Hepatitis C virus core antigen testing in liver and kidney transplant recipients.

HCV RNA levels correlate with the long-term outcome of hepatitis C in liver transplant recipients. Nucleic acid testing (NAT) is usually used to confirm HCV reinfection and to examine viral loads after liver transplantation. HCV core antigen (HCVcoreAg) testing could be an alternative to NAT with some potential advantages including very low intra- and interassay variabilities and lower costs. The performance of HCVcoreAg testing in organ transplant recipients is unknown. We prospectively studied 1011 sera for HCV RNA and HCVcoreAg in a routine real-world setting including 222 samples obtained from patients after liver or kidney transplantation. HCV RNA and HCVcoreAg test results showed a consistency of 98% with a very good correlation in transplanted patients (r > 0.85). The correlation between HCV RNA and HCVcoreAg was higher in sera with high viral loads and in samples from patients with low biochemical disease. Patients treated with tacrolimus showed a better correlation between both parameters than individuals receiving cyclosporine A. HCV RNA/HCVcoreAg ratios did not differ between transplanted and nontransplanted patients, and HCV RNA and HCVcoreAg kinetics were almost identical during the first days after liver transplantation. HCVcoreAg testing can be used to monitor HCV viral loads in patients after organ transplantation. However, the assay is not recommended to monitor antiviral therapies.

Frequency split metal artefact reduction in pelvic computed tomography.

OBJECTIVES: Artefacts from total hip replacement affect image quality and the visualisation of pelvic lesions on computed tomography (CT). We propose a frequency split (FS) approach in addition to the normalised metal artefact reduction (NMAR) algorithm that aims to suppress artefacts and improves image quality in patients with orthopaedic hardware. METHODS: Data from ten consecutive patients with metal artefacts from uni- (n = 5) and bilateral (n = 4) total hip replacement or osteosynthesis (n = 1) were reconstructed with filtered back projection (FBP), linear interpolation MAR (LIMAR), NMAR, FSLIMAR and FSNMAR and analysed for image quality and severity of artefacts. RESULTS: NMAR and FSNMAR significantly improved the assessment of the pelvic organs, lymph nodes and vessels compared with FBP, LIMAR or FSLIMAR (P < 0.05). Assessment of the metal hardware, joint and capsule was improved with the addition of FS (FSLIMAR, FSNMAR). No algorithm-related artefacts were detected in regions that did not contain metal. CONCLUSIONS: NMAR, FSLIMAR and FSNMAR have the potential to improve image quality in patients with artefacts from metal hardware and to improve the diagnostic accuracy of CT of the organs of the pelvis. Although introducing some algorithm-related artefacts, FSNMAR most accurately displayed adjacent bone and tissue next to metal implants. KEY POINTS: • Orthopaedic metallic hardware often creates serious artefacts in computed tomography, hindering diagnosis. • The normalised metal artefact reduction (NMAR) algorithm was developed to suppress such artefacts. • NMAR improves CT assessment of pelvic organs in patients with orthopaedic hardware. • Addition of the frequency split technique (FSNMAR) helps assess tissue near metal hardware. • NMAR and FSNMAR are robust and computationally effective sinogram interpolation algorithms.

Chronic hepatitis e in heart transplant recipients.

Chronic courses of hepatitis E virus (HEV) infections have been described in immunosuppressed patients. We aimed to study the role of HEV infections in heart transplant recipients (HTR). 274 HTR were prospectively screened for HEV infection using an anti-HEV-IgG ELISA and HEV-PCR. In addition, 137 patients undergoing cardiac surgery (non-HTR) and 537 healthy subjects were studied cross-sectionally. The anti-HEV-IgG seroprevalence was 11% in HTR, 7% in non-HTR and 2% in healthy controls (HTR vs. healthy controls p<0.0001; non-HTR vs. healthy controls p<0.01). Anti-HEV tested positive in 4.0% in control cohorts of other immunocompromised patients (n = 474). Four HTR (1.5%) were chronically infected with HEV as shown by HEV-PCR and all four patients had liver transaminases of >200 IU/L and histological or clinical evidence of advanced liver disease. In three patients ribavirin treatment was successful with a sustained biochemical and virological response while treatment failed in one cirrhotic patient after ribavirin dose reduction. Heart transplant recipients and patients undergoing cardiac surgery have an increased risk for HEV infections. Chronic hepatitis E may explain elevated liver enzymes in heart transplant recipients. Treatment of HEV infection with ribavirin is effective but the optimal dose and duration of ribavirin therapy remains to be determined.

Chronic hepatitis E in hematopoietic stem cell transplant patients in a low-endemic country?

