Physiological biodistribution on Ga68-PSMA PET/CT and the factors effecting biodistribution.

AIM: The study aims to determine the physiological and pathophysiological distribution of the radiopharmaceutical (Ga68-PSMA-617) and investigate whether there are differences in distribution according to the laboratory, histopathological and clinical findings that can affect image evaluation. Also, we aimed to determine cut-off values to distinguish physiological and pathological uptake in prostate, bone, and lymph nodes. MATERIALS AND METHODS: 229 prostate cancer patients who underwent Ga68-PSMA PET/CT at our department were retrospectively analyzed. The patients were grouped according to PET/CT results, Gleason scores, PSA values, received treatments, metastatic status and other laboratory values. The SUV values of the organs, tissues, and pathological lesions of the patients in these subgroups were compared among themselves. RESULTS: No significant difference was detected in the physiological uptake of lymph nodes and bone between the groups. In the group with patients that received androgen deprivation therapy (ADT), the bone metastasis SUV values were found to be higher and the SUV values of the submandibular gland and renal cortex were found to be lower (Mann-Whitney U, p = 0.043; 0.004; 0.01, respectively). In the group with patients who received radiotherapy, the normal prostate tissue SUV values were determined to be higher (Mann-Whitney U, p = 0.009). The SUV values of the submandibular gland, muscle, liver, and blood pool were found to be lower in the group of patients with high serum LDH values. The cut-off SUVmax value was determined to be 6.945 (sensitivity 89.6%, specificity 98.1%) for primary prostate lesion; 4.72 for lymph node metastasis; 4.25 for bone metastasis. The serum PSA cut-off value to distinguish the negative/positive groups was found to be 1,505 (sensitivity 79.7%, specificity 77.3%). CONCLUSION: In conclusion, PSMA-617 demonstrates a similar biodistribution with other PSMA ligands. The physiological uptake of lymph nodes and bone which are mostly metastasized in prostate cancer, are not affected by the factors we examined. It should be kept in mind that the normal prostate tissue uptake may increase in patients receiving radiotherapy, and the physiological/pathological uptake of the organs may differ due to the changes in PSMA expression in patients receiving ADT, tumor burden, and kidney function may affect the biodistribution.

Neurolymphomatosis with Spinal Nerve Root Involvement Demonstrated on 18F-FDG PET/CT.

A 56 years old woman with a diagnosis of diffuse large B-cell lymphoma had dyspnea, weakness in the left upper extremity and vocal cord paralysis after chemotherapy. She underwent cervical, thoracal and lumbosacral magnetic resonance imaging (MRI) however findings on MRI could not entirely explain the symptoms of the patient. Therefore, the patient underwent 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography and the scan revealed focal symmetrical 18F-FDG uptake on the cervical, thoracal and lumbal spinal nerve roots. Considering the symptoms of the patient and cerebrospinal fluid cytology findings, hypermetabolic spinal nerve roots were interpreted as lymphoma involvement.

FDG PET/CT and Conventional Imaging Methods in Cancer of Unknown Primary: an Approach to Overscanning.

PURPOSE: To compare the performance of fluorine-18 fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) with conventional imaging methods (CIM), including computed tomography (CT), magnetic resonance imaging (MRI), and mammography (MMG) in cancer of unknown primary (CUP). METHODS: A total of 36 patients with CUP, who referred to our clinic for a FDG PET/CT scan, were enrolled in this study. Thirty of the patients were also examined through either diagnostic CT/MRI and/or MMG. The diagnostic performance of both methods for the primary cancer location was analyzed. The results of FDG PET/CT and CIM were compared based on the standard reference of the histopathology and/or clinical and laboratory follow-up. RESULTS: The primary cancer locations were detected in 24 patients (66.6%, 24/36) by FDG PET/CT, whereas CIM identified the locations in 16 patients (53.3%, 16/30). Sensitivity, specificity, PPV, NPV, and accuracy rates of the detection of the primary tumor localizations were as follows: 83, 70, 89, 58, and 79% for FDG PET/CT; 70, 62, 84, 42, and 68% for CIM, respectively. There was no statistical significance between modalities regarding any of the categories in 30 patients. CONCLUSION: FDG PET/CT detected the primary tumors of the patients with CUP more than CIM did. However, the difference between them was not found to be statistically significant. It may be considered that FDG PET/CT scan can be performed as a first-line tool in the initial diagnosis of the patients with CUP and to add radiodiagnostic imaging in selective cases. We conclude that if the first-line examination of a CUP patient has been already performed by a CIM and the result was negative or inconclusive, FDG PET/CT can be considered to avoid unnecessary imaging procedures.

