Harald Busse1, Josephin Otto1, Alexander Schaudinn1, Nicolas Linder1, Nikita Garnov1, Minh Do2, Roman Ganzer2, Jens-Uwe Stolzenburg2, Lars-Christian Horn3, Thomas Kahn1, and Michael Moche1
1Diagnostic and Interventional Radiology Department, Leipzig University Hospital, Leipzig, Germany, 2Urology Department, Leipzig University Hospital, Leipzig, Germany, 3Institute of Pathology, University of Leipzig, Leipzig, Germany
Synopsis
Multiparametric MRI (mpMRI)
has been shown to improve detection, localization and characterization in
patients with suspected prostate cancer (PCa). The Prostate Imaging Reporting
and Data System (PIRADS) aims to establish corresponding technical parameters
and simplify reporting. While computer-aided evaluation (CAE) technology is not
required for prostate mpMRI interpretation, the current PIRADS guideline (v2) also states that
CAE may improve workflow, provide quantitative perfusion data, enhance
discrimination performance for less experienced radiologists and also
facilitate integration of MRI data for some biopsy systems. The goal of this
work was to demonstrate relevant features and benefits of an investigational
PC-based CAE tool.
Purpose
Multiparametric MRI (mpMRI) has
been shown to improve detection, localization and characterization in patients
with suspected prostate cancer (PCa). The Prostate Imaging Reporting and Data
System (PIRADS) aims to establish technical parameters and simplify reporting
for mpMRI. While computer-aided evaluation (CAE) technology is not required for prostate
mpMRI interpretation, the current PIRADS guideline (v2, 2015) also states that
CAE may improve workflow, provide quantitative perfusion data and enhance
discrimination performance for less experienced radiologists and can also
facilitate integration of MRI data for some biopsy systems [1]. The goal of
this work was to illustrate and report on features and benefits of an investigational
PC-based CAE tool for mpMRI of the prostate.
Materials and Methods
The custom-made
software was developed under IDL (Exelis VIS, Boulder, CO) and runs under a
freely available virtual machine. It consists of a preparation tool that automatically
identifies all mpMRI data from randomly ordered/ named DICOM input data and
places them into key folders (labelled _ADC, _DCE, _DWI and _T2W) along with the
original (renamed) series folders (e.g., #013 – ep2d_diff_b50_500_800). Standardized
file names are built from the DICOM tag entries patient name, slice and
acquisition number (e.g., Doe, John – SlcAcq=013.005 for 5th DCE time
point of slice #13). The workflow of the CAE tool is shown in Fig. 1. A
screenshot of the user interface is shown in Fig. 2. Figure 3 illustrates how sigmoid
function and linear fits (to delayed phase) are used to compute
semiquantitative DCE maps from the corresponding time curves (pixel by pixel). Heuristic
filtering is used to improve visual map appearance (suppress areas with
implausible results, e.g., very low contrast enhancement CE or long arrival time Δt).
Our mpMRI protocol (3 T, Magnetom Tim Trio, Siemens) minimally involved T2W,
DWI and DCE, in accordance with PIRADS v2.
Results
Illustrative cases
with proper histological validation (under IRB approval, with informed consent)
were selected from over 200 mpMRI datasets; a sample case is shown in Fig. 4. Pixel-based
computation of the DCE maps took about 45 s for a typical dataset (18 slices,
20 time points) on a quad-core CPU (Intel i7). The tool can be readily implemented
on any PC. Compressed images should be preprocessed by a client or additional
IDL tool. The main users (3 and 5 years’ experience in prostate mpMRI) considered
navigation between slices, time points and b‑values to be intuitive. In
combination with fully automatic processing, also of multiple patients (batch
mode), the tool was found to be highly beneficial for the radiological workflow.
All major processing and visualization parameters could be easily configured in
a simple text file. Simultaneous display may facilitate PIRADS assignment around
scores of 3 or in cases with equivocal findings between dominant and subsequent
sequence (DWI<> T2W) under v2. DCE maps with interactive time curves (raw
data) were found to increase confidence in dominant T2W and DWI/ADC sequences
and also assist with visual correction of potential motion between sequences (Fig.
4). In addition, this tool also accounts for potential slice offsets (different
thickness or gap) between sequences.
Conclusions
The presented CAE tool can
be used on any PC and may provide an improved workflow for the display, analysis,
interpretation and communication of mpMRI data of the prostate, in particular
for equivocal findings and less experienced radiologists. As an investigational
tool, it does not provide the full range of certified products nor replace
them.
Acknowledgements
No acknowledgement found.References
[1] PIRADS v2: http://www.acr.org/~/media/ACR/Documents/PDF/QualitySafety/Resources/PIRADS/PIRADS%20V2.pdf
(accessed on 11/10/2015)