Biomedical subjects

Christian Cohade

Publications and source records attributed to Christian Cohade.

At least 19 recordsLinked to original sources

PubMed2005

Initial experience with FDG-PET/CT in the evaluation of breast cancer.

PURPOSE: We retrospectively reviewed FDG-PET/CT images in patients with breast cancer to determine whether PET/CT improved the level of diagnostic confidence as compared with PET and to compare PET/CT and CT findings at the location of suspected malignancies. METHODS: The study included 75 patients with known breast cancer. The initial PET/CT study for each patient was retrospectively reviewed to determine whether improved diagnostic confidence (IDC) regarding lesion localization and characterization was observed with PET/CT as compared with PET alone. PET/CT and CT findings were compared regarding lesion characterization and staging in 69 of the 75 patients, and in the case of discordant findings, comparison with histological or informative follow-up results was also performed. RESULTS: Fifty of the 75 patients exhibited increased FDG uptake in a total of 95 regions. In the comparison of PET/CT and PET, PET/CT resulted in IDC in 30 (60%) of these 50 patients and in 52 (55%) of the 95 regions. In the comparison between PET/CT and CT in 69 patients, PET/CT demonstrated a significantly better accuracy than CT (P<0.05). PET/CT showed definitely positive findings in 60 regions with malignancies, among which CT exhibited positive findings in 43 (72%). PET/CT and CT accurately staged 59 (86%) and 53 (77%) of the 69 patients, respectively. CONCLUSIONS: PET/CT added incremental diagnostic confidence to PET in more than 50% of patients and regions with increased FDG uptake. PET/CT accurately detected more regions with malignancies than did CT. This initial evaluation suggests that PET/CT is preferable to PET or CT in the diagnosis of breast cancer.

Adult↗

PubMed2005

Normal FDG distribution patterns in the head and neck: PET/CT evaluation.

PURPOSE: To retrospectively evaluate the distribution of fluorine 18 fluorodeoxyglucose (FDG) in the head and neck region with combined positron emission tomography-computed tomography (PET/CT) in patients with no known abnormality in this region. MATERIALS AND METHODS: The institutional review board allowed a retrospective review of PET/CT images obtained in 78 patients with non-head and neck cancer and waived the requirement for informed consent. The accumulation of FDG in 11 normal head and neck structures was visually and quantitatively assessed retrospectively. Positive rate percentage (PRP) was defined as the sum of the percentages of patients with grade 2 and grade 3 tracer uptake intensity. Standardized uptake values (SUVs) were calculated for quantitative analysis. Mean SUVs were compared between the male and female patients by using the unpaired t test, and the correlation between FDG uptake and patient age was assessed by using the Pearson correlation coefficient test. RESULTS: Intense tracer uptake was usually seen in the palatine tonsils (PRP, 98%; mean SUV, 3.48), soft palate (PRP, 96%; mean SUV, 3.13), and lingual tonsils (PRP, 96%; mean SUV, 3.11). In the inferior concha (PRP, 4%; mean SUV, 1.56), thyroid gland (PRP, 3%; mean SUV, 1.31), and tongue (PRP, 1%; mean SUV, 1.39), uptake was typically minimal. FDG accumulation was variable in the sublingual glands (PRP, 72%; mean SUV, 2.93), spinal cord (PRP, 64%; mean SUV, 2.12), submandibular glands (PRP, 53%; mean SUV, 2.11), parotid glands (PRP, 51%; mean SUV, 1.90), and vocal cords (PRP, 19%; mean SUV, 1.77). The mean normal-tissue SUV in the soft palate was higher in male than in female patients (P <.01). A negative correlation between age and physiologic FDG uptake was seen in the palatine tonsils (r=-0.51, P <.001) and sublingual glands (r=-0.70, P <.001). CONCLUSION: Intense FDG uptake was usually observed in the palatine tonsils, lingual tonsils, and soft palate, whereas uptake in the major salivary glands was variable.