Comparison of atherosclerotic inflammation and calcification in subjects with end stage renal disease (ESRD) on hemodialysis to normal controls utilizing 18F-FDG PET/CT.

OBJECTIVE: Subjects with end stage renal disease (ESRD) are exposed to increased morbidity and mortality due to cardiovascular events. The primary underlying mechanism has been suggested as accelerated atherosclerosis in these patients. Our aim was to compare the atherosclerotic inflammation and calcification in subjects with ESRD on hemodialysis to that in normal controls utilizing fluorine-18-2-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT). SUBJECTS AND METHODS: Forthy two subjects who underwent 18F-FDG PET/CT imaging were retrospectively studied. Twenty one were subjects with ESRD on hemodialysis (67±11 years old; 14 male, 7 female) and 21 were age- and gender-matched controls. Average standardized uptake value maximum (SUVmax) and SUVmean for 4 segments of the aorta (ascending, arch, descending, abdominal) and for the common iliac arteries and common femoral arteries were measured. Standardized uptake value maximum and SUVmean for right atrial blood pool were also measured as the background. Average SUVmax, average SUVmean, average SUVmax/background ratio, and average SUVmean/background ratio were compared between subject groups for all segments. Presence or absence of macroscopic calcification on CT images for each arterial segment based on visual qualitative assessment was also noted and compared. For statistical analysis, two-sided t-test was used for continuous variables, and chi-square test was used for categorical variables. We considered a P value of <0.05 as statistically significant. RESULTS: Average SUVmax and SUVmean were statistically significantly greater in subjects with ESRD than in controls in all arterial segments. Average SUVmax/background ratios were statistically significantly greater in subjects with ESRD compared to normal controls in all arterial segments except for the left femoral artery. Average SUVmean/background ratios were statistically significantly greater in subjects with ESRD compared to normal controls in all arterial segments except for the right and left femoral arteries. Presence of calcification on CT was more frequently encountered in all arterial segments in subjects with ESRD, and was statistically significantly greater for the aortic arch, descending aorta, and right and left femoral arteries. CONCLUSION: SUV measurements representing the atherosclerotic inflammatory changes and macroscopic atherosclerotic calcifications appear to be accelerated in subjects with ESRD on hemodialysis compared to normal controls. Fluorine-18 FDG PET/CT is a valuable diagnostic tool for verifying and quantifying accelerated atherosclerosis secondary to ESRD.

Is 18F-FDG PET/CT a valuable diagnostic tool for verifying accelerated atherosclerosis secondary to diabetes mellitus on insulin in the aortic segments and large arteries?

OBJECTIVE: Fluorine-18 fluorodeoxylglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has a well-established role for detection and quantification of atherosclerotic inflammatory disease using standardized uptake value (SUV) measurements. Our aim was to compare the inflammatory and macroscopic calcification processes of atherosclerosis in the aortic segments and large arteries of subjects with insulin dependent diametes mellitus (IDDM) compared to those of age-matched controls via 18F-FDG PET/CT. PATIENTS AND METHODS: A hundred and ten subjects who underwent 18F-FDG PET/CT imaging for oncological diseases were retrospectively studied. Fifty five were diabetics on insulin and 55 were age-matched controls. Average SUVmax and SUVmean for four segments of aorta and for common iliac arteries and femoral arteries were measured and compared between subject groups. Presence or absence of macroscopic calcification on CT images for each arterial segment was also noted and compared between these groups. RESULTS: Average SUVmax and SUVmean were statistically significantly greater in subjects with IDDM compared to controls in all arterial segments (P≤0.001). Presence of calcification on CT was more frequently encountered in 6 of the 8 segments in subjects with IDDM, and there was statistically significantly difference for the descending aorta and abdominal aorta. CONCLUSION: Our results show that inflammatory component of atherosclerosis was more severe in all aortic segments in subjects with IDDM compared to those of controls. Presence of macroscopic calcification also detected to be more frequently encountered in the descending thoracic and abdominal aorta in subjects with IDDM. Fluorine-18-FDG PET/CT is a valuable diagnostic tool for detecting and semi-quantifying accelerated atherosclerotic inflammatory and calcific changes secondary to diabetes mellitus treated with insulin in the aortic segments and large arteries.

