The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation ...reaction. When interacting with a high-energy electron beam, today’s lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We present evidence of radiation reaction in the collision of an ultrarelativistic electron beam generated by laser-wakefield acceleration (ϵ>500MeV) with an intense laser pulse (a0>10). We measure an energy loss in the postcollision electron spectrum that is correlated with the detected signal of hard photons (γrays), consistent with a quantum description of radiation reaction. The generatedγrays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energyϵcrit>30MeV.
Betatron radiation from laser wakefield accelerators is an ultrashort pulsed source of hard, synchrotron-like x-ray radiation. It emanates from a centimetre scale plasma accelerator producing GeV ...level electron beams. In recent years betatron radiation has been developed as a unique source capable of producing high resolution x-ray images in compact geometries. However, until now, the short pulse nature of this radiation has not been exploited. This report details the first experiment to utilize betatron radiation to image a rapidly evolving phenomenon by using it to radiograph a laser driven shock wave in a silicon target. The spatial resolution of the image is comparable to what has been achieved in similar experiments at conventional synchrotron light sources. The intrinsic temporal resolution of betatron radiation is below 100 fs, indicating that significantly faster processes could be probed in future without compromising spatial resolution. Quantitative measurements of the shock velocity and material density were made from the radiographs recorded during shock compression and were consistent with the established shock response of silicon, as determined with traditional velocimetry approaches. This suggests that future compact betatron imaging beamlines could be useful in the imaging and diagnosis of high-energy-density physics experiments.
Background
Trans-anal excision is the surgical treatment of choice for endoscopically unresectable rectal polyps, early rectal cancers, small carcinoid tumors, and other low-risk tumors. The ...single-port robotic (SPR) platform is the newest development in robotic surgery capable of performing trans-anal minimally invasive surgery (TAMIS). In theory, the single incision design would naturally lend itself to the size limitation of the anal canal, but in practice, this method has not been tested. Herein we describe the techniques and first reports of performing TAMIS using the SPR platform.
Technique
We describe in detail how to perform the SPR-TAMIS technique using lessons and experience gained from performing this on five patients who had endoscopically unresectable rectal polyps or T1 rectal cancers. Each patient was followed for a minimum of 30 days and was seen in clinic post-operatively. A retrospective chart review was performed to obtain information on technical success, anatomic measurements, and reported complications.
Results
The SPR TAMIS was successfully performed on all five patients without any reported complications. All underwent a non-piecemeal excision and had return of regular bowel function at 30-day follow-up. All patients were discharged from the hospital the same day as their operation.
Conclusions
SPR-TAMIS is a novel, safe, and feasible procedure capable of achieving non-piecemeal resections of low-risk rectal tumors. Further study needs to be conducted to determine complication rates, functional and oncologic outcomes, and ensure the long-term safety profile.
Background
Oncological outcomes of locally advanced rectal cancer depend on the quality of surgical and oncological management. Enhanced recovery pathways (ERPs) have yet to be assessed for their ...oncological impact when used in combination with minimally invasive surgery. This study assessed outcomes with or without an ERP in patients with rectal cancer.
Methods
This was a retrospective analysis of all consecutive adult patients who underwent elective minimally invasive surgery for primary rectal adenocarcinoma with curative intent between February 2005 and April 2018. Both laparoscopic and robotic procedures were included. Short‐term morbidity and overall survival were compared between patients treated according to the institutional ERP and those who received conventional care.
Results
A total of 600 patients underwent minimally invasive surgery, of whom 320 (53·3 per cent) were treated according to the ERP and 280 (46·7 per cent) received conventional care. ERP was associated with less overall morbidity (34·7 versus 54·3 per cent; P < 0·001). Patients in the ERP group had improved overall survival on univariable (91·4 versus 81·7 per cent at 5 years; hazard ratio (HR) 0·53, 95 per cent c.i. 0·28 to 0·99) but not multivariable (HR 0·78, 0·41 to 1·50) analysis. Multivariable analysis revealed age (HR 1·46, 1·17 to 1·82), male sex (HR 1·98, 1·05 to 3·70) and complications (HR 2·23, 1·30 to 3·83) as independent risk factors for compromised overall survival. Disease‐free survival was comparable for patients who had ERP or conventional treatment (80·5 versus 84·6 per cent at 5 years respectively; P = 0·272).
Conclusion
Treatment within an ERP was associated with a lower morbidity risk that may have had a subtle impact on overall but not disease‐specific survival.
The present investigation aimed to investigate oncological outcomes, comparing enhanced recovery pathway (ERP) versus conventional care by reporting a retrospective analysis of patients undergoing minimally invasive surgery for rectal adenocarcinoma from 2005 to 2018. A total of 600 patients were included in the analysis. The results showed ERP to be associated with a non‐significant improvement in overall survival whereas complications were a main driver for long‐term mortality.
Less complications may reduce cancer risk
Background
Treatment guidelines for stage II and III rectal cancer include neoadjuvant chemoradiotherapy, surgery and postoperative adjuvant chemotherapy. Although data support this recommendation in ...younger patients, it is unclear whether this benefit can be extrapolated to elderly patients (aged 75 years or older).
