Copyright: DB Browser Help Copyright ® MIT 1997.


DB Browser Help

Choosing Files to View

Browsing a Record

Options

Searching for Annotations

Printing

This is an alpha release of the DB Browser.  A number of the controls are not yet implemented, but what is already implemented encompasses the functionality of the MS-DOS view program, with many additional features.   Please send your comments, suggestions, and bug reports to the author:

George B. Moody

MIT Room 20A-113

Cambridge, MA 02139 USA

e-mail: george@hstbme.mit.edu

You may download the most recent version of the DB Browser from our World Wide Web site (http://ecg.mit.edu).  Please do not redistribute copies of this program.  Refer anyone interested in obtaining a free copy to our web site, or to the author at the address above.


Choosing Files to View

The Choose Inputs dialog usually appears when you start the DB Browser.  It allows you to select a database record to view.  If you start the DB Browser using a command line (for example, by choosing Run... from the Program Manager's File menu), you may supply a record name and an annotator name on the command line following the name of the program (wview);  in this case, the DB Browser opens the record immediately (if it is available) without showing the Choose Inputs dialog. If you supply a record name but omit the annotator name, the DB Browser attempts to find the reference (atr) annotations.  At any time, you may pop up the Choose Inputs dialog by selecting Open... from the File menu, in order to change the record or annotator names, or the DB environment.

To select sets of signals and annotations to view, fill in the Record name: field (up to 8 characters), and the Annotator name: field (up to 3 characters).  Leave the Annotator name: field empty if the record is unannotated, or if you do not wish to view annotations.  Although the DB environment may be changed within the Choose Inputs dialog, note that the effects of any such changes are limited to the current session of the DB Browser (other DB applications and future DB Browser sessions are unaffected).

The DB path is a list of directories that are searched when you specify a record or annotator name.

The DB calibration file is a text file containing information about the relative scales of many different types of signals.


Browsing a Record

Use the scrollbar at the bottom of the window to move in either direction through the record.  If you click on the scrollbar arrows, the display scrolls by 1 second at a time in the indicated direction.  Clicking in the rectangles beside the "thumb" of the scrollbar scrolls the display by the width of the window.  You may also drag the "thumb" to move to any desired location;  while doing so, the time corresponding to the current position of the thumb appears in red near the bottom of the window.

Keyboard commands can also perform these functions and others:

<left-arrow>	back 1 second
<right-arrow>	forward 1 second
<Page Up>	back 1 screenful
<Page Down>	forward 1 screenful
<Home>	back to beginning
<End>	forward to end
<Enter>	search forward
<backspace>	search backward
<up-arrow>	zoom in (increase time scale)
<down-arrow>	zoom out (decrease time scale)
+	increase signal amplitude
-	decrease signal amplitude

You may also enter a desired time in the Recenter at field of the Find window (accessible from the Edit menu).   The DB Browser redraws the display centered on the specified time.

The times shown in the lower corners of the signal window usually indicate elapsed time from the beginning of the record in hours, minutes, and seconds (hours are omitted if the elapsed time is  less than one hour).  If the times are shown enclosed in square brackets, they indicate the actual time of day (and possibly the date) when the signals shown were recorded, determined by reference to the base time and date recorded in the header file for the record.


Options

Use the Options menu to set display and printing options.  The View Options... dialog allows you to choose display scales, turn the grid on and off, and select options for annotation and signal display.  The Print Options... dialog is very similar, but its options apply to printed output only.  (The Print Options... dialog may also be accessed via the Options... button in the Print... dialog, which may be opened from the File menu.)

Select Use default scales and options from View Options... to reset all display options to their initial values.  In Print Options..., select Use display scales and options to set the printing options to match those you have chosen for display.

If displayed or printed, the grid marks 200 ms intervals horizontally, and 0.5 mV intervals vertically.  (For signals not dimensioned in units of mV, the DB calibration file specifies the scaling factor between the physical units of the signal and mV.)  At the default scales, the grid intervals should measure 5 mm on your screen or printed output, corresponding to the standard ECG display scales of 25 mm/s and 10 mm/mV.  (If this is not the case, click on Calibrate... and follow the instructions on-screen to make appropriate adjustments for your hardware.)