Atherosclerotic 18F-FDG and MDP uptake in femoral arteries, changes with age.

OBJECTIVES: This study was carried out to evaluate the atherosclerotic changes that occur with age in the femoral arteries. To this end, a group of patients were investigated both by a fluorine-18 fluorodeoxyglucose (F-FDG) PET scan and by a whole-body bone scan. METHODS: We included 38 patients (25 women, 13 men, age range: 25-84 years) in this retrospective analysis. All patients underwent an F-FDG PET scan and a Tc-MDP bone scan. The mean interval time between the bone scans and F-FDG PET scans was 1.2±1.6 months. Patients randomly underwent the bone scan or the PET scan first. The patients were subdivided into four groups, with the following age ranges: 25-50, 51-60, 61-70, and 71-84 years. Regions of interest were drawn both over the femoral arteries and the adjacent background (BKG) both on F-FDG PET examinations and MDP bone scans, and the uptake values were calculated. Finally, we calculated and compared the uptake ratios of F-FDG/BKG and MDP/BKG in the four age groups. These ratios were obtained in the exact same way using equal regions of interest and equal drawing positions. RESULTS: The uptake ratios of F-FDG/BKG in the femoral arteries increased with age in the four age groups (P<0.05). This ratio was the highest in the oldest age group and the lowest in the youngest age group. MDP/BKG in the four age groups also increased with age in numbers. The ratio was the highest in the oldest patients group and the lowest in the youngest patient group, although this increase with age was not statistically significant. CONCLUSION: Our results indicate that in the femoral arteries, the uptake ratios of F-FDG/BKG reflects a progression of the inflammatory component of the atherosclerotic activity with age. MDP/BKG in the four age groups in femoral arteries, however, is considered the indicator of severity of the calcification component of atherosclerosis. Calcification in femoral arteries also increased with age, but with a slower progression.

Partial volume correction and image segmentation for accurate measurement of standardized uptake value of grey matter in the brain.

OBJECTIVES: Our aim was to explore a novel quantitative method [based upon an MRI-based image segmentation that allows actual calculation of grey matter, white matter and cerebrospinal fluid (CSF) volumes] for overcoming the difficulties associated with conventional techniques for measuring actual metabolic activity of the grey matter. METHODS: We included four patients with normal brain MRI and fluorine-18 fluorodeoxyglucose (F-FDG)-PET scans (two women and two men; mean age 46±14 years) in this analysis. The time interval between the two scans was 0-180 days. We calculated the volumes of grey matter, white matter and CSF by using a novel segmentation technique applied to the MRI images. We measured the mean standardized uptake value (SUV) representing the whole metabolic activity of the brain from the F-FDG-PET images. We also calculated the white matter SUV from the upper transaxial slices (centrum semiovale) of the F-FDG-PET images. The whole brain volume was calculated by summing up the volumes of the white matter, grey matter and CSF. The global cerebral metabolic activity was calculated by multiplying the mean SUV with total brain volume. The whole brain white matter metabolic activity was calculated by multiplying the mean SUV for the white matter by the white matter volume. The global cerebral metabolic activity only reflects those of the grey matter and the white matter, whereas that of the CSF is zero. We subtracted the global white matter metabolic activity from that of the whole brain, resulting in the global grey matter metabolism alone. We then divided the grey matter global metabolic activity by grey matter volume to accurately calculate the SUV for the grey matter alone. RESULTS: The brain volumes ranged between 1546 and 1924 ml. The mean SUV for total brain was 4.8-7. Total metabolic burden of the brain ranged from 5565 to 9617. The mean SUV for white matter was 2.8-4.1. On the basis of these measurements we generated the grey matter SUV, which ranged from 8.1 to 11.3. CONCLUSION: The accurate metabolic activity of the grey matter can be calculated using the novel segmentation technique that we applied to MRI. By combining these quantitative data with those generated from F-FDG-PET images we were able to calculate the accurate metabolic activity of the grey matter. These types of measurements will be of great value in accurate analysis of the data from patients with neuropsychiatric disorders.

