Response of diamond detectors in ultra-high dose-per-pulse electron beams for dosimetry at FLASH radiotherapy.

Objective.With increasing investigation of the so-called FLASH effect, the need for accurate real time dosimetry for ultra-high dose rates is also growing. Considering the ultra-high dose-per-pulse (DPP) necessary to produce the ultra-high dose rates for investigations of the FLASH effect, real time dosimetry is a major challenge. In particular, vented ionization chambers, as used for dosimetry in conventional radiotherapy, show significant deviations from linearity with increasing DPP. This is due to recombination losses in the sensitive air volume. Solid state detectors could be an alternative. Due to their good stability of the response with regard to the accumulated dose, diamond detectors such as the microDiamond could be suitable here. The aims of this work are to investigate the response of microDiamond and adapted microDiamond prototypes in ultra-high DPP electron beams, to understand the underlying effects and to draw conclusions for further detector developments.Approach.For the study, an electron beam with a DPP up to 6.5 Gy and a pulse duration of 2.5µs was used to fulfill the conditions under which the FLASH effect was observed. As a dose rate-independent reference, alanine dosimeters were used.Main Results.It has been shown that the commercially available microDiamond detectors have limitations in terms of linearity at ultra-high DPP. But this is not an intrinsic limitation of the detector principle. The deviations from linearity were correlated with the series resistance and the sensitivity. It could be shown that the linear range can be extended towards ultra-high DPP range by reducing the sensitivity in combination with a low series resistance of the detectors.Significance.The work shows that synthetic single crystal diamond detectors working as Schottky photodiodes are in principle suitable for FLASH-RT dosimetry at electron linear accelerators.

Do antidepressants influence mood patterns? A naturalistic study in bipolar disorder.

This prospective, longitudinal study compared the frequency and pattern of mood changes between outpatients receiving usual care for bipolar disorder who were either taking or not taking antidepressants. One hundred and eighty-two patients with bipolar disorder self-reported mood and psychiatric medications for 4 months using a computerized system (ChronoRecord) and returned 22,626 days of data. One hundred and four patients took antidepressants, 78 did not. Of the antidepressants taken, 95% were selective serotonin or norepinephrine reuptake inhibitors, or second-generation antidepressants. Of the patients taking an antidepressant, 91.3% were concurrently taking a mood stabilizer. The use of antidepressants did not influence the daily rate of switching from depression to mania or the rate of rapid cycling, independent of diagnosis of bipolar I or II. The primary difference in mood pattern was the time spent normal or depressed. Patients taking antidepressants frequently remained in a subsyndromal depression. In this naturalistic study using self-reported data, patients with bipolar disorder who were taking antidepressants--overwhelmingly not tricyclics and with a concurrent mood stabilizer--did not experience an increase in the rate of switches to mania or rapid cycling compared to those not taking antidepressants. Antidepressants had little impact on the mood patterns of bipolar patients taking mood stabilizers.

Multisurgeon assessment of surgical decision-making in adolescent idiopathic scoliosis: curve classification, operative approach, and fusion levels.

STUDY DESIGN: A multisurgeon assessment of curve classification, selection of operative approach, and fusion levels via a case study presentation. OBJECTIVES: To evaluate the ability of a group of scoliosis surgeons, not involved in the development of a new classification system, to accurately choose the corresponding curve classification of adolescent idiopathic scoliosis (AIS) cases and to evaluate the variability in the selection of operative approaches and both proximal and distal fusion levels in accordance with the new classification system in operative adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Recent evaluations using the King method for classifying AIS has shown poor intraobserver and interobserver reliability. A new, comprehensive classification system of AIS has been developed, but the result of a scoliosis surgeon's ability to apply the objective classification is unknown. In the surgical treatment of AIS, there are three choices for the operative approach (anterior, posterior, or both) and multiple choices for the selection of fusion levels. METHODS: During an AIS roundtable discussion at a spinal surgery meeting, 28 scoliosis surgeons were presented seven cases of operative AIS via good quality slides. Standard preoperative radiographs and clinical photographs were presented, and the reviewers were asked to classify the cases by a new classification system, choose their preferred surgical approach, and classify both proximal and distal fusion levels. RESULTS: For the seven cases presented, 84% of the curve types, 86% of lumbar modifiers, and 90% of sagittal thoracic modifiers were classified by the reviewers as described in the new classification. The case study found widely variable operative approaches and fusion levels chosen by the reviewers. There was an average of five different proximal (range, 4-8) and four different distal (range, 3-5) fusion levels chosen by the reviewers for each case. CONCLUSIONS: This case study assessment found a relatively high rate (84-90%) of agreement in curve classification of the individual components of a new classification system of AIS. This suggests the ability of a group of scoliosis surgeons to identify the specific criteria necessary for this new classification system of AIS. In addition, the high variability in selection of both operative approach and fusion levels confirms the current lack of standardized treatment paradigms. This further reinforces the need for a method to critically and objectively evaluate these variable treatments to determine the "best" radiographic and clinical results.

