ASSESSMENT OF OVERRANGING AS A FUNCTION OF PITCH, COLLIMATION AND ROTATION TIME FOR THREE OF THE MOST RECENT AND WIDESPREAD CT SCANS IN FRANCE

PURPOSE

to assess overranging (OR) as a function of pitch, collimation and rotation time for three commonly used CT models in France.

METHODS

OR was measured using XR-SP2 Gafchromic films (Ashland, USA) and computed from exposure data for three widely used CT models in France. The impact of collimation, pitch and rotation time on OR was analyzed while comparing the three CT models.

RESULTS

for a typical head protocol, measured OR was found to be equal to 1.64 cm for CT scan A, 0.5 cm for CT scan B and 3.44 cm for CT scan C. OR values were respectively of 4.47, 3.24 and 7.81 cm for the typical chest protocol and the 3 CT models. OR was lowest at pitch values <1 for CT scan A, while it linearly increased with pitch for CT scan B and was lowest for high pitch values for CT scan C. Additionally, OR increase with collimation (24 mm to 38.4 mm) was most pronounced for CT scan B (factor of 2.2 for low pitch (0.5) and 2.8 for high pitch (1.2)) while it increased linearly regardless of the pitch for CT scans A and C. Rotation time also proved to slightly affect OR mainly for CT scan B (up to 2.2 mm).

CONCLUSION

the present study shows that overranging remains an issue in modern CT scanners with large disparities across the vendors.

A year of genomic surveillance reveals how the SARS-CoV-2 pandemic unfolded in Africa

The progression of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in Africa has so far been heterogeneous, and the full impact is not yet well understood. In this study, we describe the genomic epidemiology using a dataset of 8746 genomes from 33 African countries and two overseas territories. We show that the epidemics in most countries were initiated by importations predominantly from Europe, which diminished after the early introduction of international travel restrictions. As the pandemic progressed, ongoing transmission in many countries and increasing mobility led to the emergence and spread within the continent of many variants of concern and interest, such as B.1.351, B.1.525, A.23.1, and C.1.1. Although distorted by low sampling numbers and blind spots, the findings highlight that Africa must not be left behind in the global pandemic response, otherwise it could become a source for new variants.

NATIONAL DIAGNOSTIC REFERENCE LEVELS IN INTERVENTIONAL RADIOLOGY SUITES IN LEBANON: A MULTICENTER SURVEY

Air kerma-area product (PKA), cumulative air kerma at patient entrance reference point, fluoroscopy time and number of images were retrospectively collected from 15 hospitals in Lebanon for 11282 fluoroscopically-guided interventional (FGI) procedures between March 2016 and November 2018. National diagnostic reference levels (NDRLs) were established based on the third quartile of the distribution of median values of exposure parameters per department for 27 types of FGI procedures. NDRLs were in line with international DRLs except for coronary angiography (CA), percutaneous coronary interventions (PCI) and transcatheter aortic valve implantation (TAVI) which require optimisation. Additionally, following the National Council on Radiation Protection and Measurements report 168, PCI, TAVI, triple chamber pacemaker implantation, endovascular aortic repair, nephrostomy, kyphoplasty and percutaneous transhepatic biliary drainage were classified as potentially high-dose procedures with >5% of the patients with PKA exceeding 300 Gycm2. The established NDRLs will promote dose optimisation and patient radiation protection.

P5550The prognostic and therapeutic characteristics of heart failure among elderly patients with hypertrophic cardiomyopathy

Introduction

Symptomatic heart failure is frequent among patients with hypertrophic cardiomyopathy. Once regarded a disease of mostly young adults, recently, hypertrophic cardiomyopathy has been increasingly diagnosed in older patients. There is scarce medical literature specifically dedicated to hypertrophic cardiomyopathy in elderly patients. As a result, their natural history with respect to risk of adverse events such as heart failure, stroke, and sudden cardiac death remains relatively unknown.

Purpose

We aimed to determine the prognostic and therapeutic implications of heart failure in hypertrophic cardiomyopathy patients older than 65 years old.

Methods

In this retrospective observational study, we searched our hospital's database for hypertrophic cardiomyopathy patients who were admitted due to acute decompensated heart failure between 1/1/2000 and 31/12/2016. Patients were stratified into two age groups: over 65 years old and under 65 years old (our control group).

Our primary outcomes were overall mortality and re-admissions due to acute decompensated heart failure.

