Incidental Uptake Research Articles

Comment on Minamimoto: incidental focal FDG uptake in heart is a lighthouse for considering cardiac screening

Dear Sir,An interesting article has recently been published [1] on theclinical significance of focal cardiac FDG uptake inpatients with unknown cardiac disease studied for unre-lated purposes. The topic is of great interest because thepossibility to identify unexpected cardiac disease duringPET studies could allow an early diagnosis and reduceunfavorable events. The paper suggests a correlationbetween focal cardiac FDG uptake and the likelihood ofcoronary artery disease (CAD) in patients without cardiacsymptoms and unknown cardiac disease. Apart from theinteresting analysis and the effort to identify the clinicalsignificance of focal uptakes, we agree and highlight theremarks and concerns reported by the authors in the paper.The myocardium derives energy from many sources suchas free fatty acid (FFAs), glucose, pyruvate, ketone bodies,lactate, and amino acids [2–4]. In fasting and resting con-dition, heart metabolism is mainly based on FFAs oxida-tion, the myocardial FDG uptake should be negligible,glycolysis contributes only about 30 % of substrate butdietary and hormonal conditions can modify this situation[5]. In the fasting state, the rate of myocardial FFAs oxi-dation is high, inhibiting glycolysis and glucose oxidationwith consequently low levels of glucose and insulin, while,after glucose load or during hyperglycemic condition,plasma concentrations of glucose and insulin rise reducingperipheral lipolysis, lowering plasma concentrations ofFFAs and hence reducing their availability to the myo-cardium. Glucose then becomes the dominant substrate formyocardial energy production [5, 6]. However, the myo-cardial FDG uptake in the fasting healthy subjects variesunder the clinical fasting conditions [7, 8] and increasedFDG uptake in the myocardium does not significantlycorrelate with the blood glucose level, age, or duration offasting in non-diabetic patients [7, 9]. Only in the uncon-trolled diabetic patients with high levels of blood glucosethere is absent or faint myocardial FDG uptake. Myocardialischemia strikingly alters myocardial substrate metabolism[5]. As blood flow and oxygen supply decline, oxidativemetabolism decreases but still remains the dominant sourceof residual ATP production accounting for more than 90 %[10]. Ischemia is also associated with increased glycolysisbut becomes uncoupled from glucose oxidation with excessproduction of pyruvate and lactate which impair glycolysis[4, 11]. In the normal myocardium FDG distribution pat-terns could be classified into three types (absent to faintuptake; regional uptake; diffuse uptake), but they couldhave no specific meaning [7]. Moreover, even in the sameindividual and under similar fasting conditions, the myo-cardial FDG uptake is neither stable nor reproducible andthe transition from the intense FDG uptake of a dominantlyglycolytic myocardial metabolism to the absent FDGuptake of a dominantly FFAs metabolism is not entirelyuniform either temporally or regionally [6]. In daily clini-cal practise, despite adequate fasting period, the pattern ofmyocardial FDG heart uptake varies a lot, making difficultthe differential diagnosis between physiological and path-ological uptakes. For these reasons the results of

Abstract 53: Noninvasive Detection of Inflammation of Murine Stasis Deep Venous Thrombosis (DVT) Using Integrated 18F-FDG PET/CT

