Back to blog

A Complete Guide to Selecting the Right PACS Model

A Complete Guide to Selecting the Right PACS Model
A Complete Guide to Selecting the Right PACS Model:

The field of medical imaging is ever evolving, and with it, the technologies that drive its progress. At the heart of this evolution lies Picture Archiving and Communication Systems (PACS), playing a pivotal role in storing, retrieving, presenting, and sharing medical images. As we advance further into the digital age, the deployment of PACS comes in various formats: traditional on-premises setups, cloud-based solutions, and hybrid models. Each format offers distinct advantages, disadvantages, and suitability for specific scenarios. Understanding the nuances between these architectures has become crucial to optimizing efficiency, safeguarding patient data, and ensuring regulatory compliance. 

This article intends to offer in-depth comparisons of on-premises, cloud-based, and hybrid PACS models. We assess elements including affordability, security, scalability, data accessibility, and flexibility. Our mission is to support healthcare executives, IT specialists, and physicians in making well-informed decisions that align with the demands and long-term goals of their organizations. To achieve this, we provide an unbiased analysis showing no preference for any PACS deployment options. Our goal is to present a transparent evaluation by weighing the advantages, disadvantages, and potential challenges associated with each option. By doing so, we hope to empower our readers with the necessary knowledge to make the best PACS model choice for their specific healthcare institution. 

By delving into each model's distinctive features, we aim to stimulate a discourse that will guide future PACS deployment strategies in an increasingly digital, patient-centric healthcare landscape. The narrative of this article underscores that there is no one-size-fits-all solution when it comes to PACS; instead, the optimal solution depends heavily on the specific goals, resources, and constraints inherent to each healthcare institution.  

 On-site PACS  

Onsite PACS are PACS installed on-site, within the premises of a healthcare facility. They consist of hardware components such as servers, storage devices, and workstations, as well as software components like image management software and viewing applications. Onsite PACS are typically managed and maintained by the IT staff of the healthcare facility. Here are several benefits of onsite PACS: 

  1. Control: On-site PACS give organizations complete control over their data, hardware, software, and system configuration. This allows them to tailor the system to their specific needs and preferences. 
  2. Data Security: With an on-premise PACS, data remains within the organization's physical and network boundaries. This potentially reduces the risk of data breaches, especially when robust internal security measures are in place. 
  3. Performance: Given the proximity of the servers, on-premise PACS can offer high-speed, reliable performance with low latency, especially crucial in time-sensitive healthcare settings. 
  4. Customizability: On-premise systems can be customized to a far greater extent than cloud-based or hybrid solutions. It can accommodate unique workflows, integrate with other systems, and adhere to specific organizational policies. 
  5. Compliance: With data stored on-site, organizations can ensure they meet specific industry regulations and compliance requirements that may not be guaranteed with off-site solutions. 
  6. Predictable Costs: Although the upfront costs can be high, the ongoing costs of on-premise PACS are usually predictable, with fewer surprises related to bandwidth usage or data storage than with cloud-based solutions. 
  7. Reduced Dependency: With an on-premise PACS, organizations are less dependent on internet connectivity and the uptime of cloud service providers. Data access and system performance are not contingent on external factors beyond the organization's control. 
  8. Data Sovereignty: On-site PACS ensure that data remains within the geographic boundaries of the organization, avoiding potential legal and regulatory complications associated with data crossing international borders, as it might with some cloud providers. 
  9. Long-Term Investment: While on-premise PACS entail substantial upfront costs, they can prove to be cost-effective in the long run for organizations with large amounts of data and sufficient resources to manage the system. 
  10. Physical Access: Having physical access to servers can facilitate certain types of maintenance and troubleshooting tasks, potentially allowing for quicker resolution of hardware issues. 
  11. Speed: Onsite PACS provide fast access to medical images, as the images are stored locally. This is particularly important in emergency situations where quick diagnosis and treatment are critical. 
  12. Customization: Onsite PACS can be customized to meet the specific needs of the healthcare facility. This includes the ability to integrate with other systems, such as Electronic Medical Records (EMR) and Radiology Information Systems (RIS).

