Effects of photoperiod extension on clock gene and neuropeptide RNA expression in the SCN of the Soay sheep

In mammals, changing daylength (photoperiod) is the main synchronizer of seasonal functions. The photoperiodic information is transmitted through the retino-hypothalamic tract to the suprachiasmatic nuclei (SCN), site of the master circadian clock. To investigate effects of day length change on the sheep SCN, we used in-situ hybridization to assess the daily temporal organization of expression of circadian clock genes (Per1, Per2, Bmal1 and Fbxl21) and neuropeptides (Vip, Grp and Avp) in animals acclimated to a short photoperiod (SP; 8h of light) and at 3 or 15 days following transfer to a long photoperiod (LP3, LP15, respectively; 16h of light), achieved by an acute 8-h delay of lights off. We found that waveforms of SCN gene expression conformed to those previously seen in LP acclimated animals within 3 days of transfer to LP. Mean levels of expression for Per1-2 and Fbxl21 were nearly 2-fold higher in the LP15 than in the SP group. The expression of Vip was arrhythmic and unaffected by photoperiod, while, in contrast to rodents, Grp expression was not detectable within the sheep SCN. Expression of the circadian output gene Avp cycled robustly in all photoperiod groups with no detectable change in phasing. Overall these data suggest that synchronizing effects of light on SCN circadian organisation proceed similarly in ungulates and in rodents, despite differences in neuropeptide gene expression

Development and implementation of an ultralow-dose CT protocol for the assessment of cerebrospinal shunts in adult hydrocephalus

Background: Cerebrospinal fluid shunts in the treatment of hydrocephalus, although associated with clinical benefit, have a high failure rate with repeat computed tomography (CT) imaging resulting in a substantial cumulative radiation dose. Therefore, we sought to develop a whole-body ultralow-dose (ULD) CT protocol for the investigation of shunt malfunction and compare it with the reference standard, plain radiographic shunt series (PRSS). Methods: Following ethical approval, using an anthropomorphic phantom and a human cadaveric ventriculoperitoneal shunt model, a whole-body ULD-CT protocol incorporating two iterative reconstruction (IR) algorithms, pure IR and hybrid IR, including 60% filtered back projection and 40% IR was evaluated in 18 adult patients post new shunt implantation or where shunt malfunction was suspected. Effective dose (ED) and image quality were analysed. Results: ULD-CT permitted a 36% radiation dose reduction (median ED 0.16 mSv, range 0.07–0.17, versus 0.25 mSv (0.06–1.69 mSv) for PRSS (p = 0.002). Shunt visualisation in the thoracoabdominal cavities was improved with ULD-CT with pure IR (p = 0.004 and p = 0.031, respectively) and, in contrast to PRSS, permitted visualisation of the entire shunt course (p < 0.001), the distal shunt entry point and location of the shunt tip in all cases. For shunt complications, ULD-CT had a perfect specificity. False positives (3/22, 13.6%) were observed with PRSS. Conclusions: At a significantly reduced radiation dose, whole body ULD-CT with pure IR demonstrated diagnostic superiority over PRSS in the evaluation of cerebrospinal fluid shunt malfunction

Low-dose carotid computed tomography angiography using pure iterative reconstruction

The aim of this study was to assess if a low-dose carotid computed tomography angiography (CTA) performed with pure iterative reconstruction (IR) is comparable to a conventional dose CTA protocol. Methods: Twenty patients were included. Radiation dose was divided into a low-dose acquisition reconstructed with pure IR and a conventional dose acquisition reconstructed with 40% hybrid IR. Dose, image noise, contrast resolution, spatial resolution, and carotid artery stenosis were measured. Results: Mean effective dose was significantly lower for low-dose than conventional dose studies (1.84 versus 3.71 mSv; P < 0.001). Subjective image noise, contrast resolution, and spatial resolution were significantly higher for the low-dose studies. There was excellent agreement for stenosis grading accuracy between low- and conventional dose studies (Cohen κ = 0.806). Conclusions: A low-dose carotid CTA protocol reconstructed with pure IR is comparable to a conventional dose CTA protocol in terms of image quality and diagnostic accuracy while enabling a dose reduction of 49.6%

Neurointervention for the Peripheral Radiologist: Tips and Tricks

Interventional neuroradiology is a high-risk, high-yield field with small margins for catastrophic errors. A wider range of complex vascular disorders of the brain, spine, head, and neck are now treatable with new endovascular technology. This article describes new tools and techniques in this ever-expanding field

Daylenght dependent brain plasticity: a sheep for all seasons

International audienc

Clinical audit comparing radiation dose metrics between WEB and coil embolisation in the treatment of intracranial aneurysms.

