PACS Images 2

PACS enables radiologists to view numerous images on one screen













PACS diagram













Multiple Pacs workstations

History and Advantages of Pacs

History and Advantages of PACS

PACS first emerged in the 1980s, although initially trumpeted as a solution to lost films, healthcare organisations, especially the larger ones, have found that digital images can easily be lost as well.

One of the main benefits that PACS provides is the ability to provide a timely delivered and efficient access to images, interpretations and related data throughout the organisation. This helps to ease consultations between physicians who can now simultaneously access the same images over networks, leading to a better diagnosis process.

It is also beneficial to physicians in emergency situations, as they need not wait for long periods in order to view a patient’s radiological images as these are instantly available on the network when ready.

Another feature of PACS is the ability to digitally enhance the images, providing more detailed and sharper images. This improves diagnostic capabilities at radiological examinations.

Since the 1990s, organisations have taken the steps to fully integrate PACS with RIS, when the basic features and adapt needed to mange the acquisition, processing and storage of images, becomes the responsibility of the PACS.

The high costs of PACS has led to vendors offering mini-PACS, which is a cheap alternative for organisations that cannot afford the cost of a full PACS system or those seeking to implement seeing to implement some form of a digital image management system but would rather start off with something small.

While PACS are considered to be at a minimum hospital wide, mini-PACS usually tend to be departmental-based (radiology, emergency room, or orthopedics). Mini-PACS are easy to maintain and cheap to repair, and they can gradually be upgraded to a fully functioning hospital wide PACS.

Advantages of PACS:

• Rapid access to critical information to decrease exam-to-diagnosis time. This is especially useful in emergency and operating rooms.
• Elimination of film, handling and storage costs
• Images can be easily shared between reading radiologists, other physicians and medical records.
• Images can be archived at secure locations using database servers manages the transfer, retrieval and storage of images and relevant information; the archive provides permanent image storage.
• Radiologists can access soft-copy images instantly after acquisition to expedite diagnosis and reporting at the almost any available workstation.
• Web servers can be used to most cost-effectively share images with other departments, even referring physicians across town. They can access the images using the Internet or the local intranet.
• Hardcopy films or paper printouts can be made when needed for traditional archiving or the provision of images to other departments

PACS Images

An image as stored on a picture archiving and communication system (PACS)














The same image following contrast adjustment, sharpening and measurement tags added by the system

PACS

PACS

(picture archiving communication system)

In medical imaging, picture archiving and communication systems (PACS) are computers, commonly servers, dedicated to the storage, retrieval, distribution and presentation of images. The medical images are stored in an independent format. The most common format for image storage is DICOM (Digital Imaging and Communications in Medicine). Electronic images and reports are transmitted digitally via PACS; this eliminates the need to manually file, retrieve or transport film jackets. A PACS consists of four major components: the imaging modalities such as CT and MRI, a secured network for the transmission of patient information, workstations for interpreting and reviewing images, and long and short term archives for the storage and retrieval of images and reports. Combined with available and emerging Web technology, PACS has the ability to deliver timely and efficient access to images, interpretations and related data. PACS breaks down the physical and time barriers associated with traditional film-based image retrieval, distribution and display.

Types of Images:

Most PACSs handle images from various medical imaging instruments, including ultrasound (US), magnetic resonance (MR), positron emission tomography (PET), computed tomography (CT), endoscopy (ENDO), mammograms (MG), digital radiography (DR), computed radiography (CR)

Uses:

PACS has two main uses:
Hard copy replacement: PACS replaces hard-copy based means of managing medical images, such as film archives. With the decreasing price of digital storage, PACSs provide a growing cost and space advantage over film archives in addition to the instant access to prior images at the same institution. Digital copies are referred to as Soft-copy.
Remote access: It expands on the possibilities of conventional systems by providing capabilities of off-site viewing and reporting (distance education, telediagnosis). It enables practitioners in different physical locations to access the same information simultaneously for teleradiology.
PACS is offered by virtually all the major medical imaging equipment manufacturers, medical IT companies and many independent software companies. Basic PACS software can be found free on the internet.
One difficult area in PACS is interpreting the DICOM image format. DICOM does not fully specify the metadata tags stored with images to annotate and describe them, so vendors of medical imaging equipment have latitude to create DICOM-compliant files that differ in the meaning and representation of this metadata. A feature common to most PACS is to read the metadata from all the images into a central database, allowing the PACS user to retrieve all images with a common feature no matter the originating instrument. The differences between vendors' DICOM implementations make this a difficult task.

A PACS can store volume data from exams and reconstruct 3D images
Some medical modality vendors have defined private DICOM tags to introduce added features. Tags like this are permitted according to DICOM protocol and will not impact on the images in most cases, but will not operate when the image is viewed on a different platform.

Maximum Intensity Projection Images

CT Maximum Intensity Projection:

Figure 1 a. Chest X-rays showing reduced left lung volume and herniation of hyperinflated right lung (arrow) b, c. Axial CT scan and minIP coronal reconstruction reveal hyperlucency of left lung and airways patency. d. Left pulmonary arteries have strikingly decreased caliber on contrast enhanced MIP coronal reconstruction

Maximum Intensity Projections

Maximum Intensity Projection Notes

A maximum intensity projection (MIP) is a computer visualization method for 3D data that projects in the visualization plane the voxels with maximum intensity that fall in the way of parallel rays traced from the viewpoint to the plane of projection. This implies that two MIP renderings from opposite viewpoints are symmetrical images.

This technique is computationally fast, but the 2D results do not provide a good sense of depth of the original data. To improve the sense of 3D, animations are usually rendered of several MIP frames in which the viewpoint is slightly changed from one to the other, thus creating the illusion of rotation. This helps the viewer's perception to find the relative 3D positions of the object components. However, since the projection is orthographic the viewer cannot distinguish between left or right, front or back and even if the object is rotating clockwise or anti-clockwise.

MIP is used for the detection of lung nodules in lung cancer screening programs which utilise computed tomography scans. MIP enhances the 3D nature of these nodules, making them stand out from pulmonary bronchi and vasculature.

MIP imaging was invented for use in Nuclear Medicine by Jerold Wallis, MD, in 1988, and subsequently published in IEEE Transactions in Medical Imaging [1]. In the setting of Nuclear Medicine, it was originally called MAP (Maximum Activity Projection). Additional information can be found in other articles by the same author [2], [3].

Use of depth weighting during production of rotating cines of MIP images can avoid the problem of difficulty of distinguishing right from left, and clockwise vs anti-clockwise rotation. MIP imaging is used routinely by physicians in interpreting Positron Emission Tomography (PET) or Magnetic Resonance Angiography studies.

Maximum Intensity Projections

Computerized Imaging class 2009

9/10/09 First Day of Class