The Mars 2020 Engineering Cameras and Microphone on the Perseverance Rover: A Next-Generation Imaging System for Mars Exploration.

The Mars 2020 Perseverance rover is equipped with a next-generation engineering camera imaging system that represents an upgrade over previous Mars rover missions. These upgrades will improve the operational capabilities of the rover with an emphasis on drive planning, robotic arm operation, instrument operations, sample caching activities, and documentation of key events during entry, descent, and landing (EDL). There are a total of 16 cameras in the Perseverance engineering imaging system, including 9 cameras for surface operations and 7 cameras for EDL documentation. There are 3 types of cameras designed for surface operations: Navigation cameras (Navcams, quantity 2), Hazard Avoidance Cameras (Hazcams, quantity 6), and Cachecam (quantity 1). The Navcams will acquire color stereo images of the surface with a 96 ∘ × 73 ∘ field of view at 0.33 mrad/pixel. The Hazcams will acquire color stereo images of the surface with a 136 ∘ × 102 ∘ at 0.46 mrad/pixel. The Cachecam, a new camera type, will acquire images of Martian material inside the sample tubes during caching operations at a spatial scale of 12.5 microns/pixel. There are 5 types of EDL documentation cameras: The Parachute Uplook Cameras (PUCs, quantity 3), the Descent stage Downlook Camera (DDC, quantity 1), the Rover Uplook Camera (RUC, quantity 1), the Rover Descent Camera (RDC, quantity 1), and the Lander Vision System (LVS) Camera (LCAM, quantity 1). The PUCs are mounted on the parachute support structure and will acquire video of the parachute deployment event as part of a system to characterize parachute performance. The DDC is attached to the descent stage and pointed downward, it will characterize vehicle dynamics by capturing video of the rover as it descends from the skycrane. The rover-mounted RUC, attached to the rover and looking upward, will capture similar video of the skycrane from the vantage point of the rover and will also acquire video of the descent stage flyaway event. The RDC, attached to the rover and looking downward, will document plume dynamics by imaging the Martian surface before, during, and after rover touchdown. The LCAM, mounted to the bottom of the rover chassis and pointed downward, will acquire 90 ∘ × 90 ∘ FOV images during the parachute descent phase of EDL as input to an onboard map localization by the Lander Vision System (LVS). The rover also carries a microphone, mounted externally on the rover chassis, to capture acoustic signatures during and after EDL. The Perseverance rover launched from Earth on July 30th, 2020, and touchdown on Mars is scheduled for February 18th, 2021.

HydroCoils Are Associated with Lower Angiographic Recurrence Rates Than Are Bare Platinum Coils in Treatment of "Difficult-to-Treat" Aneurysms: A Post Hoc Subgroup Analysis of the HELPS Trial.

BACKGROUND AND PURPOSE: The HydroCoil Endovascular Aneurysm Occlusion and Packing Study was a randomized controlled trial that compared HydroCoils to bare platinum coils. Using data from this trial, we performed a subgroup analysis of angiographic and clinical outcomes of patients with "difficult-to-treat" aneurysms, defined as irregularly shaped and/or having a dome-to-neck ratio of <1.5. MATERIALS AND METHODS: Separate subgroup analyses comparing outcomes of treatment with HydroCoils to that of bare platinum coils were performed for the following: 1) irregularly shaped aneurysms, 2) regularly shaped aneurysms, 3) aneurysms with a dome-to-neck ratio of <1.5, and 4) aneurysms with a dome-to-neck ratio of ≥1.5. For each subgroup analysis, the following outcomes were studied at the last follow-up (3-18 months): 1) any recurrence, 2) major recurrence, 3) re-treatment, and 4) an mRS score of ≤2. Multivariate logistic regression analysis was performed to determine if the HydroCoil was independently associated with improved outcomes in these subgroups. RESULTS: Among the patients with an irregularly shaped aneurysm, the HydroCoil was associated with lower major recurrence rates than the bare platinum coils (17 of 66 [26%] vs 30 of 69 [44%], respectively; P = .046). Among the patients with an aneurysm with a small dome-to-neck ratio, the HydroCoil was associated with lower major recurrence rates than the bare platinum coils (18 of 73 [24.7%] vs 32 of 76 [42.1%], respectively; P = .02). No difference in major recurrence was seen between HydroCoils and bare platinum coils for regularly shaped aneurysms (42 of 152 [27.6%] vs 52 of 162 [32.1%], respectively; P = .39) or aneurysms with a large dome-to-neck ratio (41 of 145 [28.3%] vs 50 of 155 [32.3%], respectively; P = .53). CONCLUSIONS: This unplanned post hoc subgroup analysis found that HydroCoils are associated with improved angiographic outcomes in the treatment of irregularly shaped aneurysms and aneurysms with a dome-to-neck ratio of <1.5. Because this was a post hoc analysis, these results are not reliable and absolutely should not alter clinical practice but, rather, may inform the design of future randomized controlled trials.

