OpenIGTLink/Protocol

<< OpenIGTLink

Header Structure

 Bytes
 0   2                       14                                      34             42               50              58
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....
 | V |          TYPE         |              DEVICE_NAME              |   TIME_STAMP  |   BODY_SIZE   |     CRC64     |   BODY  		  
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....

Byte Order

Big endian should be used for all numerical values (version, body size, crc). Unused spaces are padded with 0 (binary).

Header Fields

Data	Type	Description
V	Unsigned short (16bit)	Version number (1)
TYPE	char[8]	Type name of data
DEVICE_NAME	char[20]	Unique device name
TIME_STAMP	64 bit unsigned int	Timestamp or 0 if unused
BODY_SIZE	64 bit unsigned int	Size of body in bytes
CRC	64 bit unsigned int	64 bit CRC for body data

Data types

Data type:

• Command (get position, get status, go to target, stop, start continuous push, stop push, ready)
• Data (image, position, status)

IMAGE

Bytes
58  60  62  64          70                      82                      94                      106                     118
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| V |T|S|E|O|RI |RJ |RK |  TX   |  TY   |  TZ   |  SX   |  SY   |  SZ   |  NX   |  NY   |  NZ   |  PX   |  PY   |  PZ   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
118         124         140
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+....
|DI |DJ |DK |DRI|DRJ|DRK|   IMAGE_DATA
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+....

Descriptions:

Data	Type	Description
V	unsigned short	version number
T	8bit unsigned int	Image type (1: Scalar)
S	8bit unsigned int	Scalar type (2:int8 3:int8 4:int16 5:uint16 6:int32 7:uint32 10:float32 11:float64)
E	8bit unsigned int	Endian for image data (1:BIG 2:SMALL) (NOTE: values in image header is fixed to BIG endian)
O	8bit unsigned int	image coordinate (2:LPS 1:RAS )
RI, RJ, RK	16 bit unsigned int	Number of pixels in each direction
PX, PY, PZ	32 bit float	center position of the image
TX, TY, TZ	32 bit float	Transverse vector (direction for 'i' index) / The length represents pixel size in 'i' direction
SX, SY, SZ	32 bit float	Transverse vector (direction for 'j' index) / The length represents pixel size in 'j' direction
NX, NY, NZ	32 bit float	Normal vector of image plane(direction for 'k' index) / The length represents pixel size in 'z' direction or slice thickness
DI, DJ, DK	16 bit unsigned int	Starting index of subvolume
DRI, DRJ, DRK	16 bit unsigned int	number of pixels of subvolume
IMAGE_DATA	Binary image data ()	Image data (endian is determined by "E" field)

TRANSFORM

The transform data is upper three rows of 4x4 transformation matrix, where element (3,3) is assumed to be 1.

 Bytes (Body)
 58      62      66      70      74      78      82      86      90      94      98     102     106
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | (0,0) | (1,0) | (2,0) | (0,1) | (1,1) | (2,1) | (0,2) | (1,2) | (2,2) | (0,3) | (1,3) | (2,3) | 
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

POSITION

• 3D Position
• Optional: Orientation

STATUS

 Bytes (Body)
 58   60            68                           88
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+.....
 | C |  Sub Code   |       Status name           |   Status message (optional)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+.....

Data	Type	Description
C	Unsigned short (16bit)	Status code groups: 1-Ok, 2-Generic Error, ... (see below)
Sub Code	64 bit integer	Sub code for the error (ex. 0x200 - file not found)
Error name	char[20]	"Error", "Ok", "Starting up" - can be anything, don't relay on this
Status Message (optional)	char[ BodySize - 30 ]	Optional (English) description (ex. "File C:\test.ini not found")

Status codes:
0 No Errors Found (use status 1 instead!)
1 OK (Default status)
2 Unknown error
3 Panic mode (emergency)
4 Not found (file, configuration, device etc)
5 Access denied
6 Busy
7 Time out / Connection lost
8 Overflow / Can't be reached
9 Checksum error
10 Configuration error
11 Not enough resource (memory, storage etc)
12 Illegal/Unknown instruction (or feature not implemented)
13 Device not ready (starting up)
14 Manual mode (device does not accept commands)
15 Device disabled
16 Device not present
17 Device version not known
18 Hardware failure
19 Exiting / shut down in progress

Open questions

1. What if the application receives hundreds of "position" packets?
   Should we add "keep only the last" flag to the packet type?
2. Authentication (other than Unique Name)
3. Compression
4. Priority
5. Duplicate messages

Resources

• Slicer 3 Image Guided Therapy (IGT) suite
• Middleware features discussion
• Initial discussion about requirements
• BioImage Suite VVLink Tool (uses TCL/TK object streaming)