### 1.1 Image Processing and Analysis for Preclinical and Clinical Applications
#### 1.1.8 Principal and Clinical Applications
Among the other research papers, four of them focus on biomedical image quantification, including the early monitoring response to therapy in patients with brain lesions [17], the quantification of cancer cell mass evolution in zebrafish [18], the clinical comparison of the glomerular filtration rate calculated from different renal depths and formulae [19], and the assessment of the left atrial flow stasis in patients undergoing pulmonary vein isolation for paroxysmal atrial fibrillation [20]. [PERSON] et al. [17] evaluated new PET prognostic indices for the early assessment of response to Gamma Knife (GK) treatment. GK is an alternative to traditional brain surgery and whole-brain radiation therapy for the treatment of tumors inaccessible through conventional treatments [21]. Semi-quantitative PET parameters currently used in the clinical setting can be affected by statistical fluctuation errors and/or cannot provide information on tumor extent and heterogeneity. To overcome these limitations, the cumulative standardized uptake value histogram (CSH) and AUC were considered as additional information on the response to GK treatment. Specifically, the absolute level of [11C]-Methionine (MET) uptake was measured and its heterogeneity distribution within PET lesions was evaluated by calculating the CSH and AUC. The results showed good agreement with patient outcomes, and since no relevant correlations were found between CSH and AUC and the indices usually used in PET imaging, these innovative parameters could be a useful tool for assessing patient responses to therapy. In [18], the authors considered zebrafish as it is a model organism for the study of human cancer and, compared with the murine model, it has several properties that are ideal for personalized therapies. The transparency of the zebrafish embryos and the development of the pigment-deficient \"casper\" zebrafish line give the capacity to directly observe cancer formation and progression in the living animal. Nevertheless, the automatic quantification of cellular proliferation in vivo is still critical. For this reason, the authors proposed a new tool, namely ZFTool, to automatically quantify the cancer cellular evolution. ZFTool is capable of establishing a base threshold that eliminates the embryo autofluorescence, to automatically measure the area and intensity of green-fluorescent protein marked cells, and to define a proliferation index. As result, the proliferation index computed on different targets demonstrated the efficiency of ZFTool in providing a good automatic quantification of cancer mass evolution in zebrafish, eliminating the influence of its autofluorescence. In the study proposed by [PERSON] et al. [19], the authors aimed to compare the differences in renal depths in a camera-based method using Technetium-99 m diethylenetriaminepentaacetic acid (Tc-99 m DTPA). This method is commonly used to calculate the glomerular filtration rate (GFR) as it can easily calculate split renal function. Renal depth is the main factor affecting the measurement of GFR accuracy. For this reason, the difference in renal depths between three formulae ([PERSON]'s, [PERSON]'s, and Taylor's) and a CT scan were compared and used to calculate the GFRs using four methods. For this purpose, 51 patients underwent a laboratory test within one month and a CT scan within two months. The results showed that the renal depths measured using the three formulae were smaller than those measured using the CT scan, and the right renal depth was always larger than the left. In [20], the authors aimed to demonstrate that left atrial (LA) stasis, derived from 4D-flow, is a useful biomarker of LA recovery in patients with atrial fibrillation (AF). AF is associated with systemic thrombo-embolism and stroke events, which do not appear significantly reduced following successful pulmonary vein (PV) ablation. The authors' hypothesis was that LA recovery was associated with a reduction in LA stasis.