Adolescent↗

PubMed2005

CT appearance of bone metastases detected with FDG PET as part of the same PET/CT examination.

PURPOSE: To retrospectively evaluate lesion findings at computed tomography (CT) performed as part of a combined positron emission tomography (PET)/CT examination in patients suspected of having metastatic bone lesions-lesions that were detected with fluorine 18 fluorodeoxyglucose (FDG) PET as part of the same examination-and to correlate the CT and FDG PET findings. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval, and the need for patient informed consent was waived. Three hundred fifty-nine consecutive patients (191 male patients, 168 female patients; mean age, 56.9 years; age range, 8-92 years) underwent PET/CT. PET images were first reviewed by nuclear medicine physicians who had no clinical information regarding the presence or absence of bone metastasis by using a five-point grading system (0, a lesion was definitely negative for metastasis; 1, a lesion was probably negative; 2, a lesion was equivocal; 3, a lesion was probably positive; and 4, a lesion was definitely positive). For lesions assigned a grade of 3 or 4 at PET, CT characteristics such as the presence or absence of morphologic changes or accompanying findings (including bone destruction) were assessed by radiologists on the CT images obtained during the same imaging session. RESULTS: One hundred seventy-nine lesions in 55 patients were considered to be probable or definite bone metastases at PET. One hundred thirty-three of these lesions in 33 patients were clinically confirmed to be bone metastases at follow-up and/or histopathologic examination. CT revealed osteolytic changes in 41 (31%) and osteoblastic changes in 21 (16%) of the 133 lesions, but no or nonspecific changes were seen at CT in 49 (37%) and 22 lesions (17%), respectively. Of the 179 lesions suspected at PET, 46 ultimately proved to be nonosseous or false-positive for bone metastasis. Of these 46 lesions, 38 were not located in the bone but in adjacent tissues such as the pleura. CONCLUSION: CT images obtained as part of PET/CT scanning were useful in yielding the precise location of bone lesions and thus helping avoid misdiagnosis of bone metastasis; however, CT revealed morphologic changes in only half of the lesions assigned a grade of 3 or 4 at PET.

Adolescent↗

PubMed2005

Direct comparison of FDG PET and CT findings in patients with lymphoma: initial experience.

PURPOSE: To retrospectively compare fluorine 18 fluorodeoxyglucose (FDG) positron emission tomographic (PET) and computed tomographic (CT) findings at the same anatomic locations in patients with lymphoma by using a combined PET/CT scanner and to analyze the lesions on metabolic and anatomic bases to evaluate causes of discrepant findings between the two modalities. MATERIALS AND METHODS: The institutional review board allowed an exempt retrospective review of cancer PET database, and informed consent was waived. The study was HIPAA compliant. Fifty-three patients with lymphoma (20 Hodgkin and 33 non-Hodgkin; mean age, 43 years; range, 12-83 years) who underwent FDG PET/CT were included. The PET and CT images were interpreted by two nuclear medicine physicians and one radiologist, respectively, blinded to the other imaging findings. Concordant PET and CT findings were regarded as positive or negative for lymphoma. The site with discordant findings was defined as positive for disease if it was accompanied by other PET- and CT-positive sites in the same patient or was confirmed clinically (histologic examination or progressive disease). Staging results were also compared by one nuclear medicine physician. RESULTS: Of a total of 1537 anatomic sites in 53 patients, 48 had discordant findings between PET and CT. Forty (83%) of the 48 sites had correct PET findings (31 positive, nine negative), five had correct CT findings, and three were unresolved. The 31 PET-positive and CT-negative sites accounted for 23% of all 134 true-positive PET sites. PET provided accurate staging in an incremental nine (17%, upstaging in four and downstaging in five) of 53 patients in whom CT staging was incorrect. CT provided correct upstaging in two patients. CONCLUSION: FDG PET/CT as a combined modality may contribute substantially to lesion characterization and staging in patients with lymphoma.