HydroCoils reduce recurrence rates in recently ruptured medium-sized intracranial aneurysms: a subgroup analysis of the HELPS trial.

BACKGROUND AND PURPOSE: The HydroCoil Endovascular Aneurysm Occlusion and Packing Study (HELPS) was a randomized, controlled trial comparing HydroCoils with bare-platinum coils. The purpose of this study was to perform a subgroup analysis of angiographic and clinical outcomes of medium-sized aneurysms in the HELPS trial. MATERIALS AND METHODS: Patients with medium-sized aneurysms (5-9.9 mm) were selected from the HELPS trial. Outcomes compared between the HydroCoil and bare-platinum groups included the following: 1) any recurrence, 2) major recurrence, 3) retreatment, and 4) mRS score of ≤2. Subgroup analysis by rupture status was performed. Multivariate logistic regression analysis adjusting for aneurysm neck size, shape, use of adjunctive device, and rupture status was performed. RESULTS: Two hundred eighty-eight patients with medium-sized aneurysms were randomized (144 in each group). At 15-18 months posttreatment, the major recurrence rate was significantly lower in the HydroCoil group than in controls (18.6% versus 30.8%, P = .03, respectively). For patients with recently ruptured aneurysms, the major recurrence rate was significantly lower for the HydroCoil group than for controls (20.3% versus 47.5%, P = .003), while rates were similar between groups for unruptured aneurysms (16.7% versus 14.8%, P = .80). Multivariate analysis of patients with recently ruptured aneurysms demonstrated a lower odds of major recurrence with HydroCoils (OR = 0.27; 95% CI, 0.12-0.58; P = .0007). No difference in retreatment rates or mRS of ≤2 was seen between groups. CONCLUSIONS: HydroCoils were associated with statistically significant and clinically relevant lower rates of major recurrence for recently ruptured, medium-sized aneurysms in the HELPS trial. Because this was not a prespecified subgroup analysis, these results should not alter clinical practice but, rather, provide insight into the design of future clinical trials comparing bare platinum with second-generation coils.

Science applications of a multispectral microscopic imager for the astrobiological exploration of Mars.

Future astrobiological missions to Mars are likely to emphasize the use of rovers with in situ petrologic capabilities for selecting the best samples at a site for in situ analysis with onboard lab instruments or for caching for potential return to Earth. Such observations are central to an understanding of the potential for past habitable conditions at a site and for identifying samples most likely to harbor fossil biosignatures. The Multispectral Microscopic Imager (MMI) provides multispectral reflectance images of geological samples at the microscale, where each image pixel is composed of a visible/shortwave infrared spectrum ranging from 0.46 to 1.73 µm. This spectral range enables the discrimination of a wide variety of rock-forming minerals, especially Fe-bearing phases, and the detection of hydrated minerals. The MMI advances beyond the capabilities of current microimagers on Mars by extending the spectral range into the infrared and increasing the number of spectral bands. The design employs multispectral light-emitting diodes and an uncooled indium gallium arsenide focal plane array to achieve a very low mass and high reliability. To better understand and demonstrate the capabilities of the MMI for future surface missions to Mars, we analyzed samples from Mars-relevant analog environments with the MMI. Results indicate that the MMI images faithfully resolve the fine-scale microtextural features of samples and provide important information to help constrain mineral composition. The use of spectral endmember mapping reveals the distribution of Fe-bearing minerals (including silicates and oxides) with high fidelity, along with the presence of hydrated minerals. MMI-based petrogenetic interpretations compare favorably with laboratory-based analyses, revealing the value of the MMI for future in situ rover-mediated astrobiological exploration of Mars.

