Top Line: Many of us are now delineating and boosting intraprostatic disease with the aid of multiparametric prostate MRI. Or at least we think we are?
The Study: ReIGNITE RT Boost was a prospective international study where 44 radiation oncologists and 2 expert radiologists contoured prostate tumors in 39 patients. One of the main goals of the study was to see if using the Restriction Spectrum Imaging restriction score (RSIrs) would improve the accuracy of prostate tumor contours compared to conventional MRI sequences. So, what is RSIrs? RSI is a diffusion-weighted MRI technique that requires just a few extra minutes of scan time (usually <5 minutes) in addition to the standard prostate MRI. These sequences are then post-processed by commercially available software to generate RSIrs maps, and they can be fused with T2 weighted images for localization. RSI has been shown to strongly correlate with prostate cancer on final pathology. When fused with T2 images, they can be displayed using a heat map that is very similar in appearance to that of PET. As you can imagine, a big glowing red spot on the MRI greatly improved contouring accuracy. All measures of contouring accuracy were improved by at least 50% with the addition of RSIrs. Of the 44 radiation oncologists, 91% completely missed at least 1 of the targets with standard MRI, but this was reduced to 30% when RSIrs was included. Of all the lesions contoured, 18% were missed with standard MRI compared to just 2% with MRI+RSIrs. Even the worst two participants, who missed 45% of targets with standard MRI, missed just 5-10% with MRI+RSIrs.
TBL: ReIGNITE emphasizes the challenges of accurately delineating prostate tumors on MRI while also showing that the use of restriction spectrum imaging maps significantly improves contouring accuracy. | Lui, Int J Radiat Oncol Biol Phys 2023
The Study: ReIGNITE RT Boost was a prospective international study where 44 radiation oncologists and 2 expert radiologists contoured prostate tumors in 39 patients. One of the main goals of the study was to see if using the Restriction Spectrum Imaging restriction score (RSIrs) would improve the accuracy of prostate tumor contours compared to conventional MRI sequences. So, what is RSIrs? RSI is a diffusion-weighted MRI technique that requires just a few extra minutes of scan time (usually <5 minutes) in addition to the standard prostate MRI. These sequences are then post-processed by commercially available software to generate RSIrs maps, and they can be fused with T2 weighted images for localization. RSI has been shown to strongly correlate with prostate cancer on final pathology. When fused with T2 images, they can be displayed using a heat map that is very similar in appearance to that of PET. As you can imagine, a big glowing red spot on the MRI greatly improved contouring accuracy. All measures of contouring accuracy were improved by at least 50% with the addition of RSIrs. Of the 44 radiation oncologists, 91% completely missed at least 1 of the targets with standard MRI, but this was reduced to 30% when RSIrs was included. Of all the lesions contoured, 18% were missed with standard MRI compared to just 2% with MRI+RSIrs. Even the worst two participants, who missed 45% of targets with standard MRI, missed just 5-10% with MRI+RSIrs.
TBL: ReIGNITE emphasizes the challenges of accurately delineating prostate tumors on MRI while also showing that the use of restriction spectrum imaging maps significantly improves contouring accuracy. | Lui, Int J Radiat Oncol Biol Phys 2023