Computed Radiography ImageCIOD
CT ImageCIOD
MR ImageCIOD
Nuclear Medicine ImageCIOD
Ultrasound ImageCIOD
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Secondary Capture ImageCIOD
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Multi-frame Grayscale Byte Secondary Capture ImageCIOD
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VL Endoscopic ImageCIOD
VL Microscopic ImageCIOD
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Real-Time Video Endoscopic ImageCIOD
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Dermoscopic Photography ImageCIOD
Grayscale Softcopy Presentation StateCIOD
Color Softcopy Presentation StateCIOD
Pseudo-Color Softcopy Presentation StateCIOD
Blending Softcopy Presentation StateCIOD
Basic Structured DisplayCIOD
XA/XRF Grayscale Softcopy Presentation StateCIOD
Advanced Blending Presentation StateCIOD
Variable Modality LUT Softcopy Presentation StateCIOD
Basic Voice Audio WaveformCIOD
12-Lead ECGCIOD
General ECGCIOD
Ambulatory ECGCIOD
Hemodynamic WaveformCIOD
Basic Cardiac Electrophysiology WaveformCIOD
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Respiratory WaveformCIOD
General Audio WaveformCIOD
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ElectromyogramCIOD
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Sleep ElectroencephalogramCIOD
Multi-channel Respiratory WaveformCIOD
Body Position WaveformCIOD
General 32-bit ECGCIOD
Basic Text SRCIOD
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Key Object Selection DocumentCIOD
Mammography CAD SRCIOD
Chest CAD SRCIOD
Procedure LogCIOD
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Spectacle Prescription ReportCIOD
Colon CAD SRCIOD
Macular Grid Thickness and Volume ReportCIOD
Implantation Plan SR DocumentCIOD
Comprehensive 3D SRCIOD
Radiopharmaceutical Radiation Dose SRCIOD
Extensible SRCIOD
Acquisition Context SRCIOD
Simplified Adult Echo SRCIOD
Patient Radiation Dose SRCIOD
Planned Imaging Agent Administration SRCIOD
Performed Imaging Agent Administration SRCIOD
Rendition Selection DocumentCIOD
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MR SpectroscopyCIOD
Enhanced MR Color ImageCIOD
Raw DataCIOD
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Spatial RegistrationCIOD
Deformable Spatial RegistrationCIOD
Spatial FiducialsCIOD
Ophthalmic Photography 8 Bit ImageCIOD
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Stereometric RelationshipCIOD
Hanging ProtocolCIOD
Encapsulated PDFCIOD
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Real World Value MappingCIOD
Enhanced XA ImageCIOD
Enhanced XRF ImageCIOD
RT Ion PlanCIOD
RT Ion Beams Treatment RecordCIOD
SegmentationCIOD
Ophthalmic Tomography ImageCIOD
X-Ray 3D Angiographic ImageCIOD
X-Ray 3D Craniofacial ImageCIOD
Breast Tomosynthesis ImageCIOD
Enhanced PET ImageCIOD
Surface SegmentationCIOD
Color PaletteCIOD
Enhanced US VolumeCIOD
Lensometry MeasurementsCIOD
Autorefraction MeasurementsCIOD
Keratometry MeasurementsCIOD
Subjective Refraction MeasurementsCIOD
Visual Acuity MeasurementsCIOD
Ophthalmic Axial MeasurementsCIOD
Intraocular Lens CalculationsCIOD
Generic Implant TemplateCIOD
Implant Assembly TemplateCIOD
Implant Template GroupCIOD
RT Beams Delivery InstructionCIOD
