Frequency dependence of magnetic resonance spin-lattice relaxation of protons in biological materials

The frequency dependence of spin-lattice (T1) relaxation times of protons in tissues and other macromolecular solutions was investigated. This dependence can be principally assigned to reduced mobility of water molecules "hydrated" on the surface of macromolecular structures. The T1 relaxation time of "hydration water" was found to increase linearly with frequency in the range from 5 to 100 MHz (T1 = 1.83 f + 25.0). It is assumed that the remainder of water in the tissue has a relaxation rate that is independent of frequency, as is characteristic of bulk tap water. Variations occur in the fraction of water hydrated or bound from one organ to the next. As the observed relaxation rate is a weighted average of the two rates as described by the fast exchange model, the above empirical relationship can be used to take a tissue T1 relaxation time measured at one frequency and then calculate the tissue T1 relaxation time that would be expected at another frequency. Good agreements were obtained between such calculated tissue T1 values and the T1 values actually measured at the second frequency. Variations between the calculated and measured T1 values in some classes of tissues indicate that there are also less important secondary factors such as lipid content.     

An analysis of the ergonomic risk of surgical trainees and experienced surgeons during laparoscopic procedures

BackgroundWork-related musculoskeletal injuries have been increasingly recognized to affect surgeons. It is unknown whether such injuries also affect surgical trainees. The purpose of this study was to assess the ergonomic risk of surgical trainees as compared with that of experienced surgeons.MethodsErgonomic data were recorded from 9 surgeons and 11 trainees. Biomechanical loads during surgery were assessed using motion tracking sensors and electromyography sensors. Demanding and static positions of the trunk, neck, right/left shoulder, as well as activity from the deltoid and trapezius muscles bilaterally were recorded. In addition, participants reported their perceived discomfort on validated questionnaires.ResultsA total of 87 laparoscopic general surgery cases (48 attendings and 39 trainees) were observed. Both trainees and attendings spent a similarly high percentage of each case in static (>60%) and demanding positions (>5%). Even though residents reported overall more discomfort, all participants shared similar ergonomic risk with the exception of trainees’ trunk being more static (odds ratio: –11.42, P = .006).ConclusionSurgeons are prone to ergonomic risk. Trainees are exposed to similar postural ergonomic risk as surgeons but report more discomfort and, given that musculoskeletal injuries are cumulative over time, the focus should be on interventions to reduce ergonomic risk in the operating room.     

Periadventitial dissection of the superior mesenteric artery for locally advanced pancreatic cancer: Surgical planning with the “halo sign” and “string sign”

Most patients diagnosed with pancreatic cancer are classified as nonoperative candidates based on the contemporary guidelines of resectability. The advent of more potent control of systemic disease using neoadjuvant chemotherapy has enabled more aggressive operative interventions. In our multidisciplinary practice, patients with Stage III, locally advanced pancreatic cancer and superior mesenteric artery (SMA) encasement are now carefully triaged with high quality, preoperative imaging to determine if they can be considered candidates for operative resection with periadventitial dissection of the SMA. Patients displaying a “halo sign,” where the encased SMA remains fully patent and free from arterial invasion, are now candidates for SMA periadventitial dissection. This procedure involves the surgical stripping of the infiltrated neurolymphatic tissue off the SMA leaving behind a bare “skeletonized artery.” Alternatively, the “string sign” involving the SMA confers a more likely case of arterial invasion, where a complete oncologic resection cannot be achieved successfully. This method of patient selection in case of SMA involvement abandons the traditional metrics of circumferential degrees of the arterial encasement to guide surgical decisions. Our institutional approach has allowed us to meaningfully expand our operative methods of resection with the potential for improved longitudinal outcomes to pancreatic cancer patients who were deprived historically from the more effective and possibly curative treatment.     

Examining the relationship between the demand-control model and incident myocardial infarction and congestive heart failure in a representative sample of the employed women and men in Ontario,Canada, over a 15-year period

ObjectivesTo examine the relationship between job strain and incident myocardial infarction and congestive heart failure in a representative population of men and women in Ontario, Canada, over a 15-year period.MethodsA total of 14,508 respondents having provided responses to either the 2000/2001, 2002, or 2003 cycles of the Canadian Community Health Survey (CCHS) were aged 35 and older at the time and working. After removing respondents with pre-existing heart disease and missing data, our sample totaled 13,291 respondents. Responses were linked to administrative health care and hospitalization data to capture incident cases of myocardial infarction and congestive heart failure up to March 31, 2017. Job control and psychological demands were assessed using 5 items and 2 items respectively. A series of time-to-event regression models were run, adjusting sequentially for socio-demographic variables and health, other psychosocial work exposures, and health behaviours and body mass index.ResultsOver the study period, there were 199,583 person-years of follow-up (median follow-up: 15 years, 233 days). Higher incidence rates were observed for men (6.69 per 100 persons) than for women (2.77 per 100 persons). No clear relationship was observed for demand-control exposures and incidence of myocardial infarction and congestive heart failure in either men or women. After adjustment for socio-demographic factors, pre-existing health conditions, and other psychosocial exposures, the hazard ratio for high strain exposure (compared with low strain exposure) was 0.92 (0.46–1.84) for women and 0.75 (0.44–1.27) for men.ConclusionIn this large prospective cohort in Canada, we observed no relationship between components of the demand-control model and incident myocardial infarction and congestive heart failure over a 15-year period.     

Timebanking and the co-production of preventive social care with adults; what can we learn from the challenges of implementing person-to-person timebanks in England?

This paper explores the potential contribution of timebanking, an innovative volunteering scheme, to the co-production of preventive social care with adults in England. Interest in volunteering in social care has increased as one proposed solution to the international crisis of a rising demand for services in juxtaposition with decreased resources. Volunteering has been particularly promoted in preventive services that prevent or delay care needs arising. Despite sustained interest in volunteering and co-production in social care, little is known about how theory translates into practice. Reporting implementation data from a Realistic Evaluation of six case studies in England, this paper explores one volunteering scheme, timebanking. The research explores how timebanks were working, what contribution they can make to adult social care, and whether they are an example of co-production. Data collected included interviews, focus groups or open question responses on surveys from 84 timebank members, and semi-structured interviews with 13 timebank staff. Each timebank was visited at least twice, and all timebank activity was analysed for a period of 12 months. Data were triangulated to improve reliability. The research found that in practice, timebanks were not working as described in theory, there were small numbers of person-to-person exchanges and some timebanks had abandoned this exchange model. Timebanks faced significant implementation challenges including managing risk and safeguarding and the associated bureaucracy, a paternalistic professional culture and the complexity of the timebank mechanism which required adequate resources. Lessons for timebanks are identified, as well as transferable lessons about co-production and volunteering in social care if such schemes are to be successful in the future.     

Changes in sensory-cognitive input: effects on cerebral blood flow

Eight healthy right-handed young men were subjected to local CBF measurement by [15O]water and positron emission tomography during partial sensory deprivation and during sensory-cognitive activation; physiological, hormonal, and subjective stress measurements were also performed. Results indicated that (a) "whole-brain" CBF increased during activation; (b) the greatest increase in CBF was in the primary visual cortex; (c) differences between hemispheres were not observed, but CBF was greater anteriorly than posteriorly in the deprivation condition only; (d) within-subject variability of CBF was not influenced by the sensory-cognitive condition; and (e) the procedure was not stressful.