Methods
This was a retrospective review of patients aged at least 75 years with stage II or III rectal cancer who underwent surgery with curative intent from 1996 to 2013 at the Mayo Clinic. Kaplan–Meier analysis and log rank test were used to compare overall survival between therapy groups. Cox proportional hazards model was used to estimate the independent effect of treatment group on survival.
Results
A total of 160 elderly patients (median age 80 years) with stage II (66) and stage III (94) rectal cancer underwent surgical resection. Only 30·0 and 33·8 per cent received neoadjuvant or adjuvant therapy respectively. Among patients with stage II disease, there was no significant difference in 60‐month survival between patients who received any additional therapy and those who had surgery alone (55 versus 38 per cent respectively; P = 0·184), whereas additional therapy improved survival in patients with stage III tumours (58 versus 30 per cent respectively; P = 0·007). Multivariable analysis found a survival benefit for additional therapy in elderly patients with stage III disease (hazard ratio 0·58, 95 per cent c.i. 0·34 to 0·98).
Conclusion
A multimodal approach in elderly patients with stage III rectal cancer improved oncological outcomes.
Treatment should not be determined by age alone
Single photon counting techniques were used with an x-ray CCD camera to measure features of synchrotron-like x-ray spectra generated by betatron oscillations of electrons in a laser wakefield ...accelerator (LWFA) with different injection techniques. Measurements were made using the Hercules laser system at the University of Michigan. With a single stage gas cell, we demonstrate that pure helium gas in our wakefield accelerator will produce spectra with higher critical energies than when helium mixed with nitrogen is used. This result was not evident when a two stage gas cell was used.
Abstract
Background
Minimally invasive surgery (MIS) is the first-line approach for ileocolic resection in patients with Crohn’s disease (CD) and it is safe and feasible even in complex cases. ...However, an open approach is still required, but indications to open ileocolic resection for CD are not well described.
Methods
All consecutive adult patients with CD who underwent elective ileocolic resection in the Departments of Colon and Rectal Surgery at Mayo Clinic Rochester, Minnesota and Jacksonville, Florida between September 2014 and March 2021 were included and divided into “open” and “MIS” groups. Open approach was defined as upfront laparotomy, MIS included laparoscopic and robotic approaches, and conversion was defined as incision made earlier than planned. Indications to open approach were retrospectively reviewed by two authors, and any incongruity was resolved. Analogous indications were also assessed in the MIS group, as appropriate. Indications, baseline, perioperative characteristics, and short-term postoperative outcomes were compared between open and MIS.
Results
Among 319 ileocolic resections for CD, 45 (14.1%) were open and 274 (85.9%) MIS. Indications for open approach were severe disease, adhesions at previous surgery, history of abdominal sepsis, multifocal and extensive disease, abdominal wall involvement, concomitant open procedures, small bowel dilatation, and anaesthesiologic contraindications (Table 1). In addition, two or more of the above indications were present in 40 patients (89%) in the open group, while only in 6 patients (2%) in the MIS group (p<0.001). Compared to MIS patients, patients undergoing open ileocolic resection were older, with longer CD duration, more previous surgery and preoperative intra-abdominal abscess drainage (Table 2). Nine patients were converted in the MIS group (3.3%). Intraoperatively, open group had more adhesiolysis ≥45 min, more intraoperative complications, more blood loss, more primary stoma, less anastomosis, and longer operative time (Table 3). Postoperatively, they had more overall postoperative complications, ileus, surgical site infections, dehydration, vascular thromboembolism, higher severity by Clavien-Dindo classification, and longer length of stay (Table 4).
Conclusion
Overall rate of open approach ileocolic resection for CD was 14 % during a 7-years period in a referral centre. Open approach was the only operation performed in cases of abdominal wall involvement, concomitant open procedures, and anaesthesiologic contraindication. In addition, the presence of at least two indications,predicting high technical complexity, may be considered as a no-go for the MIS approach in ileocolic resections for CD.
Betatron radiation from laser wakefield accelerators is an ultrashort pulsed source of hard, synchrotron-like x-ray radiation. It emanates from a centimetre scale plasma accelerator producing GeV ...level electron beams. In recent years betatron radiation has been developed as a unique source capable of producing high resolution x-ray images in compact geometries. However, until now, the short pulse nature of this radiation has not been exploited. This report details the first experiment to utilise betatron radiation to image a rapidly evolving phenomenon by using it to radiograph a laser driven shock wave in a silicon target. The spatial resolution of the image is comparable to what has been achieved in similar experiments at conventional synchrotron light sources. The intrinsic temporal resolution of betatron radiation is below 100 fs, indicating that significantly faster processes could be probed in future without compromising spatial resolution. Quantitative measurements of the shock velocity and material density were made from the radiographs recorded during shock compression and were consistent with the established shock response of silicon, as determined with traditional velocimetry approaches. This suggests that future compact betatron imaging beamlines could be useful in the imaging and diagnosis of high-energy-density physics experiments.
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