Benefits of an Onsite PACS

On-premise PACS, though often preferred for the level of control and potential customization they offer, can come with a series of disadvantages that organizations need to carefully consider. 

  1. High Initial Costs: The upfront costs of implementing an on-premise PACS can be significant. These expenses include the cost of server hardware, networking equipment, storage devices, backup systems, and necessary software. Additionally, there are costs related to the physical space needed to house this infrastructure, including suitable cooling and power systems to ensure its optimal operation. 
  2. Maintenance Costs: On-premise systems require regular maintenance, upgrades, and replacements, all of which can be costly. There are also the ongoing costs for electricity, cooling, and IT personnel necessary to manage and maintain the system. 
  3. Scalability Issues: If an organization's storage needs to grow, it may need to purchase additional hardware and software, which can be expensive and time-consuming. Conversely, if storage needs to decrease, the organization may be left with unused, depreciating assets. 
  4. Disaster Recovery and Backup: On-premise PACS often require a comprehensive, often expensive, disaster recovery plan to protect against data loss from hardware failures, natural disasters, or other unforeseen circumstances. Backups often require additional hardware and off-site storage. 
  5. IT Expertise Required: On-premise PACS necessitate a high level of IT expertise to manage and troubleshoot the system. For many organizations, particularly smaller ones, it may be challenging to find and retain such expertise. 
  6. Depreciation and Obsolescence: Technology depreciates over time and can become obsolete. On-premise hardware and software require regular upgrades to stay current with technological advances and to maintain compatibility with other systems. 
  7. Security Concerns: Although on-premise PACS offer the potential for high security, achieving this requires substantial investment in security technologies and expert personnel. Without these, on-premise systems can be vulnerable to both internal and external threats. 
  8. Limited Accessibility: Unlike cloud-based systems, access to on-premise PACS is typically limited to the physical location of the servers, making remote access more challenging. 

Cloud PACS

Cloud PACS are PACS hosted on remote servers, typically in a data center. Medical images are uploaded to the cloud and accessed using a web-based viewer. Here are some of the benefits of cloud PACS: 

  1. Scalability: Cloud PACS allows organizations to easily scale up or down based on their current storage needs, providing flexibility and efficiency. 
  2. Cost Savings: Cloud PACS can potentially reduce both upfront and ongoing costs, as they typically operate on a pay-as-you-go model, eliminating the need for costly hardware, maintenance, and IT staffing.
  3. Disaster Recovery: Cloud providers typically offer robust data backup and disaster recovery solutions, protecting against data loss from various unforeseen events. 
  4. Accessibility: With a cloud-based PACS, authorized users can access data from anywhere at any time, if they have internet connection. 
  5. Up-to-Date Technology: Cloud PACS providers generally ensure that their technology is up-to-date, sparing organizations the trouble and expense of performing their own upgrades. 
  6. Security: While security is a complex issue with both pros and cons, many cloud providers offer high-level security measures including encryption and strong access controls. 
  7. Collaboration: The cloud facilitates collaboration by enabling simultaneous, real-time access to images and data by multiple authorized users regardless of location. 
  8. Reduced IT Burden: With a cloud-based PACS, much of the burden of maintaining the system falls on the provider, freeing up the organization's IT resources. 
  9. Predictable Pricing: Many cloud PACS offer predictable monthly or annual pricing based on usage, making budgeting easier. 
  10. Sustainability: By reducing the need for physical servers, cloud PACS can be a more environmentally friendly choice, reducing the organization's energy use and physical waste. 

Benefits of a Cloud PACS

Here are 10 potential disadvantages of a Cloud PACS:

