Is multidetector CT-based bone mineral density and quantitative bone microstructure assessment at the spine still feasible using ultra-low tube current and sparse sampling?

OBJECTIVE: Osteoporosis diagnosis using multidetector CT (MDCT) is limited to relatively high radiation exposure. We investigated the effect of simulated ultra-low-dose protocols on in-vivo bone mineral density (BMD) and quantitative trabecular bone assessment. MATERIALS AND METHODS: Institutional review board approval was obtained. Twelve subjects with osteoporotic vertebral fractures and 12 age- and gender-matched controls undergoing routine thoracic and abdominal MDCT were included (average effective dose: 10 mSv). Ultra-low radiation examinations were achieved by simulating lower tube currents and sparse samplings at 50%, 25% and 10% of the original dose. BMD and trabecular bone parameters were extracted in T10-L5. RESULTS: Except for BMD measurements in sparse sampling data, absolute values of all parameters derived from ultra-low-dose data were significantly different from those derived from original dose images (p<0.05). BMD, apparent bone fraction and trabecular thickness were still consistently lower in subjects with than in those without fractures (p<0.05). CONCLUSION: In ultra-low-dose scans, BMD and microstructure parameters were able to differentiate subjects with and without vertebral fractures, suggesting osteoporosis diagnosis is feasible. However, absolute values differed from original values. BMD from sparse sampling appeared to be more robust. This dose-dependency of parameters should be considered for future clinical use. KEY POINTS: • BMD and quantitative bone parameters are assessable in ultra-low-dose in vivo MDCT scans. • Bone mineral density does not change significantly when sparse sampling is applied. • Quantitative trabecular bone microstructure measurements are sensitive to dose reduction. • Osteoporosis subjects could be differentiated even at 10% of original dose. • Radiation exposure should be considered when comparing quantitative bone parameters.

Simulated cystic renal lesions: quantitative X-ray phase-contrast CT--an in vitro phantom study.

PURPOSE: To determine if grating-based x-ray phase-contrast computed tomography (CT) can allow differentiation of simulated simple, protein-rich, hemorrhagic, and enhancing cystic renal lesions in an in vitro phantom. MATERIALS AND METHODS: An in vitro phantom specifically designed to simulate simple, protein-rich, hemorrhagic, and enhancing renal cysts was scanned with an experimental grating-based phase-contrast CT setup consisting of a Talbot-Lau interferometer with a rotating anode x-ray tube and a single photon counting detector. Various combinations of serum and saline (100% and 0% to 0% and 100%), blood and saline, blood and serum (100% and 0% to 6.25% and 93.75% for both), and an iodinated contrast agent and saline (7.6-1.6 mg per milliliter of saline) were used to reproduce the chemical composition of the different types of cysts. A thickened solution of an iodinated contrast agent calibrated with a clinical multidetector CT scanner served as contrast agent-enhanced renal parenchyma (195 HU at 80 kVp, 400 mAs and 98 HU at 140 kVp, 200 mAs). Standard attenuation- and phase-contrast images were reconstructed from the raw projection data. Quantitative values for attenuation and phase contrast and image noise were determined. Contrast-to-noise ratios were calculated. Simulated lesions were assessed for visual differentiability by means of pairwise comparison of the attenuation- and phase-contrast images and both images simultaneously. RESULTS: Attenuation-contrast imaging showed large differences in Hounsfield units with increasing concentrations of iodine (118.9 HU for 1.6 mg/mL vs 331.4 HU for 7.6 mg/mL). Values for phase-contrast imaging were substantially distinguishable for saline, serum, and blood (7.9, 23.7, and 52.8 HU, respectively). Both imaging modalities combined allowed differentiation of all four types of simulated cysts (100% saline, 100% serum, 100% blood, and 1.6-7.6 mg of iodine per milliliter of saline) with one imaging acquisition. CONCLUSION: Grating-based phase-contrast CT allows differentiation of simulated simple, protein-rich, hemorrhagic, and enhancing renal cysts in an in vitro phantom through simultaneous assessment of their distinct attenuation- and phase-contrast signal.