Adolescent↗

PubMed2005

Clinically significant incidental findings on the unenhanced CT portion of PET/CT studies: frequency in 250 patients.

UNLABELLED: PET/CT technology is in rapid evolution. It remains unclear if the unenhanced CT portion, performed for attenuation correction and lesion localization, provides additional independent diagnostic information not apparent on PET alone. The objective of the current study was to evaluate the incremental added value and frequency of potentially clinically significant incidental findings from the independent reading of the unenhanced CT portion of PET/CT studies by an expert CT radiologist. METHODS: PET/CT was performed on 250 patients (123 men and 127 women; mean age, 56.5 y) referred for clinical evaluation of known or suspected cancer. Unenhanced CT studies were read without knowledge of findings from PET and PET/CT fused images. Findings from unenhanced CT were considered clinically significant if they were not detected or explained by PET findings and were considered, after examination of all available clinical data, to clearly require additional work-up. Small pulmonary nodules < 7 mm were not considered to require immediate work-up. RESULTS: Unenhanced CT revealed potentially clinically significant incidental findings in 7 patients. Three patients had indeterminate renal lesions, 1 patient had a solid renal mass, 1 patient had sclerotic bone metastases (albeit inactive on PET), 1 patient had liver cirrhosis with portal hypertension, and 1 patient had a 5 cm abdominal aortic aneurysm. These findings were generally not detected on PET. CONCLUSION: Clinically significant findings from the unenhanced CT portion of PET/CT are relatively infrequent (3%) but could be serious enough to warrant major alterations in clinical management. Thus, we believe it is most appropriate for the CT portion to be interpreted by a physician skilled in CT interpretation with special attention to the lesions that PET alone can fail to detect.

Female↗

PubMed2004

F-18 FDG PET/CT in acute respiratory distress syndrome: a case report.

F-18 FDG PET/CT has become a useful technique in the evaluation of pulmonary lesions. We present a case of markedly increased and diffuse pulmonary F-18 FDG activity in a patient with acute respiratory distress syndrome (ARDS). High rates of glucose utilization by the inflammatory cells involved in the pathogenesis of ARDS might explain the increased pulmonary F-18 FDG uptake we observed. In the proper clinical setting, ARDS should be considered in the differential diagnosis of patients with diffusely increased F-18 FDG activity in the lungs.

Aged↗

PubMed2004

PET/CT: artifacts caused by bowel motion.

BACKGROUND AND AIM: In a combined positron emission tomography (PET) and computed tomography (CT) system, the CT images can be used for attenuation correction as well as for image fusion. However, quantitative and qualitative differences have been reported between CT based attenuation corrected PET and conventional transmission scan corrected PET images. The purpose of this study was to investigate potential differences in PET/CT caused by attenuation differences in bowel due to motion. METHODS: Twelve patients had PET/CT scans performed using 68Ge transmission and CT attenuation correction methods. Three emission imaging datasets were generated including CT corrected PET, Ge corrected PET, and the difference images (CT corrected PET minus Ge corrected PET). PET difference images were used to identify regions of mismatch and to quantify possible discordance between images by using standardized uptake values (SUVs). Using the Ge corrected PET as the standard, differences in emission images were classified as an overestimation (pattern A) or an underestimation (pattern B) in these difference images. RESULTS: One hundred and twenty-three mismatched areas were identified. Among them, overestimated areas in CT corrected image were detected in 36 regions (pattern A), while underestimated areas were evaluated in the remaining 87 regions (pattern B). The mean value of the difference in pattern A (mean +/- standard deviation = 0.84 +/- 0.44) was slightly higher than that in pattern B (0.60 +/- 0.23), and statistically significant. Six of 36 regions in pattern A had an SUV of greater than 2.5 in CT corrected PET but less than 2.5 in Ge corrected PET; two of 87 regions with pattern B demonstrated an SUV greater than 2.5 in Ge corrected PET and less than 2.5 in CT corrected PET. CONCLUSION: Physiological bowel motion may result in attenuation differences and subsequent differences in SUVs. Overestimation of fluorodeoxyglucose uptake should not be misinterpreted as disease.