Ophthalmic Visual Field Static Perimetry MeasurementsCIOD
Intravascular Optical Coherence Tomography ImageCIOD
Ophthalmic Thickness MapCIOD
Surface Scan MeshCIOD
Surface Scan Point CloudCIOD
Legacy Converted Enhanced CT ImageCIOD
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Legacy Converted Enhanced PET ImageCIOD
Corneal Topography MapCIOD
Breast Projection X-Ray ImageCIOD
Parametric MapCIOD
Wide Field Ophthalmic Photography Stereographic Projection ImageCIOD
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Tractography ResultsCIOD
RT Brachy Application Setup Delivery InstructionCIOD
Planar MPR Volumetric Presentation StateCIOD
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Content Assessment ResultsCIOD
CT Performed Procedure ProtocolCIOD
CT Defined Procedure ProtocolCIOD
Protocol ApprovalCIOD
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XA Defined Procedure ProtocolCIOD
Ophthalmic Optical Coherence Tomography En Face ImageCIOD
Ophthalmic Optical Coherence Tomography B-scan Volume AnalysisCIOD
Encapsulated STLCIOD
Encapsulated OBJCIOD
PatientMModule - Patient
Clinical Trial SubjectUModule - Patient
General StudyMModule - Study
Patient StudyUModule - Study
Clinical Trial StudyUModule - Study
Encapsulated Document SeriesMModule - Series
Clinical Trial SeriesUModule - Series
Frame of ReferenceMModule - Frame of Reference
General EquipmentMModule - Equipment
(0008,0070) Manufacturer2Long String
(0008,0080) Institution Name3Long String
(0008,0081) Institution Address3Short Text
(0008,1010) Station Name3Short String
(0008,1040) Institutional Department Name3Long String
(0008,1041) Institutional Department Type Code Sequence3Sequence
(0008,1090) Manufacturer's Model Name3Long String
(0018,1000) Device Serial Number3Long String
(0018,1002) Device UID3Unique Identifier
(0018,1008) Gantry ID3Long String
(0018,100A) UDI Sequence3Sequence
(0018,100B) Manufacturer's Device Class UID3Unique Identifier
(0018,1020) Software Versions3Long String
(0018,1050) Spatial Resolution3Decimal String
(0018,1200) Date of Last Calibration3Date
(0018,1201) Time of Last Calibration3Time
(0018,1204) Date of Manufacture3Date
(0018,1205) Date of Installation3Date
(0028,0120) Pixel Padding Value1CUS or SS
Enhanced General EquipmentMModule - Equipment
Encapsulated DocumentMModule - Encapsulated Document
Manufacturing 3D ModelMModule - Encapsulated Document
ICC ProfileUModule - Encapsulated Document
SOP CommonMModule - Encapsulated Document
Common Instance ReferenceCModule - Encapsulated Document
Encapsulated MTLCIOD
RT Physician IntentCIOD
RT Segment AnnotationCIOD
RT Radiation SetCIOD
C-Arm Photon-Electron RadiationCIOD
Tomotherapeutic RadiationCIOD
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C-Arm Photon-Electron Radiation RecordCIOD
Tomotherapeutic Radiation RecordCIOD
Robotic-Arm Radiation RecordCIOD
RT Radiation Set Delivery InstructionCIOD
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Enhanced RT ImageCIOD
Enhanced Continuous RT ImageCIOD
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InventoryCIOD
Photoacoustic ImageCIOD
Confocal Microscopy ImageCIOD
Confocal Microscopy Tiled Pyramidal ImageCIOD
Basic DirectoryCIOD