Evaluation of a method for improving the detection of hepatocellular carcinoma.

OBJECTIVE: To improve the detection of liver lesions in patients with hepatocellular carcinoma (HCC) via an iodine contrast enhancement tool. METHODS: Thirty-two patients with clinically proven HCCs underwent imaging with a three-phase protocol on a 256-slice MDCT. The contrast enhancement in the reconstructed slices was improved via a post-processing tool. Mean image noise was measured in four different regions: liver lesion, healthy liver, subcutaneous fat and bone. For each image set the image noise and contrast-to-noise ratio (CNR) were assessed. For subjective image assessment, four experienced radiologists evaluated the diagnostic quality. RESULTS: While employing the post-processing algorithm, CNR between the liver lesion and healthy liver tissue improves significantly by a factor of 1.78 (CNRwithout vC = 2.30 ± 1.92/CNRwith vC = 4.11 ± 3.05) (P* = 0.01). All results could be achieved without a strengthening of artefacts; mean HU values of subcutaneous fat and bone did not significantly change. Subjective image analysis illustrated a significant improvement when employing post-processing for clinically relevant criteria such as diagnostic confidence. CONCLUSION: With post-processing we see a significantly improved detection of arterial uptake in hepatic lesions compared with non-processed data. The improvement in CNR was confirmed by subjective image assessment for small lesions and for lesions with limited uptake. KEY POINTS: • Enhancement with iodine-based contrast agents is an essential part of CT. • A new post-processing tool significantly improves the diagnostics of hepatocellular carcinoma. • It also improves detection of small lesions with limited iodine uptake.

Emergency cesarean section due to acute aortic dissection type A (Debakey I) without Marfan syndrome: a case report and review of the literature.

BACKGROUND: Acute aortic dissection during pregnancy is an uncommon but important emergency due to its lethal risk to both mother and child. The dissection usually involves the ascending aorta or the aortic arch. Although additional affection of the descending aorta up to bifurcation is possible, further increasing the risk of organ malperfusion, full-length aortic dissection (DeBakey I) is known to be very rare. Dissection during pregnancy has been reported predominantly in combination with Marfan syndrome. Acute aortic dissection Stanford type A (AADA) DeBakey I during pregnancy without signs of Marfan syndrome as a warning signal is very uncommon in the current literature. OBJECTIVES: The etiology, diagnosis, differential diagnosis, and management of this rare disease are discussed in relation to the current literature. CASE REPORT: We report the case of an athletic 34-year-old woman in the third trimester of pregnancy, without history of previous diseases, who presented to our Emergency Department after collapsing. In the resuscitation department, an emergency cesarean section was performed due to the start of circulation failure in the mother. Computed tomography scan revealed a severe aortic dissection starting from 1 cm distal the aortic valve over the full length up to the iliac arteries, involving the brachiocephalic and carotid arteries up to the level of the larynx. Emergency replacement of the ascending aorta and the aortic arch was performed. Both the mother and baby survived and were doing well 1 year postoperatively. CONCLUSION: This alarming result of AADA (DeBakey I) in late pregnancy without obvious warnings such as Marfan syndrome illustrates the importance of performing early imaging in similar cases.

A method for improving iodine contrast enhancement in abdominal computed tomography: experimental study in a pig model.

OBJECTIVES: To investigate the improvement in diagnostic image quality of an iodine contrast enhancement tool in an animal model for computed tomography (CT). METHODS: One pig was examined over several consecutive days with a CT system. The quantity of iodine as contrast medium (0.6-1.2 ml/kg) varied among different acquisitions. The contrast enhancement in the reconstructed slices was improved via a post-processing tool. The post-processing tool is an algorithm designed for enhancement of iodine contrast in CT data. Contrast-to-noise ratio (CNR), the detectability between soft-tissue and vascular structures, and quantitative image analysis were assessed. RESULTS: When reducing the quantity of contrast medium, our subjective image quality assessment revealed that it is visually possible to generate similar enhancement with less iodine. This observation was confirmed quantitatively in our CNR results. While employing the algorithm, the CNR between vascular structures and subcutaneous fat significantly improved. For unenhanced regions, we identified no change in HU values and no significant strengthening of artefacts. CONCLUSIONS: With post-processing there was a significantly improved diagnostic image quality compared with non-processed data. In particular, similar contrast enhancement could be achieved with a reduced quantity of contrast medium injected during the CT acquisition.

