Low-dose CT for quantitative analysis in acute respiratory distress syndrome

Introduction

The clinical use of serial quantitative computed tomography (CT) to characterize lung disease and guide the optimization of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS) is limited by the risk of cumulative radiation exposure and by the difficulties and risks related to transferring patients to the CT room. We evaluated the effects of tube current-time product (mAs) variations on quantitative results in healthy lungs and in experimental ARDS in order to support the use of low-dose CT for quantitative analysis.

Methods

In 14 sheep chest CT was performed at baseline and after the induction of ARDS via intravenous oleic acid injection. For each CT session, two consecutive scans were obtained applying two different mAs: 60 mAs was paired with 140, 15 or 7.5 mAs. All other CT parameters were kept unaltered (tube voltage 120 kVp, collimation 32 × 0.5 mm, pitch 0.85, matrix 512 × 512, pixel size 0.625 × 0.625 mm). Quantitative results obtained at different mAs were compared via Bland-Altman analysis.

Results

Good agreement was observed between 60 mAs and 140 mAs and between 60 mAs and 15 mAs (all biases less than 1%). A further reduction of mAs to 7.5 mAs caused an increase in the bias of poorly aerated and nonaerated tissue (-2.9% and 2.4%, respectively) and determined a significant widening of the limits of agreement for the same compartments (-10.5% to 4.8% for poorly aerated tissue and -5.9% to 10.8% for nonaerated tissue). Estimated mean effective dose at 140, 60, 15 and 7.5 mAs corresponded to 17.8, 7.4, 2.0 and 0.9 mSv, respectively. Image noise of scans performed at 140, 60, 15 and 7.5 mAs corresponded to 10, 16, 38 and 74 Hounsfield units, respectively.

Conclusions

A reduction of effective dose up to 70% has been achieved with minimal effects on lung quantitative results. Low-dose computed tomography provides accurate quantitative results and could be used to characterize lung compartment distribution and possibly monitor time-course of ARDS with a lower risk of exposure to ionizing radiation. A further radiation dose reduction is associated with lower accuracy in quantitative results.     

Executive Functioning in Older Adult Outpatients With Type 2 Diabetes Mellitus: A Preliminary Study

Given the multi-componential nature of executive functions, we compared 48 outpatients affected by Type 2 diabetes and 49 control subjects on the executive domains of inhibition, updating, shifting, and word fluency. Variables commonly associated with diabetes were considered in explaining the relationship between diabetes and executive functioning. Each participant underwent a clinical and cognitive (addressing the four executive domains) evaluation. Raw test scores were standardized per domain and compared between groups. Possible risk factors related to diabetes were examined. The diabetes group scored lower than the control subjects only in the inhibition measure, whereas no differences resulted in the other executive domains.     

A method of managing cervicomediastinal tracheal strictures

Guernelli, N, Vecchi, R, Briccoli, A, and Bragaglia, R B (1978).Thorax, 33, 508-510. A method of managing cervicomediastinal tracheal strictures. We describe our experience in managing two cases of long tracheal strictures and a method of treating extensive lesions.     

Intrafamilial spread of hepatitis B virus infection

Summary Two hundred and forth household contacts of 85 chronic HBsAg carriers were studied to assess the relationship between liver histology and ‘e’ antigen or antibody positivity in the index carrier, and evidence of HBV infection within the family. Liver biopsy results were available in 54 index carriers. The prevalence of HBsAg and anti-HBs in the families of 29 carriers with chronic hepatitis and 25 carriers with either a normal liver or minimal inflammatory changes was not significantly different. Serum from 72 index carriers was available for HBeAg and anti-HBe testing. The prevalence of HBsAg and anti-HBs in the families of 5 HBeAg positive carriers, 59 anti-HBe positive subjects, and 8 carriers negative for both HBeAg and anti-HBe was again not significantly different. Infectivity of a carrier thus does not appear to correlate either with histological evidence of liver damage or with the ‘e’ antigen or antibody positivity of the carrier.     

Performance of left brain-damaged patients on imitation of single movements and motor sequences. Frontal and parietal-injured patients compared

The aim of this study was to investigate the relation of apraxia to the sequential features of the motor task required and to the intra-hemispheric locus of lesion. A single movement and a multiple movement imitation test were given to 60 control patients and 60 left brain-damaged patients, among which patients with frontal and parietal lesion were identified, based on CT scan evidence. Both groups performed the tasks using the left limb. On either test left brain-damaged patients scored poorer than controls and parietal patients were significantly more impaired not only than controls, but also than frontal patients. Seventy five per cent of them performed lower than the poorest control patient. In comparison, the severity and the frequency of the motor deficit following frontal damage was much lower. In no case was there a significant difference between the discriminating power of the single movement test and of the sequence test. These findings suggest that the left parietal lobe has a leading role in motor planning and that the control it exerts over the motor cortex of the right hemisphere does not necessarily involve pathways running through the left premotor area.