  1. Dependency on Internet Connectivity: Cloud PACS require reliable, high-speed internet connections. Interruptions in connectivity or slow connections can hinder access to data and system performance. 
  2. Potential Cost Overruns: While cloud PACS can offer cost savings, costs can also escalate if not properly managed. Data transfer costs, particularly for large image files can add up, and increasing storage needs can raise costs over time. 
  3. Security Concerns: While many cloud providers offer robust security measures, the fact that data is stored off-site may raise concerns about data breaches. Additionally, multi-tenancy in cloud environments can potentially increase security risks. 
  4. Data Sovereignty: Data stored in the cloud may reside in different geographical locations, potentially raising legal and regulatory issues related to data sovereignty and privacy. 
  5. Vendor Lock-in: Switching between cloud providers can be challenging and costly due to differences in standards and APIs, potentially leading to vendor lock-in. 
  6. Limited Control and Customizability: With a cloud PACS, the organization may have less control over system configuration and limitations on customization compared to an on-premise solution. 
  7. Compliance: Depending on the location of the data centers and the specific practices of the cloud provider, there may be challenges in complying with regulations like HIPAA or GDPR. 
  8. Performance: While cloud providers generally offer high-performance systems, there can be latency issues, particularly when dealing with large medical imaging files. 
  9. Data Migration: Moving existing data from an on-premise PACS to a cloud-based system can be a complex and time-consuming process.
  10. Support Issues: Depending on the service level agreement with the provider, there may be issues with support, including potential delays or difficulties in resolving issues. 

In summary, the comparison between onsite PACS and cloud PACS underscores their respective merits within the field of radiology. With rapid image retrieval, heightened security, and tailored configurations, onsite PACS offers distinct advantages. Conversely, cloud PACS deliver enhanced accessibility, scalability, and economic viability. Deciding between these two hinges on the distinct requisites and assets of the healthcare establishment; cloud PACS might emerge as the prudent choice for resource-constrained facilities, whereas onsite PACS could be favored by those placing a premium on security protocols. 

The last model to examine is the Hybrid model, where a server is placed both onsite and offsite. Hybrid model is typically configured as a Cache onsite and cloud server where there is unidirectional communication.  It can also be configured to have identical servers onsite and in the cloud. These servers are configured to communicate asynchronously in real time. When the hybrid model runs asynchronously and the cache model uses unidirectional replication, the way data is stored, processed, and synchronized between the servers will change. Let us discuss how these changes affect each model: 

Asynchronous Hybrid Server Model is when the hybrid model runs asynchronously, it means that data is updated between the cloud server and the onsite server at different times, without waiting for an immediate response from the other server. This can lead to temporary inconsistencies between the two servers, but they will eventually synchronize. 

Hybrid-Cache Model


  1. Simplicity: Unidirectional replication is easier to set up and manage compared to bidirectional replication, as data only flows in one direction. 
  2. Readability: If the cloud is inaccessible, you can read off the Cache server. 
  3. Improved Performance: Frequently accessed data is stored on the onsite cache server, reducing the need to constantly fetch data from the cloud server. This reduces latency and improves overall performance. 
  4. Reduced Bandwidth Usage: As the cache server stores frequently accessed data, the amount of data being transferred between the cloud server and onsite server is reduced, leading to lower bandwidth usage. 
  5. Cost Efficiency: Storing less frequently accessed data in the cloud can help save costs on storage and maintenance, while the onsite cache server can be smaller and less resource intensive. 
  6. High-Speed Buffer: In the Onsite Cache Server and Cloud Server model, the cloud server is the primary data storage and processing location, while the onsite cache server is used to store frequently accessed data temporarily. The cache server acts as a high-speed buffer between the users and the cloud server. 

Benefits of a Hybrid-Cache Model

  1. Data Inconsistency: Temporary data inconsistencies can occur between the cloud and onsite servers until they synchronize. This can be a concern in situations where real-time data consistency is crucial. 
  2. Delayed Updates: Cache Model with Unidirectional Replication in this case, the cache model uses unidirectional replication, meaning that data flows in a single direction from the cloud server to the onsite cache server. The cache server receives updates from the cloud server but does not send any updates back. This means that the cache server only stores a read-only copy of frequently accessed data. 
  3. Limited Flexibility: The cache server primarily acts as a read-only storage, and any changes made to the data on the cache server will require manual syncing to the cloud server. This can limit the flexibility and use cases for the cache server. 
  4. Higher Initial Cost: Onsite site server and storage resources will be required. 

Hybrid-Asynchronous Model 

A Hybrid-Asynchronous Model for a Picture Archiving and Communication System (PACS) represents a unique blend of on-premise and cloud-based storage systems, attempting to bring together the best of both worlds. 