Background Noninvasive imaging of inflammation in DVT could offer new insights into the resolution of deep venous thrombosis (DVT) in living subjects. While a few clinical studies have reported incidental uptake of 18F-FDG PET in a subgroup of DVTs, limited information exists regarding the cellular mechanisms and time dependence of FDG uptake in DVT. Here we investigated whether FDG-PET could enhance murine stasis-induced DVT in acute to subacute DVT, and assessed the inflammatory cell infiltrate within DVT. Methods C57BL/6 mice (n=6) underwent ligation of the jugular vein to induce stasis DVT. At DVT timepoints from day 2 to day 7, 18F-FDG PET (25-35 μCi/g) and contrast CT venography was performed. After PET/CT imaging, animals were sacrificed and veins were resected. Gamma-counting and histological analyses of thrombus neutrophils and macrophages were then performed. Results PET/CT images demonstrated the FDG signal accumulated in thrombosed jugular veins in acute DVT, and significantly more than in contra-lateral sham veins (SUV = 1.27±0.11 vs. 0.79±0.069, SUVmax = 1.45±0.090 vs. 1.02±0.056, p<0.05, respectively). The %IDGT was significantly higher in thrombosed veins (7.21±0.17% vs. 1.54±0.47% sham vein, p<0.05). The % positive area of neutrophil in thrombus was 25 times higher than macrophages (14.1±2.9% vs. 0.58±0.091%, p<0.0001) in earlier-stage (day2-4) DVT. Conclusions Noninvasive FDG-PET/CT can visualize inflammation in experimental DVT. Thrombus neutrophils appear to be the cellular source underlying accumulated FDG signal in earlier-stage DVT. FDG-PET may enable assessment of thrombus age and provide new insights into the resolution of DVT.

Incidental focal FDG uptake in heart is a lighthouse for considering cardiac screening

Cardiac FDG uptake is known to show a variety of patterns under clinical fasting conditions. We hypothesized that focal FDG uptake in the heart (FUH) represents a sign of cardiac disease risk, especially in coronary artery disease (CAD).The aim of this study was to clarify the relationship between FUH and cardiac disease. Cases showing FUH were selected based on comments in diagnostic reports or identification on retrospective review. Quantitative analysis was performed using maximum standardized uptake value (SUVmax), with regions of interest drawn over focal uptake areas in the heart as confirmed by PET/CT and in lateral side of the same slice showing focal FDG uptake. For the 20 patients (11 men, 9 women) with confirmed FUH, coronary artery stenosis or history of treatment for coronary disease was present in 11 patients (55.0 %), and 2 patients showed apical hypertrophy. Mean SUVmax of FUH did not differ significantly between patients with confirmed cardiac disease and those with no evidence of cardiac disease (P = 0.78). FUH suggests a high likelihood of CAD in patients without myocardial symptoms. Cardiac screening or a check of the history of cardiac disease is thus worth considering when FUH is seen incidentally on FDG-PET/CT.

Incidental focal colorectal18F-fluorodeoxyglucose uptake on positron emission tomography/computed tomography

To assess the clinical significance of incidental focal colorectal ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake on ¹⁸F-FDG-positron emission tomography/computed tomography (PET/CT).The records of all the cases which had undergone colonoscopy after PET/CT within a two weeks interval were reviewed. Adenomas were considered advanced when they were villous, ≥ 10 mm in size, or had high-grade dysplasia. Colorectal cancers and advanced adenomas are collectively referred to as advanced colorectal neoplasms. Receiver-operating characteristic curve analysis was used to determine the significant predictive maximum standardized uptake value (SUVmax) cutoff value for advanced colorectal neoplasms and cancer.Ninety-five colorectal lesions matched the site of incidental focal colorectal ¹⁸F-FDG uptake on PET/CT and 146 did not. Colonoscopy showed advanced colorectal neoplasms corresponding to the site of ¹⁸F-FDG uptake in 49 of the 95 (51.5%) lesions with incidental uptake. Of the lesions without incidental uptake, only 6 of 146 (4.1%) had advanced colorectal neoplasms on colonoscopy, indicating a statistically significant difference between the two groups (P < 0.001). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of incidental focal ¹⁸F-FDG uptake in identifying advanced colorectal neoplasms were 89.1%, 75.3%, 51.6%, 95.9%, and 78.4%, respectively. In detecting only CRC, these values were 89.2%, 69.6%, 34.7%, 97.3%, and 72.6%, respectively. The significant SUVmax cutoff value for advanced colorectal neoplasms (area under the curve 0.755, P < 0.001) was 4.35, with a sensitivity, specificity, PPV, NPV, and accuracy of 75.5%, 65.2%, 69.8%, 71.4% and 70.5%, respectively. For CRC, 5.05 was the significant SUVmax cutoff value (area under the curve 0.817, P < 0.001), with a sensitivity, specificity, PPV, NPV, and accuracy of 84.8%, 71.0%, 80.9%, 89.8%, and 75.8%, respectively.The presence of incidental focal colorectal ¹⁸F-FDG uptake on PET/CT with a SUVmax ≥ 4.35 increases the likelihood of an advanced colorectal neoplasm.