Complications and results of long adult deformity fusions down to l4, l5, and the sacrum.

STUDY DESIGN: This is a consecutive study of patients having undergone surgical treatment of adult lumbar scoliosis. Follow-up ranged from 2 to 13 years (average 5 years). OBJECTIVES: To assess the complications and outcomes of patients with long fusions to L4 (n=23), L5 (n=21), or the sacrum (n=15) and determine if a "deeply seated" L5 segment is protective. SUMMARY OF BACKGROUND DATA: Few studies assess outcomes and complications in adults fused from the thoracic spine to L4, L5, or the sacrum with minimum 2-year follow-up. METHODS: Fifty-eight patients (59 cases; average age 43 years; range 21 to 60) with minimum 2-year follow-up were analyzed for subsequent spinal degeneration and complications. Outcomes were assessed from questionnaires administered at latest follow-up. RESULTS: Sixteen percent of cases (7 of 44) fused short of the sacrum displayed subsequent postoperative distal spinal degeneration, although only three patients were symptomatic. Compared with the group with no subsequent degeneration, this group had a lower improvement in function and pain relief. Other complications for patients fused short of the sacrum included two cases with crosslink breakage, one with neurologic deficit, three with pseudarthroses, one with hook pullout, and one with L5 screw pullout. For cases fused to the sacrum, two cases with deep wound infections and one with loose iliac screw requiring removal were observed. Because two of four cases fused to L5 with subsequent degeneration at L5-S1 were observed to have "deeply seated" L5 segments and two of the four did not, the authors could conclude only that "deep seating" of L5 is not absolute protection. CONCLUSIONS: Fusions short of the sacrum did not have predictable long-term results. Those fused short of the sacrum who developed distal spinal degeneration had worse outcomes. Patients fused to the sacrum did not have a higher complication rate. A "deeply seated" L5 segment does not necessarily protect the L5-S1 disc.

Long-term complications in adult spinal deformity patients having combined surgery a comparison of primary to revision patients.