Results

Our cohort included 86 patients. 54 patients were older than 65 years and 32 were younger than 65. There were significantly more women in the over 65 group. In the elderly group, significantly less patients had a history of smoking (26% vs. 47%, p=0.047), whereas more patients had known coronary artery disease (48% vs. 19%, p=0.006). The echocardiographic features of the two groups were similar.

The survival rate was not significantly different between the two age groups (10 year survival rate 41% under 65, 37% over 65, p=0.68). There were also no significant differences in the risk of re-admission due to acute decompensated heart failure between the two age groups.

Conclusion

No differences were seen in overall mortality or in re-admission due to acute decompensated heart failure between older (over 65) and younger (under 65) patients. Hence, it appears prudent to adhere to ESC guidelines for hypertrophic cardiomyopathy management in older hypertrophic cardiomyopathy patients.

MEASUREMENT OF PATIENT SKIN DOSE DISTRIBUTIONS IN THREE LEBANESE INTERVENTIONAL CARDIOLOGY SUITES

Using a mesh of 30 thermoluminescent dosemeters, adults' patient skin doses were measured for 99 coronary angiography (CA) and 89 percutaneous coronary interventions (PCI) performed in three Lebanese hospitals. Average peak skin dose (Dskin,max) were 152 mGy (range: 16-1144) for CAs and 576 mGy (range: 7-3361) for PCIs. While only four patients had a Dskin,max value exceeding the 2 Gy threshold for skin injuries, several patients had skin dose values above 1 Gy at several distinct locations proving that Dskin,max alone is not sufficient for repetitive procedures; 2D dose maps are required instead. Dskin,max correlated well with total air kerma-area product (PKA,T) for PCI in Hospitals 1 and 2 (R = 0.91 and 0.76, respectively) enabling the setup of an alert level at PKA,T = 240 and 210 Gy cm2, respectively, corresponding to a Dskin,max of 2 Gy. This was not possible for Hospital 3 due to weak correlations between Dskin,max and PKA,T.

OCCUPATIONAL DOSES FOR THE FIRST AND SECOND OPERATORS IN LEBANESE INTERVENTIONAL CARDIOLOGY SUITES

The study monitored occupational dose for 12 interventional cardiologists (first operators) and 10 technicians (second operators), from 10 different Lebanese hospitals performing coronary angiography and precutaneous coronary interventions exclusively on adult patients. Each individual wore dosemeters under and over the lead apron at chest and collar level, respectively, on the wrist and next to the left eye. The total follow-up period for each first/second operator varied between two to six bimonthly monitoring periods. For the first operator, the mean (range) effective, hand and eye lens doses were of 6 (1-41), 112 (10-356) and 15 (5-47) μSv/procedure, respectively. These were of 2.3 (0.1-8), 16 (2-109) and 7 (2-14) μSv/procedure for the second operator. Extrapolated annual eye lens doses revealed that both first and second operators may exceed 3/10th of the annual eye lens dose permissible limit thus supporting the need for dedicated eye lens monitoring.

Dose distribution of secondary radiation in a water phantom for a proton pencil beam-EURADOS WG9 intercomparison exercise

Systematic 3D mapping of out-of-field doses induced by a therapeutic proton pencil scanning beam in a 300  ×  300  ×  600 mm³ water phantom was performed using a set of thermoluminescence detectors (TLDs): MTS-7 (⁷LiF:Mg,Ti), MTS-6 (⁶LiF:Mg,Ti), MTS-N (^natLiF:Mg,Ti) and TLD-700 (⁷LiF:Mg,Ti), radiophotoluminescent (RPL) detectors GD-352M and GD-302M, and polyallyldiglycol carbonate (PADC)-based (C₁₂H₁₈O₇) track-etched detectors. Neutron and gamma-ray doses, as well as linear energy transfer distributions, were experimentally determined at 200 points within the phantom. In parallel, the Geant4 Monte Carlo code was applied to calculate neutron and gamma radiation spectra at the position of each detector. For the cubic proton target volume of 100  ×  100  ×  100 mm³ (spread out Bragg peak with a modulation of 100 mm) the scattered photon doses along the main axis of the phantom perpendicular to the primary beam were approximately 0.5 mGy Gy^-1 at a distance of 100 mm and 0.02 mGy Gy^-1 at 300 mm from the center of the target. For the neutrons, the corresponding values of dose equivalent were found to be ~0.7 and ~0.06 mSv Gy^-1, respectively. The measured neutron doses were comparable with the out-of-field neutron doses from a similar experiment with 20 MV x-rays, whereas photon doses for the scanning proton beam were up to three orders of magnitude lower.

