# MedStat Stutter

## Phantasies of a physicist fallen among physicians

### The Ballot and the Bazaar

May 8, 2017, 11:55 am

Gastric emptying can be recorded by scintigraphy or by MRI techniques. Scintigraphy returns times series data of the meal volume, MRI gives the total content of the stomach, which includes meal and secretion. To quantify secretion and emptying in clinical studies, non-linear curves are fitted to the time series, which can give strange results. When the ballot fails, the bazaar comes to the rescue.

### Multiple indexing with Stan

May 8, 2017, 11:54 am

## Summary

volume ~ normal(
v0[record] .* (1+ kappa[record] .* (minute ./ tempt[record])) .*
exp(-minute ./ tempt[record]), sigma);

## Fitting gastric emptying time series

Gastric volume times serie measured by MRI techniques can have an initial volume overshoot due to secretion. To estimate half-times and the degree of overshoot, the author of this blog has introduced the linexp function [@Fruehauf2011] with three parameters to complement the power exponential function used in earlier research [@Elashoff1982, @Elashoff1983b] with scintigraphic data.

linexp:

v = v0* (1+t*kappa/tempt)*exp(-t/t_{empt})

### Checkliste für Studiendaten in Excel

April 5, 2017, 8:36 am

Excel eignet sich nur eíngeschränkt zur statistischen Auswertung klinischer Studien, aber zu Dateneingabe und Verwaltung bei medizinischen Studienarbeiten ist es durchaus geeignet. Hier einige Rezepte, von Muss sein bis Das Beste zum Schluss.

### Crossover design with unequal weights

March 30, 2017, 6:21 pm

For a clinical study we needed a randomization table with the option to use unequal cell counts, e.g n = 8 for treatment 1 and 2 and n=12 for treatment 3 and 4. Using the R package by Kornelius Rohmeyer, I have written a little web app with Shiny.