Advances in multiscale image processing and its effects on image quality in skeletal radiography.

Multi-frequency processing (MFP) leads to enhanced image quality (IQ) of radiographs. This study is to determine the effect of third generation MFP (M3) on IQ in comparison to standard second-generation MFP (M2). 20 cadavers were examined and post-processing of radiographs was performed with both M2 and M3. Three readers blinded to the MFP used for each image independently compared corresponding image pairs according to overall IQ and depiction of bony structures and soft tissue (+ 2: notably better > 0: equal > - 2: notably worse). A significant deviation of the median grade from grade 0 (equal) (p < 0.01) for each evaluator A, B and C speaks against an equal image quality of M2- and M3-images. M3-images were categorized with better grades (+ 1, + 2) in 87.7% for overall image quality, in 90.4% for soft tissue and 81.8% for bony structures. M3 images showed significant higher averaged SNR and CNR for all investigated lower extremities than that of M2 images (0.031 < p < 0.049). The newest generation of MFP leads to significantly better depiction of anatomical structures and overall image quality than in images processed with the preceding generation of MFP. This provides increased diagnostic accuracy and further decreased radiation exposure.

Image quality is resilient against tube voltage variations in post-mortem skeletal radiography with a digital flat-panel detector.

In recent phantom studies low-contrast detectability was shown to be independent from variations in tube voltage in digital radiography (DR) systems. To investigate the transferability to a clinical setting, the lower extremities of human cadavers were exposed at constant detector doses with different tube voltages in a certain range, as proposed in the phantom studies. Three radiologists independently graded different aspects of image quality (IQ) in a comparative analysis. The grades show no correlation between IQ and kV, which means that the readers were not able to recognize a significant IQ difference at different kV. Signal-to-noise and contrast-to-noise ratios showed no significant differences in IQ despite the kV-setting variations. These findings were observed from a limited kV range setting. Higher kV-settings resulted in lowest patient exposure at constant IQ. These results confirm the potential of DR-systems to contribute to standardization of examination protocols comparable to computed tomography. This may prevent the trend to overexpose. Further investigations in other body regions and other DR-systems are encouraged to determine transferability.

Evaluation of ankle ligaments with CT: A feasibility study.

PURPOSE: This study aims to systematically investigate if normal ankle ligaments can be assessed with CT imaging, using MRI as reference standard. METHODS: 35 patients (mean age: 47 ±â€¯15 years; female n = 19) with combined CT and MRI exams and without MR-morphologic signs of ankle ligamental injury were retrospectively identified. 3 readers independently evaluated the syndesmotic, the lateral and medial ankle ligaments in terms of visibility on a 4-point Likert scale (0-3 points) in multiplanar MDCT images in standard bone kernel reconstructions. In consensus CT-based ligament density and thickness were measured and the appearance was rated for each ligament. Results were compared and validated with corresponding MRI images. RESULTS: Almost all ankle ligaments identified in MRI images could be adequately depicted in standard multiplanar bone kernel CT images with a mean visual score of 2.7/3 (± 0.2). Difficulties in CT morphological delineation of ankle ligaments occurred in cases of filiform TNL and TCL and in cases of concurrent soft tissue edema. Interreader agreement for the CT-assessment of ankle ligaments was excellent, with Fleiss Kappa values >0.8. Mean density of evaluated medial and lateral ankle ligaments was 68 ±â€¯2.9 HU, with substantially inter- and intraindividual variations. Thickness measurements and assessment of appearance of ankle ligaments showed a good concordance between CT and MRI. CONCLUSIONS: Assessment of normal ankle ligaments via standard CT in bone kernel reconstructions is feasible, with some restrictions concerning the medial collateral ligaments and in the presence of soft tissue edema.

[Pretreatment mass casualty incident workflow analysis : Comparison of two level 1 trauma centers]. / Prätherapeutische Ablaufanalyse bei einem Massenanfall von Verletzten : Vergleich von zwei Traumazentren der höchsten Versorgungsstufe.

BACKGROUND: Mass casualty incidents (MCI) have particularly high demands on patient care processes but occur rather rarely in daily hospital routine. Therefore, it is common to use simulations to train staff and to optimize institutional processes. OBJECTIVES: Aim of study was to compare the pre-therapeutic in-house workflow of two differently structured level 1 trauma sites in the case of a simulated mass casualty incident (MCI). MATERIALS AND METHODS: A MCI of 70 patients was simulated by actors in a manner that was as realistic as possible. The on-site triage assigned 7 cases to trauma site A with relatively long in-house distances and 4 patients to an independent trauma site B in which these distances were relatively short. During in-house treatment, time intervals for reaching milestones were measured and compared using the Mann-Whitney U test. RESULTS: As no simultaneous patient arrival occurred, the Patient Distribution Matrix proved to be effective. Site A needed more time (minutes) from admission to endpoints (A: 31.85 ± 7.99; B: 21.62 ± 4.76; p = 0.059). In detail, the time intervals were particularly longer for both patient stay in trauma room (A: 8.46 ± 3.02; B: 2.73 ± 0.78, p < 0.01) and transfer time to the CT room (A: 1.81 ± 0.62; B: 0.06 ± 0.03, p < 0.01). A shorter stay in the CT room did not compensate these effects (A: 8.86 ± 1.84; B: 10.40 ± 2.89, p = 0.571). For both sites, image calculation and distribution were relatively time consuming (17.36 ± 3.05). CONCLUSIONS: Although short in-house distances accelerated pretherapeutic treatment processes significantly, both sites remained clearly within the "golden hour". The strongest potential bottleneck was the time interval until images were available at the endpoints.