In this model, part of the data storage and management occurs on local servers (on-premise) and part on a cloud-based server. The specific division between on-premise and cloud storage can vary based on the needs and preferences of the organization. It involves keeping frequently accessed or particularly sensitive data on-premise while less frequently accessed data is stored in the cloud. 

The term "asynchronous" in this context usually refers to how data is transferred and synchronized between the on-premise and cloud-based components of the system. Rather than simultaneously updating data in both locations (a synchronous approach), an asynchronous model updates the data at different times. This could be done based on a schedule or specific triggers, such as when data reaches a certain age or has not been accessed for a specified period. 

The Hybrid-Asynchronous Model can provide increased flexibility, scalability, and cost-effectiveness compared to a purely on-premise or cloud-based PACS. By keeping frequently accessed data on-premise, organizations can ensure fast, reliable access to that data, while also benefiting from the broader accessibility and scalability of cloud storage. 

However, this model also comes with its own challenges. It can be more complex to manage and secure, and it requires careful planning and coordination to ensure that data remains synchronized and accessible when needed. As with any technology decision, healthcare organizations must weigh these factors against their specific needs, resources, and strategic objectives when considering a Hybrid-Asynchronous Model for PACS. 

  1. Scalability: A Hybrid PACS model provides the flexibility to scale resources up or down as needed. This is particularly useful when dealing with fluctuating demand. 
  2. Cost-Efficient: By balancing on-premise and cloud storage, organizations can optimize their costs by keeping frequently accessed data on-site and moving older less frequently accessed data to the cloud.
  3. High Availability: This model provides high availability as data can be accessed both from the on-premise servers and the cloud. If one system encounters issues, the other can serve as a reliable backup. 
  4. Disaster Recovery: Hybrid systems offer robust disaster recovery solutions. With data stored in multiple locations, the risk of total data loss is significantly reduced. 
  5. Security: The Hybrid PACS model allows sensitive data to be kept on-premise while other data is stored in the cloud, giving organizations greater control over their data security.
  6. Performance: Frequently used data can be kept on-premise for fast access, while the cloud component offers the benefit of remote accessibility. This balance can result in optimal performance. 
  7. Flexibility: A hybrid approach allows an organization to tailor their PACS according to their specific needs and adjust over time as those needs change. 
  8. Regulatory Compliance: The hybrid model can help meet regulatory compliance by allowing sensitive data to be stored on-premise (meeting data sovereignty requirements) while taking advantage of the cloud's flexibility for other data
  9. Innovation Opportunities: By freeing up on-premise resources, a Hybrid PACS can provide more room for innovation in the organization's IT infrastructure. 
  10. Smooth Transition: For organizations transitioning from a fully on-premise system, a hybrid model allows them to move to the cloud at their own pace, reducing potential disruption. 

Benefits of a Hybrid-Asynchronous Model

While the Hybrid-Asynchronous Model for PACS presents numerous benefits, it is equally important to consider the potential challenges. Here are 10 possible disadvantages to this approach: 

  1. Complexity: A hybrid PACS model can be more complex to manage than a purely on-premise or cloud-based system because it requires managing and coordinating two different environments. 
  2. Cost Management: While a hybrid approach can be cost-effective, it may also lead to unexpected costs if not properly managed. These costs could include data transfer charges and costs associated with maintaining two different environments. 
  3. Security Concerns: While a hybrid model can offer increased control over data, it also introduces additional security considerations, as data must be protected in both on-premise and cloud environments. 
  4. Data Synchronization: Keeping data synchronized between the on-premise and cloud components of a hybrid PACS can be a challenging task. This could potentially lead to data discrepancies. 
  5. Interoperability: There may be compatibility issues between on-premise and cloud components, particularly if they are from different vendors. 
  6. Vendor Lock-In: Similar to cloud PACS, a hybrid model may also lead to vendor lock-in, making it difficult to switch vendors due to differences in standards and APIs. 
  7. Network Dependency: While less reliant on network connectivity than a fully cloud-based system, a hybrid PACS still requires a reliable internet connection for the cloud component. 
  8. Compliance: Compliance can be more challenging in a hybrid environment, as regulations must be met for both on-premise and cloud storage. 
  9. Data Management: Effective data management can be more complex and time-consuming in a hybrid system, requiring the classification and organization of data based on where it should be stored and accessed. 
  10. Support and Expertise Requirements: A hybrid PACS requires IT personnel to have knowledge and skills in managing both on-premise and cloud environments. Adequate support from vendors or external IT specialists might be required, which could potentially increase costs. 