Abdominal Neoplasms↗

PubMed2004

Recombinant human thyrotropin stimulation of fluoro-D-glucose positron emission tomography uptake in well-differentiated thyroid carcinoma.

TSH stimulates thyrocyte metabolism, glucose transport, and glycolysis. 2-Deoxy-2-[18F]fluoro-D-glucose (FDG) is a glucose analog used in positron emission tomography (PET) to detect occult well-differentiated thyroid carcinoma. The objective of this study was to examine the effects of recombinant human TSH (rTSH) on FDG PET uptake in patients with residual or recurrent disease. Seven patients with well-differentiated thyroid carcinoma, negative 131-I scintigraphy, and biochemical evidence of residual disease were randomized and prospectively studied with FDG PET both on thyroid hormone suppression and rTSH stimulation within 1 wk. All lesions seen on the TSH suppression scans were seen on the rTSH stimulation studies. rTSH stimulation studies identified four additional lesions not seen on TSH suppression. One patient was positive on rTSH stimulation alone. The mean (2.54 +/- 0.72 vs. 1.79 +/- 0.88) and maximum (2.49 +/- 0.95 vs. 1.74 +/- 0.81) lesion to background ratios were significantly higher with rTSH stimulation, compared with TSH suppression (P = 0.02 for both). rTSH stimulation improves the detectability of occult thyroid metastases with FDG PET, compared with scans performed on TSH suppression.

Adult↗

PubMed2004

Intense (18)F-FDG uptake in brown fat can be reduced pharmacologically.

UNLABELLED: Physiologic (18)F-FDG uptake in areas of supraclavicular fat in humans ("USA-Fat") has recently been recognized as (18)F-FDG uptake in apparent brown adipose tissue (BAT) using fused PET/CT technology. In this study, we evaluated (18)F-FDG uptake in BAT of rats to determine whether pharmacologic or physiologic interventions affect the uptake, knowing that BAT has a high density of adrenergic innervation. METHODS: Seven- to 8-wk-old female Lewis rats receiving intravenous (18)F-FDG injections were examined under various conditions to evaluate (18)F-FDG biodistribution into interscapular BAT and major organs. In series 1, rats were given ketamine-based anesthesia or were exposed to cold (4 degrees C for 4 h) to determine whether these interventions increased (18)F-FDG uptake in BAT. In series 2, anesthetized rats (ketamine-based anesthesia) were given propranolol, reserpine, or diazepam intraperitoneally before (18)F-FDG injection to determine whether the drug reduced (18)F-FDG uptake in BAT. The control and treated groups in series 2 were also evaluated with (18)F-FDG PET/CT imaging. RESULTS: In series 1, anesthesia or exposure to cold increased (18)F-FDG uptake in BAT to levels 14-fold and 4.9-fold, respectively, greater than the control nonstimulated values. BAT uptake was high, comparable to that in the brain. In series 2, (18)F-FDG uptake in BAT was significantly decreased to less than 30% of the control level after propranolol or reserpine (P < 0.05). Diazepam did not significantly decrease (18)F-FDG uptake in BAT. (18)F-FDG PET/CT findings reflected these biodistribution data: The control and diazepam groups exhibited intense (18)F-FDG uptake in BAT, whereas the propranolol and reserpine groups showed only faint to mild (18)F-FDG uptake in BAT. Among several organs whose (18)F-FDG uptake was affected after predosing drugs, the heart exhibited considerable decreases in tracer uptake with propranolol or reserpine. CONCLUSION: This rodent study demonstrated that BAT can exhibit high (18)F-FDG uptake under stimulated conditions including exposure to cold and that propranolol or reserpine treatment can remarkably reduce the high (18)F-FDG uptake in BAT. The effect of these drugs on (18)F-FDG uptake in human BAT, as well as on tracer accumulation in other organs, should carefully be evaluated clinically to minimize the USA-Fat artifact.