Built with by Innolitics, a team of medical imaging software developers.

Data synced with official DICOM standard on 18 April 2024. The DICOM Standard is under continuous maintenance, and the current official version is available at http://www.dicomstandard.org/current/. DICOM Parts 3, 4, and 6, © NEMA. Please note that the most recent PDF version of the standard is the official reference, and should checked when making technical decisions.

Pixel Padding Value Attribute

Tag(0028,0120)
TypeConditionally Required (1C)
KeywordPixelPaddingValue
Value Multiplicity1
Value RepresentationUS or SS
Example Values
  • 0
  • -2000
  • 63536

Single pixel value or one limit (inclusive) of a range of pixel values used in an image to pad to rectangular format or to signal background that may be suppressed or that may be rendered "transparently" when superimposing images. See Section C.7.5.1.1.2 for further explanation.

Required if Pixel Padding Range Limit (0028,0121) is present and either Pixel Data (7FE0,0010) or Pixel Data Provider URL (0028,7FE0) is present. May be present otherwise only if Pixel Data (7FE0,0010) or Pixel Data Provider URL (0028,7FE0) is present.

Note

  1. The Value Representation of this Attribute is determined by the value of Pixel Representation (0028,0103).

  2. This Attribute is not used in Presentation State Instances; there is no means in a Presentation State to "override" any Pixel Padding Value (0028,0120) specified in the referenced images.

  3. This Attribute does apply to RT Dose and Segmentation Instances, since they include Pixel Data.

  4. This Attribute does not apply when Float Pixel Data (7FE0,0008) or Double Float Pixel Data (7FE0,0009) are used instead of Pixel Data (7FE0,0010); Float Pixel Padding Value (0028,0122) or Double Float Pixel Padding Value (0028,0123), respectively, are used instead, and defined at the Image, not the Equipment, level.

  5. Only a single Value is allowed for this Attribute, so it only applies to images with Samples per Pixel (0028,0002) of 1, i.e., images with a Photometric Interpretation (0028,0004) of MONOCHROME1, MONOCHROME2 or PALETTE COLOR. See Section C.7.5.1.1.2 for details.

Section C.7.5.1.1.2

C.7.5.1.1.2 Pixel Padding Value and Pixel Padding Range Limit

Pixel Padding Value (0028,0120) is typically used to pad grayscale images (those with a Photometric Interpretation (0028,0004) of MONOCHROME1 or MONOCHROME2), or color images with a Photometric interpretation (0028,0004) of PALETTE COLOR, to rectangular format. The native format of some images is not rectangular. It is common for devices with this format to pad the images, to the rectangular format required by the DICOM Standard, with a specific pixel value that is not contained in the native image. Further, when resampling, such as after spatial registration, padding may need to be used to fill previously non-existent pixels.

Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) are also used to identify pixels to be excluded from the rendering pipeline for other reasons, such as suppression of background air. Pixel Padding Range Limit (0028,0121) is defined in the Image Pixel Module.

Note

  1. The "native image" is that which is being padded to the required rectangular format, e.g., the area within the circular reconstruction perimeter of a CT image, or the subset of the rectangular area that contains useful image information, i.e., which is not to be suppressed, or e.g., is that part of a pseudo-colored image that might be superimposed on top of another image. For other mechanisms, see Section N.2.6 “Advanced Blending Transformations” in PS3.4.

  2. The Pixel Padding Value is explicitly described in order to prevent display applications from taking it into account when determining the dynamic range of an image, since the Pixel Padding Value will be outside the range between the minimum and maximum values of the pixels in the native image

  3. No pixels in the native image will have a value equal to Pixel Padding Value (0028,0120).

Pixel Padding Value (0028,0120) specifies either a single value of this padding, or when combined with Pixel Padding Range Limit (0028,0121), a range of values (inclusive) that are padding.

The values of Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) shall be valid values within the constraints defined by Bits Allocated (0028,0100), Bits Stored (0028,0101), and High Bit (0028,0102).

The Pixel Padding Value shall correspond to a value in the original stored pixel data, before the Modality LUT Transformation or any other transformations are applied.

Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) shall not be present when padding is performed but the pixel value used for padding does occur in the native image.

If Photometric Interpretation (0028,0004) is MONOCHROME2 or PALETTE COLOR, Pixel Padding Value (0028,0120) shall be less than (closer to or equal to the minimum possible pixel value) or equal to Pixel Padding Range Limit (0028,0121). If Photometric Interpretation (0028,0004) is MONOCHROME1, Pixel Padding Value (0028,0120) shall be greater than (closer to or equal to the maximum possible pixel value) or equal to Pixel Padding Range Limit (0028,0121).

Note

  1. When the relationship between pixel value and X-Ray Intensity is unknown, it is recommended that the following values be used to pad with black when the image is unsigned:

    • 0 if Photometric Interpretation (0028,0004) is MONOCHROME2.