The importance of relative mutant level for evaluating impact on outcome of KIT, FLT3 and CBL mutations in core-binding factor acute myeloid leukemia.

Several different mutations collaborate with the fusion proteins in core-binding factor acute myeloid leukemia (CBF-AML) to induce leukemogenesis, but their prognostic significance remains unclear. We screened 354 predominantly younger (<60 years) adults with t(8;21) (n=199) or inv(16) (n=155) entered into UK MRC trials for KIT, FLT3 tyrosine kinase domain (FLT3(TKD)), N-RAS, K-RAS and c-CBL mutations and FLT3 internal tandem duplications (FLT3(ITD)) and assessed the impact of relative mutant level on outcome. Overall, 28% had KIT, 6% FLT3(ITD), 10% FLT3(TKD), 27% RAS and 6% CBL mutations. Mutant levels for all genes/loci were highly variable. KIT mutations were associated with a higher cumulative incidence of relapse but in multivariate analysis this was only significant for cases with a higher mutant level of 25% or greater (95% confidence interval (CI)=1.01-1.52, P=0.04). Similarly, only FLT3(ITD-HIGH) was a significant adverse factor for overall survival (OS; CI=1.27-5.39, P=0.004). Conversely, FLT3(TKD-HIGH) and CBL(HIGH) were both favorable factors for OS (CI= 0.31-0.89, P=0.01 and CI=0.05-0.85, P=0.02, respectively). KIT mutations were frequently lost at relapse, which is relevant to minimal residual disease detection and the clinical use of KIT inhibitors. These results indicate that relative mutant level should be taken into account when evaluating the impact of mutations in CBF-AML.

The use of CT angiography in acute subarachnoid haemorrhage in Eastern Scotland.

INTRODUCTION: Early confirmation of aneurysmal cause for SAH can expedite patient management and thus minimise rebleed risk. CT Angiography is the first-line method for diagnosing the cause of SAH in most UK regions. We wanted to assess the use of CTA in this context in the East of Scotland and determine how imaging delays contribute to overall delay from ictus to aneurysm treatment. METHODS: A prospective audit of aneurysmal SAH admissions over a three month period to the Neurosciences Unit in Edinburgh was performed. The time from diagnosis of SAH to aneurysm imaging with CTA and/or DSA and time from aneurysm confirmation to definitive treatment was ascertained. RESULTS: Twenty nine patients with aneurysmal SAH were admitted during the audit. Four patients had CTA expeditiously after SAH was diagnosed; the remaining 25 patients had a substantially greater wait for aneurysm imaging, involving transfer to a neuroscience centre. Average excess delay was 17 hours for CTA (72 hours for DSA). DISCUSSION: CTA widely available and accurate method of determining the cause of SAH. Performing immediate CTA after SAH is confirmed could reduce delays to aneurysm treatment by up to 64%. By thus reducing rebleeds post SAH, immediate CTA could reduce poor outcomes in the East of Scotland.

Assessment of factors affecting MRI measurement of intracranial volume changes and elastance index.

Non-invasive measurement of cerebral hydrodynamic parameters may be of great use in the study and treatment of conditions involving abnormal intracranial pressure (ICP). ICP can be assessed indirectly in humans by calculation of intracranial volume changes and elastance using MRI. These two hydrodynamic parameters are derived from mathematical analysis of the relationships between blood flow to and from the brain, CSF flow and heart rate. This paper examines the variability in these three critical subject specific parameters. Three healthy adult males had measurements of blood and CSF flow to and from the brain made on three occasions. Inter-individual variation in vasculature and intra-individual variation in heart rates led to modest repeatability (defined as standard deviation divided by the mean) of intracranial volume change and elastance index in two subjects and poor repeatability in the third. Particular care is required in the selection of image planes and the blood vessels to include, and the analysis is very sensitive to differences in heart-rate. Because of these difficulties, caution is required in the interpretation of results obtained from a single examination. Techniques and methods that may reduce the variability in the derived hydrodynamic parameters are discussed.

