Single source dual energy CT: What is the optimal monochromatic energy level for the analysis of the lung parenchyma?

OBJECTIVE

To determine the optimal monochromatic energy level for lung parenchyma analysis in spectral CT.

METHODS

All 50 examinations (58% men, 64.8±16yo) from an IRB-approved prospective study on single-source dual energy chest CT were retrospectively included and analyzed. Monochromatic images in lung window reconstructed every 5keV from 40 to 140keV were independently assessed by two chest radiologists. Based on the overall image quality and the depiction/conspicuity of parenchymal lesions, each reader had to designate for every patient the keV level providing the best diagnostic and image quality.

RESULTS

72% of the examinations exhibited parenchymal lesions. Reader 1 picked the 55keV monochromatic reconstruction in 52% of cases, 50 in 30% and 60 in 18%. Reader 2 chose 50keV in 52% cases, 55 in 40%, 60 in 6% and 40 in 2%. The 50 and 55keV levels were chosen by at least one reader in 64% and 76% of all patients, respectively. Merging 50 and 55keV into one category results in an optimal setting selected by reader 1 in 82% of patients and by reader 2 in 92%, with a 74% concomitant agreement.

CONCLUSION

The best image quality for lung parenchyma in spectral CT is obtained with the 50-55keV monochromatic reconstructions.

[Contribution of mathematical models and biomechanical properties in predicting the risk of abdominal aortic aneurysm rupture]

INTRODUCTION

Rupture is the worst outcome of abdominal aortic aneurysm (AAA). The decision to operate should include counterbalancing the risk of aneurysm rupture against the risk of aneurysm repair, within the context of a patient's overall life expectancy. Current surgical guidelines are based on population studies, and important variables are missed in predicting individual risk of rupture.

METHODS

In this literature review, we focused on the contribution of biomechanical and mathematical models in predicting risk of AAA rupture.

RESULTS

Anatomical features as diameter asymmetry and lack of tortuosity are shown to be anatomical risk factors of rupture. Wall stiffness (due to modifications of elastin and collagen composition) and increased inflammatory response are also factors that affect the structural integrity of the AAA wall. Biomechanical studies showed that wall strength is lower in ruptured than non-ruptured AAA. Intra-luminal thrombus also has a big role to play in the occurrence of rupture. Current mathematical models allow more variables to be included in predicting individual risk of rupture.

CONCLUSION

Moving away from using maximal transverse diameter of the AAA as a unique predictive factor and instead including biological, structural and biomechanical variables in predicting individual risk of rupture will be essential in the future and will help gain precision and accuracy in surgical indications.

[Post-denervation renal artery stenosis - a matter of concern?]

Renal denervation, an invasive technique indicated in resistant hypertension patients insufficiently controlled by antihypertensive drugs, has a good safety profile. However, an increasing number of post-denervation renal artery stenosis cases has recently been reported. We describe the case of a 49-year-old woman with resistant hypertension who was referred to our university hypertension center for renal sympathetic denervation. Her daily treatment included six antihypertensive drugs. CT angiography prior to denervation showed no renal artery stenosis or vessel wall lesions. A standard renal denervation procedure using the St Jude protocol was performed. After an initial improvement in blood pressure profile, she presented with a blood pressure impairment at 3 months after renal denervation leading to the diagnosis of a severe right renal artery stenosis.

Current optimal morphological evaluation of peripheral arterial diseases

Imaging plays a central role in the management of peripheral arterial diseases (PAD), emphasized by the continuously increasing use of modern cross-sectional imaging and the corresponding decline of digital subtraction angiography (DSA) in the diagnostic setting. Imaging is sometimes used as a screening tool in high-risk individuals. In symptomatic patients, imaging is mandatory to make an accurate positive diagnosis, grade the severity and the extent of the abnormalities, carefully choose and plan the best therapeutic option and provide adequate follow-up. Non-invasive diagnosis of PAD can be made by Doppler ultrasonography, magnetic resonance angiography (MRA) and computed tomography angiography (CTA). Given the major technological breakouts over the last decade, MRA and especially CTA are nowadays mature and precise enough to properly answer all the questions raised in symptomatic patients. This review article aims at describing state-of-the-art non-invasive imaging of PAD, its involvement in the decision-making for the vascular surgeon and the future trends and developments expected in the coming years.

