Mean Retention Index Research Articles

18F-FDG PET/CT feature of pancreatic adenosquamous carcinoma with pathological correlation.

To investigate 18F-FDG PET/CT feature of pancreatic adenosquamous carcinoma (PASC) in contrast with conventional pancreatic ductal adenocarcinoma (PDAC), and its correlation with pathological findings. Patients with PASC or PDAC confirmed by surgical pathology, who underwent FDG PET/CT scanning before surgical resection, were retrospectively studied. PASC group and conventional PDAC group included 13 and 104 patients, respectively. Delayed phase of PET/CT scanning was performed in 12 patients with PASC and 99 with PDAC. Maximum standardized value (SUVmax) was measured, and the mean retention index (RI) was calculated by ([PET120min SUVmax]-[PET 60min SUVmax]) ÷ PET 60min SUVmax × 100%. On PET/CT, all lesions of PASC group showed intense FDG uptake, and the SUVmax were significantly higher than the lesions of conventional PDAC group both on the early [10.43 ± 5.10 (4.37-24.00) vs. 7.31 ± 3.86 (1.93-21.08), P = 0.011] and delayed phase [13.29 ± 6.04 (5.72-28.16) vs. 8.84 ± 5.14 (1.92-27.58), P = 0.005]. On the delayed phase, all lesions of PASC group had increased SUVmax with positive RI value (27.04% ± 8.87%, 7.14-39.27%). For conventional PDAC group, 81 lesions had increased SUVmax with positive RI value (27.25% ± 19.10%, 1.09-104.49%), while eighteen (18.18%) lesions of PDAC group had slightly decreased SUVmax, and their RI value were negative (- 11.35% ± 13.50%, - 43.17 to - 0.14%). The proliferative index (Ki-67) of lesions of PASC group was positively correlated with both the early (P = 0.034, r = 0.671) and delayed SUVmax (P = 0.019, r = 0.721). The RI value of lesions with adjacent organ invasion in PASC group was significantly higher than those without invasion (33.25% ± 4.92% vs. 20.83% ± 7.49%, P = 0.007). PASC has more intense FDG uptake than conventional PDAC both on early and delayed phase. RI value of PASC was positive. Negative RI value may be helpful for differentiating PDAC from PASC. SUVmax and RI value may be helpful for prediction of its malignancy and invasion.

Positron emission tomography (15O-water, 11C-acetate, 11C-HED) risk markers and nonsustained ventricular tachycardia in hypertrophic cardiomyopathy

BackgroundThe objectives of the study were to describe positron emission tomography (PET) parameters, using the tracers 15O-water at rest/stress, 11C-acetate, and 11C-HED, with regard to nonsustained ventricular tachycardia (NSVT) in hypertrophic cardiomyopathy (HCM). PET offers quantitative assessment of pathophysiology throughout the left ventricular segments, including the endocardium/epicardium. The potential use PET in risk stratification remains to be elucidated. NSVT provides a marker for sudden cardiac death. MethodsPatients with a validated diagnosis of HCM who had an implantable cardioverter-defibrillator were interrogated at 12 months and independently of PET-examinations. ResultsIn total, 25 patients (mean age 56.8 ± 12.9 years, 76% males) were included and 10 reported NSVT. Mean myocardial blood flow (MBF) at rest was 0.91 ml/g/min and decreased at stress, 1.59 ml/g/min. The mean gradient (endocardium/epicardium quotient) at rest was 1.14 ± 0.09, while inverse at stress (mean 0.92 ± 0.16). Notably, MBF gradient at stress was significantly lower in patients with NSVT (p = 0.022) and borderline at rest (p = 0.059) while global MBF at rest and stress were not. Mean myocardial oxygen consumption (MVO2) was 0.088 ml/g/min (higher in NSVT, p = 0.023) and myocardial external efficiency 18.5%. Using 11C-HED, the mean retention index was 0.11 min−1 and a higher volume of distribution (p = 0.089) or transmural gradient of clearance rate (p = 0.061) or lower clearance rate (p = 0.052) showed a tendency of association of NSVT. ConclusionsThe endocardium/epicardium MBF gradient at stress is significantly lower in HCM patients with NSVT. This provides a novel approach to further refine risk stratification of sudden cardiac death.

