < 0.01). No significant difference between groups in perivenous artifacts was seen. Up to 5.5% savings in cost resulted from the use of a higher concentration of iodine, with no increase in adverse reactions. CONCLUSIONS: Use of higher-concentration contrast media provides a higher degree of contrast enhancement and image quality for a routine chest CT on a 16-slice multidetector CT. It also contributes to considerable cost savings with no increased risk of adverse reactions compared with low-concentration contrast media.