Marker bars, if displayed or printed, show the exact locations of each annotation.  Note that policies for placement of ECG annotations may vary between records (for example, in the MIT-BIH Arrhythmia Database,  QRS annotations are placed at the R-wave peak,  but in the AHA Database, these annotations are placed at the PQ junction).

Normally, the DB Browser shows only the mnemonic corresponding to  the primary annotation type (the anntyp field) of each annotation.  Exceptions include RHYTHM annotations (for which the rhythm, encoded in the aux field of the annotation, is shown);  LINK annotations (for which descriptive data encoded in the aux field are shown); NOISE annotations (for which signal quality data encoded in the subtyp field is shown);  and STCH, TCH, and NOTE annotations (for which the contents of the aux field are shown).  To make it easier to identify these exceptions, RHYTHM annotations appear below the level of ordinary annotations, and the others appear above the level of ordinary annotations.  The representation matches that used in the MIT-BIH Arrhythmia Database Directory and other directories, which contain complete lists of the mnemonics used in each database.

By selecting the appropriate items from View options... or Print options..., you can view or print the contents of the optional annotation fields (subtyp, chan, num, and aux, shown from top to bottom in that order if more than one is selected).  See the ECG Database Programmer's Guide for further information about optional annotation fields.

Signal baselines, if selected, are displayed or printed only for signals for which absolute levels are significant, such as blood pressure.  Such signals are referred to as DC-coupled signals, since they must be digitized without being passed through high-pass filters in order to preserve absolute levels.  In signals such as ECGs, only variations in level, rather than absolute levels, are significant.  These AC-coupled signals are high-pass filtered before digitization, in order to remove any DC component, so that the gain can be chosen optimally for the range of variation in the signal.  By default, signal names appear at the left margin slightly above each signal;  deselect Signal names to suppress this output.  The header file for each record specifies signal names, and which signals are DC-coupled;  see the ECG Database Programmer's Guide for further information.

If the time of the beginning of the record is specified in its header file, the DB Browser can display absolute times at the lower left and right corners of the window.  By default, the DB Browser displays elapsed times from the beginning of the record;  check Absolute time if you prefer to see absolute times (and dates) when looking at records for which this information is available.


Searching for Annotations

Select Find... from the Edit menu to bring up the Find dialog.   Enter an annotation mnemonic (e.g., V) in the Search forward or Search backward field.  Click on the radio button to the left of the chosen search direction, then click on OK.  The DB Browser redraws the signals, centered on the next annotation of the specified type that was not visible in the previous screenful.  If the search is unsuccessful, the Find window remains visible, so that you can modify the search criteria.

In addition to standard annotation mnemonics (listed in the ECG Database Programmer's Guide), you may enter signal quality strings (as displayed by the DB Browser for NOISE annotations), or aux strings (as displayed for RHYTHM, ST and T change, and NOTE annotations).  In short, you may search for any string that the DB Browser uses when drawing annotations.  When specifying aux strings, a prefix is sufficient as a search target (for example, "(S" matches any annotation with an aux string beginning with these characters, such as "(SVTA" or "(ST0+").

To repeat a search forward, press the <enter> key;  to repeat a search backward, press the <backspace> key.  If you use these keyboard shortcuts without having defined a search target, <enter> behaves in the same way as <Page Down>, and <backspace> in the same way as <Page Up> (moving to the adjacent screenful in the appropriate direction).


Printing

You can print the current contents of the main DB Browser window or any selected segment of the current record by selecting Print... from the File menu to bring up the Print dialog.  Choose the output device from the Printer list.  Select the range (time interval) to be printed by choosing either Entire Record, Current Contents of Window (the default), or Segment.  If you choose Segment, enter the times of the beginning and end of the desired segment in the From: and To: fields.   Press OK to begin printing, or Cancel to return to the DB Browser without printing.

The Setup... button opens the printer-specific setup dialog for the selected printer.  The Options... button opens the Print Options dialog (also accessible via the Options menu), which allows you to select scales and grid, annotation, and signal printing options.  By default, these match the current display scales and options.