Focal thyroid incidental uptake detected by 18F-fluorodeoxyglucose positron emission tomography

SummaryAim: To perform a meta-analysis of published data on the prevalence and risk of malignancy of focal thyroid incidental uptake (FTIs) detected by Fluorine-18-Fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) or PET/CT. Methods: A comprehensive literature search of studies published up to and including December 2012 was performed. Pooled prevalence and malignancy risk of FTIs were calculated, including a sub-analysis for the geographic areas of origin of the studies. Results: 34 studies including 215 057 patients were selected. Pooled prevalence of FTIs was 1.92% (95% confidence interval [95%CI]: 1.87–1.99%). Overall, 1522 FTIs underwent histopathology evaluation. Pooled risk of malignancy was 36.2% (95%CI: 33.8–38.6%), without significant differences among various geographic areas. Conclusions: FTIs are observed in about 2% of 18F-FDG-PET or PET/CT scans and carry a significant risk of malignancy. Therefore, further investigation is warranted whenever FTIs are detected by 18F-FDG-PET or PET/CT.

F18-FDG-PET/CT thyroid incidentalomas: a wide retrospective analysis in three Italian centres on the significance of focal uptake and SUV value

Thyroid incidental uptake is defined as a thyroid uptake incidentally and newly detected by imaging techniques performed for an unrelated purpose and especially for non-thyroid diseases. Aim of the study was to establish the prevalence and pathological nature of focal thyroid incidentalomas detected at F18-FDG-PET/CT in patients studied for oncological purposes and not for thyroid disease. Secondary end point was to establish a possible maximum standardised uptake value cut-off over which a malignant lesion should be suspected. We have retrospectively evaluated 49519 patients who underwent F18-FDG-PET/CT for oncologic purposes in three Nuclear Medicine Centres (N.1 = 11278, N.2 = 31076, N.3 = 7165). A focal incidental thyroid uptake was diagnosed in 729 (1.5 %) patients (287-39.4 % male and 442-60.6 % female; average age: 65.26). Of 729 thyroid incidentalomas 211 (28.9 %) underwent further investigation to determine the nature of the nodule; 124/211 (58.8 %) incidentalomas were benign, 72/211 (34.1 %) malignant, 4/211 (1.9 %) non-diagnostic at cytological examination in the absence of surgery and histological evaluation and 11/211 (5.2 %) were indeterminate at cytological examination. A centre-based receiver operating curve (ROC) analysis of the patients with a definitive diagnosis was performed to identify a SUVmax cut-off useful in differentiating benign from malignant incidentalomas. In the centre N.1 it was 4.8 (sensitivity = 95.7 %, specificity = 46.4 %, area under the curve = 0.758); 5.3 in the centre N.2 (sensitivity = 76.3 %, specificity = 72.5 %, area under the curve = 0.815); 7 in the centre N.3 (sensitivity = 57.1 %, specificity = 79.3 %, area under the curve = 0.627). F18-FDG-PET/CT thyroid incidentalomas are a relevant diagnostic reality which requires further investigations and clinical management especially considering that, despite mainly benign, approximately one third of focal thyroid uptakes are malignant.

Incidental uptake of 123I MIBG in brown fat

Incidental uptake of 123I MIBG in brown fat

Metachronous pancreatic acinar cell carcinoma discovered in early stage during follow-up of breast cancer: report of a case.

