Modality

A DICOM data object consists of a number of attributes, including items such as name, ID, etc., and also one special attribute containing the image pixel data. 
One of attributes - DICOM modality, that represents DICOM file type. In addition, each attribute also has a Value Multiplicity to indicate the number of data elements contained in the attribute.

DICOM	 Modality

Value		Description
AR		Autorefraction	 
AS		Angioscopy				Retired
ASMT		Content Assessment Results	 
AU		Audio	 
BDUS		Bone Densitometry (ultrasound)	 
BI		Biomagnetic imaging	 
BMD		Bone Densitometry (X-Ray)	 
CD		Color flow Doppler			Retired
CF		Cinefluorography			Retired
CP		Colposcopy				Retired
CR		Computed Radiography	 
CS		Cystoscopy				Retired
CT		Computed Tomography	 
DD		Duplex Doppler				Retired
DF		Digital fluoroscopy			Retired
DG		Diaphanography	 
DM		Digital microscopy			Retired
DOC		Document
DS		Digital Subtraction Angiography		Retired
DX		Digital Radiography	 
EC		Echocardiography			Retired
ECG		Electrocardiography	 
EPS		Cardiac Electrophysiology	 
ES		Endoscopy	 
FA		Fluorescein angiography			Retired
FID		Fiducials	 
FS		Fundoscopy				Retired
GM		General Microscopy	 
 	 
Value		Description
HC		Hard Copy	 
HD		Hemodynamic Waveform	 
IO		Intra-Oral Radiography	 
IOL		Intraocular Lens Data	 
IVOCT		Intravascular Optical Coherence Tomography	 
IVUS		Intravascular Ultrasound	 
KER		Keratometry	 
KO		Key Object Selection	 
LEN		Lensometry	 
LP		Laparoscopy				Retired
LS		Laser surface scan	 
MA		Magnetic resonance angiography		Retired
MG		Mammography	 
MR		Magnetic Resonance	 
MS		Magnetic resonance spectroscopy		Retired
NM		Nuclear Medicine	 
OAM		Ophthalmic Axial Measurements	
OCT		Optical Coherence Tomography (non-Ophthalmic)	 
OP		Ophthalmic Photography	 
OPM		Ophthalmic Mapping	 
OPR		Ophthalmic Refraction			Retired
OPT		Ophthalmic Tomography	 
OPV		Ophthalmic Visual Field	 
OSS		Optical Surface Scan	 
OT		Other	 
 	 
Value		Description
PLAN		Plan	 
PR		Presentation State	 
PT		Positron emission tomography (PET)	 
PX		Panoramic X-Ray	 
REG		Registration	 
RESP		Respiratory Waveform	 
RF		Radio Fluoroscopy	 
RG		Radiographic imaging (conventional film/screen)	 
RTDOSE		Radiotherapy Dose	 
RTIMAGE		Radiotherapy Image	 
RTPLAN		Radiotherapy Plan	 
RTRECORD	RT Treatment Record	 
RTSTRUCT	Radiotherapy Structure Set	 
RWV		Real World Value Map	 
SEG		Segmentation	 
SM		Slide Microscopy	 
SMR		Stereometric Relationship	 
SR		SR Document	 
SRF		Subjective Refraction	 
ST		Single-photon emission computed tomography (SPECT)	Retired
STAIN		Automated Slide Stainer	 
TG		Thermography	 
US		Ultrasound	 
VA		Visual Acuity	 
VF		Videofluorography					Retired
XA		X-Ray Angiography	 
XC		External-camera Photography	 

Retired - those from earlier versions of the standard that will not be supported in future DICOM releases. www.dicomlibrary.com