Use of 111In-pentetreotide scan in a subject with treatment refractory atypical meningioma.

A 57-year-old man with a history of multiple recurrent atypical meningiomas (World Health Organization grade II) had several surgical resections including γ knife resection of the parafalcine meningioma, followed with a stereotactic radiosurgical ablation. Despite these treatments, an MRI scan performed 7 months later showed progression of the disease. The patient remained symptomatic with intermittent severe headaches associated with nausea, vomiting, and visual disturbance. He had a positive In-pentetreotide indicating the presence of somatostatin receptors. Therefore, he was placed on systemic Sandostatin (octreotide acetate) treatment, and at follow-up, he was clinically responsive to treatment.

Atherosclerotic inflammatory activity in the aorta and its correlation with aging and gender as assessed by 18F-FDG-PET.

Recent literature demonstrates the potential of fluorine-18 fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) to detect, localize, and quantify the degree of inflammatory changes in the arterial wall due to early atherosclerosis. Our aim was to assess the correlation between the age and 18F-FDG uptake of aortic segments and determine its correlation with respect to in both age and genders. Fluorine-18-FDG uptake in aortic segments in 143 subjects (58 men, 85 women; ages 5-82 years) was evaluated in this study. Subjects were initially grouped according to the gender, and then by age (below or above 50) with at least 26 subjects per group. Mean standardized uptake value (SUV) of ascending aorta, arch, descending thoracic aorta, and abdominal aortic segments were calculated in each subject. Correlative analyses between age and mean SUV of aortic segments in all subjects were undertaken. Mean SUV between genders for all groups were also compared. There was a positive correlation between age and mean SUV of all aortic segments. The correlation values in all aortic segments were higher in subjects below 50 years old compared to those above 50 years in the entire group of patients as well as when they were subdivided and analyzed according to both genders (P<0.001). Descending thoracic and ascending aortic segments in men below 50 years of age had the highest correlation of 18F-FDG uptake and age (0.85 and 0.80, respectively) whereas abdominal aortic segments in men the above 50 years age group had the lowest correlation value (0.20). Comparison between mean SUV in four visible arterial segments between the two genders did not reveal any statistically significant difference. In conclusion, 18F-FDG uptake in aortic segments increases with age irrespective of genders. The increase with age is more significant in younger subjects compared to older subjects for both men and women. This finding may indicate a deceleration in the inflammatory component of atherosclerosis with aging in older subjects.

Intermittent cystocele diagnosed on 18F-FDG PET/CT scan.

A 78-year-old woman was diagnosed with stage III diffuse large B-cell lymphoma, and treated with chemotherapy in 2004. Imaging follow-up was performed by serial 6-month diagnostic PET/CT scans. A PET/CT scan performed in June 2011 showed an unusual hourglass appearance of activity in the pelvis that prompted further investigation. Retrospective review of the prior diagnostic PET/CT scans revealed that the patient had a sliding bladder, located either above or below the pubococcygeal line at different imaging times, but during this scan, the bladder was "caught" moving up to its normal position.

Nuclear imaging of a pregnant patient: should we perform nuclear medicine procedures during pregnancy?

UNLABELLED: Although it is extremely rare, nuclear imaging of a pregnant woman presents a unique challenge to the nuclear medicine physician because of the high concern for radiation risk to the embryo or the fetus. This challenge has been exacerbated due to recent heightened public concern of medical procedures involving radiation. This awareness also has been emphasized to the referring physicians to the extent that the risks of most nuclear medicine scans are overstressed relative to the benefit. Radionuclide procedures are reluctantly ordered by clinicians in pregnant patients, because of the malpractice fear or because of uncertainty regarding fetal radiation dose. However, when used appropriately, the benefits of nuclear imaging procedures usually outweigh the minimal risks associated with small amount of radiation even in pregnant patients. CONFLICT OF INTEREST: None declared.