Validation of ELDO approaches for retrospective assessment of cumulative eye lens doses of interventional cardiologists-results from DoReMi project

The first validation results of the two approaches developed in the ELDO project for retrospective assessment of eye lens doses for interventional cardiologists (ICs) are presented in this paper. The first approach (a) is based on both the readings from the routine whole body dosimeter worn above the lead apron and procedure-dependent conversion coefficients, while the second approach (b) is based on detailed information related to the occupational exposure history of the ICs declared in a questionnaire and eye lens dose records obtained from the relevant literature. The latter approach makes use of various published eye lens doses per procedure as well as the appropriate correction factors which account for the use of radiation protective tools designed to protect the eye lens. To validate both methodologies, comprehensive measurements were performed in several Polish clinics among recruited physicians. Two dosimeters measuring whole body and eye lens doses were worn by every physician for at least two months. The estimated cumulative eye lens doses, calculated from both approaches, were then compared against the measured eye lens dose value for every physician separately. Both approaches results in comparable estimates of eye lens doses and tend to overestimate rather than underestimate the eye lens doses. The measured and estimated doses do not differ, on average, by a factor higher than 2.0 in 85% and 62% of the cases used to validate approach (a) and (b), respectively. In specific cases, however, the estimated doses differ from the measured ones by as much as a factor of 2.7 and 5.1 for method (a) and (b), respectively. As such, the two approaches can be considered accurate when retrospectively estimating the eye lens doses for ICs and will be of great benefit for ongoing epidemiological studies.

Influence of beam incidence and irradiation parameters on stray neutron doses to healthy organs of pediatric patients treated for an intracranial tumor with passive scattering proton therapy

PURPOSE

In scattering proton therapy, the beam incidence, i.e. the patient's orientation with respect to the beam axis, can significantly influence stray neutron doses although it is almost not documented in the literature.

METHODS

MCNPX calculations were carried out to estimate stray neutron doses to 25 healthy organs of a 10-year-old female phantom treated for an intracranial tumor. Two beam incidences were considered in this article, namely a superior (SUP) field and a right lateral (RLAT) field. For both fields, a parametric study was performed varying proton beam energy, modulation width, collimator aperture and thickness, compensator thickness and air gap size.

RESULTS

Using a standard beam line configuration for a craniopharyngioma treatment, neutron absorbed doses per therapeutic dose of 63μGyGy(-1) and 149μGyGy(-1) were found at the heart for the SUP and the RLAT fields, respectively. This dose discrepancy was explained by the different patient's orientations leading to changes in the distance between organs and the final collimator where external neutrons are mainly produced. Moreover, investigations on neutron spectral fluence at the heart showed that the number of neutrons was 2.5times higher for the RLAT field compared against the SUP field. Finally, the influence of some irradiation parameters on neutron doses was found to be different according to the beam incidence.

CONCLUSION

Beam incidence was thus found to induce large variations in stray neutron doses, proving that this parameter could be optimized to enhance the radiation protection of the patient.

Measurement of maximum skin dose in interventional radiology and cardiology and challenges in the set-up of European alert thresholds

To help operators acknowledge patient dose during interventional procedures, EURADOS WG-12 focused on measuring patient skin dose using XR-RV3 gafchromic films, thermoluminescent detector (TLD) pellets or 2D TL foils and on investigating possible correlation to the on-line dose indicators such as fluoroscopy time, Kerma-area product (KAP) and cumulative air Kerma at reference point (CK). The study aims at defining non-centre-specific European alert thresholds for skin dose in three interventional procedures: chemoembolization of the liver (CE), neuroembolization (NE) and percutaneous coronary interventions (PCI). Skin dose values of >3 Gy (ICRP threshold for skin injuries) were indeed measured in these procedures confirming the need for dose indicators that correlate with maximum skin dose (MSD). However, although MSD showed fairly good correlation with KAP and CK, several limitations were identified challenging the set-up of non-centre-specific European alert thresholds. This paper presents preliminary results of this wide European measurement campaign and focuses on the main challenges in the definition of European alert thresholds.

