|Author||Giovanni Cardone and Maria Spletter|
|Initial release||November 2017|
|Category||Analysis, Scripting, Plugins|
The MyofibrilJ plugin provides two scripts to analyse fibril morphology. Given a fluorescence image of muscle fibers, the scripts measure myofibrils dimensions and sarcomere length. The scripts were initially developed for the analysis of both longitudinal and cross sections of myofibrils stained with rhodamine-phalloidin.
Two distinct commands are provided to analyse either cross-sections or longitudinal sections of fibers.
The sarcomere length is estimated by means of Fourier analysis. Because of the periodic nature of sarcomere organization, the position of the periodic peaks on the horizontal axis of the Fourier transformed imaged is strictly related to the lenght of sarcomeres. The width of the fibrils is estimated in two different manners. One estimate is obtained from the autocorrelation image, by measuring the position of the first minimum in its vertical intensity profile. Furthermore, the width of the cross-profile of multiple fibrils is measured in the original image and combined to provide an additional average width.
An initial estimate of the diameter of the fibrils is obtained by finding the first minimum in the radial average profile of the autocorrelation image, while their position is determined by examining the peak intensities. This estimate is used to determine the optimal crop area around all the cross-sections in the image. All of the detected fibrils cross sections are then cropped from the image, the size of the crop being proportional to the the initial diameter estimate, and combined to obtain a noise-free average representation of the fibril section. The diameter is estimated from this average as the full width of its radial profile, where the intensity is 26% of the maximum range. In addition to their diameter, the level of clustering of the fibrils is characterized by nearest neighbor analysis and summarized by the Nearest Neighbor Index (NNI).
The easiest way to install MyofibrilJ is by first adding the update site, by clicking the Add update site button in the site management dialog button and filling in the name of your choice for the site and http://sites.imagej.net/MyofibrilJ/ for the URL, and then by subscribing to it.