Introduction: Intrasaccular flow disruption is a new and effective endovascular treatment for intracranial aneurysms. While endovascular treatment is a minimally invasive procedure, it does carry a radiation risk. As radiation dose should be kept as low as reasonably achievable (ALARA), the main objective of this study was to analyse KAP (kerma area product), fluoroscopy and procedure time during the treatment of aneurysms treated with coiling and the Woven-EndoBridge (WEB) device. A secondary objective was to look at the reference air kerma (RAK) to determine if the patient receives a dose that could cause tissue effects. Methods: KAP, fluoroscopy and procedure time were retrospectively analysed in patients who had an aneurysm treatment. Aneurysms with diameters of 4-11mm, over a four-year period, in the anterior and posterior circulation of the brain were analysed in this study. Patients were treated by coiling or WEB. RAK were summed together in the working projection to give an estimated entrance surface dose (ESD) in cases with the highest KAP. Results: A total of 47 aneurysms treated with WEB and 104 aneurysms treated with coiling techniques met the inclusion criteria. The average KAP was 6884.1 ± 2774.4μGym2 with coiling techniques and 5658.7 ± 1602.5μGym2 with WEB (p=0.006; CI =363-2086μGym2). This demonstrates an 18% reduction with WEB. Mean fluoroscopy time for coiling was 63.5 ± 42.6minutes and 33.8 ± 28.8minutes for WEB (p=<0.001; CI=16–43minutes). Fluoroscopy time was reduced by nearly 50% with WEB. On average, there was a 27-minute reduction of procedure time when using WEB compared to coiling. The RAK determined for the working projections did not exceed the 2Gy threshold for tissue effects. Conclusion: Treatment of aneurysms using the WEB shows a reduction in KAP, fluoroscopy, and procedure time. This study further demonstrates the benefits of intrasaccular flow disruption for treatment of intracranial aneurysms

Neuropeptide gene expression in the sheep SCN.

<p>The left panel shows daily mRNA expression profiles for the neuropeptides <i>Avp</i> and <i>Vip</i>. <i>Avp</i> shows a pronounced daily rhythm of expression, but this was unaffected by the photoperiod manipulation. <i>Vip</i> expression shows no significant changes during the daily cycle, or in response to photoperiod manipulation. Data presentation in the graphs is as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159201#pone.0159201.g001" target="_blank">Fig 1</a>. The right panels show representative images for each of the 3 neuropeptide genes studied, with phases from which images were taken. Note the absence of <i>Grp</i> expression in the SCN despite strong labelling in the neighbouring supraoptic and paraventricular nuclei. Scale bar = 4 mm.</p

Monitoring neurointerventional radiation doses using dose-tracking software: implications for the establishment of local diagnostic reference levels

Objectives: There is potential for high radiation exposure during neurointerventional procedures. Increasing regulatory requirements mandate dose monitoring of patients and staff, and justification of high levels of radiation exposure. This paper demonstrates the potential to use radiation dose-tracking software to establish local diagnostic reference levels. Methods: Consecutive neurointerventional procedures, performed in a single institution within a one-year period, were retrospectively studied. Dose area product (DAP) data were collected using dose-tracking software and clinical data obtained from a prospectively generated patient treatment database. Results: Two hundred and sixty-four procedures met the selection criteria. Median DAP was 100 Gy.cm2 for aneurysm coiling procedures, 259 Gy.cm2 for arteriovenous malformation (AVM) embolisation procedures, 87 Gy.cm2 for stroke thrombolysis/thrombectomy, and 74 Gy.cm2 for four-vessel angiography. One hundred and nine aneurysm coiling procedures were further studied. Six significant variables were assessed using stepwise regression analysis to determine effect on DAP. Aneurysm location (anterior vs posterior circulation) had the single biggest effect (p = 0.004). Conclusions: This paper confirms variable radiation exposures during neurointerventional procedures. The 75th percentile (used to define diagnostic reference levels) of DAP measurements represents a reasonable guidance metric for monitoring purposes. Results indicate that aneurysm location has the greatest impact on dose during coiling procedures and that anterior and posterior circulation coiling procedures should have separate diagnostic reference levels. Key Points: Dose-tracking software is useful for monitoring patient radiation dose during neurointerventional procedures; This paper provides a template for methodology applicable to any interventional suite; Local diagnostic reference levels were defined by using the 75th percentile of DAP as per International Commission on Radiological Protection recommendations; Aneurysm location is the biggest determinant of radiation dose during coiling procedures.; Anterior and posterior circulation coiling procedures should have separate diagnostic reference levels