Application of the ELDO approach to assess cumulative eye lens doses for interventional cardiologists

In preparation of a large European epidemiological study on the relation between eye lens dose and the occurrence of lens opacities, the European ELDO project focused on the development of practical methods to estimate retrospectively cumulative eye lens dose for interventional medical professionals exposed to radiation. The present paper applies one of the ELDO approaches, correlating eye lens dose to whole-body doses, to assess cumulative eye lens dose for 14 different Finnish interventional cardiologists for whom annual whole-body dose records were available for their entire working period. The estimated cumulative left and right eye lens dose ranged from 8 to 264 mSv and 6 to 225 mSv, respectively. In addition, calculations showed annual eye lens doses sometimes exceeding the new ICRP annual limit of 20 mSv. The work also highlights the large uncertainties associated with the application of such an approach proving the need for dedicated dosimetry systems in the routine monitoring of the eye lens dose.

Configuration and validation of an analytical model predicting secondary neutron radiation in proton therapy using Monte Carlo simulations and experimental measurements

PURPOSE

This study focuses on the configuration and validation of an analytical model predicting leakage neutron doses in proton therapy.

METHODS

Using Monte Carlo (MC) calculations, a facility-specific analytical model was built to reproduce out-of-field neutron doses while separately accounting for the contribution of intra-nuclear cascade, evaporation, epithermal and thermal neutrons. This model was first trained to reproduce in-water neutron absorbed doses and in-air neutron ambient dose equivalents, H*(10), calculated using MCNPX. Its capacity in predicting out-of-field doses at any position not involved in the training phase was also checked. The model was next expanded to enable a full 3D mapping of H*(10) inside the treatment room, tested in a clinically relevant configuration and finally consolidated with experimental measurements.

RESULTS

Following the literature approach, the work first proved that it is possible to build a facility-specific analytical model that efficiently reproduces in-water neutron doses and in-air H*(10) values with a maximum difference less than 25%. In addition, the analytical model succeeded in predicting out-of-field neutron doses in the lateral and vertical direction. Testing the analytical model in clinical configurations proved the need to separate the contribution of internal and external neutrons. The impact of modulation width on stray neutrons was found to be easily adjustable while beam collimation remains a challenging issue. Finally, the model performance agreed with experimental measurements with satisfactory results considering measurement and simulation uncertainties.

CONCLUSION

Analytical models represent a promising solution that substitutes for time-consuming MC calculations when assessing doses to healthy organs.

Secondary neutron doses in proton therapy treatments of ocular melanoma and craniopharyngioma

Monte Carlo simulations were used to assess secondary neutron doses received by patients treated with proton therapy for ocular melanoma and craniopharyngioma. MCNPX calculations of out-of-field doses were done for ∼20 different organs considering realistic treatment plans and using computational phantoms representative of an adult male individual. Simulations showed higher secondary neutron doses for intracranial treatments, ∼14 mGy to the salivary glands, when compared with ocular treatments, ∼0.6 mGy to the non-treated eye. This secondary dose increase is mainly due to the higher proton beam energy (178 vs. 75 MeV) as well as to the impact of the different beam parameters (modulation, collimation, field size etc.). Moreover, when compared with published data, the assessed secondary neutron doses showed similar trends, but sometimes with sensitive differences. This confirms secondary neutrons to be directly dependent on beam energy, modulation technique, treatment configuration and methodology.

Efficiency of radiation protection equipment in interventional radiology: a systematic Monte Carlo study of eye lens and whole body doses

Monte Carlo calculations were used to investigate the efficiency of radiation protection equipment in reducing eye and whole body doses during fluoroscopically guided interventional procedures. Eye lens doses were determined considering different models of eyewear with various shapes, sizes and lead thickness. The origin of scattered radiation reaching the eyes was also assessed to explain the variation in the protection efficiency of the different eyewear models with exposure conditions. The work also investigates the variation of eye and whole body doses with ceiling-suspended shields of various shapes and positioning. For all simulations, a broad spectrum of configurations typical for most interventional procedures was considered. Calculations showed that 'wrap around' glasses are the most efficient eyewear models reducing, on average, the dose by 74% and 21% for the left and right eyes respectively. The air gap between the glasses and the eyes was found to be the primary source of scattered radiation reaching the eyes. The ceiling-suspended screens were more efficient when positioned close to the patient's skin and to the x-ray field. With the use of such shields, the Hp(10) values recorded at the collar, chest and waist level and the Hp(3) values for both eyes were reduced on average by 47%, 37%, 20% and 56% respectively. Finally, simulations proved that beam quality and lead thickness have little influence on eye dose while beam projection, the position and head orientation of the operator as well as the distance between the image detector and the patient are key parameters affecting eye and whole body doses.

