Filter function of graphene oxide: Trapping perfluorinated molecules.

We need clean drinking water, but current water purification methods are not always sufficient. This study examines the binding and binding mechanisms when graphene oxide is used as a filter material for removing perfluorinated substances and trihalomethanes. We use density functional theory calculations to examine the binding of the harmful molecules on graphene oxide. Our results indicate that the binding energies between graphene oxide and the investigated molecules are in the range of 370-1450 meV per molecule, similar to the binding energies obtained in other studies, where adsorption of similar size molecules onto graphene oxide has been investigated. This indicates that graphene oxide has the potential to separate the molecules of interest from the water. Significant contribution to the binding energies comes from the van der Waals (dispersion) interaction between the molecule and graphene oxide, while the hydrogen bonding between the functional groups of graphene oxide and the hydrogen atoms in functional groups on the molecules also plays a role in the binding.

Reduction of arterial partial volume effects for improved absolute quantification of DSC-MRI perfusion estimates: comparison between tail scaling and prebolus administration.

PURPOSE: To evaluate and mutually compare the tail-scaling approach and the prebolus administration concept for reduction of arterial partial volume effects (PVEs), because reproducible absolute quantification of cerebral blood flow (CBF) by dynamic susceptibility contrast magnetic resonance imaging (MRI) is often hampered by PVEs in the arterial input function (AIF) registration. MATERIALS AND METHODS: Twenty healthy volunteers were scanned in a test-retest study with 7-20 days between investigations to examine the quantitative values and the repeatability of CBF estimates obtained from the tail-scaling and the prebolus administration approaches. RESULTS: Average grey matter CBF was 80 ± 18 mL/100 g/min (mean ± SD) using tail-scaling and 56 ± 18 mL/100 g/min using prebolus administration. The intraclass correlation coefficient was 0.52 for the tail-scaling approach and 0.86 for the prebolus administration concept. CONCLUSION: Both correction methods resulted in considerably reduced arterial PVEs, leading to quantitative estimates of perfusion approaching those typically obtained by other perfusion modalities. The CBF estimates obtained using the prebolus administration concept showed superior repeatability. Potential sources of uncertainty in the tail-scaling approach include the use of venous concentration curves influenced by PVEs or by geometric distortions (ie, vessel pixel shifts) in the steady-state period.

Intravoxel incoherent motion (IVIM) imaging at different magnetic field strengths: what is feasible?

BACKGROUND: Due to limited SNR the cerebral applications of the intravoxel incoherent motion (IVIM) concept have been sparse. MRI hardware developments have resulted in improved SNR and this may justify a reassessment of IVIM imaging for non-invasive quantification of the cerebral blood volume (CBV) as a first step toward determining the optimal field strength. PURPOSE: To investigate intravoxel incoherent motion imaging for its potential to assess cerebral blood volume (CBV) at three different MRI field strengths. MATERIALS AND METHODS: Four volunteers were scanned twice at 1.5 T, 3 T as well as 7 T. By correcting for field-strength-dependent effects of relaxation, estimates of corrected CBV (cCBV) were obtained in deep gray matter (DGM), frontal gray matter (FGM) and frontal white matter (FWM), using Bayesian analysis. In addition, simulations were performed to facilitate the interpretation of experimental data. RESULTS: In DGM, FGM and FWM we obtained cCBV estimates of 2.2 ml/100 ml, 2.7 ml/100 ml, 1.4 ml/100 ml at 1.5 T; 3.7 ml/100 ml, 5.0 ml/100 ml, 3.2 ml/100 ml at 3 T and 15.5 ml/100 ml, 20.3 ml/100 ml, 7.0 ml/100 ml at 7 T. CONCLUSION: Quantitative cCBV values obtained at 1.5 T and 3 T corresponded better to physiological reference values, while 7 T showed the largest deviation from expected values. Simulations of synthetic tissue voxels indicated that the discrepancy at 7 T can partly be explained by SNR issues. Results were generally more repeatable at 7 T (intraclass correlation coefficient, ICC=0.84) than at 1.5 T (ICC=0.68) and 3 T (ICC=0.46).

Absolute quantification of perfusion by dynamic susceptibility contrast MRI using Bookend and VASO steady-state CBV calibration: a comparison with pseudo-continuous ASL.

OBJECTIVE: Dynamic susceptibility contrast MRI (DSC-MRI) tends to return elevated estimates of cerebral blood flow (CBF) and cerebral blood volume (CBV). In this study, subject-specific calibration factors (CFs), based on steady-state CBV measurements, were applied to rescale the absolute level of DSC-MRI CBF. MATERIALS AND METHODS: Twenty healthy volunteers were scanned in a test-retest approach. Independent CBV measurements for calibration were accomplished using a T1-based contrast agent steady-state method (referred to as Bookend), as well as a blood-nulling vascular space occupancy (VASO) approach. Calibrated DSC-MRI was compared with pseudo-continuous arterial spin labeling (pCASL). RESULTS: For segmented grey matter (GM) regions of interests (ROIs), pCASL-based CBF was 63 ± 11 ml/(min 100 g) (mean ± SD). Nominal CBF from non-calibrated DSC-MRI was 277 ± 61 ml/(min 100 g), while calibrations resulted in 56 ± 23 ml/(min 100 g) (Bookend) and 52 ± 16 ml/(min 100 g) (VASO). Calibration tended to eliminate the overestimation, although the repeatability was generally moderate and the correlation between calibrated DSC-MRI and pCASL was low (r < 0.25). However, using GM instead of WM ROIs for extraction of CFs resulted in improved repeatability. CONCLUSION: Both calibration approaches provided reasonable absolute levels of GM CBF, although the calibration methods suffered from low signal-to-noise ratio, resulting in weak repeatability and difficulties in showing high degrees of correlation with pCASL measurements.