We present an extremely rare case of early-stage acinar cell carcinoma of the pancreas. A 49-year-old woman, who had undergone radical surgery for breast cancer 3years earlier, was suspected to have a rib metastasis during follow-up. She also had a family history of cancer. No accumulation was seen in the left rib on (18)F-fluorodeoxyglucose positron emission tomography with computed tomography, but incidental high uptake into the pancreatic head suggested malignant pancreatic tumor. The tumor was completely resected by pancreatoduodenectomy, and pancreatic acinar cell carcinoma was demonstrated histopathologically. To the best of our knowledge, this is the first reported case of a pancreatic acinar cell carcinoma smaller than 1cm to be detected by (18)F-fluorodeoxyglucose positron emission tomography and computed tomography.

Timely investigation of incidental focal colorectal fluorodeoxyglucose uptake

Timely investigation of incidental focal colorectal fluorodeoxyglucose uptake

Analysis of incidental focal hypermetabolic uptake in the breast as detected by 18F-FDG PET/CT: clinical significance and differential diagnosis

With the widespread use of PET/CT, incidental hypermetabolic foci unrelated to the known malignancy have been described with increasing frequency. To determine the frequency and clinical significance of incidental focal hypermetabolic uptake in the breast as detected by 18F-FDG PET/CT, and to explore factors differentiating benign and malignant breast uptake. From January 2005 to June 2010, a total of 51,971 whole-body FDG PET/CT examinations were performed in our clinic. After excluding 7254 sets of PET/CT data from patients known to have breast cancer, we retrospectively identified patients showing incidental focal hypermetabolic activity in the breast. Of 44,717 PET/CT examinations conducted on 32,988 patients, we identified 131 patients with no previous known or suspected benign and malignant breast disease. The etiology, mean SUV(max), and diameter of breast lesions were assessed. We also compared the presentation of the lesions on CT, mammography, and ultrasonography. Of the 131 patients, 60 were histologically diagnosed with breast lesions, including 32 with malignant and 28 with benign lesions. An additional 11 patients were followed-up for more than 2 years and were clinically considered to have benign lesions. The remaining 60 patients who had neither histologic confirmation nor followed-up for more than 2 years were excluded. Therefore, 71 patients were finally included. The mean SUV(max) of 39 benign lesions and 32 malignant lesions were 2.02 ± 1.52 and 3.71 ± 3.83, respectively (P = 0.0001). At a cut-off value of 2.3, the rate of malignancy and specificity of the mean SUVmax for differentiating benign and malignant breast lesions were 61.3%, 76.3, respectively. The CT data from PET/CT revealed that the mean diameters of benign and malignant lesions were 1.19 ± 0.97 cm and 2.26 ± 1.96 cm, respectively (P = 0.0009). Incidental focal 18F-FDG uptake in the breast as detected by PET/CT was indicative of malignancy in 45% of patients. Both mean SUV(max) and diameter were greater for malignant than benign lesions.

Predictive value according to location of incidental focal colorectal fluorodeoxyglucose uptake on positron emission tomography scans

Predictive value according to location of incidental focal colorectal fluorodeoxyglucose uptake on positron emission tomography scans

Incidental colonic 18F-FDG uptake in gastric cancer patients: Correlation with colonoscopic and histopathologic findings.

