Mobile Mammography with DICOM Capacitor

This document describes the key functions of DICOM Capacitor (also known as the 'Flux Box' by Flux Inc.) for mobile mammography. As a smart DICOM store-and-forward router, it ensures reliable data handling and smooth integration with hospital Picture Archiving and Communication System (PACS) and Worklist servers.

The Challenge

Mobile units face challenges including:

• Unreliable or expensive cellular networks for large image transfers, especially for tomosynthesis studies.
• Needing access to patient worklists even when offline.
• Transferring images to PACS in a timely manner for radiologists to read.
• Using bandwidth efficiently when connected.
• Integrating smoothly with multiple facility PACS systems across different sites.

Capacitor addresses these issues using smart caching, network-aware operations, scheduling, and compression.

Key Entities

For the diagrams below, the key entities are:

• Mammo: The mobile imaging unit and workstation.
• Flux Box: The Flux DICOM Capacitor installed on a NUC mini device, mounted on the Mammo Truck.
• Worklist/PACS: Hospital central systems, including the DICOM Worklist server and the PACS/VNA for image storage and access.

Key Functions

1. Smart Caching of Images During Exams

Capacitor caches images from the mammography unit directly on the Flux Box in the mobile truck. This ensures all exam data is stored locally as it is captured, regardless of network status. It queues images for transfer and automatically retries failed transfers to ensure data integrity.

2. Scheduled Transfers During Optimal Connectivity

To avoid transferring large image files over unreliable or costly cellular connections, Capacitor can transfer cached images during optimal times. This typically occurs when the mobile unit returns to base with a stable, high-bandwidth connection (like Wi-Fi) or during off-peak hours.

Note: Capacitor can limit transmission to particular blocks of time.

3. Network-Aware Transmission

Capacitor detects the network type (e.g., local facility network vs. cellular, often by subnet mask). This ensures image transfers only start on approved, high-bandwidth networks, preventing accidental data use over cellular plans while the truck is mobile.

Note: Detects local network presence by subnet mask.

4. Cached Worklist for Offline Operation

Capacitor can query and cache the DICOM Modality Worklist from the hospital's Worklist server. It pre-downloads patient details and schedules. This cached worklist is available to the mammography modality on the truck, so technologists can select patients and start exams even when offline. The worklist syncs automatically whenever the network returns.

5. Compression to Optimize Bandwidth Usage

To optimize data transfer and save storage space, Capacitor can compress DICOM images (e.g., using JPEG2000 lossless compression) before sending them to PACS. This significantly reduces image file sizes without losing diagnostic quality. JPEG2000 lossless compression, for instance, can reduce study sizes by up to 35%. This speeds up transfers and improves efficiency, especially over limited connections.

One advantage of this approach, is that compression happens asynchronously to the imaging process, so it doesn't impact the imaging workflow. By the time the images are transferred to the hospital, they are already compressed.

Combined Workflow Overview

The following diagram shows how these functions work together to support the mobile mammography workflow:

6. Optional Prior Study Pre-fetching

Optionally, Capacitor can send DICOM Query/Retrieve (C-FIND/C-MOVE) requests to the hospital PACS/VNA. Patient data from new studies triggers this. This pre-fetches relevant prior studies to the central PACS/VNA for radiologists to use for comparison. Prior studies are pre-fetched to central hospital systems only, not back to the mobile unit.