Quantification of pulmonary perfusion with free-breathing dynamic contrast-enhanced MRI--a pilot study in healthy volunteers.

PURPOSE: The assessment of pulmonary perfusion using dynamic contrast-enhanced (DCE) MRI is still limited in the clinical routine due to the necessity of breath holding. An acquisition technique for the quantitative assessment of pulmonary perfusion in free breathing was investigated in our study. MATERIALS AND METHODS: 10 healthy male volunteers underwent pulmonary DCE-MRI on a 1.5 T scanner. Each volunteer was examined twice: (a) in breath-hold half expiration and (b) during shallow free breathing. The pulmonary parenchyma was segmented automatically. The pulmonary plasma flow (PPF) and pulmonary plasma volume (PPV) were determined pixel-wise using a one-compartment model. RESULTS: All examinations were of diagnostic image quality. The measured mean values of the PPV were significantly lower in the breath-hold technique than during free breathing ((10.2 ±â€Š2.8) ml/100 ml vs. (12.7 ±â€Š3.9) ml/100 ml); p < 0.05). A significant difference was also observed between both PPF measurements (mean PPF (206.2 ±â€Š104.0) ml/100 ml/min in breath-hold technique vs. (240.6 ±â€Š114.0) ml/100 ml/min during free breathing; p < 0.05). CONCLUSION: Free-breathing DCE-MRI appears to be suitable for the quantitative assessment of the pulmonary perfusion in healthy volunteers. The proposed segmentation and quantification approach does not suffer from the increased motion, as compared to the breath-holding measurement. The increased PPV and PPF during free breathing are in accordance with the results of previous studies concerning breathing influence on perfusion parameters. Overall, free-breathing DCE-MRI may be a promising technique for the assessment of pulmonary perfusion in various pathologies.

Upgrade to iterative image reconstruction (IR) in MDCT imaging: a clinical study for detailed parameter optimization beyond vendor recommendations using the adaptive statistical iterative reconstruction environment (ASIR) Part2: The chest.

PURPOSE: To compare the image quality in dose-reduced 64-row CT of the chest at different levels of adaptive statistical iterative reconstruction (ASIR) to full-dose baseline examinations reconstructed solely with filtered back projection (FBP) in a realistic upgrade scenario. MATERIALS AND METHODS: A waiver of consent was granted by the institutional review board (IRB). The noise index (NI) relates to the standard deviation of Hounsfield units in a water phantom. Baseline exams of the chest (NI = 29; LightSpeed VCT XT, GE Healthcare) were intra-individually compared to follow-up studies on a CT with ASIR after system upgrade (NI = 45; Discovery HD750, GE Healthcare), n = 46. Images were calculated in slice and volume mode with ASIR levels of 0 - 100 % in the standard and lung kernel. Three radiologists independently compared the image quality to the corresponding full-dose baseline examinations (-2: diagnostically inferior, -1: inferior, 0: equal, + 1: superior, + 2: diagnostically superior). Statistical analysis used Wilcoxon's test, Mann-Whitney U test and the intraclass correlation coefficient (ICC). RESULTS: The mean CTDIvol decreased by 53 % from the FBP baseline to 8.0 ± 2.3 mGy for ASIR follow-ups; p < 0.001. The ICC was 0.70. Regarding the standard kernel, the image quality in dose-reduced studies was comparable to the baseline at ASIR 70 % in volume mode (-0.07 ± 0.29, p = 0.29). Concerning the lung kernel, every ASIR level outperformed the baseline image quality (p < 0.001), with ASIR 30 % rated best (slice: 0.70 ± 0.6, volume: 0.74 ± 0.61). CONCLUSION: Vendors' recommendation of 50 % ASIR is fair. In detail, the ASIR 70 % in volume mode for the standard kernel and ASIR 30 % for the lung kernel performed best, allowing for a dose reduction of approximately 50 %.

[Arterial closure devices. What device for which clinical situation?]. / Arterielle Verschlusssysteme. Welches wofür?