STUDY DESIGN: This is a comparison of primary (N = 18) to revision (N = 26) combined (anterior and posterior surgery) adult spinal deformity patients with regard to late (>6 months) complications and radiographic/functional outcomes at a minimum 2-year follow-up. OBJECTIVES: To determine whether revision status increases the risk of late complications or offers a poor prognosis for functional outcome in adult deformity patients. SUMMARY OF BACKGROUND DATA: It is known that patients who have combined surgery for adult deformity have a high incidence of perioperative complications. Long-term complications and the effect of revision status have not been clarified in the literature. The functional outcomes for these patients are unclear as to whether or not there is a difference between primary and revision patients. Outside the arena of adult spinal deformity the functional outcomes for revision cases have been disappointing. METHODS: A consecutive series of 44 patients who underwent combined procedures for adult spinal deformity were followed for a minimum of 2 years (average follow-up 42 months). Clinical data were obtained by chart and radiographic review. Major complications were considered to be deep wound infection, pseudarthrosis, transition syndrome, neurologic deficit, and death. Minor complications considered were asymptomatic instrumentation failure (without loss of correction), instrumentation prominence requiring removal, and proximal or distal junctional segmental kyphosis (5-10 degrees ) or subsequent disc space narrowing of 2-5 mm without clinical symptoms. The patients also completed the AAOS Lumbar/Scoliosis MODEMS questionnaires aimed at assessing pain, function, and satisfaction. RESULTS: Minor complications were comparable in both groups: 4 of 18 (22%) in the primary group and 6 of 26 (23%) in the revision group. Major complications were slightly more frequent in the primary group with five complications in 4 patients (4 of 18 patients) (22%) compared with 3 of 26 patients (12%) in the revision group. The incidence of pseudarthrosis was 22% (4 of 18) for the primary group and 4% (1 of 26) for the revision group (P< 0.14). Forty of 44 patients completed the questionnaires. The primary patients functioned at a slightly higher level after surgery than the revision group. The level of pain was also slightly lower at final follow-up in the primary group. Despite these differences, the revision group had a higher level of patient satisfaction. CONCLUSION: At a minimum 2-year follow-up the late complications were not higher in the revision patients than in the primary group. The rate of major long-term complications, specifically pseudarthroses, was higher in the primary group. Patient satisfaction was higher in the revision patients, probably because they were experiencing a greater level of perceived pain and dysfunction at the time of their reconstruction.

Prospective randomization of parenteral hyperalimentation for long fusions with spinal deformity: its effect on complications and recovery from postoperative malnutrition.

STUDY DESIGN: A prospective randomized study of total parenteral nutrition for long spinal deformity fusions as well as its effect on complications and recovery from postoperative malnutrition was performed. OBJECTIVES: To determine whether the administration of total parenteral nutrition to patients undergoing same-day or staged long spinal fusions has an effect on postoperative nutritional parameter depletion, time for return to preoperative nutritional baseline, and complication rate. SUMMARY OF BACKGROUND DATA: Several studies have suggested, but only one has demonstrated, that perioperative administration of total parenteral nutrition to patients undergoing spinal reconstructive surgery may reduce postoperative nutritional depletion, thereby decreasing postoperative complications. METHODS: In this study, 46 patients undergoing same-day or staged spinal reconstruction surgery (> or = 10 levels) were randomized to receive or not receive total parenteral nutrition after surgery. The nutritional parameters of albumin, prealbumin, transferrin, total protein, and absolute lymphocyte count were obtained before surgery and at regular intervals after surgery until at least four out of five parameters were within 10% of their preoperative baseline value. Perioperative data and complications were tallied. RESULTS: There were no complications related to total parenteral nutrition administration. There was no statistical difference in total complications between those who did and those who did not receive total parenteral nutrition. However, there was a trend (P < 0.073) for the total parenteral nutrition group to return to nutritional baseline quicker. A significant increase in transferrin (P < 0.0082) and prealbumin (P < 0.015) depletion occurred in the patients who did not receive total parenteral nutrition. The anterior/posterior-same-day patients receiving total parenteral nutrition had more major complications (P < 0.033) and significantly more total protein depletion (P < 0.018) than the anterior/posterior-staged patients receiving total parenteral nutrition, possibly because the anterior/posterior-staged group received significantly more days(P < 0.0155) of total parenteral nutrition than the anterior/posterior-same-day group. In controlling for the number of days of total parenteral nutrition, no significant difference between type of surgery and complications was found. CONCLUSIONS: The administration of postoperative total parenteral nutrition to patients with spinal deformity is safe. No statistical reduction in complications occurred in the total parenteral nutrition group despite a trend toward more rapid normalization of nutritional parameters and a decrease in postoperative nutritional depletion. The anterior/posterior-staged group with the administration of total parenteral nutrition had a lower overall complication rate and a decreased incidence of postoperative nutritional depletion than the one-stage reconstruction group. The difference in the complication rates between the two groups may relate as much to the staging as to the administration of total parenteral nutrition per se. For certain cases it may be more advisable to stage patients and deliver total parenteral nutrition than to manage the cases in a continuous (i.e., same-day) fashion.

Analysis of titanium mesh cages in adults with minimum two-year follow-up.