Wound ballistic evaluation of the Taser® XREP ammunition.

The Taser® eXtended Range Electronic Projectile (XREP®) is a wireless conducted electrical weapon (CEW) designed to incapacitate a person from a larger distance. The aim of this study was to analyze the ballistic injury potential of the XREP. Twenty rounds were fired from the Taser®X12 TM shotgun into ballistic soap covered with artificial skin and clothing at different shooting distances (1-25 m). One shot was fired at pig skin at a shooting distance of 10 m. The average projectile velocity was 67.0 m/s. The kinetic energy levels on impact varied from 28-52 J. Depending on the intermediate target, the projectiles penetrated up to 4.2 cm into the ballistic soap. On impact the nose assembly did not separate from the chassis, and no electrical activation was registered. Upon impact, a skin penetration of the XREP cannot be excluded. However, it is very unlikely at shooting distances of 10 m or more. Clothing and a high elasticity limit of the target body area can significantly reduce the penetration risk on impact.

Initial performance characterization of a clinical noise-suppressing reconstruction algorithm for MDCT.

OBJECTIVE: The number of CT examinations is increasing relatively dramatically, hence the radiation dose of the associated population. Thus, there is a need for efficient reconstruction methods with dose reduction potential that also maintain the image quality. In this article, we present the initial performance evaluation of such a reconstruction algorithm (iDose, Philips Healthcare). MATERIALS AND METHODS: iDose is a hybrid iterative reconstruction algorithm that provides enhanced image quality while reducing the radiation dose compared with the current clinical standard reconstruction. To quantify the advantages of this algorithm in image quality and dose reduction, we compared iDose with the conventional filtered back projection algorithm. Furthermore, we describe the performance of iDose with respect to several image quality metrics. RESULTS: The HU values remain stable while employing iDose. With iDose, the noise is significantly reduced. This is reflected by an improvement in the contrast-to-noise ratio and in the noise power spectrum compared with a standard reconstruction. The measurements of the modulation transfer function confirm that, with iDose, there is no decline in spatial resolution. CONCLUSION: We conclude that iDose is an important tool in the reduction of radiation dose in CT. However, continuous efforts to reduce radiation dose should be pursued.

Spectral Angiography Material Decomposition Using an Empirical Forward Model and a Dictionary-Based Regularization.

By resolving the energy of the incident X-ray photons, spectral X-ray imaging with photon counting detectors offers additional material-specific information compared to conventional X-ray imaging. This additional information can be used to improve clinical diagnosis for various applications. However, spectral imaging still faces several challenges. Amplified noise and a reduced signal-to-noise ratio on the decomposed basis material images remain a major problem, especially for low-dose applications. Furthermore, it is challenging to construct an accurate model of the spectral measurement acquisition process. In this paper, we present a novel algorithm for projection-based material decomposition. It uses an empirical polynomial model that is tuned by calibration measurements. We combine this method with a statistical model of the measured photon counts and a dictionary-based joint regularization approach. We focused on spectral coronary angiography as a potential clinical application of projection-based material decomposition with photon counting detectors. Numerical and real experiments show that spectral angiography with realistic dose levels and gadolinium contrast agent concentrations are feasible using the proposed decomposition algorithm and currently available photon-counting detector technology.

Joint Statistical Iterative Material Image Reconstruction for Spectral Computed Tomography Using a Semi-Empirical Forward Model.