Accurate analysis and visualization of cardiac 11C-PIB uptake in amyloidosis with semiautomatic software

Background11C-PIB PET is a promising non-invasive diagnostic tool for cardiac amyloidosis. Semiautomatic analysis of PET data is now available but it is not known how accurate these methods are for amyloid imaging. The aim of this study was to evaluate the feasibility of one semiautomatic software tool for analysis and visualization of 11C-PIB left ventricular retention index (RI) in cardiac amyloidosis. Methods and resultsPatients with systemic amyloidosis and cardiac involvement (n = 10) and healthy controls (n = 5) were investigated with dynamic 11C-PIB PET. Two observers analyzed the PET studies with semiautomatic software to calculate the left ventricular RI of 11C-PIB and to create parametric images. The mean RI at 15-25 min from the semiautomatic analysis was compared with RI based on manual analysis and showed comparable values (0.056 vs 0.054 min−1 for amyloidosis patients and 0.024 vs 0.025 min−1 in healthy controls; P = .78) and the correlation was excellent (r = 0.98). Inter-reader reproducibility also was excellent (intraclass correlation coefficient, ICC > 0.98). Parametric polarmaps and histograms made visual separation of amyloidosis patients and healthy controls fast and simple. ConclusionAccurate semiautomatic analysis of cardiac 11C-PIB RI in amyloidosis patients is feasible. Parametric polarmaps and histograms make visual interpretation fast and simple.

Dual-phase 18F-FDG PET/CT imaging in the characterization of pancreatic lesions: does it offer prognostic information?

The primary aim of our prospective study was to evaluate the usefulness of dual-phase F-fluoro-deoxy-glucose PET/computed tomography (F-FDG PET/CT) in the characterization of pancreatic masses. The secondary aim was to assess whether delayed imaging revealed any prognostic information. Fifty patients with periampullary or pancreatic masses on conventional imaging were included in this study. Early and delayed PET/CT was performed, followed by pathological examination in all patients. PET/CT parameters including uptake pattern, SUVearly, SUVdelayed, lesion to background ratio (L/B), and retention index (RI) were assessed for their ability to differentiate benign from malignant lesions. Patients with malignant lesions were followed up for a median duration of 26 months. The association of 11 variables with survival was analyzed by univariate and multivariate methods. Thirty-one patients had malignant lesions and 19 had benign lesions. The mean SUVearly, L/B, SUVdelayed, and RI between the malignant and benign lesions were statistically significant. The F-FDG uptake pattern of the lesions had higher sensitivity (93.5%) and specificity (100%) compared with RI (cutoff 25.7%) (84 and 37%, respectively) for diagnosing malignancy (P<0.05). In univariate analysis both RI (>18.7%) and tumor size (>2.6 cm) predicted significantly poor survival, whereas in multivariate analysis RI (P=0.04) was the only predictor of poor survival. Dual-phase F-FDG PET/CT is not useful in characterizing pancreatic masses as it cannot differentiate benign from malignant lesions, and focal uptake on early PET imaging is the best indicator of malignancy. A possible benefit in performing a delayed scan is that a high RI (>18.7) can predict poor survival and hence may be useful in treatment planning.

