Hanging Protocol

A hanging protocol A hanging protocol defines how a radiologist prefers to look at an image set, and the term comes from how a technologist used to hang the films on an alternator. This means that the radiologist does not have to re-order, flip, or rotate the images, invert the grayscale, or perform other operations on a display monitor to present them in the order needed. For the correct hanging protocol to be applied, the viewing software needs to know the current orientation, body part, and patient positioning of the image, all of which must be available in the image header. The following attributes are typically needed by the software to define the appropriate algorithm and display the images correctly:

• Anatomic Region (such as Breast, Chest, or Head)

• Image Laterality (such as Left or Right)

• Viewing Code (such as Lateral or Medial Oblique)

• Patient Orientation (such as A/FR)

is the series of actions performed to arrange images for optimal softcopy viewing. The term originally referred to the arrangement of physical films on a light box or hanging of films on a film alternator. Now the term also includes the concept of displaying softcopy images on a PACS workstation. In either application, the goal of a hanging protocol is to present specific types of studies in a consistent manner, and to reduce the number of manual image ordering adjustments performed by the radiologist.

Hanging protocols vary based on modality, body part, department, personal preference, and even training. For example, one radiologist may want to look at a chest image series with the PA view on the left, while another radiologist prefers the PA on the right.

On a full-featured PACS workstation, an appropriate hanging protocol is automatically applied based on the characteristics of the study being loaded. Information such as modality, body part, study or series description or CPT code must be available to ensure proper selection. In addition, information such as series IDs, image orientation (image laterality and view code), and patient positioning must be available to organize the images properly.

Most PACS workstations allow hanging protocols to be customized by each user, and some systems store hanging protocols at a central location, making them available at any workstation accessed by a particular radiologist.

Often, hanging protocols for PACS workstations are defined in vendor-proprietary manner. To make it possible to share hanging protocol among workstations from different vendors, the DICOM standard has defined a Hanging Protocol Service Class and a Hanging Protocol Composite IOD.