Three-dimensional assessment of MR imaging-guided percutaneous cryotherapy using multi-performer repeated segmentations: the value of supervised learning.

RATIONALE AND OBJECTIVES: Accurate and reproducible segmentations of two-dimensional images are an important prerequisite for assessing tumor ablations three dimensionally (3D). We evaluated whether supervised learning methods would improve multiperformer repeated segmentations of magnetic resonance images (MRI) obtained before and after MRI-guided cryotherapy of renal cell carcinoma. MATERIALS AND METHODS: Three medical students independently performed five manual segmentations of a biopsy-proven renal cell carcinoma that was treated with percutaneous MRI-guided cryotherapy. Using pretreatment (T2-weighted fast recovery fast spin echo [FRFSE]) and posttreatment (T1-weighted, fat-suppressed, dynamically enhanced) MRIs, regions of tumor cryonecrosis were segmented. The same tasks were repeated after an experienced abdominal radiologist provided supervised learning. Segmentation sensitivity was compared with an estimated 3D-ground truth via voxel counts for regions of tumor, both before and after treatment, and for the regions of cryonecrosis. The sensitivity of each repeated segmentation was compared against the estimated ground truth using sensitivity, overlap index, and volume (mL). RESULTS: Supervised learning significantly improved posttreatment segmentation sensitivity (P = .03). With supervised learning, the ranges of the performance metrics over the segmentation performers were: pretreated tumor, sensitivity 0.902-0.999, overlap index 0.935-0.961, and volume 19.15-23.71 mL; posttreated tumor, sensitivity 0.923-0.991, overlap index 0.952-0.981, and volume 20.67-22.70 mL; in the ablation zone, sensitivity 0.938-0.969, overlap index 0.940-0.962, and volume 31.79-32.36 mL. CONCLUSIONS: Supervised learning improved multiperformer repeated segmentations of MRIs obtained before and after MRI-guided percutaneous cryotherapy of renal cell carcinoma. These methods may prove useful in aiding the 3D assessment of percutaneous tumor ablations.

Regulation of IDO-mediated bacteriostasis in macrophages: role of antibiotics and anti-inflammatory agents.

Induction of IDO is also under strict control by the immune system and we have previously shown that there are a number of cytokines involved in the down-regulation of IDO induction. In clinical practice anti-inflammatory substances and antibiotics are commonly used and may influence the outcome of bacterial infection. We analysed the IFNgamma-dependant IDO induction and bacteriostasis of Staphylococcus aureus and Group A Streptococcus (GAS) in monocyte-derived-macrophages (MDM) from cord blood and peripheral blood of healthy adult donors with attention to the effect of down-regulatory cytokines and of two commonly used anti-inflammatory agents, hydrocortisone and indomethacin, on both IDO activity and bacterial growth. In addition to this we were interested in the effect of sub-inhibitory concentrations of the antibiotic ampicillin on this IDO-mediated effect, the premise being that for a substantial period of antibiotic therapy the infection site is exposed to sub-inhibitory concentrations of antibiotic. We found that after stimulation with IFNgamma, MDM inhibited streptococcal growth. This was due to IFNgamma-induced IDO activity as demonstrated by reconstitution of growth by supplemental tryptophan. This IDO-mediated bacteriostasis was inhibited by the cytokines IL-10, IL-4 and TGFbeta. Furthermore, addition of indomethacin to IFNgamma stimulated MDM also resulted in the abrogation of the IDO-induced bacteriostasis, a result of the inhibition of IDO induction. Surprisingly, co-stimulation with hydrocortisone and IFNgamma apparently increased the IDO activity in cord blood MDM, but had no effect on the IDO-activity of adult peripheral blood MDM. Bacteriostasis in cord blood MDM, on the other hand, was not affected by co-stimulation with hydrocortisone. Ampicillin, in sub-inhibitory concentrations had no effect on the IDO activity itself but did have a synergistic effect on the IDO-induced bacteriostasis in MDM cultures. We conclude that therapy with indomethacin may increase the risk of clinically important bacterial infection due to the inhibition of the IDO-induced bacteriostasis. In addition sub-inhibitory concentrations of ampicillin may play a role in the area of infection where IFNgamma stimulated macrophages are to be found in abundance.