By acquiring tomographic measurements with several distinct photon energy spectra, spectral computed tomography (spectral CT) is able to provide additional material-specific information compared with conventional CT. This information enables the generation of material selective images, which have found various applications in medical imaging. However, material decomposition typically leads to noise amplification and a degradation of the signal-to-noise ratio. This is still a fundamental problem of spectral CT, especially for low-dose medical applications. Inspired by the success for low-dose conventional CT, several statistical iterative reconstruction algorithms for spectral CT have been developed. These algorithms typically rely on detailed knowledge about the spectrum and the detector response. Obtaining this knowledge is often difficult in practice, especially if photon counting detectors are used to acquire the energy specific information. In this paper, a new algorithm for joint statistical iterative material image reconstruction is presented. It relies on a semi-empirical forward model which is tuned by calibration measurements. This strategy allows to model spatially varying properties of the imaging system without requiring detailed prior knowledge of the system parameters. We employ an efficient optimization algorithm based on separable surrogate functions to accelerate convergence and reduce the reconstruction time. Numerical as well as real experiments show that our new algorithm leads to reduced statistical bias and improved image quality compared with projection-based material decomposition followed by analytical or iterative image reconstruction.

Accuracy of iodine quantification in dual-layer spectral CT: Influence of iterative reconstruction, patient habitus and tube parameters.

PURPOSE: Evaluation of the influence of iterative reconstruction, tube settings and patient habitus on the accuracy of iodine quantification with dual-layer spectral CT (DL-CT). MATERIAL AND METHODS: A CT abdomen phantom with different extension rings and four iodine inserts (1, 2, 5 and 10 mg/ml) was scanned on a DL-CT. The phantom was scanned with tube-voltages of 120 and 140 kVp and CTDIvol of 2.5, 5, 10 and 20 mGy. Reconstructions were performed for eight levels of iterative reconstruction (i0-i7). Diagnostic dose levels are classified depending on patient-size and radiation dose. RESULTS: Measurements of iodine concentration showed accurate and reliable results. Taking all CTDIvol-levels into account, the mean absolute percentage difference (MAPD) showed less accuracy for low CTDIvol-levels (2.5 mGy: 34.72%) than for high CTDIvol-levels (20 mGy: 5.89%). At diagnostic dose levels, accurate quantification of iodine was possible (MAPD 3.38%). Level of iterative reconstruction did not significantly influence iodine measurements. Iodine quantification worked more accurately at a tube voltage of 140 kVp. Phantom size had a considerable effect only at low-dose-levels; at diagnostic dose levels the effect of phantom size decreased (MAPD <5% for all phantom sizes). CONCLUSION: With DL-CT, even low iodine concentrations can be accurately quantified. Accuracies are higher when diagnostic radiation doses are employed.

Ultra Low Dose CT Pulmonary Angiography with Iterative Reconstruction.

OBJECTIVE: Evaluation of a new iterative reconstruction algorithm (IMR) for detection/rule-out of pulmonary embolism (PE) in ultra-low dose computed tomography pulmonary angiography (CTPA). METHODS: Lower dose CT data sets were simulated based on CTPA examinations of 16 patients with pulmonary embolism (PE) with dose levels (DL) of 50%, 25%, 12.5%, 6.3% or 3.1% of the original tube current setting. Original CT data sets and simulated low-dose data sets were reconstructed with three reconstruction algorithms: the standard reconstruction algorithm "filtered back projection" (FBP), the first generation iterative reconstruction algorithm iDose and the next generation iterative reconstruction algorithm "Iterative Model Reconstruction" (IMR). In total, 288 CTPA data sets (16 patients, 6 tube current levels, 3 different algorithms) were evaluated by two blinded radiologists regarding image quality, diagnostic confidence, detectability of PE and contrast-to-noise ratio (CNR). RESULTS: iDose and IMR showed better detectability of PE than FBP. With IMR, sensitivity for detection of PE was 100% down to a dose level of 12.5%. iDose and IMR showed superiority to FBP regarding all characteristics of subjective (diagnostic confidence in detection of PE, image quality, image noise, artefacts) and objective image quality. The minimum DL providing acceptable diagnostic performance was 12.5% (= 0.45 mSv) for IMR, 25% (= 0.89 mSv) for iDose and 100% (= 3.57 mSv) for FBP. CNR was significantly (p < 0.001) improved by IMR compared to FBP and iDose at all dose levels. CONCLUSION: By using IMR for detection of PE, dose reduction for CTPA of up to 75% is possible while maintaining full diagnostic confidence. This would result in a mean effective dose of approximately 0.9 mSv for CTPA.