Although your Printer selection is retained for the current session of the DB Browser, changing it does not change the Windows default printer, which is the initial printer selection whenever a new DB Browser session begins.  To choose a different Windows default printer, use the Printer applet in the Windows Control Panel.


Annotator name:  A string (of up to 3 characters under MS-DOS) that identifies a set of annotations (labels) associated with a given record.  Annotator names vary, but most standard databases include reference annotation files with the annotator name atr (a shortened form of atruth , as these files are named on UNIX and most other operating systems).  To get a list of available annotators for a given record, find files matching the pattern record.* (in any of the directories named in the DB path, where record is the record name);  the suffix of the name (omitting the "record.") of each such file may be an annotator name.  Note that files with dat or hea suffixes are not annotation files;  there may be other non-annotation files associated with records as well.


DB calibration file: A text file containing specifications for customary plotting scales and calibration pulses of many different types of signals.  If the record you wish to view contains signals other than ECGs, make sure that the DB calibration file is available to the DB Browser, by setting the MS-DOS environment variable DBCAL to the name of the DB calibration file (or by filling in the corresponding field in the  Choose Inputs dialog).  Include the drive letter and directory name in the value of DBCAL only if the file is not in one of the directories named in the DB path.  A sample DB calibration  file (called dbcal) is provided with the DB Browser.  Unless a non-standard configuration was chosen during installation, dossetdb.bat sets DBCAL appropriately.  See the ECG Database Applications Guide for further information about the DB calibration file.


DB environment: A set of MS-DOS environment variables shared by the DB Browser and other applications built using the MIT DB library.  The DB environment should generally be initialized before starting Windows, typically using the batch file dossetdb.bat (installed together with the DB Browser, and often invoked automatically from autoexec.bat whenever your system is rebooted).  The DB environment consists of the DB path and the DB calibration file.


DB path: A list of directories where DB files (signal files, annotation files, and header files) may be found.  You may initialize the DB path before starting Windows, by setting the MS-DOS environment variable DB, either using dossetdb.bat, or a command of the form:

    set DB=;c:\database;d:\mitdb

where the value assigned contains the list of directories to be searched, with semicolons (;) used to separate pairs of directories. In the example, the initial semicolon specifies that the current directory (represented by an empty string) is to be searched first.  See the ECG Database Programmer's Guide for further information about the DB path.


Header file: A text file that names and describes the signals belonging to a given record.  Under MS-DOS, header files have names of the form record.hea, where record is the record name;  different conventions are used under other operating systems.  See the ECG Database Applications Guide for further information about header files.


Annotation: A label, associated with a particular sample (and optionally, a particular signal), that describes a feature of the signal(s) at that time. In ECG records, most annotations are beat (QRS) labels and indicate the QRS type (normal, PVC, SVPB, etc.).


Annotation file: A binary file that contains a time-ordered set of annotations for some or all of the signals belonging to a given record.  Under MS-DOS, annotation files have names of the form record.ann, where record is the record name, and ann is the annotator name;  different conventions are used under other operating systems.  See the ECG Database Applications Guide for further information about annotation files.


Signal file: A binary file that contains a time-ordered set of digitized samples of one or more signals belonging to a DB record.  A record may contain more than one signal file;  all signal files belonging to a given record are named in the record's header file.  There are no restrictions on signal file names other than those imposed by the operating system.  Commonly, signal files are given names of the form record.dat, where record is the record name.


Record: A set of files that may include signal files, annotation files, and a header file, all of which are associated with the same original signals.  Only the header file is mandatory.  Although records are sometimes called tapes for historical reasons, records are now more commonly maintained on optical or magnetic disks than on tape.


Record name: A string (of up to 8 characters) that identifies a DB record. Record names for the MIT-BIH Arrhythmia Database are 3-digit numbers beginning with 1 or 2 (e.g., 100, 203; not all such numbers are assigned as record names, however).  Record names for other databases follow different conventions.  To get a list of available records, find files matching the pattern *.hea (in any of the directories named in the DB path);  the first part of the name (omitting the ".hea" suffix) of each such file is the name of the record with which it is associated.