Popliteal artery entrapment syndrome

Intermittent claudication is frequently encountered in vascular surgical practice in atherosclerotic patients. However, it may also be observed in a younger subset of patients without any cardiovascular risk factors and can represent a challenging diagnosis. Popliteal artery entrapment syndrome is rare but can cause intermittent claudication in young people. There is a lack of consensus about optimal strategies or diagnosis and management, particularly for variants such as functional popliteal entrapment. Since the first description in 1959, knowledge of the pathology and the underlying anatomic abnormalities was advanced through sporadic publications of case reports and small case series, but popliteal artery entrapment syndrome still remains a rare anatomic abnormality. It can be difficult to differentiate from other causes of lower limb pain in young patients, and diagnosis can be challenging. We propose to review clinical symptomatology, classification, radiological diagnosis and treatment of popliteal entrapment syndrome.

Experimental demonstration of four-party quantum secret sharing

Secret sharing is a multiparty cryptographic task in which some secret information is split into several pieces which are distributed among the participants such that only an authorized set of participants can reconstruct the original secret. Similar to quantum key distribution, in quantum secret sharing, the secrecy of the shared information relies not on computational assumptions, but on laws of quantum physics. Here, we present an experimental demonstration of four-party quantum secret sharing via the resource of four-photon entanglement.

Modern MRI tools for the characterization of acute demyelinating lesions: value of chemical shift and diffusion-weighted imaging

Acute demyelinating lesions occur in various inflammatory disorders of the CNS. Apart from multiple sclerosis, most cases can be attributed to an overshooting immunological response to infectious agents called acute disseminated encephalomyelitis (ADEM). ADEM, which is mostly characterized by a monophasic course, has a multiphasic variant (MDEM). The early application of corticosteroids has been shown to be beneficial for the outcome; thus, an early diagnosis is highly desirable. Furthermore, the differential diagnosis ruling out neoplastic disorders may be difficult using conventional MRI alone. The potential diagnostic value of advanced MR techniques such as chemical shift imaging (CSI) and diffusion-weighted imaging (DWI) was investigated in a patient with MDEM, who had a new lesion in continuity with the initial disease manifestation. CSI was performed at 1.5 T with a long echo time of 135 ms for the evaluation of N-acetyl-aspartate (NAA) and choline (Cho) and with short TE of 30 ms for macromolecules (mm) and myo-Inositol (mI). DWI was performed using a single-shot isotropic EPI sequence. Whereas acute and chronic areas of demyelination were neither distinguishable on T2- nor on contrast-enhanced T1-weighted images, CSI and DWI revealed different metabolite concentrations and diffusion characteristics within the composite lesion, clearly separating acute from chronic areas of demyelination. In conclusion, the addition of CSI and DWI may add to the diagnostic power of MRI in the setting of demyelinating disorders by identifying areas of acute and chronic demyelination, even in the absence of contrast enhancement.

Improved survival and amelioration of nephrotoxic nephritis in intercellular adhesion molecule-1 knockout mice

Intercellular adhesion molecule-1 (ICAM-1) expression is upregulated in nephrotoxic nephritis, a model of human rapidly progressive glomerulonephritis. To evaluate the pathogenetic relevance of ICAM-1 in this model, nephrotoxic nephritis was induced in ICAM-1 knockout mice and genetic controls. Mice were preimmunized with rabbit IgG in complete Freund's adjuvant. Seven days later they received rabbit anti-mouse glomerular basement membrane IgG. The early humoral immune responses (levels of circulating mouse anti-rabbit IgG, glomerular deposition of rabbit and mouse IgG and mouse C3c) were not altered in ICAM-1 knockout mice. During 28 d of follow-up, 3 of 19 control nephritic mice and 0 of 16 ICAM-1 knockout mice died. Proteinuria was high in nephritic control mice (means 10 to 12 mg/24 h at all time points investigated) and significantly reduced in nephritic ICAM-1 knockout mice (means <4.4 mg). Mean serum creatinine rose from 29 micromol/L at day -7 to 48 micromol/L (day 28) in nephritic control mice. This increase in serum creatinine was significantly lower in ICAM-1 knockout mice: 27 (day -7) and 36 micromol/L (day 28). Histologic analysis at day 28 revealed that ICAM-1 deficiency in nephrotoxic nephritis mice led to significantly reduced glomerular crescent formation (2+/-3% in ICAM-1 knockout mice versus 13+/-8% in nephritic controls) and tubulointerstitial injury (score 0.4+/-0.4 versus 2.0+/-1.1). By immunohistochemistry, ICAM-1 deficiency in nephritic mice led to significantly reduced (peri-)glomerular and/or interstitial macrophage influx, alpha-smooth muscle actin expression, and type IV collagen accumulation. These data indicate that ICAM-1 is a central mediator of glomerular and tubulointerstitial injury in murine nephrotoxic nephritis.