    • 2Bits Stored - 1 if Photometric Interpretation (0028,0004) is MONOCHROME1.

    and when the image is signed:

    • -2Bits Stored-1 if Photometric Interpretation (0028,0004) is MONOCHROME2.

    • 2Bits Stored-1 - 1 if Photometric Interpretation (0028,0004) is MONOCHROME1.

  2. For projection radiography, when the relationship between pixel value and X-Ray Intensity is known (for example as defined by Pixel Intensity Relationship (0028,1040) and Pixel Intensity Relationship Sign (0028,1041)), it is recommended that a pixel value equivalent to, or rendered similarly to, air (least X-Ray absorbance) be used for padding. However, if such a value may occur in the native image, the Pixel Padding Value (0028,0120) Attribute itself should not be present.

    E.g., for an XRF image obtained with an image intensifier, if air is black then a padded perimeter, if any, should also appear black. Typically though, if unpadded, this area would be collimated with a circular collimator, in which case the pixels would appear natively as white (greatest X-Ray absorbance) and a circular shutter would be necessary to neutralize them as black. Whether collimated areas are detected and treated as padded, or neutralized with shutters is at the discretion of the application. See also the Display Shutter Module Section C.7.6.11.

  3. The conditional requirement for the Pixel Padding Range Limit (0028,0121) in the Image Pixel Module means that it shall not be present unless Pixel Padding Value (0028,0120) is also present.

  4. The range of values to be suppressed between Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) is specified as being inclusive, that is the values themselves as well as all values between are suppressed.

  5. When Pixel Padding Range Limit (0028,0121) is present, but not supported by a rendering application, the constraint that Pixel Padding Value (0028,0120) is closest to the "blackest" value, which is typically the most frequently occurring background pixel, will most often result in an acceptable display, permitting "backward compatibility" in the majority of cases.

When modifying equipment changes the Pixel Padding Value in the image, it shall change the values of Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121), if present. If modifying equipment changes the Pixel Padding Values in the image to values present in the native image, the Attribute Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) shall be removed.

Note

  1. For example, if a CT image containing signed values from -1024 to 3191 and a Pixel Padding Value (0028,0120) of -2000 and a Rescale Intercept (0028,1052) of 0 is converted to an unsigned image with a Rescale Intercept (0028,1052) of -1024 by adding 1024 to all pixels and clipping all more negative pixels to 0, then the padding pixels will be indistinguishable from some of the modified native image pixels, and hence Pixel Padding Value (0028,0120) needs to be removed.

  2. If the modification involves lossy compression, which may result in changes to the pixel values, then the application of Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) may result in a different appearance, and hence these Attributes may need different values also.

Section C.7.5.1.1.2

C.7.5.1.1.2 Pixel Padding Value and Pixel Padding Range Limit

Pixel Padding Value (0028,0120) is typically used to pad grayscale images (those with a Photometric Interpretation (0028,0004) of MONOCHROME1 or MONOCHROME2), or color images with a Photometric interpretation (0028,0004) of PALETTE COLOR, to rectangular format. The native format of some images is not rectangular. It is common for devices with this format to pad the images, to the rectangular format required by the DICOM Standard, with a specific pixel value that is not contained in the native image. Further, when resampling, such as after spatial registration, padding may need to be used to fill previously non-existent pixels.

Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) are also used to identify pixels to be excluded from the rendering pipeline for other reasons, such as suppression of background air. Pixel Padding Range Limit (0028,0121) is defined in the Image Pixel Module.

Note

  1. The "native image" is that which is being padded to the required rectangular format, e.g., the area within the circular reconstruction perimeter of a CT image, or the subset of the rectangular area that contains useful image information, i.e., which is not to be suppressed, or e.g., is that part of a pseudo-colored image that might be superimposed on top of another image. For other mechanisms, see Section N.2.6 “Advanced Blending Transformations” in PS3.4.