Lifetrack in Action

In conclusion, the selection between onsite PACS and cloud PACS is intricately tied to the unique requirements and available resources of each healthcare facility. Therefore, it is essential that healthcare providers tailor their PACS implementation plan to fit their unique needs and be aware of the potential for technological disruption and costs associated with PACS. 

Common Myths 

Common myths associated with onsite PACS, Cloud PACS, and hybrid models in healthcare imaging management often revolve around misconceptions regarding their functionality, security, implementation and compliance. Below are some of the most common Myths about each PACS model: 

All PACS are made the same: While PACS systems share a common purpose of managing medical images, they are not all made the same. Healthcare organizations must carefully evaluate their requirements, conduct thorough research, and consider factors such as features, integration capabilities, scalability, support, and regulatory compliance when selecting a PACS solution that best fits their needs.

You need AI to operate at peak performance: AI can offer significant benefits for PACS systems, it is not a prerequisite for PACS to operate at peak performance. Healthcare organizations should carefully evaluate their needs, consider the potential benefits and challenges of AI integration, and explore alternative solutions to optimize PACS functionality and performance based on their specific requirements.

Even Cloud deployments require hardware to be deployed onsite: There are many vendors who prefer that you add an onsite appliance that will send your DICOM to their cloud. In this method your data is encrypted through TLS. In many instances there is an additional monthly charge for the software, it also means the vendor does not need to build or maintain any VPNs. Sending from any site to a cloud through a VPN secures transmission and eliminates the need for any onsite hardware. 

You can only deploy an HL7 (ORM/ORU) if have an onsite deployment: You can deploy an HL7 regardless of PACS location.  Regardless of how you have your architecture it is important to connect to your vendors early to ensure compatibility and costs.  

Cloud PACS are not secure: Cloud PACS providers use a variety of security measures to protect patient data, including encryption, access control, and audit logging. In fact, cloud PACS are often more secure than traditional on-premises PACS, which can be vulnerable to cyberattacks. 

Cloud PACS are too expensive: Cloud PACS pricing has become increasingly competitive in recent years, and there are now several affordable options available. Additionally, cloud PACS can help organizations to save money on IT costs, such as hardware maintenance and software upgrades. 

Cloud PACS are difficult to use: Cloud PACS are designed to be user-friendly, even for users with no prior experience with medical imaging systems. Most cloud PACS providers also offer comprehensive training and support to help users get started. 

Cloud PACS are not reliable: Cloud PACS providers offer high levels of uptime and reliability. Additionally, cloud PACS are typically backed up by multiple data centers, so that data is not lost in the event of a disaster. 

Cloud PACS are not scalable: Cloud PACS are highly scalable and can be easily scaled up or down to meet the needs of your organization. This can be especially beneficial for organizations that are experiencing rapid growth. 

Cloud PACS are not HIPAA compliant: Cloud PACS providers must comply with HIPAA regulations to protect patient data. Additionally, many cloud PACS providers offer HIPAA compliance services to help organizations meet their HIPAA requirements. 

Cloud PACS are not suitable for all organizations: Cloud PACS are suitable for organizations of all sizes, from small practices to large hospitals. In fact, cloud PACS can be especially beneficial for small practices, as they can help to reduce IT costs and improve efficiency. 

Cloud PACS are a new technology: Cloud PACS have been around for over a decade and are now a mature and well-established technology. Many healthcare organizations have already successfully transitioned to cloud PACS. 

On-site PACS are more secure than cloud-based PACS: While on-site PACS can be secure, they are also vulnerable to cyberattacks. In fact, on-site PACS have been the target of a number of high-profile cyberattacks in recent years. On the other hand, cloud-based PACS providers use a variety of security measures to protect patient data, including encryption, access control, and audit logging. Additionally, cloud-based PACS are typically backed up by multiple data centers, so that data is not lost in the event of a disaster. 

