High-repetition rate solid target delivery system for PW-class laser-matter interaction at ELI Beamlines

L3-HAPLS (High-repetition-rate Advanced Petawatt Laser System) at ELI (Extreme Light Infrastructure) Beamlines currently delivers 0.45 PW pulses (12 J in 27 fs) at 3.3 Hz repetition rate. A fresh target surface for every shot was placed at the laser focus using an in-house tape target system designed to withstand large laser intensities and energies. It has been tested for different material thicknesses (25 and 7.6 µm), while L3-HAPLS delivered laser shots for energies ranging from 1 to 12 J. A technical description of the tape target system is given. The device can be used in diverse geometries needed for laser-matter interaction studies by providing an ≈300° free angle of view on the target in the equatorial plane. We show experimental data demonstrating the shot-to-shot stability of the device. An x-ray crystal spherical spectrometer was set up to measure the Kα yield stability, while a GHz H-field probe was used to check the shot-to-shot electromagnetic pulse generation. Finally, we discuss short and mid-term future improvements of the tape target system for efficient user operation.

Plate size does not affect perception of food portion size

BACKGROUND

Evidences have suggested that larger utensils may provoke 'size-contrast illusions', influencing the perceived volume and food consumption.

OBJECTIVE

To analyse the influence of plate size on the visual estimate of food portion size.

METHODS

Two 400 g portions of pasta with tomato sauce were presented on two plates of different diameters (24.0 and 9.0 cm). Each participant visually estimated on an individual basis the quantities of the pasta portions (g) present on each plate. In addition, each subject classified the size of the portions on each plate as 'small', 'medium' and 'large'. The mean estimates of the amount of pasta on each plate were compared by the nonparametric Mann-Whitney. The differences in the frequencies of portion classifications between plates were evaluated by the chi-squared test.

RESULTS

Forty-eight students (average 25.8 ± 8.9 years) participated in the study. There was no difference in the median amount of pasta estimated for the large and small plates (150 g; range 50-500 and 115 g; range 40-500 g, respectively). The classification of the portion size as 'large' was reported by a significantly greater number of persons when they evaluated the amount of pasta arranged on the large plate compared to the small plate (47.9 versus 22.9%, respectively; P = 0.018).

CONCLUSION

The size of the plate did not influence the estimate of food portions, even though it did influence the classification of portion size.

Prevalence of buried Barrett's metaplasia in patients before and after radiofrequency ablation

BACKGROUND AND STUDY AIM

Radiofrequency ablation (RFA) to treat Barrett's esophagus is increasingly accepted. Description of the etiology, natural history, and prevalence of buried Barrett's metaplasia (BBM) following RFA is limited, although BBM continues to pose a clinical dilemma. We aimed to assess the prevalence, characteristics, and eradication rate of BBM in patients with both dysplastic and nondysplastic Barrett's esophagus, treated with RFA and followed over time.

PATIENTS AND METHODS

The presence of Barrett's esophagus, dysplasia, and BBM, before and after RFA, was assessed by two gastrointestinal pathologists in a retrospective chart review of patients who had undergone RFA at our center and had completed appropriate follow-up.

RESULTS

We identified 112 patients with completed treatment and no further planned RFA. In 108, no residual Barrett's esophagus was seen after RFA; 4 patients with persistent Barrett's tissue underwent surgery. Regarding BBM, 17/112 patients (15.2%) had evidence of BBM during evaluation. In 12/17 (70.5%) BBM was found during the RFA treatment, with 8 having previously undergone non-RFA therapy and RFA for Barrett's esophagus and 4 having no previous intervention. In 5/17 (29.4%), BBM was seen only after RFA monotherapy. All 17 showed no evidence of BBM at final evaluation and were classified in the complete remission group (108/112).

CONCLUSION

Both Barrett's esophagus and BBM were completely eradicated in all patients with long-term follow-up after RFA. Almost half of the patients with BBM had a prior history of non-RFA therapy for Barrett's esophagus compared with 26% the non-BBM cohort. All patients with previously identified Barrett's esophagus and BBM were completely cleared of disease at final follow-up.