Evaluation of an iterative model-based reconstruction algorithm for low-tube-voltage (80 kVp) computed tomography angiography.

The objective of this study was to investigate the improvement in diagnostic quality of an iterative model-based reconstruction (IMBR) algorithm for low-tube-voltage (80-kVp) and low-tube-current in abdominal computed tomography angiography (CTA). A total of 11 patients were imaged on a 256-slice multidetector computed tomography for visualization of the aorta. For all patients, three different reconstructions from the low-tube-voltage data are generated: filtered backprojection (FBP), IMBR, and a mixture of both [Formula: see text]. To determine the diagnostic value of IMBR-based reconstructions, the image quality was assessed. With IMBR-based reconstructions, image noise could be significantly reduced, which was confirmed by a highly improved contrast-to-noise ratio. In the image quality assessment, radiologists were able to reliably detect more third-order and higher aortic branches in the IMBR reconstructions compared to FBP reconstructions. The effective dose level was, on average, 3.0 mSv for 80-kVp acquisitions. Low-tube-voltage CTAs significantly improve vascular contrast as presented by others; however, this effect in combination with IMBR enabled yet another substantial improvement of diagnostic quality. For IMBR, a significant improvement of image quality and a decreased radiation dose at low-tube-voltage can be reported.

Does iterative reconstruction lower CT radiation dose: evaluation of 15,000 examinations.

PURPOSE: Evaluation of 15,000 computed tomography (CT) examinations to investigate if iterative reconstruction (IR) reduces sustainably radiation exposure. METHOD AND MATERIALS: Information from 15,000 CT examinations was collected, including all aspects of the exams such as scan parameter, patient information, and reconstruction instructions. The examinations were acquired between January 2010 and December 2012, while after 15 months a first generation IR algorithm was installed. To collect the necessary information from PACS, RIS, MPPS and structured reports a Dose Monitoring System was developed. To harvest all possible information an optical character recognition system was integrated, for example to collect information from the screenshot CT-dose report. The tool transfers all data to a database for further processing such as the calculation of effective dose and organ doses. To evaluate if IR provides a sustainable dose reduction, the effective dose values were statistically analyzed with respect to protocol type, diagnostic indication, and patient population. RESULTS: IR has the potential to reduce radiation dose significantly. Before clinical introduction of IR the average effective dose was 10.1±7.8mSv and with IR 8.9±7.1mSv (p*=0.01). Especially in CTA, with the possibility to use kV reduction protocols, such as in aortic CTAs (before IR: average14.2±7.8mSv; median11.4mSv /with IR:average9.9±7.4mSv; median7.4mSv), or pulmonary CTAs (before IR: average9.7±6.2mSV; median7.7mSv /with IR: average6.4±4.7mSv; median4.8mSv) the dose reduction effect is significant(p*=0.01). On the contrary for unenhanced low-dose scans of the cranial (for example sinuses) the reduction is not significant (before IR:average6.6±5.8mSv; median3.9mSv/with IR:average6.0±3.1mSV; median3.2mSv). CONCLUSION: The dose aspect remains a priority in CT research. Iterative reconstruction algorithms reduce sustainably and significantly radiation dose in the clinical routine. Our results illustrate that not only in studies with a limited number of patients but also in the clinical routine, IRs provide long-term dose saving.

Bisphosphonate related osteonecrosis of the jaw: A minipig large animal model.