Cases of chronic hepatitis E have been described in patients after kidney and liver transplantation. In addition, hepatitis E virus (HEV) reactivation was reported after hematopoietic stem cell transplantation (HSCT). We here evaluated if HEV infection might explain elevated liver enzymes in a well selected cohort of allogeneic HSCT patients with biochemical evidence of hepatitis (n = 52). Of note, none of the subjects tested positive for HEV RNA, including 2 HSCT patients who had been infected with HEV already before transplantation. Thus, both chronic courses of HEV infections and HEV reactivations seem to be rather rare events in HSCT patients in a non-endemic country.

Hepatitis E: an emerging infectious disease in Germany?

Increased frequencies of HEV infections have been reported in several industrialized countries. We suggest that this finding might be explained by a better awareness of the disease and not by an increased incidence. Although reported HEV infections increased more than 6-fold in Germany in recent years, the seroprevalence remained unchanged (2 %).

Virological and clinical characteristics of delta hepatitis in Central Europe.

Hepatitis D virus (HDV) or delta hepatitis has mainly been studied in Asian and Mediterranean cohorts, but data on virological and clinical characteristics of HDV-infected Central and Northern European patients are limited. We investigated virological patterns, as well as biochemical and clinical features of liver disease in 258 HDV infected patients recruited over a period of 15 years at Hannover Medical School. Virological parameters were compared to 2083 anti-HDV negative hepatitis B surface antigen (HBsAg) positive individuals. In this cohort, (i) HDV infection was associated with both suppressed hepatitis B virus (HBV) and hepatitis C virus (HCV) replication, (ii) the suppression of HBV-DNA and HCV-RNA was not related to HDV-RNA replication, (iii) mean HBsAg levels did not significantly differ between HBV-monoinfected patients and individuals with delta hepatitis, (iv) HCV coinfection was rather frequent as about one third of our delta hepatitis patients tested anti-HCV positive, however, without being associated with more advanced liver disease, (v) delta hepatitis patients presented in a high frequency with an advanced stage of liver disease, and (vi) the course of delta hepatitis did not differ between Turkish-born, Eastern European (EE)-born and German-born patients. In summary, in this cohort of patients which is the largest so far Central European single centre group of delta hepatitis patients, we confirm the presence of frequently severe disease and describe novel virological profiles which require consideration in the management of this difficult to treat group of patients.

Combined 18F-FDG-PET/CT imaging of the head and neck. An approach to metal artifact correction.

UNLABELLED: PET/CT imaging is particularly promising for head/neck malignancies, but dental implants lead to biased CT attenuation and PET activity values following CT-based attenuation correction (CT-AC). OBJECTIVE: Here, we implement a metal artifact correction procedure (MAR) as part of the CT-AC for PET/CT imaging. RESULTS: Phantom studies indicate a maximum quantitative bias in CT and PET of 1000 HU and 30 %, which is reduced to 230 HU and 6 %, respectively following MAR. These results were verified in selected patients. CONCLUSION: Artifacts and biases from dental implants can be reduced in PET/CT imaging by applying a simple MAR as part of the CT-AC.

Novel iterative reconstruction method with optimal dose usage for partially redundant CT-acquisition.

In CT imaging, a variety of applications exist which are strongly SNR limited. However, in some cases redundant data of the same body region provide additional quanta. Examples in dual energy CT, the spatial resolution has to be compromised to provide good SNR for material decomposition. However, the respective spectral dataset of the same body region provides additional quanta which might be utilized to improve SNR of each spectral component. Perfusion CT is a high dose application, and dose reduction is highly desirable. However, a meaningful evaluation of perfusion parameters might be impaired by noisy time frames. On the other hand, the SNR of the average of all time frames is extremely high.In redundant CT acquisitions, multiple image datasets can be reconstructed and averaged to composite image data. These composite image data, however, might be compromised with respect to contrast resolution and/or spatial resolution and/or temporal resolution. These observations bring us to the idea of transferring high SNR of composite image data to low SNR 'source' image data, while maintaining their resolution.It has been shown that the noise characteristics of CT image data can be improved by iterative reconstruction (Popescu et al 2012 Book of Abstracts, 2nd CT Meeting (Salt Lake City, UT) p 148). In case of data dependent Gaussian noise it can be modelled with image-based iterative reconstruction at least in an approximate manner (Bruder et al 2011 Proc. SPIE 7961 79610J). We present a generalized update equation in image space, consisting of a linear combination of the previous update, a correction term which is constrained by the source image data, and a regularization prior, which is initialized by the composite image data. This iterative reconstruction approach we call bimodal reconstruction (BMR). Based on simulation data it is shown that BMR can improve low contrast detectability, substantially reduces the noise power and has the potential to recover spatial resolution of the source image data.For different CT applications: dual energy imaging, liver imaging, spiral imaging, cardiac imaging, we show that SNR can efficiently be transferred from the composite image to the source image data at constant patient dose, while maintaining resolution properties of the source data.