CLINICAL/METHODICAL ISSUE: Access site complications after endovascular catheterization sometimes require open surgery and negatively impair safety, patient comfort and reimbursement. Increasing numbers of procedures and patients with multiple anticoagulants as well as cost pressure explain the demand for an immediate and stable access site closure. STANDARD RADIOLOGICAL METHODS: Manual compression followed by compression bandage and bed rest for 4-24 h is still the gold standard but is unable to prevent access site complications in all cases. METHODICAL INNOVATIONS: Arterial vascular closure devices allow immediate and stable closure of the puncture channel either by suture or by implantation of occluding foreign bodies or gluing fluids. PERFORMANCE: The safety has been proven in several clinical trials. The main advantage lies in closing large lumen access sites without surgery and in patients treated with multiple anticoagulants as well as in outpatient procedures. ACHIEVEMENTS: They have become a valuable supplement to the interventional arsenal. PRACTICAL RECOMMENDATIONS: The physician, however, has to decide between different systems and mechanisms with respect to patient constitution, selected access vessel and level of calcification and diameter. Furthermore, all systems require a defined training prior the first use.

Dual Energy CT lung perfusion imaging--correlation with SPECT/CT.

OBJECTIVE: Aims were (1) to determine the diagnostic accuracy of Dual Energy CT (DECT) in the detection of perfusion defects and (2) to evaluate the potential of DECT to improve the sensitivity for PE. METHODS: 15 patients underwent Dual Energy pulmonary CT angiography (DE CTPA) and a combination of lung perfusion SPECT/CT and ventilation scintigraphy. CTPA and DE iodine distribution maps as well as perfusion SPECT/CT and inhalation scintigrams were reviewed for pulmonary embolism (PE) diagnosis. DECT and SPECT perfusion images were assessed regarding localization and extent of perfusion defects. Diagnostic accuracy of DE iodine (perfusion) maps was determined with reference to SPECT/CT. Diagnostic accuracies for PE detection of DECT and of SPECT/CT with ventilation scintigraphy were calculated with reference to the consensus reading of all modalities. RESULTS: DE CTPA had a sensitivity/specificity of 100%/100% for acute PE, while the combination of SPECT/CT and ventilation scintigraphy had a sensitivity/specificity of 85.7%/87.5%. For perfusion defects, DECT iodine maps had a sensitivity/specificity of 76.7% and 98.2%. CONCLUSION: DECT is able to identify pulmonary perfusion defects with good accuracy. This technique may potentially enhance the diagnostic accuracy in the assessment of PE.

Oxygen-enhanced MRI of the lungs: intraindividual comparison between 1.5 and 3 tesla.

PURPOSE: To assess the feasibility of oxygen-enhanced MRI of the lung at 3 Tesla and to compare signal characteristics with 1.5 Tesla. MATERIALS AND METHODS: 13 volunteers underwent oxygen-enhanced lung MRI at 1.5 and 3 T with a T 1-weighted single-slice non-selective inversion-recovery single-shot half-Fourier fast-spin-echo sequence with simultaneous respiratory and cardiac triggering in coronal orientation. 40 measurements were acquired during room air breathing and subsequently during oxygen breathing (15 L/min, close-fitting face-mask). The signal-to-noise ratio (SNR) of the lung tissue was determined with a difference image method. The image quality of all acquisitions was visually assessed. The mean values of the oxygen-induced relative signal enhancement and its regional coefficient of variation were calculated and the signal enhancement was displayed as color-coded parameter maps. Oxygen-enhancement maps were visually assessed with respect to the distribution and heterogeneity of the oxygen-related signal enhancement at both field strengths. RESULTS: The mean relative signal enhancement due to oxygen breathing was 13 % (± 5.6 %) at 1.5 T and of 9.0 % (± 8.0 %) at 3 T. The regional coefficient of variation was significantly higher at 3 T. Visual and quantitative assessment of the enhancement maps showed considerably less homogeneous distribution of the signal enhancement at 3 T. The SNR was not significantly different but showed a trend to slightly higher values (increase of about 10 %) at 3 T. CONCLUSION: Oxygen-enhanced pulmonary MRI is feasible at 3 Tesla. However, signal enhancement is currently more heterogeneous and slightly lower at 3 T.

[Upper abdominal pain with recurrent cholangitis and pyelonephritis]. / Oberbauchschmerzen bei rezidivierenden Cholangitiden und Pyelonephritiden.

A 38-year-old man presented with pain in the right upper abdomen combined with elevated C-reactive protein (5.37 mg/dl) and creatinine levels (2.0 mg/dl). The medical history revealed recurrent abdominal pain. Duplex sonography showed large intrahepatic cystic structures, partially combined with a ribbon-shaped flow signal inside, as well as multiple cysts in the kidneys. The following MRI identified these findings as dilatated bile ducts surrounding the portal vein branches. This is known as the central dot sign. Overall, this special constellation is indicative of Caroli's disease, a rare congenital cystic dilatation of the intrahepatic bile ducts. The imaging results substantiated the diagnosis, especially in combination with cystic renal disease and recurrent cholangitis. Depending on the grade of liver involvement the treatment is partial hepatectomy or, as in our case transplantation, which also eliminates the risk of associated cholangiocarcinoma.