  2. The Pixel Padding Value is explicitly described in order to prevent display applications from taking it into account when determining the dynamic range of an image, since the Pixel Padding Value will be outside the range between the minimum and maximum values of the pixels in the native image

  3. No pixels in the native image will have a value equal to Pixel Padding Value (0028,0120).

Pixel Padding Value (0028,0120) specifies either a single value of this padding, or when combined with Pixel Padding Range Limit (0028,0121), a range of values (inclusive) that are padding.

The values of Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) shall be valid values within the constraints defined by Bits Allocated (0028,0100), Bits Stored (0028,0101), and High Bit (0028,0102).

The Pixel Padding Value shall correspond to a value in the original stored pixel data, before the Modality LUT Transformation or any other transformations are applied.

Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) shall not be present when padding is performed but the pixel value used for padding does occur in the native image.

If Photometric Interpretation (0028,0004) is MONOCHROME2 or PALETTE COLOR, Pixel Padding Value (0028,0120) shall be less than (closer to or equal to the minimum possible pixel value) or equal to Pixel Padding Range Limit (0028,0121). If Photometric Interpretation (0028,0004) is MONOCHROME1, Pixel Padding Value (0028,0120) shall be greater than (closer to or equal to the maximum possible pixel value) or equal to Pixel Padding Range Limit (0028,0121).

Note

  1. When the relationship between pixel value and X-Ray Intensity is unknown, it is recommended that the following values be used to pad with black when the image is unsigned:

    • 0 if Photometric Interpretation (0028,0004) is MONOCHROME2.

    • 2Bits Stored - 1 if Photometric Interpretation (0028,0004) is MONOCHROME1.

    and when the image is signed:

    • -2Bits Stored-1 if Photometric Interpretation (0028,0004) is MONOCHROME2.

    • 2Bits Stored-1 - 1 if Photometric Interpretation (0028,0004) is MONOCHROME1.

  2. For projection radiography, when the relationship between pixel value and X-Ray Intensity is known (for example as defined by Pixel Intensity Relationship (0028,1040) and Pixel Intensity Relationship Sign (0028,1041)), it is recommended that a pixel value equivalent to, or rendered similarly to, air (least X-Ray absorbance) be used for padding. However, if such a value may occur in the native image, the Pixel Padding Value (0028,0120) Attribute itself should not be present.

    E.g., for an XRF image obtained with an image intensifier, if air is black then a padded perimeter, if any, should also appear black. Typically though, if unpadded, this area would be collimated with a circular collimator, in which case the pixels would appear natively as white (greatest X-Ray absorbance) and a circular shutter would be necessary to neutralize them as black. Whether collimated areas are detected and treated as padded, or neutralized with shutters is at the discretion of the application. See also the Display Shutter Module Section C.7.6.11.

  3. The conditional requirement for the Pixel Padding Range Limit (0028,0121) in the Image Pixel Module means that it shall not be present unless Pixel Padding Value (0028,0120) is also present.

  4. The range of values to be suppressed between Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) is specified as being inclusive, that is the values themselves as well as all values between are suppressed.

  5. When Pixel Padding Range Limit (0028,0121) is present, but not supported by a rendering application, the constraint that Pixel Padding Value (0028,0120) is closest to the "blackest" value, which is typically the most frequently occurring background pixel, will most often result in an acceptable display, permitting "backward compatibility" in the majority of cases.

When modifying equipment changes the Pixel Padding Value in the image, it shall change the values of Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121), if present. If modifying equipment changes the Pixel Padding Values in the image to values present in the native image, the Attribute Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) shall be removed.

Note

  1. For example, if a CT image containing signed values from -1024 to 3191 and a Pixel Padding Value (0028,0120) of -2000 and a Rescale Intercept (0028,1052) of 0 is converted to an unsigned image with a Rescale Intercept (0028,1052) of -1024 by adding 1024 to all pixels and clipping all more negative pixels to 0, then the padding pixels will be indistinguishable from some of the modified native image pixels, and hence Pixel Padding Value (0028,0120) needs to be removed.

  2. If the modification involves lossy compression, which may result in changes to the pixel values, then the application of Pixel Padding Value (0028,0120) and Pixel Padding Range Limit (0028,0121) may result in a different appearance, and hence these Attributes may need different values also.