Secondary neutron doses received by paediatric patients during intracranial proton therapy treatments

This paper's goal is to assess secondary neutron doses received by paediatric patients treated for intracranial tumours using a 178 MeV proton beam. The MCNPX Monte Carlo model of the proton therapy facility, previously validated through experimental measurements for both proton and neutron dosimetry, was used. First, absorbed dose was calculated for organs located outside the clinical target volume using a series of hybrid computational phantoms for different ages and considering a realistic treatment plan. In general, secondary neutron dose was found to decrease as the distance to the treatment field increases and as the patient age increases. In addition, secondary neutron doses were studied as a function of the beam incidence. Next, neutron equivalent dose was assessed using organ-specific energy-dependent radiation weighting factors determined from Monte Carlo simulations of neutron spectra at each organ. The equivalent dose was found to reach a maximum value of ∼155 mSv at the level of the breasts for a delivery of 49 proton Gy to an intracranial tumour of a one-year-old female patient. Finally, a thorough comparison of the calculation results with published data demonstrated the dependence of neutron dose on the treatment configuration and proved the need for facility-specific and treatment-dependent neutron dose calculations.

A correlation study of eye lens dose and personal dose equivalent for interventional cardiologists

This paper presents the dosimetry part of the European ELDO project, funded by the DoReMi Network of Excellence, in which a method was developed to estimate cumulative eye lens doses for past practices based on personal dose equivalent values, H(p)(10), measured above the lead apron at several positions at the collar, chest and waist levels. Measurement campaigns on anthropomorphic phantoms were carried out in typical interventional settings considering different tube projections and configurations, beam energies and filtration, operator positions and access routes and using both mono-tube and biplane X-ray systems. Measurements showed that eye lens dose correlates best with H(p)(10) measured on the left side of the phantom at the level of the collar, although this correlation implicates high spreads (41 %). Nonetheless, for retrospective dose assessment, H(p)(10) records are often the only option for eye dose estimates and the typically used chest left whole-body dose measurement remains useful.

Construction of an extended library of adult male 3D models: rationale and results

In order to best cover the possible extent of heights and weights of male adults the construction of 25 whole body 3D models has been undertaken. Such a library is thought to be useful to specify the uncertainties and relevance of dosimetry calculations carried out with models representing individuals of average body heights and weights. Representative 3D models of Caucasian body types are selected in a commercial database according to their height and weight, and 3D models of the skeleton and internal organs are designed using another commercial dataset. A review of the literature enabled one to fix volume or mass target values for the skeleton, soft organs, skin and fat content of the selected individuals. The composition of the remainder tissue is fixed so that the weight of the voxel models equals the weight of the selected individuals. After mesh and NURBS modelling, volume adjustment of the selected body shapes and additional voxel-based work, 25 voxel models with 109 identified organs or tissue are obtained. Radiation transport calculations are carried out with some of the developed models to illustrate potential uses. The following points are discussed throughout this paper: justification of the fixed or obtained models’ features regarding available and relevant literature data; workflow and strategy for major modelling steps; advantages and drawbacks of the obtained library as compared with other works. The construction hypotheses are explained and justified in detail since future calculation results obtained with this library will depend on them.

Development of a new CBR-based platform for human contamination emergency situations

In the case of a radiological emergency situation, involving accidental human exposure, it is necessary to establish as soon as possible a dosimetry evaluation. In most cases, this evaluation is based on numerical representations and models of the victims. Unfortunately, personalised and realistic human representations are often unavailable for the exposed subjects. Hence, existing models like the 'Reference Man' representative of the average male individual are used. However, the accuracy of the treatment depends on the similarity of the phantom to the victim. The EquiVox platform (Research of Equivalent Voxel phantom) developed in this work uses the case-based reasoning principles to retrieve, from a set of existing phantoms, the most adapted one to represent the victim. This paper introduces the EquiVox platform and gives the example of in vivo lung monitoring optimisation to prove its efficiency in choosing the right model. It also presents the artificial neural network tools being developed to adapt the model to the victim.