STUDY DESIGN: This is a study of 66 consecutive adult patients (ages 20-81 years) with sagittal deformities who underwent surgery in which structural titanium mesh cages were implanted into the anterior column during posterior instrumentation and fusion. Follow-up ranged from 24 to 62 months (mean, 33 months). OBJECTIVES: To assess the complications and outcomes of patients with structural cages implanted into the anterior column. SUMMARY OF BACKGROUND DATA: Structural cages for the anterior column are popular in the treatment of adult spinal disorders. Few studies to determine their efficacy have a minimum 2-year follow-up. METHODS: Sixty-six patients with minimum 2-year follow-up were analyzed for cage, spinal fusion, and instrumentation status. Outcomes were assessed by analysis of responses to questionnaires administered to the patients at latest follow-up. RESULTS: No cage failure or extrusion was observed. The average segmental improvement in lordosis with cage implantation was 11 degrees with a loss of correction of less than 1 degrees at latest follow-up. The readability of plain radiographs for assessment of anterior fusions was better than for posterior fusions. The agreement level for judging spines to be fused was two of three for 78% of the anterior levels and 47% of the posterior levels. The remaining posterior fusion levels were unassessable. No statistical difference was found in outcome between the group of patients with suspected nonfused anterior levels and the group with all levels fused. CONCLUSIONS: Structural titanium mesh cages implanted into the anterior column function appropriately to maintain sagittal correction, with rare radiographic complications. Seventy-eight percent of the anterior levels were judged to be fused by observers examining plain radiographs. The outcome at latest follow-up for patients with suspected nonfused anterior levels was similar to that in the group of patients with fusions rated solid at every level.

In vivo anteroposterior femorotibial translation of total knee arthroplasty: a multicenter analysis.

A study was conducted to determine in vivo femorotibial contact patterns for subjects having a posterior cruciate retaining or posterior cruciate substituting total knee arthroplasty. Femorotibial contact of 72 subjects implanted with a total knee replacement, performed by five surgeons, was analyzed using video fluoroscopy. Thirty-one subjects were implanted with a posterior cruciate retaining total knee replacement with a flat polyethylene posterior lipped insert, 12 with a posterior cruciate retaining total knee replacement with a curved insert, and 29 with a posterior cruciate substituting total knee replacement. Each subject performed successive deep knee bends to maximum flexion. Video images at 0 degree, 30 degrees, 60 degrees, and 90 degrees flexion were downloaded onto a workstation computer. Femorotibial contact paths were determined for the medial and lateral condyles using an interactive model fitting technique. Femorotibial contact anterior to the tibial midline in the sagittal plane was denoted as positive and contact posterior was denoted as negative. Analysis of average femorotibial contact pathways of both posterior cruciate retaining designs revealed posterior femorotibial contact in full extension with anterior translation of femorotibial contact commonly observed in midflexion and terminal flexion. In posterior cruciate substituting designs, anterior femoral translation was seen medially at 30 degrees to 60 degrees flexion but rarely was observed laterally. Posterior femoral rollback laterally from full extension to 90 degrees flexion was seen in 100% of subjects implanted with a posterior cruciate substituting total knee replacement, versus 51.6% (posterior lipped polyethylene insert) and 58.3% (curved insert) of those with a posterior cruciate retaining total knee replacement. Data from this multicenter study are remarkably similar to previous fluoroscopy data from a single surgeon series, showing a lack of customary posterior femoral rollback in both posterior cruciate retaining designs, and conversely showing an average anterior femoral translation with knee flexion. Posterior femoral rollback, less than in normal knees, routinely was observed in posterior cruciate substituting total knee arthroplasty, attributed to engagement of the femoral component cam with the tibial post. The abnormal anterior femoral translation observed in posterior cruciate retaining total knee arthroplasty may be a factor in premature polyethylene wear observed in retrieval studies.

Microculture of western white pine (Pinus monticola) by induction of shoots on bud explants from 1- to 7-year-old trees.

