Are the thousands of images generated by each ultrafast dynamic contrast enhancement (DCE) MRI of breast cancer effectively summarized by color intensity projection (CIP) images?
Keith S Cover1, Katya M Duvivier1, Pim de Graaf1, Rianne Wittenberg1, Ruth Smit1, Joost PA Kuijer1, Mark MB Hofman1, Ben J Slotman1, and Ruud M Verdaasdonk1

1VU University Medical Center, Amsterdam, Netherlands


Ultrafast dynamic contrast enhancement (DCE) is a MRI sequence that, when used standalone, can serially screen for breast cancer in 2 minutes. However, each acquisition generates thousands of 2D images in a 4D stack. Color intensity projections (CIP) images are 2 parameter color images that encode the time of arrival (ToA) of contrast agent in the hue (red, orange, yellow, green, cyan, blue) and the amount of contrast enhancement in the brightness. A CIP image of each ultrafast slice provides an informative summary to radiologists with the same sensitivity and specificity to malignancies as the ultrafast 4D stack.


Current protocols screening for breast cancer take about 20 minutes of MRI acquisition time. Abbreviated protocols are being developed that take less than 5 minutes [KuhlCK2014, HeacockL2016, MachidaY2016, MangoVL2016, MoschettaM2016] for screening women at high risk of breast cancer [KuhlCK2005, LeachMO2005, KuhlCK2010, SardanelliF2011, HeijnsdijkEA2012, PassaperumaK2012, ObdeijnIM2014, EmausMJ2015, ZelstJCM2017]. The standalone 4D ultrafast DCE MRI sequence [BoetesC1994, SardanelliF2000, SaranathanM2012, LeY2012, MannRM2014, PlatelB2014, AbeH2016, MusRD2017] takes about 4 minutes including localizers but generates thousands of images per acquisition placing a burden on radiologists. The purpose of this study was to assess whether color intensity projections (CIP) images [CoverKS2007] are an effective summary of the ultrafast 4D stack of images.


The 115 second ultrafast DCE sequence acquired 19 consecutive frames every 4.26 seconds with 152 slices per frame yielding a 4D stack with 2,888 2D images for each of water and fat. For each of the 89 patients in the study, two radiologists - with 8 and 4 years of experiences reading breast cancer MRIs respectively - recorded a BIRADS [DOrsiCJ2013] using only the CIP images first, and subsequently using both the CIP images and the 4D stack. No prior MRI images were used in the study. A total of 26 patients had malignancies. The p-value for the CIP and 4D sensitivities and specificities were calculated using the Fisher exact test [EmausMJ2015].

CIP summarizes a time series of greyscale images into a single color image by encoding the time of arrival (ToA) of contrast agent at each voxel in the hue (red, orange, yellow, green, cyan, blue) and the amount of contrast agent in the brightness. The time of arrival (ToA) of contrast agent for each voxel was defined as the frame which had the largest increase in signal from the previous frame (Figure 1). The enhancing of the aortic arch was defined as the zero frame and indicated with the red hue. The CIP images for the study were uploaded to clinical PACS so they could be read using the same PACS workstation as the clinical images but clearly labelled for research only.


For reader 1, the CIP and 4D sensitives were 96% and 96% (p=1.0) with specificities of 59% and 70% (p=0.26) respectively. The statistics for reader 2 were 96% and 100% (p=1.0) with 62% and 71% (p=0.34) specificities, respectively. Therefore, there was no statistically significant difference between CIP and 4D stack, in terms of the sensitivity and specificity, when distinguishing between malignancies and benign tumors. The readers could not assign a BIRADS score to CIP in 1 and 5 patients respectively, primarily because of enhancing background [GiessCS2014]. These undefined BIRADS scores resulted in the slightly lower sensitivities and specificities provided above.

Figures 2, 3 and 4 provide examples of CIP for two patients.


As the current study shows, CIP provides an effective summary of the thousands of images provided by each ultrafast acquisition. For each voxel, the encoding of the ToA in the hue combined with the amount of contrast agent seems to provide much of the information required by radiologist to detect malignancies while recognizing benign lesions. However, as with any processed version of the ultrafast 4D stack, the original 4D stack should always be reviewed for breast cancer screening with CIP only providing supplementary information.

While the current study was conducted without prior DCE images to aid the radiologists, with serial screening prior DCE images are readily available. Prior DCE images should significantly improve the specificity of the standalone ultrafast sequence found in the current study. The current full diagnostic protocols (FDP) for MRI screening of breast cancer has additional sequences to improve specificity when prior DCE images are not available [AbramoviciG2011]. The FDP typically includes both pre and post contrast high resolution T1 sequences, a high resolution T2 sequence, and/or a DWI sequence, and more recently, an ultrafast sequence.

While the ultrafast sequence runs in about 2 minutes, if used standalone for serial screening for breast cancer, inclusion of the localizers would bring the total acquisition time to about 4 minutes.


At one color image per slice, rather than the 10 or 20 greyscale images for the ultrafast 4D stack, and with the same sensitivity and specificity, CIP provides an effective summary of the ultrafast images for screening for breast cancer. CIP images may provide an effective assist to radiologists reading the thousands of images generated by each ultrafast DCE MRI sequence, especially when only PACS workstations - without advanced viewing tools for MRIs of breast cancer - are available.


Funded by Cancer Center Amsterdam.


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Fig 1. A CIP image for breast cancer is two parameter image composed of a brightness and hue (right). The brightness of the CIP encodes the amount of images enhancement due to contrast agent as indicated by the T1 enhanced subtracted image (left). The hue encodes the time of arrival (ToA) of the contrast agent at each voxel from the aortic arch (middle). Any voxels which are greyscale indicate the contrast agent arrived at the voxel before it arrived at the aortic arch.

Figure 2. Maximum projection intensity (MIP) through all 152 slices of CIP (a) and T1 (b) images. The T1 is 4 frames (25 s) after the contrast agent arrived at the heart. The (ToA) of the contrast agent at each voxel relative to the aortic arch is indicated by the hue. For example, the yellow and green of the lesion (arrow) indicates delays of 8.5 s and 12.8 s. The patient is 49 years and presented with a palpable mass in her right breast. Histology found a triple negative invasive carcinoma NST grade III, without lymph node metastasis (T2N0Mx).

Figure 3. CIP (a) and post contrast T1 (b) slices of a 48 year old women who attended the doctors with a palpable lesion (arrow) in the left breast, which proved to be a grade one invasive ductal carcinoma (IDC) with a diameter of 1.1 cm.

Figure 4, Same patient as Figure 3 but a different slice. The fibroadenoma (arrow) was detected by mammography and ultrasound and confirmed by pathology. The fibroadenoma is visible on the CIP (a), post contrast agent T1 (b) and is bright on the T2 (c).

Proc. Intl. Soc. Mag. Reson. Med. 26 (2018)