Acepromazine↗

PubMed2003

Fluorodeoxyglucose uptake in the aortic wall at PET/CT: possible finding for active atherosclerosis.

PURPOSE: To evaluate fluorine 18 fluorodeoxyglucose (FDG) uptake in the thoracic aortic wall at combined positron emission tomography (PET)/computed tomography (CT) and compare uptake with aortic wall calcification. MATERIALS AND METHODS: Records of 85 consecutive cancer patients who underwent FDG PET/CT were evaluated retrospectively. One hour after FDG injection, CT followed by PET was performed from ear to middle of the thigh. CT, PET, and fused PET/CT images were generated. FDG uptake and calcification were evaluated visually and semiquantitatively. FDG uptake was graded according to intensity; calcification, according to thickness. Unpaired t test was used for comparison of patient age with and without FDG uptake and with and without calcification. The relationship between the score (sum of grades along all aortic segments) of positive FDG uptake and calcification and patient age was analyzed with Spearman rank correlation. Comparison of frequency of FDG uptake and calcification with age, sex, risk factors for cardiovascular disease (CVD), or history of CVD was performed with chi2 analysis. RESULTS: Fifty patients had at least one area of FDG uptake in thoracic aortic wall, 14 of whom showed focal FDG uptake. Intermediate to intense FDG uptake tended to be observed in the descending aorta. Forty-five patients had at least one measurable aortic calcification. Thick calcification was observed most often at the aortic arch. Twelve patients had 13 uptake areas at the calcification site. Patients with positive findings were on average older (P <.05 for both increased uptake and calcification); the older patient group had higher frequency of both aortic wall uptake (P <.005) and calcification (P <.001). The calcification score correlated with age (rho = 0.60, P <.001) but the FDG uptake score did not. Women, patients with hyperlipidemia, and patients with history of CVD tended to show increased FDG uptake (P =.073,.080, and.068, respectively), whereas patients with diabetes had significantly more calcifications (P <.05). CONCLUSION: PET/CT depicted FDG uptake commonly in the thoracic aortic wall. The FDG uptake site was mostly distinct from the calcification site and may possibly be located in areas of metabolic activity of atherosclerotic changes.

Adolescent↗

PubMed2003

PET-CT: accuracy of PET and CT spatial registration of lung lesions.

PET-CT scanners offer the unique ability to acquire PET and CT data with rapid full body registration. The purpose of this study was to evaluate the accuracy of spatial registration between PET and CT data in patients with fluorine-18 fluoro-2-deoxy- D-glucose (FDG)-avid lung lesions. PET, CT and fused PET-CT images from 244 consecutive clinical patients undergoing whole-body FDG PET-CT imaging (GE Discovery LS, CT attenuation correction, OSEM reconstruction) were evaluated. Inclusion criteria for this analysis were lung lesions clearly defined on both PET and CT, lesion diameter less than 5 cm and clear borders. Patients were allowed to breathe freely during both PET and CT image acquisitions. The spatial coordinates of the visually estimated centers of the lesion were determined independently for PET and CT images and compared. Thirty-six patients (26 females, 10 males) with a total of 48 lesions were included (19 lung cancer patients with 26 lesions, 17 patients with 22 lung metastases). The average lung lesion diameter was 15.6+/-9 mm. The mean distance between the center of lesions independently determined for both PET and CT was 7.55+/-4.73 mm. Misregistration tended to be more pronounced in the lower lungs (10.2+/-6.55 mm) than in the upper lungs (6.67+/-4.28 mm) ( P=0.063). Misregistration also tended to be slightly more pronounced in the left lung (8.33+/-5.05 mm) than in the right lung (6.25+/-3.92 mm) ( P=0.059). In conclusion, with a dedicated PET-CT scanner and this clinically practical imaging algorithm, registration is usually accurate, but spatial misregistration of primary lung lesions does occur.