Voxel-based analysis of 201Tl SPECT for grading and diagnostic accuracy of gliomas: comparison with ROI analysis

PurposeThe aim of this retrospective study was to assess the utility of a voxel-based analysis (VBA) method for 201Tl SPECT in glioma, compared to conventional ROI analysis.MethodsWe recruited 24 patients with glioma (high-grade 15; low-grade 9), for whom pre-operative 201Tl SPECT and MRI were performed. SPECT images were coregistered with MRI. The uptake ratio (UR) images of tumor to contralateral normal tissue were measured on early and delayed images, and the 201Tl retention index (RI) map was calculated from the early and delayed uptake ratio maps. In the ROI analysis, tumors were traced on a UR map, and the mean and maximal uptake ratio values on the early images were, respectively, defined as the mean and maximal UR. The mean and maximal RI values (mean and maximal RI) were calculated by division of the mean and maximal UR, respectively, on the delayed image by the mean and maximal UR on the early image. For the RI map calculated voxel by voxel, the maximal RI value was defined as VBA-RI. We evaluated sensitivity and accuracy of differential analysis with the mean and maximal UR, RI, and VBA-RI.ResultsThe high- and low-grade groups showed no significant difference in mean and maximal RI (0.98 ± 0.12 vs. 1.05 ± 0.09 and 0.98 ± 0.18 vs. 1.05 ± 0.14, respectively). The AUC and accuracy of the mean and maximal RI were 0.681 and 66.7 %, and 0.622 and 62.5 %, respectively. In contrast, VBA-RI was higher in high-grade than in low-grade glioma (1.69 ± 0.27 vs. 0.68 ± 0.66, p < 0.001). The AUC and accuracy of VBA-RI were 0.963 and 95.8 %, which are higher than those obtained for mean (p < 0.05) and maximal RI (p < 0.01). There was no significant difference in ROC between the VBA-RI and the mean UR (0.911, p = 0.456) and maximal UR (0.933, p = 0.639); however, the AUC, sensitivity, and diagnostic accuracy of VBA-RI were all higher than those of the mean and maximal UR.ConclusionThe voxel-based analysis method of 201Tl SPECT may improve diagnostic performance for gliomas, compared with ROI analysis.

Correlation of MIB-1 staining index and 201Tl-SPECT retention index in preoperative evaluation of malignancy of brain tumors

MIB-1 staining provides a useful index of the malignancy of brain tumors. However, because of the difficulty of evaluating malignancy based on the preoperative imaging findings, we investigated the correlation between the (201)Tl-SPECT retention index (RI) and MIB-1 staining index (MIB-1 SI) to determine the usefulness of RI for preoperative evaluation of the malignancy of brain tumors. The subjects of this study were 47 patients who underwent tumor removal surgery at our hospital in 2006 and 2007. The tumors consisted of 16 intraaxial tumors (all gliomas: 9 glioblastomas, 2 anaplastic astrocytomas, 2 anaplastic oligoastrocytomas, 1 oligodendroglioma, and 2 ependymomas), 8 other malignant brain tumors, and 23 extraaxial tumors (10 meningiomas, 7 pituitary adenomas, and 6 schwannomas). The mean RI and mean MIB-1 SI of the intraaxial tumors were 0.628% and 32.0%, respectively, and after MIB-1 SI was converted to the natural logarithm (log MIB-1 SI), Pearson's coefficient for the correlation between them was significant (r = 0.752, P < 0.001). The mean RI and mean MIB-1 SI of the extraaxial tumors were 0.377% and 3.01%, respectively, and after MIB-1 SI was converted to log MIB-1 SI, Pearson's coefficient for the correlation between them was significant (r = 0.803, P < 0.001). Thus, the MIB-1 SI values of highly malignant intraaxial tumors was strongly correlated with their RI values, and the (201)Tl-SPECT RI values were useful as an index of malignancy. RI values may also be useful for evaluating apparently benign extraaxial tumors for possible malignancy.

