Significance of splenic uptake on somatostatin receptor imaging studies

Spleen shows a high physiological uptake on radionuclide somatostatin receptor (SSTR) imaging studies. Autoradiography and immunohistochemistry studies showed that SSTRs are mainly located in the red pulp of the spleen. In this review article we will summarize the significance of splenic uptake in SSTR imaging studies and will also present high resolution splenic images of Ga-68 DOTANOC PET in which splenic distribution of the radiotracer appears to be correlating with the distribution of red pulp.

Assessing the correlation between FDG PET findings of IDC breast carcinoma and histopathology of coexisting ductal carcinoma in-situ

Background: Ductal carcinoma in-situ (DCIS) often coexists with invasive ductal carcinoma (IDC) of the breast. DCIS is considered as a non-obligate precursor of IDC when both coexist. 18F-fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) imaging is commonly used in the staging and follow-up assessment of breast cancer. In this study, we aimed to assess if there is any correlation between primary tumor PET and histopathology findings and histopathological features of the coexisting DCIS. Material and methods: FDG PET/CT images and histopathology results of the patients with newly diagnosed breast cancer (IDC) with coexisting DCIS were analyzed in this retrospective study. The grade and size of the primary tumor and histopathological features of the coexisting DCIS (nuclear grade and architectural pattern) were obtained from the postoperative histopathology results. Maximum standardized uptake values (SUV: SUVmax and SULmax) of the primary tumor normalized by weight and lean body mass were measured. Statistical analysis was performed to assess the correlation between various parameters of IDC and DCIS. Results: This study included sixty-two (62) patients with IDC-DCIS. Primary tumor grade was significantly correlated and associated with the nuclear grade of the coexisting DCIS (polychoric correlation r = 0.736, and Fisher exact test, PV < 0.001, respectively). Primary tumor SUV was not correlated with the nuclear grade and architectural pattern of the coexisting DCIS (polyserial correlation r = 0.172, PV = 0.155, and Point Bi-Serial correlation r = –0.009, PV = 0.955, respectively). Median primary tumor size was marginally significantly different among DCIS nuclear grades but it was not significantly different in comedo and non-comedo cases (Kruskal-Wallis test PV = 0.053, and Mann-Whitney U test PV = 0.890, respectively). Conclusions: Primary tumor grade is correlated with the nuclear grade of the coexisting DCIS. SUV of primary tumor does not seem to be correlated with the histopathological features of coexisting DCIS (nuclear grade and architectural pattern) but this may be further studied in a larger number of patients

Combined use of preoperative 18F FDG-PET imaging and intraoperative gamma probe detection for accurate assessment of tumor recurrence in patients with colorectal cancer

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to combine intraoperative gamma probe (GP) detection with preoperative fluorine 18-fluoro-2-deoxy-glucose positron emission tomography (¹⁸F FDG-PET) imaging in order to improve detection of tumor recurrence in colorectal cancer (CRC) patients.</p> <p>Methods</p> <p>Twenty-one patients (12 females, 9 males) with a mean age of 54 years (range 31–78) were enrolled. Patients were suspected to have recurrent CRC by elevated CEA (n = 11), suspicious CT findings (n = 1), and clinically suspicious findings (n = 9). Preoperative FDG-PET scan and intraoperative GP study were performed in all patients. Mean time interval between preoperative FDG-PET scan and surgery was 16 days (range 1–41 days) in 19 patients. For intraoperative GP studies, 19 patients were injected with a dose of 10–15 mCi ¹⁸F FDG at approximately 30 minutes before the planned surgery time. In two patients, the intraoperative GP study was performed immediately after preoperative FDG-PET scan.</p> <p>Results</p> <p>Preoperative FDG-PET and intraoperative GP detected 48 and 45 lesions, respectively. A total of 50 presumed site of recurrent disease from 20 patients were resected. Thirty-seven of 50 presumed sites of recurrent disease were histological-proven tumor positive and 13 of 50 presumed sites of recurrent disease were histological-proven tumor negative. When correlated with final histopathology, the number of true positive lesions and false positive lesions by preoperative FDG-PET and intraoperative GP were 31/9 and 35/8, respectively. Both preoperative FDG-PET and intraoperative GP were true positive in 29 lesions. Intraoperative GP detected additional small lesions in the omentum and pelvis which were not seen on preoperative FDG-PET scan. FDG-PET scan demonstrated additional liver metastases which were not detected by intraoperative GP. Preoperative FDG-PET detected distant metastasis in the lung in one patient. The estimated radiation dose received by a surgeon during a single 18F FDG GP surgery was below the occupational limit.</p> <p>Conclusion</p> <p>The combined use of preoperative FDG-PET and intraoperative GP is potentially helpful to the surgeon as a roadmap for accurately locating and determining the extent of tumor recurrence in patients with CRC. While intraoperative GP appears to be more sensitive in detecting the extent of abdominal and pelvic recurrence, preoperative FDG-PET appears to be more sensitive in detecting liver metastases. FDG-PET is also a valuable method in detecting distant metastases.</p