HydroCoil Endovascular Aneurysm Occlusion and Packing Study (HELPS trial): procedural safety and operator-assessed efficacy results.

BACKGROUND AND PURPOSE: Coated coils have been in clinical use for several years without robust evidence to determine their safety/efficacy. The HydroCoil Endovascular Aneurysm Occlusion and Packing Study (HELPS) addresses this deficiency for the HydroCoil embolic system. This article reports periprocedural safety/operator-assessed angiographic results from HELPS. MATERIALS AND METHODS: Patients were randomized to the hydrogel coil or control arms by using concealed allocation with minimization matching groups. Any bare platinum coils were allowed in the control arm, and assist devices could be used as clinically required. Both recently ruptured and not recently ruptured/unruptured aneurysms were included. Analysis was on an intention-to-treat basis. RESULTS: Four hundred ninety-nine patients were recruited. Coiling was successful in 98.6%. Mean aneurysm size was 6.5 mm (26% were > or =10 mm), 53% were recently ruptured aneurysms, and an assist device was used in 46%. Seventy procedural adverse events were reported in hydrogel coils and 86 in control arms. The 3-month mortality rate was 3.6% in hydrogel coils and 2.0% in control arms; the difference was not significant (P = .6). There was a lower 2-month mortality rate in the HELPS subarachnoid hemorrhage cohort (4.1%) than would be anticipated from the International Subarachnoid Aneurysm Trial (7%). There was a trend toward increased adverse events when assist devices were used, which was substantial for stents deployed in recently ruptured aneurysms. Ninety-six percent of patients discharged were World Federation of Neurosurgeons grade 0-2 at discharge. No difference was found between arms in the operator assessment of angiographic occlusions (P = .3). CONCLUSION: These HELPS results reinforce coiling as an effective treatment for aneurysms, with an excellent technical success rate. Hydrogel coils can be used in a wide spectrum of aneurysms with a risk profile equivalent to that of bare platinum.

Spinocerebellar ataxia type 8 in Scotland: frequency, neurological, neuropsychological and neuropsychiatric findings.

OBJECTIVES: The objectives of this study were to: (i) establish whether the spinocerebellar ataxia type 8 (SCA 8) expansion is associated with ataxia in Scotland; (ii) test the hypothesis that SCA 8 is associated with neuropsychological impairment; and (iii) review neuroradiological findings in SCA 8. METHODS: The methods included: (i) measurement of SCA 8 expansion frequencies in ataxic patients and healthy controls; (ii) comprehensive neuropsychological assessment of patients with SCA 8 and matched controls, neuropsychiatric interview; and (iii) comparison of patient and matched control magnetic resonance imaging (MRI) scans. RESULTS: (i) 10/694 (1.4%) unrelated individuals with ataxia had combined CTA/CTG repeat expansions >100 compared to 1/1190 (0.08%) healthy controls (P < 0.0005); (ii) neuropsychological assessment revealed a dysexecutive syndrome among SCA 8 patients, not readily explained by motor or mood disturbance; neuropsychiatric symptoms occurred commonly; (iii) cerebellar atrophy was the only salient MRI abnormality in the patient group. CONCLUSIONS: The SCA 8 expansion is associated with ataxia in Scotland. The disorder is associated with a dysexecutive syndrome.

Differences between intracranial vascular malformation types in the characteristics of their presenting haemorrhages: prospective, population-based study.

