Modern neurosurgery is dependent on high resolution medical imaging techniques. Clinical neurosurgeons rely on precise medical imaging data and visualization in order to prepare surgery.
For planning, the surgeon:
- visualizes the brain pathology,
- identifies dangerous areas, vessels and anatomical landmarks and
- chooses the angle of attack and the necessary opening of the skull (craniotomy).
The operative approach to a brain tumor is the key to its successful treatment. Its planning is one of the most important steps before surgery commences.
What is the Data Basis?
Mostly, imaging data consists of CT scans (computed tomography) and MRI (magnetic resonance imaging) of the skull and the brain. The radiology department or the radiologist usually deliver data sets with images of axial, coronar and sagittal planes and different slice thicknesses. The surgeon can scroll the images and examine them. Such a standard image set usually consists of T1 and T2 images, a T1 sequence with contrast and some additional specific sequences. Examples are the investigation of hemoglobin concentration in blood or diffusion behavior of tissue in the brain.
The thickness of slices varies between 1 and 5 millimeters. Thickness depends on the quality of the radiologist, the technician and the MRI scanner. The thicker the slice, the faster the image acquisition, but the fewer the information for the surgeon.
Isotropic 3D data sets have the same resolution in all dimensions. They are mostly T1-weighted sequences with contrast-die. This type of data contains the most information and is the most important one for neurosurgeons in general. This so called MP-Rage is usually the basis for intraoperative neuro-navigation. All standard imaging viewers can process such images.
Important Features of Viewers in Medical Imaging for Clinicians
From the doctors perspective it is essential to always put the user and his needs in the center of medical imaging software development. Craig Schere is senior partner and co-founder of
Insight Product Development. Take a look at the following figure and consider the statements of Craig Schere as guideline for the interaction with the user.
Offer 3D-Function in a Standard PC Setup
Before surgery, the physician loads the available images to the computer. He or she then scrolls through the images to visualize the approach to the given brain pathology in all 3 axes.
The surgeon needs to avoid so-called eloquent areas. These have specific, non-redundant functions and should not be injured during surgery.
The best visualization is possible by reconstructing a 3D data set in real-time on the computer. It visualizes the data set in all three axis. The user can scroll through one dimension and see the current position in both other dimensions at the same time. Without this function, a surgeon can only view a MP-Rage data set in the plane of acquisition, mostly in the sagittal plane.
The 3D function requires sufficient computing power that must be provided by a standard desktop computer. This may sound trivial, but it is the most important feature in medical imaging software for neurosurgeons. It offers the possibility to freely define axes and sections in the imaging data set. This allows the surgeon to precisely plan the surgical procedure.
Therefore, it is not understandable that some manufacturers do not include 3D routinely in their viewing-clients.
Some manufacturers of DICOM software (Digital Imaging and Communications in Medicine) offer this function only in their basic-versions. This turns the software into a much less useful tool for neurosurgical planning. Others only allow this function in the extended (and much costlier) versions of their viewing software.
Realize the importance of the 3D function that makes the software incredibly useful for surgical planning.
Make Measuring of Free-Hand Curves Possible!
Secondly, modern medical imaging and the corresponding viewing software should allow to measure as many dimensions as possible. This includes e.g. distances and angles and Hounsfield-Units. However, when measuring distances not only straight lines should be allowed, but also consecutive lines and, most importantly, the distance of free-hand curves! Note, that the human body consists not only of parallel and perpendicular straight objects. Sometimes the surgeon must quantify a distance that includes a curve as well.
Implement measurement functions in clinical versions. Often they are simply forgotten .
Simultaneous Handling of Data Sets is Important
Thirdly, modern medicine demands consecutive imaging, e.g. repetitive MRI-studies accompanying a tumor therapy. The clinician compares baseline images with MRI sequences from several months and years later. Quickly, the user loads 4 or 5 data sets into the viewing software in order to compare them. If many image sets are loaded, they appear in the left or right column (loaded-images-section). From there they are drawn into the viewing-section.
In the loaded-images-section, they should be sorted in order of date. So the user can identify the most recent and the oldest data sets. This may sound trivial, too. But there are manufacturers which just load the image sets and pile them up in the “loaded-images-section” in random order. By this it is incredibly difficult for the user to find the most recent, second recent and oldest image set.
Instead include a function which allows the user to unload image-sets which are not needed in the specific session once they were accidentally loaded. Poor software forces the user to load another patient in order to unload the whole image set of the previous patient.
More Useful Functions to Support User Interaction
Another very useful function is the direct comparison of data sets. Some viewers allow to align one data set on top of the other and change the transparency of each data set with a slider. This allows to directly compare to data sets and see the differences by moving the roll-bar from left to the right.
A modern imaging viewer should allow to anonymously export single or whole sets of images into a picture format, powerpoint presentation or even a video.
If you want to provide a good software let the user choose which information should be included on the images!
Finally, some very good viewers include a segmentation and rendering tool allowing the user to visualize medical images as three-dimensional objects. This is both interesting for doctors to make the pathology more visible, and for patients and their relatives in order to explain a planned surgical procedure to them.
Help clinicians with the following improvements:
- Take care that the software allows the user to reconstruct 3D-images in real-time on the computer in the basic version.
- Implement distance-measuring of free-hand curves to facilitate daily work.
- Ensure that loaded image-sets are sorted by date, and don’t randomly pile them up in the list.
- Let the user unload not-needed datasets.
- Allow direct comparison of datasets by adding a function to align the sets and change their specific transparency.
- Let the user export images or image-sets with adjustable information on the images, including anonymization.
- Implement segmentation and rendering tools for making medical data more understandable for both doctors, patients and their relatives.
- Realize that most recommended improvements are more than “nice to have”. Moreover, these contribute also to patient safety and, thus, to the risk management of your medical imaging software.