43 Background: The ability of integrated positron emission tomography and computed axial tomography (PET-CT) to detect synchronous colonic pathology in gastric cancer patients is not fully defined. Methods: Between Jan 2009 and July 2010, total 370 patients diagnosed as primary gastric cancer underwent curative resection in our institution. Among them 147 patients had taken PET-CT and colonoscopy preoperatively. The FDG uptake pattern were reviewed and classified as focal (showed foci of FDG uptake&gt;3.5 SUV max), diffuse (showed FDG uptake&lt;3.5 SUVmax without any foci of uptake) and absent uptake (showed no FDG uptake pattern). Patients with history of known colonic malignancy or colon surgery were excluded. Results: Among the 18 patients who had discovered as focal incidental FDG uptake in colon without any previous colonic pathology, in six patients, has revealed unexpected colonic adenocarcinoma. The mean SUVmax value of focal uptake group(Group A) is 7.3 (±2.3), for those six patients, it was 9.4 (±2.9,p=0.02). And in the diffuse uptake group, most common colonic pathology was tubular adenoma with low grade dysplasia following hyperplastic polyp. The age, gender and primary gastric cancer stage was not differed between the groups. Conclusions: In conclusion, the focal uptake pattern in colon on preoperative PET-CT in gastric cancer patients should be followed by colonoscopy evaluation for incidental significant colonic pathology even colon cancer. However, there was no cut off SUVmax value for the mandatory colonoscopy evaluation based on PET-CT.

The Role of 18F-Fluorodeoxyglucose Positron Emission Tomography in the Diagnosis of Incidental Thyroid Lesions

Objective: The aim of this study was to determine the diagnostic accuracy of incidental FDG-PET/CT uptake in the thyroid in patients with cancers of nonthyroidal origin, in order to reduce the number of thyroidectomies performed on nodules that subsequently proved to be benign. Material and methods: From January to September 2011 a total of 2510 patients were evaluated at our institution with whole-body FDG-PET. The studies were done for a variety of diagnoses including metastatic work-up for lymphoma, head and neck cancer, and other nonthyroidal malignant nodules. 30 patients were identified with incidental focal or diffuse uptake in thyroid bed. All patients underwent measurement of serum level of thyroid hormones and ultrasonography (US). While the patients with focal uptake underwent fine needle aspiration biopsy, FNAB. Results: PET incidentaloma was observed in 30 patients (0.12% of the whole population) with normal thyroid functions and there weren’t known clinical manifestations of thyroid disease. FDG PET uptake pattern was diffuse in 8 patients (26.7%) and focal in 22 patients (73.3%). SUVmax was included between 2.5 and 20. The patients with focal uptake underwent FNAB which demonstrated 4 patients with TIR1 (18.2%), 3 patients with TIR2 (13.6%), 11 patients with TIR3 (50%), 2 patients with TIR4 (9.1%), 1 patient with TIR5 (4.5) and 1 patient with TIR6 (4.5%). All 4 patients with TIR4, TIR5 and TIR6 underwent to thyroidectomy and the final diagnosis was papillary carcinoma. Conclusions: The results of this study suggest that incidentally found thyroid lesions by FDG-PET/CT, especially a focal FDG uptake and a high SUV, have a high probability of thyroid malignancy.

FDG PET/CT Imaging Suggests Lymphoma Involving Prostate May Be More Resistant to Treatment

FDG PET imaging is generally not useful for prostate cancer. Nevertheless, incidental intense FDG uptake in the prostate warrants further evaluation to assess for prostatic malignancy. We report a case where intense FDG uptake was incidentally noted in an enlarged prostate on FDG PET/CT scan performed for a large left hilar/mediastinal mass (that was also intensely FDG avid along with several additional FDG-avid lesions elsewhere). Biopsy of the prostate and mediastinal lesions revealed large B-cell non-Hodgkin lymphoma at both sites. Serial FDG PET/CT imaging in this patient revealed that the prostatic lymphomatous lesions showed a slower and incomplete response to chemotherapy compared with other sites of lymphomatous involvement (that showed a rapid and complete response to chemotherapy) in the same patient.

Symmetric increased skeletal muscular uptake of F-18 fluoro-deoxyglucose: A clue for the diagnosis of Graves′ disease

F-18 fluoro-deoxyglucose (FDG) uptake in the thyroid and thymus is well reported in patients with Graves’ disease. Incidental skeletal muscle uptake has also been reported in other non-musculoskeletal (benign and malignant) pathologies. We report a patient of Graves’ disease showing symmetrical skeletal muscle uptake but no thyroidal or thymus uptake of FDG.

