Disease evaluation by imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) is an accurate,
reproducible, and easily accessible methodology used in pharmaceutical trials. The value of imaging tools in the evaluation
of response to chemotherapeutic agents and other disease modifying agents has been noted in the literature.1,2
Imaging tools such as CT, MRI, and positron emission tomography (PET) scans have complemented serological markers like CEA
(carcino-embryogenic antigen) and PSA (prostate-specific antigen) in disease-response evaluation following chemotherapy in
patients with colon carcinoma and prostate carcinoma. Imaging tools give detailed information regarding extent and spread
of the cancer when compared to the biochemical markers during disease response evaluation.1
Response evaluation by biochemical markers can give false positive and often inaccurate assessment of tumor response. Imaging
modalities such as CT and MRI are advantageous because subtle and early changes in lesion progression can be documented more
accurately.
Disease response evaluation by imaging has complemented conventional biochemical markers; there are established protocols
like RECIST (Response Evaluation Criteria In Solid Tumors) and WHO (World Health Organization) criteria3,4 for tumor assessment.
Imaging core labs coordinate clinical trials workflow using imaging modalities as the follow-up tool. The images are acquired
at various sites all over the world and sent to the imaging core lab, which is analogous to a radiology department. The images
received from various sites are either hard-copy films or soft-copy images on magneto-optical disks (MODs) and CDs. The image
visualization on computer monitors is analogous to image interpretation using picture archiving and communication systems
(PACS) in hospital settings.
PACS in hospitals Over the past two decades, groups of computer scientists, electronic design engineers, and physicians from universities and
industry have achieved an electronic environment for the practice of radiology, with PACS comprising the radiology component
of this revolution. It has become evident recently that the efficiencies and cost savings of PACS are more fully realized
when they are part of an enterprise-wide electronic medical record. The installation of PACS requires careful planning by
all the various stakeholders over many months prior to installation. All of the users must be aware of the initial disruption
that will occur as they become familiar with system processes and procedures.
Figure 1. The ideal workflow in a clinical trial with image review at an imaging core lab.
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Modern fourth-generation PACS is linked to radiology and hospital information systems.5 PACS consist of electronic acquisition
sites-a robust network intelligently managed by a server as well as multiple viewing sites and an archive. The details of
how these components are linked and their workflow analysis determines the success of PACS. As PACS evolves over time, components
are frequently replaced, and the users must continually learn about new and improved functionalities. The digital medical
revolution is rapidly being adopted in many medical centers, improving patient care.
PACS was introduced to clinical practice in the late 1990s. Though initial setup of such a system met with difficulties such
as technical incompetence, economic insufficiency, bureaucratic hurdles, and psychological inertia from the clinicians, PACS
has become acceptable to the clinicians in general and radiologists in particular.
The PACS workflow itself must be described before we elaborate on its role in network systems. Image acquisition by cassettes
using films is replaced by specially designed filmless cassettes, which can be used several times. The basic components of
any PACS system include an image acquisition device (such as film cassettes, video frame grabbers, and digital imaging modalities
like CT or MRI), an image display station, and database management and image storage devices. Patient images are acquired
from the radiography or digital imaging modalities and sent to the PACS workstation. The images are viewed and interpreted
there, and the interpretation results are made available to the physicians within the hospital network. An image storage backup
system stores images on optical disks and MODs. Images are stored for a time period specified in each hospital's state and
local rules.
The images from a hospital without a radiologist can be sent to other hospitals. Modalities including CT, MRI, ultrasound,
computed radiography, and nuclear medicine send images to PACS servers in other hospitals directly or via a network gateway.
Images can be transmitted on a regional hospital local area network (LAN), then onto high-speed phone circuits to reach the
hospital with PACS. They then go onto the network core and PACS servers.
Advantages of PACS in a hospital scenario One of the important advantages of PACS is the time saved in comparison with conventional radiology processing. Twair et al.
compared a group of 100 radiologic studies performed in a conventional radiology department with an equal number performed
in a completely filmless PACS department to assess the difference in the radiologist report turnaround time. There was a statistically
significant (P < .00001) decrease in the median imaging-to-dictation time (IDT) of the PACS group (3 hours and 40 minutes)
in comparison with the pre-PACS group (25 hours and 19 minutes). This can be attributed to the fact that PACS eliminates all
the workload associated with hard-copy films, thus improving the department's efficiency and decreasing the number of lost
films.