Pilot series of radiofrequency ablation of Barrett's esophagus with or without neoplasia

BACKGROUND AND STUDY AIMS

Radiofrequency ablation is a rapidly evolving therapeutic modality for Barrett's esophagus. The aim of this ongoing 12-month trial is to assess Barrett's esophagus eradication after radiofrequency ablation using a balloon-based (HALO-360) and a plate-based (HALO-90) device. We report here our experience with the first 10 patients (out of 40) who have completed 12 months of follow-up.

PATIENTS AND METHODS

Following radiofrequency ablation using the HALO-360 device all patients were maintained on double-dose proton pump inhibitor therapy. Endoscopic evaluation was performed at 3 and 12 months postablation. Patients with residual Barrett's esophagus at 3 months underwent repeat ablation. Ten patients, seven with nondysplastic Barrett's esophagus, two with low-grade and one with high-grade dysplasia have completed the study to date.

RESULTS

Complete Barrett's esophagus eradication was achieved in seven patients, and partial eradication was achieved in three. There were no major complications. One case of buried Barrett's metaplasia was encountered and successfully re-ablated, with complete Barrett's esophagus eradication achieved at 12 months.

CONCLUSIONS

In this study, Barrett's eradication rates were comparable to previously published reports. One case of buried Barrett's metaplasia was identified out of 247 biopsies and was eradicated with repeat ablation.

External beam radiation for retinoblastoma: results, patterns of failure, and a proposal for treatment guidelines

PURPOSE

To analyze treatment results and patterns of failure following external beam radiation for retinoblastoma and propose treatment guidelines according to specific clinical variables.

METHODS AND MATERIALS

We analyzed 27 patients (34 eyes) with retinoblastoma who received external beam radiation as initial treatment at Hahnemann University Hospital from October 1980 to December 1991 and have been followed for at least 1 year. Of the 34 eyes, 14 were Groups I-II (Reese-Ellsworth classification), 7 were Group III, and 13 were Groups IV-V. Doses ranged from 34.5-49.5 Gy (mean 44.3 Gy, median 45 Gy) in 1.5-2.0 Gy fractions generally delivered through anterior and lateral wedged pair fields.

RESULTS

At a mean follow up of 35.2 months (range 12-93 months), local tumor control was obtained in 44% (15 out of 34) of eyes with external beam radiation alone. Salvage therapy (plaque brachytherapy, cryotherapy, and/or photocoagulation) controlled an additional 10 eyes (29.5%), so that overall ocular survival has been 73.5%. Local tumor control with external beam radiotherapy alone was obtained in 78.5% (11 out of 14) of eyes in Groups I-II, but in only 20% (4 out of 20) of eyes in Groups III-V. A total of 67 existing tumors were identified prior to treatment in the 34 treated eyes and local control with external beam radiation alone was obtained in 87% (46 out of 53) of tumors measuring 15 mm or less and in 50% (7 out of 14) of tumors measuring more than 15 mm. When analyzing patterns of failure in the 19 eyes that relapsed, a total of 28 failure sites were identified and consisted of progression of vitreous seeds in seven instances (25% of failure sites) recurrences from previously existing tumors in 10 instances (36% of failure sites) and development of new tumors in previously uninvolved retina in 11 instances (39% of failure sites).

CONCLUSIONS

1) We find that external beam radiation to a dose of 45 Gy in fractions of 1.5 to 2.0 Gy provides adequate tumor control in retinoblastoma eyes Groups I-II (Reese-Ellsworth classification) or tumors measuring 15 mm in diameter or less. Eyes in more advanced group staging or containing tumors larger than the 15 mm seem to require higher radiation doses. We propose treatment guidelines for external beam radiation of retinoblastoma that specifically take into account the important clinical variables of tumor stage and patient age. 2) External beam radiation does not prevent the appearance of new tumors in clinically uninvolved retina. Therefore, the traditional belief that external beam radiation can treat the retina "prophylactically" should be seriously questioned. Due to this finding and their significant less morbidity, focal treatment modalities (plaque brachytherapy, photocoagulation, and/or cryotherapy), when clinically feasible, should be considered the treatment of choice for intraocular retinoblastoma. External beam radiation should be considered only when focal treatment modalities are not clinically indicated.