Gamma probes and their use in tumor detection in colorectal cancer

The purpose of this article is to summarize the role of gamma probes in intraoperative tumor detection in patients with colorectal cancer (CRC), as well as provide basic information about the physical and practical characteristics of the gamma probes, and the radiopharmaceuticals used in gamma probe tumor detection. In a significant portion of these studies, radiolabeled monoclonal antibodies (Mabs), particularly 125I labeled B72.3 Mab that binds to the TAG-72 antigen, have been used to target tumor. Studies have reported that intraoperative gamma probe radioimmunodetection helps surgeons to localize primary tumor, clearly delineate its resection margins and provide immediate intraoperative staging. Studies also have emphasized the value of intraoperative gamma probe radioimmunodetection in defining the extent of tumor recurrence and finding sub-clinical occult tumors which would assure the surgeons that they have completely removed the tumor burden. However, intraoperative gamma probe radioimmunodetection has not been widely adapted among surgeons because of some constraints associated with this technique. The main difficulty with this technique is the long period of waiting time between Mab injection and surgery. The technique is also laborious and costly. In recent years, Fluorine-18-2-fluoro-2-deoxy-D-glucose (18F-FDG) use in gamma probe tumor detection surgery has renewed interest among surgeons. Preliminary studies during surgery have demonstrated that use of FDG in gamma probe tumor detection during surgery is feasible and useful

Breast Cancer and PET Imaging

Breast cancer is the most common malignancy in women and among the most common indications of oncologic positronemission tomography (PET) studies. In this review article, updated anatomical, pathological, and clinical information aboutbreast cancer were provided for Nuclear Medicine physicians to better understand breast cancer and interpret PET imagesand a review of the literature on the use of PET imaging in breast cancer was summarized

Status of F-18 fluorodeoxyglucose uptake in normal and hibernating myocardium after glucose and insulin loading

Objective: F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has been increasingly used in myocardial viability imaging. In routine PET viability studies, oral glucose and intravenous insulin loading is commonly utilized. In an optimal study, glucose and insulin loading is expected to cause FDG uptake both in hibernating and normal myocardium. However, in routine studies it is not uncommon to see absent or reduced FDG uptake in normal myocardium. In this retrospective study we further analyzed our PET viability images to evaluate FDG uptake status in myocardium under the oral glucose and intravenous insulin loading protocol that we use in our hospital. Methods: Patients who had both myocardial perfusion single photon emission computed tomography (SPECT) and FDG PET cardiac viability studies were selected for analysis. FDG uptake status in normal and abnormal myocardial segments on perfusion SPECT was evaluated. Based on SPECT and PET findings, patients were divided into two main groups and four subgroups. Group 1 included PET viable studies and Group 2 included PET-nonviable studies. Subgroups based on FDG uptake in normal myocardium were 1a and 2a (normal uptake) and 1b and 2b (absent or significantly reduced uptake). Results: Seventy-one patients met the inclusion criteria. Forty-two patients were PET-viable and 29 were PET-nonviable. In 33 of 71 patients (46.4%) there was absent or significantly reduced FDG uptake in one or more normal myocardial segments, which was identified more in PET-viable than PET-nonviable patients (59.5% vs. 27.5%, p = 0.008). This finding was also more frequent in diabetic than nondiabetic patients (53% vs. 31.8%), but the difference was not significant (p = 0.160). Conclusions: In nearly half of our patients, one or more normal myocardial segments showed absent or significantly reduced FDG uptake. This finding, particularly if it is diffuse, could be from suboptimal study, inadequacy of current glucose and insulin loading protocols, or various other patient-related causes affecting FDG uptake both in the normal and hibernating myocardium. In cases with significantly reduced FDG uptake in normal myocardium, PET images should be interpreted cautiously to prevent false-negative results for viability. Keywords: Fluorodeoxyglucose, Glucose loading, Insulin loading, Myocardial viability, Positron emission tomograph