Rare case of Primary Pulmonary Extranodal Non-Hodgkin's Lymphoma in a Patient with Sjogren's Syndrome: Role of FDG-PET/CT in the Initial Staging and Evaluating Response to Treatment.

UNLABELLED: A 64-year old woman with a long standing Sjogren's syndrome was undergoing evaluation for renal transplant surgery when two pulmonary opacities were detected on chest CT. Subsequent biopsy revealed extranodal marginal B-cell non-Hodgkin's lymphoma (NHL). An FDG-PET/CT scan was then performed which demonstrated isolated FDG avid pulmonary involvement. After therapy, FDG-PET/CT scans showed good response to treatment with near complete resolution of FDG avidity. This rare case illustrates the rare pulmonary manifestation of extranodal lymphoma in a patient with Sjogren's syndrome and emphasizes the value of FDG PET/CT in the initial staging and evaluation of response to treatment, which has not previously been published. CONFLICT OF INTEREST: None declared.

Improved Benefit of SPECT/CT Compared to SPECT Alone for the Accurate Localization of Endocrine and Neuroendocrine Tumors.

OBJECTIVE: To assess the clinical utility of SPECT/ CT in subjects with endocrine and neuroendocrine tumors compared to SPECT alone. MATERIAL AND METHODS: 48 subjects (31 women;17 men; mean age 54±11) with clinical suspicion or diagnosis of endocrine and neuroendocrine tumor had 50 SPECT/CT scans (32 Tc-99m MIBI, 5 post treatment I-131, 8 In-111 Pentetreotide, and 5 I-123 MIBG). SPECT alone findings were compared to SPECT/CT and to pathology or radiological follow up. RESULTS: From the 32 Tc-99m MIBI scans, SPECT accurately localized the lesion in 22 positive subjects while SPECT/CT did in 31 subjects. Parathyroid lesions not seen on SPECT alone were smaller than 10 mm. In five post treatment I-131 scans, SPECT alone neither characterized, nor localized any lesions accurately. SPECT/CT revealed 3 benign etiologies, a metastatic lymph node, and one equivocal lesion. In 8 In-111 Pentetreotide scans, SPECT alone could not localize primary or metastatic lesions in 6 subjects all of which were localized with SPECT/CT. In five I-123 MIBG scans, SPECT alone could not detect a 1.1 cm adrenal lesion or correctly characterize normal physiologic adrenal uptake in consecutive scans of the same patient with prior history of adrenelectomy, all of which were correctly localized and characterized with SPECT/CT. CONCLUSION: SPECT/CT is superior to SPECT alone in the assessment of endocrine and neuroendocrine tumors. It is better in lesion localization and lesion characterization leading to a decrease in the number of equivocal findings. SPECT/CT should be included in the clinical work up of all patients with diagnosis or suspicion of endocrine and neuroendocrine tumors. CONFLICT OF INTEREST: None declared.

Tc-99m red blood cell bleeding scan in a pregnant woman presenting with hematemesis: a brief review of indications and guidelines for radionuclide scans during pregnancy.

A 6-month pregnant 35-year-old woman with hematemesis and dark blood in her stool was evaluated for location of an active gastrointestinal bleeding site. The findings from 2 esophagogastroduodenoscopies and a colonoscopy were negative. The patient was referred for a Tc-99m red blood cell scintigraphy, for location of an active bleeding site. As the patient was 6 months pregnant, the necessity of the case was discussed with the patient's referring physician and after determining that this study was necessary, the risk of radiation exposure to the fetus was discussed with the radiation safety officer and the patient. The procedure was performed after the patient signed informed consent regarding the considerations of radiation safety to the fetus. The Tc-99m red blood cell bleeding scan clearly shows activity in the fetus in addition to a large arteriovenous malformation in the patient. The visualized fetus prompted this report to discuss radiation risks concerns and a brief review of indications and guidelines for performing nuclear medicine procedures in pregnant patients.

Increased 18F-FDG uptake within the reticuloendothelial system in patients with active lung cancer on PET imaging may indicate activation of the systemic immune response.