Female↗

PubMed2003

Accuracy of image fusion of normal upper abdominal organs visualized with PET/CT.

Although PET/CT scanners have the potential for precise fused registration of structures visualized on both PET and CT, physiological motion during the acquisition of both studies may alter the appearance of organ shape, size or location. The degree of possible mismatch in abdominal organ size and position between PET and CT has not been evaluated. The aim of this study was to assess the consistency in location and measured size of upper abdominal organs with PET and CT using a combined PET/CT system. Forty-six consecutive inpatients who underwent clinical PET/CT scans for suspected cancer were evaluated. CT and PET images attenuation corrected by both CT and germanium-68 transmission scans were obtained, and we separately determined the location of the top and bottom (height), anterior and posterior margins (thickness), and right and left margins (width) for each organ, including liver, spleen, and bilateral kidneys, using CT and both sets of PET images. Differences between the two modalities in terms of location and measured organ size were investigated. In the upper margin of the liver and lower margin of the spleen, more than 10% of the cases showed a larger discrepancy (>20 mm) between CT-based and Ge-corrected PET-based measurements, although the differences in the positions of the edges were less than 10 mm in most cases. The center of the liver tended to be located cephalad and to the right of the body, and that of the spleen tended to be cephalad and posterior on PET, as compared with CT. Moreover, the center of both kidneys tended to be seen cephalad, posterior, and to the right on PET. The liver appeared slightly larger on PET than CT in thickness (CT vs CT-corrected PET vs Ge-corrected PET = 156 mm vs 162 mm vs 162 mm) and width (186 mm vs 189 mm vs 188 mm). By contrast, the spleen appeared slightly smaller on PET than CT in height (84 mm vs 77 mm vs 80 mm) and width (85 mm vs 81 mm vs 80 mm). A similar tendency was observed in the left kidney (105 mm vs 100 mm vs 99 mm in height, and 64 mm vs 59 mm vs 58 mm in width) and the right kidney (99 mm vs 93 mm vs 93 mm in height, and 64 mm vs 59 mm vs 60 mm in width). These differences between the two modalities were statistically significant ( P<0.05). In conclusion, minor mismatches in location and organ size were found to exist between CT and PET images, in part due to physiological motion. Although these differences could potentially affect the quality of the image registrations, they were generally of a modest nature.

Abdomen↗

PubMed2003

Respiratory motion artifacts on PET emission images obtained using CT attenuation correction on PET-CT.

PET-CT scanners allow generation of transmission maps from CT. The use of CT attenuation correction (CTAC) instead of germanium-68 attenuation correction (Ge AC) might be expected to cause artifacts on reconstructed emission images if differences in respiratory status exist between the two methods of attenuation correction. The aim of this study was to evaluate for possible respiratory motion artifacts (RMA) in PET images attenuation corrected with CT from PET-CT in clinical patients. PET-CT scans were performed using a Discovery LS PET-CT system in 50 consecutive patients (23 males, 27 females; mean age 58.2 years) with known or suspected malignancy. Both CTAC and Ge AC transmission data obtained during free tidal breathing were used to correct PET emission images. Cold artifacts at the interface of the lungs and diaphragm, believed to be due to respiratory motion (RMA), that were seen on CTAC images but not on the Ge AC images were evaluated qualitatively on a four-point scale (0, no artifact; 1, mild artifact; 2, moderate artifact; 3, severe artifact). RMA was also measured for height. Curvilinear cold artifacts paralleling the dome of the diaphragm at the lung/diaphragm interface were noted on 84% of PET-CT image acquisitions and were not seen on the (68)Ge-corrected images; however, these artifacts were infrequently severe. In conclusion, RMA of varying magnitude were noted in most of our patients as a curvilinear cold area at the lung/diaphragm interface, but were not diagnostically problematic in these patients.