OBJECTIVE: To determine the imaging and demographic characteristics of intracranial haemorrhages, which are subsequently found to be due to an underlying intracranial vascular malformation (IVM). METHODS: We compared the demographic and brain imaging characteristics of adults presenting with intracranial haemorrhage, subsequently found to be due to a brain arteriovenous malformation (BAVM), dural arteriovenous fistula (DAVF) or cavernous malformation (CM) in a prospective, population-based cohort of adults diagnosed for the first time with an IVM (The Scottish IVM Study (SIVMS)). RESULTS: Of the 141 adults in SIVMS who presented with intracranial haemorrhage, those with CMs presented at a younger age and were less handicapped. A total of 115 (82%) had intracerebral haemorrhage (ICH) with or without subarachnoid, intraventricular or subdural extension. ICH without extension into other compartments accounted for all CM bleeds, but only 50% of BAVM and DAVF bleeds. Median haematoma volumes differed (Kruskal-Wallis, p<0.0001): ICH due to BAVM (16.0 cm3, inter-quartile range (IQR) 4.7 to 42.0) and DAVF (14.1 cm3, IQR 4.9 to 21.5) were similar, but CM haematoma volumes were smaller (median 1.8 cm3, IQR 1.3 to 4.3). These findings were robust in sensitivity analyses. Small haematoma volumes occurred among all IVM types; the largest haematoma volume due to CM was 12 cm3, and volumes of >34 cm3 were only due to BAVM. CONCLUSIONS: Intracranial haemorrhages found to be due to IVMs differ in adults' age of presentation and clinical severity, as well as the volume and distribution of the haematoma within the brain compartments.

Comparison of relative signal-to-noise ratios of different classes of imaging spectrometer.

The continued development of new and fundamentally different classes of imaging spectrometer has increased both the scope and the complexity of comparisons of their relative signal-to-noise ratios. Although the throughput and multiplex advantages of Fourier-transform spectrometers were established in the early 1950s, the application of this terminology to imaging spectrometers is often ambiguous and has led to some confusion and debate. For comparisons of signal-collection abilities to be useful to a system designer, they must be based on identical requirements and constraints. We present unambiguous definitions of terminology for application to imaging spectrometers and comparisons of signal-collection abilities and signal-to-noise-ratios on a basis that is useful to a systems designer and inclusive of six fundamentally different classes (both traditional and novel) of imaging spectrometers.

Peduncular hallucinations following subarachnoid haemorrhage.

We describe the case of a 56-year-old woman who suffered vivid visual hallucination following subarachnoid haemorrhage (SAH). These occurred from day 9 to day 28 after the haemorrhage. An association with sleep disturbance, clinical findings, and the nature of the hallucinations suggested peduncular hallucinosis. Putative mechanisms in this case are discussed.

Fogging on T2-weighted MR after acute ischaemic stroke: how often might this occur and what are the implications?

"Fogging" is the temporary loss of visibility of an infarct on CT which occurs in the subacute phase at about 2 weeks after stroke. It occurs in up to 40% of medium to large infarcts on CT. It is unclear whether or how often fogging occurs on T2-weighted MR, but if it does occur, it can cause underestimation of true infarct size. This study examined the possible frequency and time scale of "fogging" on T2-weighted MR. We conducted a blinded, independent review of prospectively collected MR scans from patients with symptoms of cortical ischaemic stroke, scanned sequentially up to 7 weeks after stroke. On each scan maximum infarct area was measured, and the infarct extent and swelling were coded on a validated scale. "Fogging" was suggested by reduced infarct extent between initial and subsequent scans. In 30 patients (with 74 scans) there was some apparent "fogging" in 50% of patients between 6 and 36 days (median 10 days) after stroke. Reduction in infarct extent on T2-weighted MR which may be attributed to "fogging" occurs in a significant proportion of patients with cortical infarcts. This may lead to an underestimation of true final infarct extent. This suggests that true infarct extent on T2-weighted MR can probably only be assessed on scans obtained beyond 7 weeks after stroke.

The endovascular management of pericallosal artery aneurysms.

AIM: to describe our experience with a series of 18 patients with pericallosal artery aneurysms, in whom endovascular coil insertion was attempted. METHOD: the CT and angiographic appearances, coiling techniques and patient outcomes are discussed. RESULTS: we encountered a higher than expected level of technical difficulty and procedure related complication than when coiling aneurysms in more common locations. In particular the distal position of the aneurysms lead to poorer control over the microcatheter position. Procedure related rupture occurred in three cases. Coiling was not possible in one case only. An association between an angulated bifurcation of the anterior cerebral artery and a sidewall aneurysm configuration was noted. CONCLUSION: despite the technical difficulties and high procedure related rupture rate, coiling of pericallosal aneurysms is feasible and has good outcome.