Influence of image registration on apparent diffusion coefficient images computed from free-breathing diffusion MR images of the abdomen.

BACKGROUND: To evaluate the influence of image registration on apparent diffusion coefficient (ADC) images obtained from abdominal free-breathing diffusion-weighted MR images (DW-MRIs). METHODS: A comprehensive pipeline based on automatic three-dimensional nonrigid image registrations is developed to compensate for misalignments in DW-MRI datasets obtained from five healthy subjects scanned twice. Motion is corrected both within each image and between images in a time series. ADC distributions are compared with and without registration in two abdominal volumes of interest (VOIs). The effects of interpolations and Gaussian blurring as alternative strategies to reduce motion artifacts are also investigated. RESULTS: Among the four considered scenarios (no processing, interpolation, blurring and registration), registration yields the best alignment scores. Median ADCs vary according to the chosen scenario: for the considered datasets, ADCs obtained without processing are 30% higher than with registration. Registration improves voxelwise reproducibility at least by a factor of 2 and decreases uncertainty (Fréchet-Cramér-Rao lower bound). Registration provides similar improvements in reproducibility and uncertainty as acquiring four times more data. CONCLUSION: Patient motion during image acquisition leads to misaligned DW-MRIs and inaccurate ADCs, which can be addressed using automatic registration.

Functional imaging biomarkers for assessing response to treatment in liver and lung metastases.

Management of patients with metastatic cancer and development of new treatments rely on imaging to provide non-invasive biomarkers of tumour response and progression. The widely used size-based criteria have increasingly become inadequate where early measures of response are required to avoid toxicity of ineffective treatments, as biological, physiologic, and molecular modifications in tumours occur before changes in gross tumour size. A multiparametric approach with the current range of imaging techniques allows functional aspects of tumours to be simultaneously interrogated. Appropriate use of these imaging techniques and their timing in relation to the treatment schedule, particularly in the context of clinical trials, is fundamental. There is a lack of consensus regarding which imaging parameters are most informative for a particular disease site and the best time to image so that, despite an increasing body of literature, open questions on these aspects remain. In addition, standardization of these new parameters is required. This review summarizes the published literature over the last decade on functional and molecular imaging techniques in assessing treatment response in liver and lung metastases.

Effectiveness of semi-quantitative multiphase dynamic contrast-enhanced MRI as a predictor of malignancy in complex adnexal masses: radiological and pathological correlation.

OBJECTIVES: To determine whether threshold criteria using semi-quantitative multiphase-dynamic contrast-enhanced magnetic resonance imaging (DCE- MRI) can improve prediction of malignancy in complex adnexal masses. METHODS: MRI features of 70 complex adnexal masses with enhancing components in 63 patients were reviewed and correlated with histopathology (n = 67) or radiological follow-up (n = 3). Masses were categorised as benign (n = 34) or borderline/invasive malignant (n = 36). Borderline lesions (n = 6) were also analysed separately. Using the semi-quantitative breast analysis software, regions of interest were drawn around the most avidly enhancing component of each lesion. Maximum absolute enhancement of signal intensities (SI(max)), maximum relative enhancement (SI(rel)) and wash-in rate (WIR) were recorded. Optimal threshold criteria were established to predict borderline/invasive malignancy. RESULTS: There was a significant difference in mean SI(max) (P < 0.05), SI(rel) (P < 0.01) and WIR (P < 0.001) between benign and borderline/invasive malignant groups. A cut-off WIR ≥ 9.5 l/s had a specificity of 88% and positive predictive value of 86% for predicting malignancy, significantly better than conventional MRI (62%, P < 0.01). WIR <8.2 l/s had a negative predictive value of 94%. CONCLUSION: Threshold criteria using semi-quantitative multiphase DCE-MRI improves specificity in the prediction of malignancy in complex adnexal masses with enhancing components and is complementary to standard qualitative assessment. KEY POINTS: Semi-quantitative DCE-MRI threshold criteria are effective for predicting ovarian malignancy. The surgical approach may be altered depending on DCE-MRI threshold criteria analysis. Borderline tumours demonstrate significant overlap with benign lesions using DCE-MRI threshold criteria.

Dynamic MDCT of the pancreas: is time-density curve morphology useful for the differential diagnosis of solid lesions? A preliminary report.

PURPOSE: CT perfusion has been proposed for pancreatic lesion characterization. However, scan and analysis protocols influence numerical data. To overcome this, the purpose of our study is to evaluate the use of time-density curves obtained from MDCT perfusion of the pancreas for the characterization of normal parenchyma, adenocarcinoma, chronic pancreatitis and endocrine tumors. METHODS: 31 patients with solid pancreatic lesions and 21 patients with renal cell carcinoma underwent 64-row MDCT perfusion of the pancreas after injection of 50 cc of a 370 mg I/ml solution at 5 cc/s. 63 time-density curves were obtained from normal parenchyma (21 patients), adenocarcinoma (25), endocrine tumors (4) and atrophic parenchyma (13). Two readers independently categorized the 63 time-density curves into 4 different morphologies: normal wash-in and wash-out (A), low wash-in followed by plateau (B), low wash-in followed by faint wash-out (C) and high wash-in and wash-out (D). Interobserver agreement was calculated with kappa statistics. Fisher test was used to calculate sensitivity, specificity, positive (PPV) and negative (NPV) predictive values for each type of curve. RESULTS: Interobserver agreement was very good (Kappa=0.849). Curve A had 94.4% sensitivity, 91.1% specificity, 80.95% PPV, 97.6% NPV for 'normal parenchyma'. Curve B had 74.19% sensitivity, 93.75% specificity, 92% PPV, 78.95% NPV in diagnosing 'adenocarcinoma'. Curve C had 45.45% sensitivity, 84.62% specificity, 38.46% PPV, 88% NPV for 'chronic pancreatitis'. Curve D had 100% sensitivity, 98.33% specificity, 75% PPV, 100% NPV for 'endocrine tumor'. CONCLUSIONS: The morphology of MDCT perfusion time-density curves appears to be useful in characterizing pancreatic lesions, and might help overcome the differences in scan and postprocessing techniques.

[Correlation between pathologic features and perfusion CT of renal cancer: a feasibility study]. / Correlazione tra le caratteristiche anatomopatologiche e di TC con perfusione della neoplasia renale: studio di fattibilità.

OBJECTIVES: The computerized tomography with perfusion technique (pCT) has proved to have some potentialities in the oncologic field as a possible tool to identify neoangiogenesis in vivo. The purpose of the present job is to test the correlations existing between perfusion data and pathologic features in the evaluation of vascularization in kidney cancer. METHODS: 6 patients with clinical diagnosis of renal tumor awaiting surgical treatment underwent preoperatively pCT scans. Axial images encompassing the greatest diameter of the cancer were compared with the respective histological sections. RESULTS: A correlation between tumor histological subtype and perfusion index was observed and shown. Moreover, clear cell RCC of different Fuhrman grades showed statistically significant differences in perfusion values (T test). Specifically, high perfusion indexes were associated with high density of microvessels with abnormal architecture at the microscopic evaluation of tumor specimen. Conversely, lower perfusion index were detected in tumors with lower microvascular density. CONCLUSIONS: pCT scans can provide significant data on tumor angiogenesis and, eventually, suggest tumor histological subtype. The possibility of identifying preoperatively tumor histotype can be of particular relevance in patients with small renal tumors, suitable for minimally-invasive surgery or active surveillance program.