Female workers and in vivo lung monitoring: a simple model for morphological dependence of counting efficiency curves

This paper addresses the question of the morphological dependence of counting efficiency curves for in vivo lung monitoring of workers, with a particular focus on the case of female workers for whom different chest girth and cup size are considered. A library of 24 female torsos, with chest girth varying from 85 to 120 and cup size from A to F, was constructed using mesh and NURBS formats. The anatomical realism and usefulness of these models for simulating in vivo counting measurements are illustrated and simulations are reported for a typical 4-germanium (Ge) counting system. A simple analytic formula describing the relation between efficiency curves obtained for each female phantom is given. This formula uses the mass attenuation coefficient for adipose tissue and two parameters which are dependant on lung volume and breast weight. The model is tested against Monte Carlo simulated data, experimental data obtained with the Livermore phantom and published data. The model correctly describes the efficiency curve and, since the parameters depend on the counting geometry, it is shown how to estimate them from experimental measurements.

Postoperative hypercapnic respiratory failure in patients with obstructive sleep apnoea: treatment with non-invasive ventilation

Acute hypercapnic respiratory failure is a rare but life-threatening complication in grossly obese patients with severe obstructive sleep apnoea (OSA). Facial trauma or upper airway surgery, respiratory tract infections, bronchospasm, use of pain medication and concomitant obstructive or restrictive pulmonary impairment predispose to the development of respiratory failure in such patients. We present a case of a morbidly obese male patient in whom moderately severe OSA (the apnoea-hypoponea index, AHI of 37/hour) was treated with uvulapalatopharyngoplasty (UPPP) because he declined treatment with non-invasive ventilation. The early postoperative period was complicated by severe hypercapnic respiratory failure in association with worsening of OSA: arterial PO2 was 4.14 kPa, PCO2 9.7 kPa, AHI increased to 93.8/hour, minimal nocturnal arterial oxygen saturation was 46%. Therapy with non-invasive ventilation using bi-level positive airway pressure (BiPAP) was initiated immediately, and resulted in marked improvements in the patient's clinical condition, in association with the improvements in arterial blood gases. Before the discharge, nocturnal continuous positive airway pressure (CPAP) therapy to treat OSA on the long-term basis was initiated. Two months after the release, the patient's blood gases were within the normal range, and he reported marked improvements in his clinical condition including alleviation of daytime sleepiness and increased physical endurance. Our case demonstrates that in the presence of severe OSA, life-threatening hypoxaemia and hypercapnia were successfully alleviated using BiPAP in the postoperative period after UPPP.

Fast electron transfer from cytochrome c6 and plastocyanin to photosystem I of Chlamydomonas reinhardtii requires PsaF

To study the function of the PsaF subunit of photosystem I (PSI), the interactions between plastocyanin or cytochrome c6 and PSI isolated from wild-type and a PsaF-deficient mutant of Chlamydomonas reinhardtii have been examined using cross-linking techniques and flash absorption spectroscopy. We show that efficient electron transfer from both plastocyanin and cytochrome c6 to PSI depends on PsaF. A remarkable feature of the PSI complex of C. reinhardtii is that both plastocyanin and cytochrome c6 reduce P700+ with first-order kinetics and a half-time of 3 micros, which is unique among photosynthetic organisms examined.

Isolation of a psaF-deficient mutant of Chlamydomonas reinhardtii: efficient interaction of plastocyanin with the photosystem I reaction center is mediated by the PsaF subunit

The PsaF polypeptide of photosystem I (PSI) is located on the lumen side of the thylakoid membrane and its precise role is not yet fully understood. Here we describe the isolation of a psaF-deficient mutant of the green alga Chlamydomonas reinhardtii generated by co-transforming the nuclear genome of the cw15-arg7A strain with two plasmids: one harboring a mutated version of the psaF gene and the other containing the argininosuccinate lyase gene conferring arginine prototrophy. This psaF mutant still assembles a functional PSI complex and is capable of photoautotrophic growth. However, electron transfer from plastocyanin to P700+, the oxidized reaction center chlorophyll dimer, is dramatically reduced in the mutant, indicating that the PsaF subunit plays an important role in docking plastocyanin to the PSI complex. These results contrast with those obtained previously with a cyanobacterial psaF-, psaJ- double mutant where no phenotype was apparent.

William Beaumont Hospital Imaging Center design update

The William Beaumont Imaging Center is designed to bridge the gap between conventional and totally digital imaging technology. Reverse capacity and flexibility are designed into the building and it's systems to facilitate the transition at minimal cost and disruption to daily operations.