On-site PACS are more reliable than cloud-based PACS: On-site PACS can be reliable, but they are also susceptible to hardware failures and other disruptions. Cloud-based PACS, on the other hand, offer high levels of uptime and reliability. Additionally, cloud-based PACS providers have teams of experts who are constantly monitoring and maintaining their systems. 

On-site PACS are more scalable than cloud-based PACS: On-site PACS can be difficult and expensive to scale. Cloud-based PACS, on the other hand, are highly scalable and can be easily scaled up or down to meet the needs of your organization. This is especially beneficial for organizations that are experiencing rapid growth. 

On-site PACS are more cost-effective than cloud-based PACS: On-site PACS can be expensive to purchase and maintain. Cloud-based PACS, on the other hand, are typically more affordable, and can be paid for on a subscription basis. Additionally, cloud-based PACS can help organizations to save money on IT costs, such as hardware maintenance and software upgrades. 

On-site PACS are more user-friendly than cloud-based PACS: On-site PACS can be complex and difficult to use, even for experienced users. Cloud-based PACS, on the other hand, are designed to be user-friendly, even for users with no prior experience with medical imaging systems. Additionally, cloud-based PACS providers offer comprehensive training and support to help users get started. 

On-site PACS are more suitable for all organizations: Cloud-based PACS are suitable for organizations of all sizes, from small practices to large hospitals. On-site PACS, on the other hand, can be especially expensive and complex for small practices to manage. 

Hybrid PACS models are too complex: Hybrid PACS models can be more complex to implement and manage than traditional on-site or cloud-based PACS. However, there are a number of vendors that offer hybrid PACS solutions that are designed to be easy to implement and manage. Additionally, these vendors offer comprehensive support to help users get started and keep their systems running smoothly. 

Hybrid PACS models are not secure: Hybrid PACS models can be just as secure as traditional on-site or cloud-based PACS. In fact, some hybrid PACS solutions offer enhanced security features, such as multi-factor authentication and data encryption. Additionally, hybrid PACS models allow organizations to store their most sensitive data on-site, while still having the flexibility to access their data from anywhere in the world. 

Hybrid PACS models are not scalable: Hybrid PACS models are highly scalable and can be easily scaled up or down to meet the needs of your organization. This is especially beneficial for organizations that are experiencing rapid growth. 

Hybrid PACS models are not cost-effective: Hybrid PACS models can be more cost-effective than traditional on-site or cloud-based PACS, especially for organizations that have a large volume of data to store and manage. Hybrid PACS models also allow organizations to save money on IT costs, such as hardware maintenance and software upgrades. 

Hybrid PACS models are only suitable for large organizations: Hybrid PACS models are suitable for organizations of all sizes, from small practices to large hospitals. In fact, hybrid PACS can be especially beneficial for small practices, as they can help to reduce IT costs and improve efficiency. 

  1. Johnson, A. J., Chen, M. Y., Swan, J. S., Applegate, K. E., & Littenberg, B. (2001). Radiology house staff satisfaction with picture archiving and communication systems: An analysis using the Herzberg motivation-hygiene theory. Journal of Digital Imaging, 14(3), 195-200.
  2. Pandey, A. K., Venkatraman, B., & Agrawal, R. (2014). Comparison of onsite and cloud-based PACS in a tertiary hospital: A retrospective evaluation from India. Journal of Medical Systems, 38(9), 87.
  3. Goyen, M., Woesner, R., Achenbach, S., Stoeckelhuber, B. M., & Wittenberg, G. (2001). A hybrid PACS architecture for the integration of RIS, HIS, and EMR based on HL7 V3. Journal of Digital Imaging, 14(3), 139-147.
  4. Khadanga, S., Singh, B., & Gupta, A. K. (2014). Cloud-based PACS: A feasibility study in India. Journal of Digital Imaging, 27(5), 638-643.
  5. Kawamoto, K., Houlihan, C. A., Balas, E. A., & Lobach, D. F. (2005). Improving clinical practice using clinical decision support systems: a systematic review of trials to identify features critical to success. BMJ, 330(7494), 765.