Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment.

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment.

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion.

An international dosimetry exchange for BNCT part II: computational dosimetry normalizations.

The meaningful sharing and combining of clinical results from different centers in the world performing boron neutron capture therapy (BNCT) requires improved precision in dose specification between programs. To this end absorbed dose normalizations were performed for the European clinical centers at the Joint Research Centre of the European Commission, Petten (The Netherlands), Nuclear Research Institute, Rez (Czech Republic), VTT, Espoo (Finland), and Studsvik, Nyköping (Sweden). Each European group prepared a treatment plan calculation that was bench-marked against Massachusetts Institute of Technology (MIT) dosimetry performed in a large, water-filled phantom to uniformly evaluate dose specifications with an estimated precision of +/-2%-3%. These normalizations were compared with those derived from an earlier exchange between Brookhaven National Laboratory (BNL) and MIT in the USA. Neglecting the uncertainties related to biological weighting factors, large variations between calculated and measured dose are apparent that depend upon the 10B uptake in tissue. Assuming a boron concentration of 15 microg g(-1) in normal tissue, differences in the evaluated maximum dose to brain for the same nominal specification of 10 Gy(w) at the different facilities range between 7.6 and 13.2 Gy(w) in the trials using boronophenylalanine (BPA) as the boron delivery compound and between 8.9 and 11.1 Gy(w) in the two boron sulfhydryl (BSH) studies. Most notably, the value for the same specified dose of 10 Gy(w) determined at the different participating centers using BPA is significantly higher than at BNL by 32% (MIT), 43% (VTT), 49% (JRC), and 74% (Studsvik). Conversion of dose specification is now possible between all active participants and should be incorporated into future multi-center patient analyses.

Normalisation of prescribed dose in BNCT.

Normalisation of prescribed dose in boron neutron capture therapy (BNCT) is needed to facilitate combining clinical data from different centres in the world to help expedite development of the modality. The approach being pursued within the BNCT community is based upon improving precision in the measurement and specification of absorbed dose. Beam characterisations using a common method are complete as are comparative dosimetry measurements between clinical centres in Europe and the USA. Results from treatment planning systems at these centres have been compared with measurements performed by MIT, and the scale factors determined are being confirmed with independent tests using measurements in an ellipsoidal water phantom. Dose normalisations have successfully been completed and applied to retrospectively analyse treatment plans from Brookhaven National Laboratory (1994-99) so that reported doses are consistently expressed with the trials performed during 1994-2003 at Harvard-MIT. Dose response relationships for adverse events and other endpoints can now be more accurately established.

Improved dose targeting for a clinical epithermal neutron capture beam using optional (6)Li filtration.

PURPOSE: The aim of this study was to construct a (6)Li filter and to improve penetration of thermal neutrons produced by the fission converter-based epithermal neutron beam (FCB) for brain irradiation during boron neutron capture therapy (BNCT). METHODS AND MATERIALS: Design of the (6)Li filter was evaluated using Monte Carlo simulations of the existing beam line and radiation transport through an ellipsoidal water phantom. Changes in beam performance were determined using three figures of merit: (1) advantage depth (AD), the depth at which the total biologically weighted dose to tumor equals the maximum weighted dose to normal tissue; (2) advantage ratio (AR), the ratio of the integral tumor dose to that of normal tissue averaged from the surface to the AD; and (3) advantage depth dose rate (ADDR), the therapeutic dose rate at the AD. Dosimetry performed with the new filter installed provided calibration data for treatment planning. Past treatment plans were recalculated to illustrate the clinical potential of the filter. RESULTS: The 8-mm-thick Li filter is more effective for smaller field sizes, increasing the AD from 9.3 to 9.9 cm, leaving the AR unchanged at 5.7 but decreasing the ADDR from 114 to 55 cGy min(-1) for the 12 cm diameter aperture. Using the filter increases the minimum deliverable dose to deep seated tumors by up to 9% for the same maximum dose to normal tissue. CONCLUSIONS: Optional (6)Li filtration provides an incremental improvement in clinical beam performance of the FCB that could help to establish a therapeutic window in the future treatment of deep-seated tumors.

Development and application of an unconstrained technique for patient positioning in fixed radiation beams.

A flexible technique for positioning patients in fixed orientation radiation fields such as those used in neutron capture therapy (NCT) has been developed. The positioning technique employs reference points marked on the patient in combination with a 3D digitizer to determine the beam entry point and a template fitted to the patient's head is used to determine the proper beam orientation. A coordinate transformation between the CT image data and reference points on the patient determined by a least squares algorithm based on singular value decomposition is used to map the beam entry point from the planning system onto the patient. The technique was validated in a phantom study where the mean error in entry point placement was 1.3 mm. Five glioblastoma multiforme patients have been treated with NCT using this positioning technique.

Anomalous absorption of high-energy green laser light in high- z plasmas.

We observe strong anomalous absorption of green laser light in mm-scale high-temperature gold plasmas. Both the laser light absorption and the resulting increase of the electron temperature, which was measured independently with Thomson scattering, have been successfully modeled by including enhanced collisions due to heat-flux driven ion acoustic fluctuations. Calculations that include only inverse bremsstrahlung significantly underestimate the experimental laser absorption and the electron temperature.

Effect of metronidazole in patients with preterm birth in preceding pregnancy and bacterial vaginosis: a placebo-controlled, double-blind study.

OBJECTIVE: Our purpose was to determine whether treatment of bacterial vaginosis with metronidazole in patients with preterm delivery in the penultimate pregnancy from preterm labor or premature rupture of membranes reduces the risk of subsequent preterm birth. STUDY DESIGN: From January 1989 to June 1992 patients with a singleton gestation between 13 and 20 weeks and a history of preterm birth in the preceding pregnancy from either idiopathic preterm labor or premature rupture of membranes were screened for bacterial vaginosis. Those with a positive screen were randomized to receive 250 mg of metronidazole three times a day for 7 days or placebo in a double-blind design. Data were analyzed with Student t and chi 2 tests, and differences considered significant at p < 0.05. RESULTS: Of 94 eligible patients, 80 were enrolled and completed the study, of which 44 received metronidazole. Both groups were comparable in number of entry variables. Compared with the placebo group, patients in the metronidazole group had significantly fewer hospital admissions for preterm labor, 12 (27%) versus 28 (78%); preterm births, eight (18%) versus 16 (39%); births of infants weighing < 2500 gm, six (14%) versus 12 (33%); and premature rupture of membranes, two (5%) versus 12 (33%). CONCLUSION: Treatment of bacterial vaginosis with metronidazole was effective in reducing preterm births in patients with a history of prematurity in the preceding pregnancy.

Complications of wound repair.

In the consideration of wound healing and complications that impede its progress, one should keep in mind that detrimental factors generally affect more than one aspect of the repair process. Wound healing considerations should begin with a thorough history and physical examination upon a patient's first office visit. Factors that affect a patient's ability to heal successfully are listed in Tables 3 and 4.

Necessary dorsiflexion of the first metatarsophalangeal joint during gait.

Previous studies of first metatarsophalangeal joint range of motion have resulted in varying values for dorsiflexion of this joint. These values reflect assisted dorsiflexion of the first metatarsophalangeal joint, which has been believed to be the same value that would be obtained during the toe-off phase of gait. These values range from 60 degrees to 90 degrees. This study attempts to obtain measurements during toe-off and to compare obtained values with those of assisted dorsiflexion from the previously mentioned studies.