The reticuloendothelial system (RES) cells are in the defense against certain pathogens, and in the removal of dying cells, cell debris, microorganisms, and malignant cells. Liver, spleen, and bone marrow represent the major organs with high RES activity. We hypothesized that in subjects with active lung cancer, the metabolic activity of these organs would be greater than that of the subjects with no active tumor. We have studied two groups of subjects who had undergone (18)F-FDG-PET imaging for clinical purposes. The first group consisted of 39 subjects (20 women, 19 men, mean age 64.8+/-10.2 years) with benign lung nodules as demonstrated by (18)F-FDG-PET imaging. The second group consisted of 30 subjects (18 women, 12 men; mean age 65.1+/-11 years) who were known to have active lung cancer with or without distant metastases as seen on (18)F-FDG-PET imaging. The subjects in the second group did not have any evidence of liver, spleen, bone marrow, or heart involvement on (18)F-FDG-PET images. We measured the mean SUV of the liver, spleen, bone marrow, heart, and of the contralateral unaffected lung, and compared the average SUV for these organs between the two groups. We found that the mean SUV of the liver, bone marrow, and spleen were significantly greater in subjects with evidence of active primary or metastatic lung cancer compared with those of subjects who had benign lung nodules and no evidence of active malignant disease. There was a statistically significant difference between mean SUV for organs noted above between the two groups (P<0.05). In contrast, mean SUV for the heart and contralateral normal lung did not show any significant difference between the two groups. In conclusion, the mean SUV for the major organs of RES, liver, spleen, and bone marrow were higher in subjects with active lung cancer with or without metastases than in those without active malignancy. We believe these differences in SUV may indicate a differential activation of the systemic immune response, related to the presence or absence of active lung cancer, which can be detected and quantified non-invasively through (18)F-FDG-PET imaging.

Quantitative assessment of the hepatic metabolic volume product in patients with diffuse hepatic steatosis and normal controls through use of FDG-PET and MR imaging: a novel concept.

AIMS AND OBJECTIVES: The aim of this study was to compare hepatic standardized uptake values (SUVs) and hepatic metabolic volumetric products (HMVP) between patients of diffuse hepatic steatosis and control subjects with normal livers. MATERIALS AND METHODS: Twenty-seven subjects were included in the study (13 men and 14 women; age range, 34-72 years). All had 18F-2-fluoro-2-D-deoxyglucose-positron emission tomography (FDG-PET) and magnetic resonance imaging (MRI) scans with an interscan interval of 0-5 months. Twelve of 27 subjects had diffuse hepatic steatosis on MRI. The remaining 15 were selected as age-matched controls based on normal liver parenchyma on MRI. Mean and maximum hepatic SUVs were calculated for both patient groups on FDG-PET images. Hepatic volumes were measured from MRI. HMVP in each subject was subsequently calculated by multiplication of hepatic volume by mean hepatic SUV. HMVPs as well as mean and maximum hepatic SUVs were compared between the two study groups. RESULTS: HMVPs, mean hepatic SUVs, and maximum hepatic SUVs were greater (statistically significant, p < 0.05) in subjects with diffuse hepatic steatosis compared to those in the control group. CONCLUSION: The increase in HMVP is the result of increased hepatic metabolic activity likely related to the diffuse hepatic steatosis. The active inflammatory process related to the diffuse hepatic steatosis is the probable explanation for the increase in hepatic metabolic activity on FDG-PET study.

Tumor metabolism measured by partial volume corrected standardized uptake value varies considerably in primary and metastatic sites in patients with lung cancer. A new observation.