Plaque radiotherapy for residual or recurrent retinoblastoma in 91 cases

Plaque radiotherapy has been used successfully as primary treatment for selected solitary retinoblastomas. However, there is relatively little information on its role as a secondary treatment after other methods have failed to control the tumor. We have used solitary plaque radiotherapy to treat 91 children with residual or recurrent retinoblastoma after failure of one or more treatment modalities, which included external beam radiotherapy in 63 children, plaque radiotherapy in 9, cryotherapy in 26, and photocoagulation in 18, for a total of 116 treatments in the 91 children. Despite the fact that enucleation was considered to be the only remaining option in many of these children, tumor regression was achieved in 81 cases (89%) and recurrence developed in only 10 cases (11%) during a mean follow up lf 52 months. Treatment of the recurrence following plaque radiotherapy in these 10 cases included repeat plaque radiotherapy in 6 cases, enucleation in 3 cases, and external beam radiotherapy in 1 case. In view of the fact that enucleation was being considered as the only remaining option in many of these children, control of the tumor with plaque radiotherapy in 89% of the cases is very encouraging. Plaque radiotherapy should be considered as an important option for recurrent retinoblastoma after failure of other methods to achieve tumor control.

Conservative treatment of retinoblastoma. The use of plaque brachytherapy

Retinoblastoma is the most common intraocular malignancy in childhood. The tumor arises from multipotential retinal cells. Treatment options include enucleation, external beam radiotherapy, episcleral plaque radiotherapy, photocoagulation, cryotherapy or a combination of these modalities. In retinoblastoma 10% have a positive family history and of the remaining 90%, 35% represent germinal chromosomal mutations while 65% represent somatic chromosomal mutations. Therefore, approximately 40% of all retinoblastomas are hereditary and are transmitted as a highly penetrant autosomal dominant trait. In the Wills Eye/Hahnemann University experience an analysis of 400 consecutive patients, 103 tumors in 103 eyes were treated with solitary plaque radiotherapy. Tumor regression was observed in all patients initially. After 40 months mean follow-up, persistent regression was observed in 89 cases (87%) and recurrences in 13 cases (13%). Of the 13 recurrences, five were in the group treated primarily (5/31) and eight in the group treated after failing other modalities (8/72). Plaque brachytherapy is an important tool in the management of retinoblastoma. Our preliminary data suggest that plaque brachytherapy is an effective treatment modality for primary treatment as well as after failure using other modalities.

Analogs of palmitoyl-CoA that are substrates for myristoyl-CoA:protein N-myristoyltransferase

Saccharomyces cerevisiae myristoyl-CoA:protein N-myristoyltransferase (Nmt1p; EC 2.3.1.97) is an essential enzyme that is highly selective for myristoyl-CoA in vivo. It is unclear why myristate (C14:0), a rare cellular fatty acid, has been selected for this covalent protein modification over more abundant fatty acids such as palmitate (C16:0), nor is it obvious how the enzyme's acyl-CoA binding site is able to discriminate between these two fatty acids. Introduction of a cis double bond between C5 and C6 of palmitate [(Z)-5-hexadecenoic acid] or a triple bond between C4 and C5 or C6 and C7 (Y4- and Y6-hexadecenoic acids) yields compounds that, when converted to their CoA derivatives, approach the activity of myristoyl-CoA as Nmt1p substrates in vitro. Kinetic studies of 42 C12-C18 fatty acids containing triple bonds, para-phenylene, or a 2,5-furyl group, as well as cis and trans double bonds, suggest that the geometry of the enzyme's acyl-CoA binding site requires that the acyl chain of active substrates assume a bent conformation in the vicinity of C5. Moreover, the distance between C1 and the bend appears to be a critical determinant for optimal positioning of the acyl-CoA in this binding site so that peptide substrates can subsequently bind in the sequential ordered bi-bi reaction mechanism. Identification of active, conformationally restricted analogs of palmitate offers an opportunity to "convert" wild-type or mutant Nmts to palmitoyltransferases so that they can deliver these C16 fatty acids to critical N-myristoylproteins in vivo. nmt181p contains a Gly-451-->Asp mutation, which causes a marked reduction in the enzyme's affinity for myristoyl-CoA. Strains of S. cerevisiae containing nmt1-181 exhibit temperature-sensitive myristic acid auxotrophy: their complete growth arrest at 37 degrees C is relieved when the medium is supplemented with 500 microM C14:0 but not with C16:0. The CoA derivatives of (Z)-5-hexadecenoic and Y6-hexadecynoic acids are as active substrates for the mutant enzyme as myristoyl-CoA at 24 degrees C. However, unlike C16:0, they produce growth arrest of nmt181p-producing cells at this "permissive" temperature, suggesting that these C16 fatty acids do not allow expression of the biological functions of essential S. cerevisiae N-myristoylproteins.