A phase I study of the nitroimidazole hypoxia marker SR4554 using 19F magnetic resonance spectroscopy

Background:SR4554 is a fluorine-containing 2-nitroimidazole, designed as a hypoxia marker detectable with 19F magnetic resonance spectroscopy (MRS). In an initial phase I study of SR4554, nausea/vomiting was found to be dose-limiting, and 1400 mg m−2 was established as MTD. Preliminary MRS studies demonstrated some evidence of 19F retention in tumour. In this study we investigated higher doses of SR4554 and intratumoral localisation of the 19F MRS signal.Methods:Patients had tumours ⩾3 cm in diameter and ⩽4 cm deep. Measurements were performed using 1H/19F surface coils and localised 19F MRS acquisition. SR4554 was administered at 1400 mg m−2, with subsequent increase to 2600 mg m−2 using prophylactic metoclopramide. Spectra were obtained immediately post infusion (MRS no. 1), at 16 h (MRS no. 2) and 20 h (MRS no. 3), based on the SR4554 half-life of 3.5 h determined from a previous study. 19Fluorine retention index (%) was defined as (MRS no. 2/MRS no. 1)*100.Results:A total of 26 patients enrolled at: 1400 (n=16), 1800 (n=1), 2200 (n=1) and 2600 mg m−2 (n=8). SR4554 was well tolerated and toxicities were all ⩽grade 1; mean plasma elimination half-life was 3.7±0.9 h. SR4554 signal was seen on both unlocalised and localised MRS no. 1 in all patients. Localised 19F signals were detected at MRS no. 2 in 5 out of 9 patients and 4 out of 5 patients at MRS no. 3. The mean retention index in tumour was 13.6 (range 0.6–43.7) compared with 4.1 (range 0.6–7.3) for plasma samples taken at the same times (P=0.001) suggesting 19F retention in tumour and, therefore, the presence of hypoxia.Conclusion:We have demonstrated the feasibility of using 19F MRS with SR4554 as a potential method of detecting hypoxia. Certain patients showed evidence of 19F retention in tumour, supporting further development of this technique for detection of tumour hypoxia.

Dual-time point PET/CT with F-18 FDG for the differentiation of malignant and benign bone lesions

The purpose of the present study was to evaluate whether 2-fluoro[fluorine-18]-2-deoxy-D: -glucose (F-18 FDG) positron emission tomography (PET) could differentiate malignant and benign bone lesions and whether obtaining delayed F-18 FDG PET images could improve the accuracy of the technique. In a prospective study, 67 patients with bone lesions detected by computed tomography (CT) or magnetic resonance imaging were included. Whole body PET/CT imaging was performed at 1 h (early) after the F-18 FDG injection and delayed imaging at 2 h post injection was performed only in the abnormal region. Semiquantitative analysis was performed using maximum standardized uptake value (SUV(max)), obtained from early and delayed images (SUV(maxE) and SUV(maxD), respectively). The retention index (RI) was calculated according to the equation: RI = (SUV(maxD) - SUV(maxE)) x 100/SUV(maxE.) Histopathology of surgical specimens and follow-up data were used as reference criteria. The SUV(maxE) and RI were compared between benign and malignant lesions. The final diagnoses revealed 53 malignant bone lesions in 37 patients and 45 benign lesions in 30 patients. There were statistically significant differences in the SUV(maxE) between the malignant and benign lesions (P = 0.03). The mean SUV(maxE) was 6.8 +/- 4.7 for malignant lesions and 4.5 +/- 3.3 for benign lesions. However, a considerable overlap in the SUV(maxE) was observed between some benign and malignant tumors. With a cutoff value of 2.5 for the SUV(maxE), the sensitivity, specificity, and accuracy were 96.0%, 44.0%, and 72.4%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 67.1% and 90.9%, respectively. There were significant differences in the RI between the malignant and benign lesions (P = 0.004). But there was overlap between the two groups. The mean RI was 7 +/- 11 for the benign lesions and 18 +/- 11 for the malignant lesions. When an RI of 10 was used as the cutoff point, the sensitivity, specificity, and accuracy were 90.6%, 76.0%, and 83.7.0%, respectively. The PPV and NPV were 81.4% and 87.1%, respectively. The results of this study indicate that dual-time point F-18 FDG PET may provide more help in the differentiation of malignant tumors from benign ones.