Abdominal Neoplasms↗

PubMed2003

Clinically occult recurrent ovarian cancer: patient selection for secondary cytoreductive surgery using combined PET/CT.

OBJECTIVE: The aim of this study was to evaluate the utility of combined positron emission tomography/computed tomography (PET/CT) for identifying ovarian cancer tumor masses > or =1 cm in patients with clinically occult recurrent disease by conventional CT imaging. METHODS: Twenty-two patients with epithelial ovarian cancer, rising serum CA125 levels, and negative or equivocal conventional CT imaging > or =6 months after primary therapy underwent combined PET/CT imaging followed by surgical reassessment. Fisher's exact test was used to measure the ability of PET/CT to predict macroscopic disease > or =1 cm. RESULTS: The median patient age was 55 years, and 91% of patients had FIGO Stage IIIC/IV disease. The median increase in serum CA125 was 24 U/ml (range 10 to 330 U/ml). Conventional CT was reported as negative (n = 15) or equivocal (n = 7) in all cases. Eighteen patients were ultimately found to harbor recurrent ovarian cancer measuring > or =1 cm at the time of surgery, with a median maximal tumor diameter of 2.3 cm (range 1.5 to 3.2 cm). The overall patient-based accuracy of PET/CT in detecting recurrent disease > or =1 cm was 81.8%, with a sensitivity of 83.3% and positive predictive value of 93.8% (P = 0.046). Of patients with recurrent ovarian cancer > or =1 cm, complete cytoreduction to no gross residual tumor was accomplished in 72.2%. CONCLUSION: PET/CT imaging demonstrates high sensitivity and positive predictive value in identifying potentially resectable, macroscopic recurrent ovarian cancer among patients with biochemical evidence of recurrence and negative or equivocal conventional CT findings. In appropriately selected patients, early identification of macroscopic recurrent disease may facilitate complete surgical cytoreduction.

CA-125 Antigen↗

PubMed2003

Applications of positron emission tomography/computed tomography image fusion in clinical positron emission tomography-clinical use, interpretation methods, diagnostic improvements.

Positron emission tomography (PET)/computed tomography (CT) scanners with combined dedicated high performance PET and CT scanners have been introduced recently in PET imaging. Oncological imaging with fluorodeoxyglucose (FDG) is currently the dominant application of PET. The addition of CT to PET offers many advantages, including obtaining a fast and relatively low-noise transmission scan, shortening the duration of the examination, adding precise anatomical information to FDG imaging, and providing additional diagnostic information. However, the use of CT for attenuation correction can lead to some artifacts that need to be considered when interpreting a PET/CT study: quantitative measurements may be altered, high density IV and oral and metallic objects may produce artifacts, and the registration of PET and CT may occasionally be suboptimal. Areas where using PET/CT offers particular potential advantages include the head and neck region, abdomen, and pelvis. Even in the thorax, PET/CT offers some advantages. Although clinical data evaluating the added value of PET/CT over PET are presently limited, preliminary results are very encouraging. More studies are warranted to clearly define the clinical impact of PET/CT over PET; however, it is clear this dedicated fusion technology will be very important for patient imaging in the coming years.

Artifacts↗

PubMed2003

Sacral fractures: a potential pitfall of FDG positron emission tomography.

OBJECTIVE: Positron emission tomography (PET) with FDG is useful for tumor imaging, but false-positive results can occur. The purpose of this study is to describe three oncology patients with sacral fractures in whom FDG uptake in the sacrum increased on PET. CONCLUSION: Sacral fractures can show increased uptake of FDG on PET. Therefore, correlative cross-sectional imaging is necessary to avoid the erroneous diagnosis of sacral metastases on PET and prevent inappropriate treatment of patients.