Brachytherapy of choroidal melanomas

In the management of patients with primary malignant melanoma of the uvea, treatment techniques have included not only enucleation but also photocoagulation, cryotherapy, photoradiation, a limited resection, as well as circumstances indicating exenteration of the orbit. Surgical management has been the primary treatment program for over 100 years. In a compilation of nine reported series consisting of 2,024 enucleations, the five- and ten-year survivals following surgery were 63% and 43%, respectively. The 25-year survival has been reported to be 40%. In 1974 at Wills Eye Hospital and Hahnemann University, the cobalt-60 plaques technique was introduced. During the following years, other radioactive isotopes were introduced including iridium-192, iodine-125, ruthenium-106/rhodium-106 and more recently palladium-103. At the present time, iodine-125 is the most widely used radionuclide. Until now, 302 patients treated with plaque brachytherapy showed an actuarial survival of 77% and 67.8% at five and eight years, respectively. There was no significant survival difference when compared with a similar group of patients undergoing enucleation. Other retrospective studies show similar excellent results. In spite of these convincing results, the decision making process in management melanoma remains unsettled primarily due to the absence of prospective randomized trials. Because of this, the Collaborative Ocular Melanoma Study was initiated. From the standpoint of toxicity, the data are available on ocular radiation toxicity. In an analysis of 77 patients from the Wills Eye Hospital with pretreatment visual acuities of 20/25 or better, it was noted that 90% of patients who had received less than 500 Gy to the fovea retained visual acuity of 20/200 or better while only 52% of patients receiving more than 5,000 Gy to the fovea had vision of 20/200 or better. A serious late effect of radioactivity plaque treatment is scleral necrosis which may require repair or enucleation even in the absence of tumor progression. Enucleation may be necessary in approximately 10% of patients. We conclude that malignant melanoma of the uvea can be safely treated with radioactive plaques.

Accelerated fractionation radiotherapy for hospitalized glioblastoma multiforme patients with poor prognostic factors

The standard 6 week course of post-operative radiotherapy for glioblastoma multiforme (astrocytoma grade IV) is lengthy, considering the poor prognosis. The standard schedule is especially unsuitable for hospitalized patients and for those with poor prognostic factors (such as old age and poor performance status) since their survival is particularly short. In order to improve the survival-treatment time ratio, we entered a total of 14 hospitalized patients with glioblastoma multiforme (GBM) and poor prognostic factors (mean age 62, mean KPS 57%) into a Phase I trial of accelerated fractionation (AF) external beam radiotherapy. A total tumor dose of 5400-5500 cGy was given in 3 weeks: 4300-4500 cGy whole brain using 100 cGy tid fractions on weekdays plus a 900-1200 cGy boost using single daily fractions of 150-200 cGy on weekends. Only one patient entered did not complete therapy, due to the development of pulmonary embolism resulting in death. Mean survival for all 14 patients from the time of surgical diagnosis was 30.4 weeks. The schedule was well tolerated and resulted in a substantial decrease in treatment time compared to conventional fractionation in these patients. AF schedules should continue to be explored since they may be more appropriate than conventional fractionation schedules for GBM patients with poor prognostic factors, particularly when hospitalized.

"Aggressive" osteoblastoma of the maxilla

A case of osteoblastoma in the maxilla of a 6-year-old boy is reported. The tumor was clinically characterized by locally aggressive behavior but histologically consisted of a relatively well-circumscribed mass of bone-producing epithelioid osteoblasts and occasional multinucleated osteoclasts characteristic of osteoblastoma. Radiographically the tumor appeared to penetrate the cortical plate. Because of the size of the lesion, its histologic features, and the clinical and radiographic impression of its being poorly confined, the diagnosis of "aggressive" osteoblastoma was rendered. The problem of differentiating between benign and aggressive forms of osteoblastoma is discussed.