Evaluation of delayed18F-FDG PET in differential diagnosis for malignant soft-tissue tumors

Positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) has been used for the evaluation of soft-tissue tumors. However, the range of accumulation of 18F-FDG for malignant soft-tissue lesions overlaps with that of benign lesions. The aim of this study is to investigate the usefulness of delayed 18F-FDG PET imaging in the differentiation between malignant and benign soft-tissue tumors. Fifty-six patients with soft-tissue tumors underwent whole body 18F-FDG PET scan at 1 hour (early scan) and additional scan at 2 hours after injection (delayed scan). The standardized uptake value (SUV(max)) of the tumor was determined, and the retention index (RI) was defined as the ratio of the increase in SUV(max) between early and delayed scans to the SUV(max) in the early scan. Surgical resection with histopathologic analysis confirmed the diagnosis. Histological examination proved 19 of 56 patients to have malignant soft-tissue tumors and the rest benign ones. In the scans of all 56 patients, there was a statistically significant difference in the SUV(max) between malignant and benign lesions in the early scan (5.50 +/- 5.32 and 3.10 +/- 2.64, respectively, p < 0.05) and in the delayed scan (5.95 +/- 6.40 and 3.23 +/- 3.20, respectively, p < 0.05). The mean RI was not significantly different between malignant and benign soft-tissue tumors (0.94 +/- 23.04 and -2.03 +/- 25.33, respectively). In the current patient population, no significant difference in the RI was found between malignant and benign soft-tissue lesions. Although the mean SUV(max) in the delayed scan for malignant soft-tissue tumors was significantly higher than that for benign ones, there was a marked overlap. The delayed 18F-FDG PET scan may have limited capability to differentiate malignant soft-tissue tumors from benign ones.

Periodontal conditions in a randomly selected population in Switzerland.

The aim of the present study was to evaluate the periodontal conditions of a randomly selected population in the Canton of Berne, Switzerland. From a total of 350 selected persons, 206 (59%) attended the examinations. The Plaque Index (PlI), Gingival Index (GI) and Retention Index (RI), the width of the keratinized gingiva, pocket probing depth (PD) and loss of probing attachment (LA) were recorded on four surfaces per tooth in the entire dentition of the subjects. The statistical analyses were performed using the Statistical Analysis System (SAS). A total of 4253 teeth were scored. On average the patients had 20.7 teeth. The mean PlI of this population was 1.16, the mean GI was 1.34 and the mean RI was 0.81. All three indices were higher in older age groups. 72% of all measurements for pocket probing depths were less than or equal to 3 mm, 26% were between 4 and 6 mm, and only 2% were more than 6 mm. 76% of all sites had lost less than or equal to 3 mm of probing attachment, 21% of the sites had lost between 4 and 6 mm and only 3% had lost more than 6 mm. There were no statistically significant differences either between females and males or between the rural and the urban populations. These results indicate that only a relatively small percentage of the sample representative for the respective area in Switzerland suffered from advanced periodontitis, while the great majority may be treated by rather conservative approaches to periodontal therapy.

Characterization and selection of stationary phases for gas—liquid chromatography by pattern recognition methods

The classification of stationary phases in gas—liquid chromatography and the quantitation of their retention characteristics, which is generally described as ‘polarity’, were investigated by pattern recognition methods, especially by the hierarchical clustering and the minimum spanning tree techniques. It is demonstrated that the hierarchical clustering with a distant function and the minimum spanning tree method gives similar results with respect to the ranking and the differentiation of liquid stationary phases. New measures of the retention characteristics of liquid stationary phases were defined and tested. The potential of the various measures of solvent polarity is discussed. The mean retention index was found to be the best polarity characteristic. With a view to the rationalization of experimental work, an optimized procedure for the classification of liquid stationary phases and the calculation of their polarity with the minimum number of characteristic test solutes was elaborated. The set of characteristic solutes selected gives the best representation of the total number of solutes and covers all types of molecular interactions included in the term polarity.