Tobias Fält

POST-PROCESSING IMAGE FILTRATION ENABLING DOSE REDUCTION IN STANDARD ABDOMINAL CT.

The collective effective radiation dose to the population is increasing due to a higher use of computerised tomography. SharpView AB, Linköping, Sweden, has developed an adaptive non-linear post-processing image filtration that may enable the use of lower radiation doses. The present study assessed if a lower dose with image filtration had the same image quality as a higher dose without the filter applied. All imaging was performed on a Siemens Somatom Sensation 16 CT. The parameters used were 120 kV and 200 mAs (40 patients) and 130 mAs without and with image filtering (40 patients), respectively. All studies were quantitatively evaluated for noise and image quality was assessed by visual grading characteristics (VGC) analysis. After image filtration, the noise in the processed images was lowered and the image quality was improved as shown by the VGC analysis. However, images using the higher dose were still ranked as the best in five out of eight criteria as shown by the VGC analysis. Image filtration enhances CT images significantly and further studies will show if 130 mAs with image filtration may be sufficient for clinically general abdominal CT.

PCR-denaturing gradient gel electrophoresis and two feces antigen tests for detection of Helicobacter pylori in mice

PCR-denaturing Gradient Gel Electrophoresis (PCR-DGGE), a method suitable for the detection of microbial species in complex ecosystems, was evaluated for the detection and identification of Helicobacter spp. in feces and stomach tissue of mice. Two commercially available stool antigen tests for clinical diagnostics in humans were also evaluated in the C57B1/6 mouse model of H. pylori infection. PCR-DGGE detected only Helicobacter ganmani in feces from H. pylori-infected as well as control animals, whereas in stomach specimens it demonstrated the presence of H. pylori in challenged and H. ganmani in control animals. Hence, the method detected DNA only of the predominant Helicobacter spp., which was also shown in cell dilution experiments. The Amplified IDEIA Hp StAR feces antigen test detected H. pylori in feces from all infected animals and generated no false-positive results, whereas the Premier Platinum HpSA-test also detected H. pylori in all infected animals but generated false-positive or equivocal results in 50% of the control animals. Premier Platinum HpSA, as opposed to Hp StAR, cross-reacted with non-pylori Helicobacter spp. in vitro.

Material decomposition in dual-energy computed tomography separates high-Z elements from iodine, identifying potential contrast media tailored for dual contrast medium examinations

Objective The aim of this study was to determine the potential of different high-Z elements to act as contrast media (CMs) alongside iodine (I) in dual-CM, dual-energy (DE) computed tomography examinations. Methods Gadolinium (Gd), tantalum (Ta), wolfram (W), gold (Au), and bismuth (Bi) in addition to I were examined at all available kilovolt settings in a DE computed tomography scanner. Dual-energy ratios were calculated by dividing attenuation at low kilovolt by attenuation at high kilovolt. Dual-energy data sets were loaded into material decomposition software to evaluate separation of the elements from I. Results The DE ratios of Ta, W, and Au ranged between 0.9 and 1.2, being considerably lower than I at 1.9 to 2.6. These elements were completely separated from I using material decomposition. Gadolinium and Bi were more similar to I at 1.4 to 1.9. However, separation was nearly complete for Bi and suboptimal for Gd. Conclusions Tantalum, W, and Au are ideal candidates for dual-CM examinations, whereas Bi is a slightly weaker candidate.

Seesaw Balancing Radiation Dose and IV Contrast Dose: Evaluation of a New Abdominal CT Protocol for Reducing Age-Specific Risk

OBJECTIVE The purpose of this study was to evaluate an abdominal CT protocol in which radiation dose was reduced and i.v. contrast dose increased for young patients and radiation dose was increased and i.v. medium dose decreased for elderly patients. The hypothesis was that these adjustments would result in constant image quality and a reduction in age-specific risk. MATERIALS AND METHODS Patients were divided into four age groups of 25 patients each: group 1, 16-25 years; group 2, 26-50 years; group 3, 51-75 years; and group 4, older than 75 years. The quality reference tube load ranged from 100 to 300 mAs, and the i.v. contrast dose ranged from 600 to 350 mg I/kg. Group 3 was the reference group. Signal-to-noise and contrast-to-noise ratios for a hypothetical hypovascular liver metastatic lesion were calculated. Subjective image quality was evaluated by visual grading characteristic analysis in which four readers assessed the reproduction of seven image-quality criteria. RESULTS Radiation dose was reduced 57% in the youngest group, and the i.v. contrast dose was reduced 18% in elderly patients. There were no statistically significant differences between the groups with respect to signal-to-noise and contrast-to-noise ratios. Subjective image quality was graded significantly lower for four criteria in group 1 compared with group 3. No significant difference was found in comparisons of groups 2 (except for one criterion) and 4 with group 3. CONCLUSION It is possible to balance radiation dose and contrast dose against each other and maintain signal-to-noise and contrast-to-noise ratios. Subjective image quality was affected by increased noise level on the images but was judged acceptable in all groups except the one with the lowest radiation dose.