Dynamic susceptibility contrast MRI with a prebolus contrast agent administration design for improved absolute quantification of perfusion.

PURPOSE: Arterial partial-volume effects (PVEs) often hamper reproducible absolute quantification of cerebral blood flow (CBF) and cerebral blood volume (CBV) obtained by dynamic susceptibility contrast MRI (DSC-MRI). The aim of this study was to examine whether arterial PVEs in DSC-MRI data can be minimized by rescaling the arterial input function (AIF) using a sagittal-sinus venous output function obtained following a prebolus administration of a low dose of contrast agent. METHODS: The study was carried out as a test-retest experiment in 20 healthy volunteers to examine the repeatability of the CBF and CBV estimates. All subjects were scanned twice with 7-20 days between investigations. RESULTS: DSC-MRI returned an overestimated average whole-brain CBF of 220 ± 44 mL/100 g/min (mean ± SD) before correction and 44 ± 15 mL/100 g/min when applying the prebolus design, averaged over all scans. Average whole-brain CBV was 20 ± 2.0 mL/100 g before correction and 4.0 ± 1.0 mL/100 g after prebolus correction. CONCLUSION: Quantitative estimates of CBF and CBV, obtained with the proposed prebolus DSC-MRI technique, approached those typically obtained by other perfusion modalities. The CBF and CBV estimates showed good repeatability.

A prospective randomized study comparing two different expander approaches in implant-based breast reconstruction: one stage versus two stages.

BACKGROUND: Implant-based reconstruction is performed in the majority of women offered primary reconstruction for breast cancer. METHODS: Two different expander implants were compared prospectively. The primary endpoint was the number of operations needed in each group to obtain patient satisfaction. Secondary endpoints were evaluation of breast volume and shape and aspects of quality of life. Seventy consecutive breast cancer patients were randomized to either a one-stage reconstruction with a round permanent expander implant (Becker 25; n=35) or a two-stage reconstruction with a crescent-shaped expander (LV 133; n=35), later replaced by a form-stable anatomical implant. Thirty patients had to be excluded and 40 patients, 20 in each group, were evaluated. The median follow-up for both groups was 3.5 years (range, 1.5 to 5 years). Plastic cups, plastic casts, and two -and three-dimensional scanning techniques were used for objective assessment of breast volume and shape. The aesthetic outcome was evaluated by a panel of experts and lay people, and by the patients. Quality of life was evaluated with a validated questionnaire (36-Item Short Form Health Survey). RESULTS: Of the patients in the one-stage group, 70 percent had revision surgery, mostly because of upper pole fullness and poor ptosis. These findings agreed with the data from the two-dimensional scanning and from the expert panel and the patients' subjective judgment. Quality of life was similar in the two groups. CONCLUSIONS: The permanent expander method failed significantly as a one-stage procedure. The crescent two-stage method gave the most acceptable results both objectively and subjectively. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, I.

Evaluation of volume and shape of breasts: comparison between traditional and three-dimensional techniques.

There have been many attempts to evaluate the shape, volume, and contour of breasts both before and after operation. To evaluate and compare results objectively in a reproducible, low-cost way is difficult. The aim of this study was to compare three-dimensional techniques with traditional methods in evaluating the volume and shape of breasts. Twelve patients with breast cancer were evaluated, 6 patients preoperatively and 6 patients postoperatively, using plastic cups, thermoplastic casts, magnetic resonance imaging (MRI), and three-dimensional imaging techniques. Thermoplastic casts and plastic cups measured better accordance with the volume of the operated breast than either the three-dimensional technique or MRI, which resulted in significantly higher values. The three-dimensional technique offered a new possibility to evaluate the shape of breasts objectively.

Cerebral perfusion information obtained by dynamic contrast-enhanced phase-shift magnetic resonance imaging: comparison with model-free arterial spin labelling.

Phase-shift time curves following a bolus injection of gadolinium contrast agent were registered for grey-matter regions and large vessels in 14 subjects. Deconvolving a tissue phase-shift curve with a phase-based arterial input function resulted in a tissue residue function R(t). The peak value of R(t) provided a relative cerebral blood flow (CBF) index, while the area-to-height ratio of R(t) provided quantitative mean transit time (MTT). For comparison, quantitative CBF values in grey matter were acquired using model-free arterial spin labelling (ASL). The phase-based relative CBF estimates showed good linear correlation with ASL-based CBF (r = 0.82). Grey-matter MTT was 4.9 +/- 1.1 s (mean +/- SD).