Aged↗

PubMed2003

Uptake in supraclavicular area fat ("USA-Fat"): description on 18F-FDG PET/CT.

UNLABELLED: The supraclavicular region is a common site for lymph node metastases. A commonly reported type of nonmalignant (18)F-FDG uptake on PET imaging in the supraclavicular region is "muscle uptake" purportedly due to muscle contraction in tense patients during the (18)F-FDG uptake phase. PET/CT offers the unique opportunity to correlate PET findings with CT anatomy in the supraclavicular region. METHODS: Images from the first 359 consecutive clinical whole-body studies (in 347 patients) using (18)F-FDG and a PET/CT scanner (with CT attenuation correction and ordered-subsets expectation maximization [OSEM] reconstruction) were retrospectively reviewed. The supraclavicular region was evaluated for the presence of abnormal uptake on PET images, and the corresponding CT findings were assessed. Three distinct patterns of abnormal (18)F-FDG uptake were noted: pattern A (uptake localizing to supraclavicular area fat [USA-fat], i.e., without corresponding lymph node or muscle uptake on CT), pattern B (uptake localizing to muscle on CT), and pattern C (uptake localizing to lymph nodes or soft-tissue masses on CT). RESULTS: Forty-nine patients (14.1%) (32 female, 17 male; mean age, 51.4 +/- 15.6 y; age range, 12-77 y) showed abnormal (18)F-FDG uptake in the supraclavicular region. Twenty patients (5.8%) had muscle uptake (group B); 15 (4.3%) had definite abnormal lymph nodes (group C). However, 14 patients (4.0%) had USA-fat (group A) and foci of very low Hounsfield units on CT. These foci were also present on (68)Ge attenuation-corrected images (when obtained) and non-attenuation-corrected images. Uptake in USA-fat was typically bilateral and symmetric, intense, more often multifocal than linear, and located in fat on PET/CT. Age was not significantly different for group C versus the 2 other groups. Intensity; mean standardized uptake value, lean (SUV(L MEAN)); or maximum standardized uptake value, lean (SUV(L MAX)), did not allow differentiation between patterns A and C (P > 0.05). Standardized uptake values (SUV(L MAX), 3.1; SUV(L MEAN), 2.1) were significantly lower in group B than in the 2 other groups (P < 0.005). CONCLUSION: So-called muscle uptake in the supraclavicular region may be caused in a significant proportion of cases by an unrelated process we call the USA-fat finding, with (18)F-FDG uptake in tissues of low-Hounsfield (fat) density. This finding most likely reflects an underlying nonpathologic process that we hypothesize to be in foci of brown fat. This intense supraclavicular uptake should be recognized and should not be misinterpreted as a malignant metastatic process or as muscle uptake.

Adipose Tissue↗

PubMed2003

Clinically significant inaccurate localization of lesions with PET/CT: frequency in 300 patients.

UNLABELLED: This study evaluated lesion mislocalization between PET and CT on PET/CT studies when CT instead of germanium is used for attenuation correction (AC). METHODS: PET/CT scans were obtained for 300 clinical patients. Both CT and germanium scans were used to correct PET emission data. Cases were noted of suspected inaccurate localization of lesions on any of the 5 sets of images (PET using germanium AC [GeAC] fused and not fused with CT, PET using CT AC fused and not fused with CT, and PET with no AC [NAC]). Independent CT or MRI was used to determine true lesion locations. RESULTS: Six of 300 patients (2%) had lesion mislocalization when CT was used for AC or fusion. True liver dome lesions were mislocalized to the right lung base on PET/CT, likely because of a respiratory motion difference between PET and CT. No mislocalization was present on NAC PET or non-CT-fused GeAC PET images. CONCLUSION: Serious lesion mislocalization on PET/CT studies may occur, albeit very infrequently, when CT is used for either AC or fusion.

Adult↗