CT Metal Artifact Reduction in the Spine: Can an Iterative Reconstruction Technique Improve Visualization?

BACKGROUND AND PURPOSE: Metal-related artifacts from spine instrumentation can obscure relevant anatomy and pathology. We evaluated the ability of CT images reconstructed with and without iterative metal artifact reduction to visualize critical anatomic structures in postoperative spines and assessed the potential for implementation into clinical practice. MATERIALS AND METHODS: We archived CT projection data in patients with instrumented spinal fusion. CT images were reconstructed by using weighted filtered back-projection and iterative metal artifact reduction. Two neuroradiologists evaluated images in the region of spinal hardware and assigned a score for the visualization of critical anatomic structures by using soft-tissue and bone windows (critical structures totally obscured, n = 0; anatomic recognition with high diagnostic confidence, n = 5). Using bone windows, we measured the length of the most pronounced linear artifacts. For each patient, neuroradiologists made recommendations regarding the optimal use of iterative metal artifact reduction and its impact on diagnostic confidence. RESULTS: Sixty-eight patients met the inclusion criteria. Visualization of critical soft-tissue anatomic structures was significantly improved by using iterative metal artifact reduction compared with weighted filtered back-projection (median, 1 ± 1.5 versus 3 ± 1.3, P < .001), with improvement in the worst visualized anatomic structure in 88% (60/68) of patients. There was not significant improvement in visualization of critical osseous structures. Linear metal artifacts were reduced from 29 to 11 mm (P < .001). In 87% of patients, neuroradiologists recommended reconstructing iterative metal artifact reduction images instead of weighted filtered back-projection images, with definite improvement in diagnostic confidence in 32% (22/68). CONCLUSIONS: Iterative metal artifact reduction improves visualization of critical soft-tissue structures in patients with spinal hardware. Routine generation of these images in addition to routine weighted filtered back-projection is recommended.

Performance evaluation of a 64-slice CT system with z-flying focal spot.

The meanwhile established generation of 16-slice CT systems enables routine sub-millimeter imaging at short breath-hold times. Clinical progress in the development of multidetector row CT (MDCT) technology beyond 16 slices can more likely be expected from further improvement in spatial and temporal resolution rather than from a mere increase in the speed of volume coverage. We present an evaluation of a recently introduced 64-slice CT system (SOMATOM Sensation 64, Siemens AG, Forchheim, Germany), which uses a periodic motion of the focal spot in longitudinal direction (z-flying focal spot) to double the number of simultaneously acquired slices. This technique acquires 64 overlapping 0.6 mm slices per rotation. The sampling scheme corresponds to that of a 64 x 0.3 mm detector, with the goal of improved longitudinal resolution and reduced spiral artifacts. After an introduction to the detector design, we discuss the basics of z-flying focal spot technology (z-Sharp). We present phantom and specimen scans for performance evaluation. The measured full width at half maximum (FWHM) of the thinnest spiral slice is 0.65 mm. All spiral slice widths are almost independent of the pitch, with deviations of less than 0.1 mm from the nominal value. Using a high-resolution bar pattern phantom (CATPHAN, Phantom Laboratories, Salem, NY), the longitudinal resolution can be demonstrated to be up to 15 lp/cm at the isocenter independent of the pitch, corresponding to a bar diameter of 0.33 mm. Longitudinal resolution is only slightly degraded for off-center locations. At a distance of 100 mm from the isocenter, 14 lp/cm can be resolved in the z-direction, corresponding to a bar diameter of 0.36 mm. Spiral "windmill" artifacts presenting as hyper- and hypodense structures around osseous edges are effectively reduced by the z-flying focal spot technique. Cardiac scanning benefits from the short gantry rotation time of 0.33 s, providing up to 83 ms temporal resolution with 2-segment ECG-gated reconstruction.

Computer programs used to aid in the selection of DNA hybridization probes.

This paper describes a package of three programs which used together aid in selecting the best possible sequence to be used as a DNA hybridization probe. This system searches an amino acid sequence for four adjacent amino acids with the fewest possible corresponding mRNA sequences, calculates their probability of occurrence, and locates the positions of wobbles and mismatches between the DNA hybridization probe and the possible mRNA sequences.