Given a passage, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Pathologic change in Alzheimer disease (AD) begins some years before symptoms. MRS has the potential to detect metabolic abnormalities reflecting this early pathologic change. Presenilin 1 (PS1) and amyloid precursor protein (APP) mutation carriers have a nearly 100% risk of developing AD and may be studied prior to symptom onset.', 'Short echo time proton MR spectra were acquired from a midline posterior cingulate voxel in presymptomatic carriers of PS1 or APP mutations ("presymptomatic mutation carriers" [PMCs]; n = 7) and age- and sex-matched control subjects (n = 6). Ratios of N-acetyl aspartate (NAA), myo-inositol (MI), and choline-containing compounds (Cho) to creatine (Cr) were measured and NAA/MI calculated. Regression analyses and t tests were performed after log transformation.', 'PMC and control subjects were matched for age and sex. PMC subjects were 1.7 to 21.6 years (mean 9.8 years) before expected symptom onset, predicted from family-specific mean age at onset. Age did not significantly affect metabolite ratios. Geometric mean ratios in control subjects were as follows: NAA/Cr = 1.75, MI/Cr = 0.59, and NAA/MI = 2.95. NAA/Cr and NAA/MI were significantly reduced in PMC relative to controls (NAA/Cr mean decrease 10% [95% CI 2 to 18%]; NAA/MI mean decrease 25% [95% CI 3 to 44%]). MI/Cr was increased in PMC, but the differences did not achieve significance (19% increase [95% CI 1% decrease to 41% increase]; p = 0.07)). In PMCs, reduction in NAA/MI (p = 0.001) and MI/Cr (p = 0.002) were related to proximity of expected age at onset.
Does mRS show abnormalities before symptoms in familial Alzheimer disease?

A distinct velocity pattern represented by a "notch" is observed during the time interval between the end of the systolic and the onset of the early diastolic velocity wave on longitudinal myocardial velocity curve. The origin of the post-systolic velocity notch (PSN) has not been resolved.', 'The high frame rate color tissue Doppler imaging of the apical longitudinal axis was performed in 32 healthy subjects.', 'The time delays of the PSN onset at the posterior aortic wall (AW), the mid anteroseptal wall (MAS) and the posterior mitral annulus (MA) relatively to the anterior aortic annulus (AA) were found to be significantly longer than zero (5.1 ± 2.2, 6.0 ± 2.3, 6.8 ± 2.8 ms; p < 0.001). The amplitude was the highest at the AA when compared to the AW, the MAS and the MA (4.77 ± 1.28 vs. 2.88 ± 1.11, 2.15 ± 0.73, 2.44 ± 1.17 cm/s; p < 0.001). A second PSN spike was identifiable in 10/32 (31%) of the studied subjects at the AA. Of these, 9 (28%) exhibited a second PSN spike at the AW, 3 (9%) at the MAS and no one at the MA.
Does the tissue Doppler imaging derived post-systolic velocity notch originate at the aortic annulus?

To determine the effect of diagnostic ureteroscopy on intravesical recurrence in patients with upper tract urothelial carcinoma (UTUC) after radical nephroureterec¬tomy (RNU).', 'We conducted a retrospective analysis of 664 patients who were treated with RNU for UTUC from June 2000 to December 2011, excluding those who had concomitant/prior bladder tumors. Of the 664 patients, 81 underwent di¬agnostic ureteroscopy (URS). We analyzed the impact of diagnostic ureteroscopy on intravesical recurrence (IVR) using the Kaplan-Meier method. Univariate and multi¬variate analyses were used to determine the independent risk factors.', 'The median follow-up time was 48 months (interquartile range (IQR): 31- 77 months). Patients who underwent ureteroscopy were more likely to have a small (p<0.01), early-staged (p=0.019), multifocality (p=0.035) and ureteral tumor (p<0.001). IVR occurred in 223 patients during follow-up within a median of 17 months (IQR: 7-33). Patients without preoperative ureteroscopy have a statistically significant better 2-year (79.3%±0.02 versus 71.4%±0.02, p<0.001) and 5-year intravesical recurrence-free survival rates (64.9%±0.05 versus 44.3%±0.06, p<0.001) than patients who un¬derwent ureteroscopy. In multivariate analysis, the diagnostic ureteroscopy (p=0.006), multiple tumors (p=0.001), tumor size <3cm (p=0.008), low-grade (p=0.022) and pN0 stage tumor (p=0.045) were independent predictors of IVR.

Is diagnostic Ureteroscopy for Upper Tract Urothelial Carcinoma Independently Associated with Intravesical Recurrence after Radical Nephroureterectomy?