We developed a protocol for the production of shoots from bud explants from 1- to 7-year-old trees of western white pine (Pinus monticola Dougl.). The best explant was a 2-mm-thick cross-sectional slice of the early winter bud. Genotype of the donor tree was a significant factor affecting shoot production, but more than 80% of the genotypes tested produced shoots. Of the media tested, bud slices from 1- to 3-year-old trees grew best in Litvay's medium containing N(6)-benzyladenine in the range of 1 to 30 micro M, whereas bud slices from older trees grew best in Gupta and Durzan's DCR medium with zeatin riboside. Up to 400 shoots more than 3 mm in height were obtained from 100 bud-slice explants taken from 7-year-old western white pine trees.

Micropropagation of western white pine (Pinus monticola) starting with mature embryos.

As part of a program to develop micropropagation protocols for western white pine, the production of adventitious shoots from mature embryos was investigated. Litvay's medium proved to be the best of the six media formulations tried. The optimum concentration of N6-benzyladenine was 30 µM for 21 days. BiTek agar which had an optimum at 8 g/L produced significantly more shoots than GelGro gellan gum which had an optimum at 5 g/L. There was no significant difference in the shoot production between three different seed lots, two from interior British Columbia and one from coastal British Columbia, with this protocol. Harvested adventitious shoots survived best on the medium of Gresshoff and Doy at half-strength. Using the protocol described here, it was possible to obtain 500 to 600 shoots for every 100 embryos explanted. Up to 80 percent of the shoots continued to grow three months after excision from the explants.

Acoustically modulated optical transmission for low level gaseous species measurement.

A new optical technique has been developed for low level optical extinction measurements in gaseous media. It is a variation on direct light transmission where the sample gas density in a cell is modulated acoustically by a loudspeaker. The amplitude variation of the light transmission is proportional to the gas density and is insensitive to window contamination and detector instabilities. Preliminary analysis and experiments indicate tat the instrument promises to measure light absorption to < 1%/m. The technique has been demonstrated through the use of an absorbing gas, namely, 200 ppm of NO(2) in N(2) which produces 2.5% absorption over the observed path length of 10 cm.

Visualization of turbulent flame fronts with planar laser-induced fluorescence.

This report concerns the quantitative time-resolved visualization of reaction zones in laminar, transitional, and turbulent nonpremixed flames. Two-dimensional OH molecular concentrations were measured with planar laser-induced fluorescence excited by a sheet of light (formed from a single tunable ultraviolet laser pulse) and detected with a two-dimensional, image-intensified photodiode array camera. From the resulting data details of instantaneous flame front structures (including positions, shapes, and widths) were obtained.

Single-pulse, laser-saturated fluorescence measurements of OH in turbulent nonpremixed flames.

A single-pulse, laser-saturated fluorescence technique has been developed for absolute OH concentration measurements with a temporal resolution of 2 nsec, a spatial resolution of <0.1 mm(3), and an estimated accuracy of +/-30%. It has been applied in laminar, transitional, and turbulent hydrogen-air diffusion flames, providing the first reported quantitative measurements of average values, rms fluctuations, and probability density functions of OH radical concentration in nonpremixed flames.

Fatty acid composition of Rhizobium spp.

The fatty acid composition of 42 isolates belonging to the major plant affinity groups of Rhizobium has been determined and found to vary reproducible with culture age. Numerical taxonomic techniques applied to the 15 major fatty acid components of log-phase cultures of comparable physiological age showed that the rhizobia constitute a uniform group. However, two clusters comprising soybean-cowpea isolates and pea-bean isolates were evident. These observations, based on a simple analysis of only one group of chemical components, indicate relationships among rhizobia which differ from the conventional plant-affinity groupings but which are consistent with other proposed relationships established using a variety of biochemical and physiological criteria.

Raman scattering from flames.

Laser Raman scattering data for nitrogen, oxygen, and water vapor have been obtained from hydrogen-air and hydrogen-oxygen flames. The resulting ground-state and upper-state vibrational bands exhibit strong asymmetrical broadening. Experimental spectral profiles have been fitted theoretically to give a new measurement technique for the determination of rotational and vibrational excitation temperatures.