Bisphosphonate related osteonecrosis of the jaw (BRONJ) is rare but potentially severe, and the etiopathology and risk factors are poorly defined. To date, it has not been possible to induce BRONJ in a large animal model, a shortfall this study aims to redress. Ten two-year-old adult Göttingen minipigs were split into two groups. Five pigs (group 1) were administered intravenously a weekly dose of a bisphosphonate (zoledonate 0.05mg/kg body weight, approximating the oncologic dose in humans) and five pigs (group 2) served as controls. After 6 weeks, tooth extractions were performed in the upper and lower jaw (both groups) and the bisphosphonate administration continued for a further 10 weeks (group 1 only). Clinical and blood parameters were monitored throughout the entire experiment; thereafter, the jaw-bones were subjected to macroscopic, radiological (CT) and histological investigations. Whilst the extraction sites in the control group healed within two weeks, all animals in the bisphosphonate group exhibited exposed bone and impaired wound healing, indicators that are synonymous of macroscopically advanced osteonecrosis. Radiological and in particular histological investigations confirmed the presence of BRONJ in the animals from group 1. This paper demonstrates that the administration of bisphosphonates, in combination with tooth extractions, induces BRONJ in a minipig model. The ability to study BRONJ in miniature pigs, animals with a bone structure not dissimilar to humans, may improve our knowledgebase regarding the etiopathology, the prophylaxis and potentially uncover new therapies of BRONJ.

Development of a disease-specific model to evaluate endothelial dysfunction in patients with diabetes mellitus.

Diabetic patients have an increased cardiovascular risk. We propose to characterize the endothelial dysfunction in a disease-specific in vitro model. Human saphenous vein endothelial cells (HSVEC) were isolated from coronary artery bypass patients without and with non-insulin-dependent diabetes mellitus. Growth kinetics and proinflammatory responses (expression of adhesion molecules, cytokines) were documented under non-stimulating conditions. Diabetic HSVEC showed delayed growth kinetics with reduced cell densities of about 40%. During exponential growth of diabetic EC, the surface expression of adhesion molecules was increased 10-fold (p< or =0.05). However, in a monolayer the expression adapted to low levels of non-diabetic EC. In addition, diabetic EC produced significantly more soluble E-selectin, VCAM-1, IL-6 and MCP-1. Our results suggest a link between the pathologically proinflammatory basic state of diabetic EC and the endothelial dysfunction in diabetic disease. Therefore, this in vitro model could be used for investigating early dysfunction and environmental effects on pathological endothelium.

Impact of diabetic serum on endothelial cells: an in-vitro-analysis of endothelial dysfunction in diabetes mellitus type 2.

Diabetic endothelial dysfunction was characterized by altered levels of adhesion molecules and cytokines. Aim of our study was to evaluate the effects of diabetic serum on cell-growth and proinflammatory markers in human saphenous vein endothelial cells (HSVEC) from diabetic and non-diabetic patients. Diabetic serum showed (1) complementary proliferative activity for non-diabetic and diabetic HSVEC, (2) unchanged surface expression of adhesion molecules, and (3) elevated levels of sICAM-1 in HSVEC of all donors. The concentration of sVCAM-1 was increased only in diabetic cells. The proinflammatory state of diabetic HSVEC characterized by increased levels of cytokines was compensated. We concluded that even under normoglycemic conditions the serum itself contains critical factors leading to abnormal regulation of inflammation in diabetics. We introduced an in vitro model of diabetes representing the endothelial situation at the beginning of diabetes (non-diabetic cells/diabetic serum) as well as the diabetic chronic state (diabetic cells/diabetic serum).

Hyperglycemia increases the levels of vascular cellular adhesion molecule-1 and monocyte-chemoattractant-protein-1 in the diabetic endothelial cell.

Hyperglycemia is the major cause of diabetic angiopathy. Aim of our study was to evaluate the impact of high glucose on cell growth and function of human "diabetic" endothelial cells (EC). Incubation of non-diabetic EC with glucose moderately inhibited cell growth and increased the expression of ICAM-1 and E-selectin. In the disease-specific EC, glucose treatment resulted also in moderately inhibited cell growth by 5-10%, increased basal expression of VCAM-1 by 10-20%, and an enhanced release of monocyte-chemoattractant-protein-1 (MCP-1) by 40-70%. The expression of ICAM-1 and E-selectin and the release of IL-6 and IL-8 was not affected. The usage of our disease-specific EC model might evaluate the impact of systemic factors of diabetic patients in the progression of endothelial dysfunction, and may be suitable to develop relevant therapeutic regimens.