Fluorine-18 fluorodeoxyglycose -position emission tomography ((18)F-FDG-PET) as an efficient staging tool for lung carcinoma; allows description and characterization of the primary tumor and of local and distant metastases in a single examination. One of the important limiting factors in quantification of metabolic parameters with PET is the partial volume effect. Our aim for this study was to delineate tumor (size) both in the primary and metastatic lesions in patients with lung cancer by using partial volume correction techniques. Thirty two patients with proven lung cancer who had (18)F-FDG-PET and computerized tomography (CT) within the last 80 days were involved in this study. They were 18 women and 14 men, with age range 43-83 years. Maximum standardized uptake values (SUVmax) in primary and metastatic lesions for all patients were measured. The lesions were categorized into 4 different Groups according to their site. Partial volume corrections were applied using the CT sizes of lesions to obtain corrected SUVmax values. Average corrected SUVmax in each lesion site was calculated and compared between the 4 Groups. A total of 81 primary and metastatic lesions were included in this analysis. They were 28 mediastinal-hilar lymph node lesions, 26 lung lesions, 11 solid organ lesions, and 16 bone marrow lesions. The average uncorrected SUVmax for the primary lung lesions, mediastinal-hilar lymph node lesions, solid organ lesions, and the bone marrow lesions before application of partial volume correction formula were 7.2+/-3.2; 7.0+/-2.7; 6.3+/-3.4 and 7.0+/-3.4, respectively. The average corrected SUVmax for the lesions in the above mentioned regions were 11+/-6, 10+/-4, 13+/-7, and 18+/-13, respectively. A statistically significant difference was observed in the average SUVmax values between lung lesions and nodal lesions compared to the bone marrow lesions. In conclusion, our findings indicate that metabolic activities of lung cancer lesions vary depending on the sites of metastatic disease.

A pilot study of changes in (18)F-FDG uptake, calcification and global metabolic activity of the aorta with aging.

Our aim was to quantify changes in the inflammatory and calcific components of atherosclerosis in the aortic wall using fluoro-18-2-fluoro-2-deoxy-D-glucose positron emission tomography (18)F-FDGPET and contrast enhanced computerized tomography (CECT) with increasing age. Twelve subjects, 8 men and 4 women aged from 21-80 years who had both (18)F-FDG-PET and CECT of the chest and abdomen were included in this study. Subjects were grouped into three according to age. (18)F-FDG uptake in four segments of the aorta was measured. Using CECT images, aortic segmental wall volumes were measured. Wall calcification volume in each aortic segment was also measured via adaptation of a coronary artery calcium-scoring program to the aorta. Calcification volumes were then subtracted from aortic wall volumes. Each net segmental aortic wall volume was then multiplied by the accompanying mean SUV of the segment to calculate global metabolic activity (GMA) for each aortic segment. Our results showed that in each aortic wall segment, mean SUV, wall volumes, wall calcification volumes, and GMA statistically significantly increased with age. In conclusion, (18)F-FDG uptake, wall volume, wall calcification volume, and GMA in the aorta increase with aging. The (18)F-FDG uptake represents the early inflammatory component of the atherosclerotic process, whereas calcification generally represents a later and irreversible stage of the disease. Measurement and combination of PET and CECT parameters to calculate GMA may allow for optimal morphologic and functional noninvasive quantitative assessment of global aortic atherosclerotic disease.

A recovery coefficient method for partial volume correction of PET images.

OBJECTIVES: Correction of the "partial volume effect" has been an area of great interest in the recent times in quantitative PET imaging and has been mainly studied with count recovery models based upon phantoms that incorporate hot spheres in a cold background. The goal of this research study was to establish a similar model that is closer to a biological imaging environment, namely hot spheres/lesions in a warm background and to apply this model in a small cohort of patients. METHODS: A NEMA phantom with six spheres (diameters 1-3.7 cm) was filled with (18)FDG to give sphere:background activity ratios of 8:1, 6:1, and 4:1 for three different acquisitions on a Philips Allegro scanner. The hot sphere SUVmax and the background average SUV were measured for calculation of recovery coefficients (RCs). Using the RCs, the lesion diameters, and the lesion:background ratio, the SUVmax of 64 lesions from 17 patients with biopsy proven lung cancer were corrected. RESULTS: The RCs versus sphere diameters produced characteristic logarithmic curves for each phantom (RCs ranged from 80% to 11%). From a cohort of 17 patients with biopsy proven lung cancer, 64 lesions combined had a mean SUVmax of 7.0 and size of 2.5 cm. After partial volume correction of the SUVmax of each lesion, the average SUVmax increased to 15.5. CONCLUSIONS: Hot spheres in a warm background more closely resemble the actual imaging situation in a living subject when compared to hot spheres in a cold background. This method could facilitate generation of equipment specific recovery coefficients for partial volume correction. The clinical implications for the increased accuracy in SUV determination are certainly of potential value in oncologic imaging.