Incidental Uptake of In-111 Ibritumomab Tiuxetan in Surgically Treated Fracture

In-111 ibritumomab tiuxetan pretherapy imaging is performed prior to radioimmunotherapy with Y-90 ibritumomab tiuxetan in patients with lymphoma in order to estimate the biodistribution of the radiolabeled antibodies. We report the case of a 61-year-old woman with relapsed follicular lymphoma. In-111 ibritumomab tiuxetan pretherapy imaging showed tracer accumulation in a surgically treated fracture of the left calcaneus as well as in the involved lesions. The patient had fractured her left calcaneus 6 months before the radioimmunotherapy, and fracture of the left calcaneus without lymphoma involvement had been revealed operatively at that time. Clinical features and magnetic resonance imaging (MRI) indicated an inflammatory response in the left heel. We concluded that this inflammation played an important role in the uptake on pretherapy imaging. It should be kept in mind that the inflammation is a differential diagnosis of lymphoma involvement in In-111 ibritumomab tiuxetan pretherapy imaging. To the best of our knowledge, this is the first case report of In-111 ibritumomab tiuxetan uptake in a surgically treated fracture.

T1214 Clinical Significance of Incidental Gastrointestinal FDG Uptake Found on PET/PET-CT Scans During Staging of Multiple Myeloma

T1214 Clinical Significance of Incidental Gastrointestinal FDG Uptake Found on PET/PET-CT Scans During Staging of Multiple Myeloma

Incidental head and neck 18F-FDG uptake on PET/CT without corresponding morphological lesion: early predictor of cancer development?

Incidental head and neck 18F-FDG uptake on PET/CT without corresponding morphological lesion: early predictor of cancer development?

W1993 Mixed Hyperplastic-Adenomatous Polyps Are Distinct from Sessile Serrated Adenomas with Low-Grade Dysplasia

spective study of patients who underwent colonoscopy within 1 month after PET-CT from January 2006 to January 2008. The PET image obtained 1hour after F-18 FDG 15mCi injection and non-contrast CT images used for attenuation correction were fused for analysis. The intensity of FDG uptake was quantified using the maximal standardized uptake value (SUVmax). In the case of colonoscopic focal lesion, we reviewed the described location, size and histologic finding. RESULTS: Total 1092 patients were enrolled, except 778 patients who were previously conformed colorectal cancer. Of total 1092, incidental colorectal FDGuptake foci were found in 64 (5.8%) patents. In 24 (37%) of 64 patients, the colonoscopic lesions were detected in the same location of incidental colorectal FDG-uptake (true positive) and remnant 40 (63%) patients were false positive. Among these lesions of 24 patients, 16 lesions were premalignant colorectal lesions or colorectal cancers (5 advanced adenomas that was larger adenoma than 1 cm size, villous tissue or high grade dysplasia, 11 colorectal cancer) and 8 lesions were small adenomas (5 patients) or hyperplastic polyps (3 patients). There was no difference of mean SUVmax between true-positive (SUVmax = 7.1) and falsepositive (SUVmax = 7.2) colorectal FDG-uptake foci. CONCLUSION: In PET-CT, incidental colorectal FDG-uptake suggests the possibility of premalignant colorectal lesion and colorectal cancer, therefore it is necessary to confirm whether incidental colorectal FDG uptake focus is malignant or not with colonoscopy.

Spectrum of Focal Benign Musculoskeletal 18F-FDG Uptake at PET/CT of the Shoulder and Pelvis

The purpose of this article is to illustrate the spectrum of common benign intraarticular and extraarticular disorders associated with focal (18)F-FDG uptake in the shoulder and pelvic areas in oncology patients referred for PET/CT. A wide spectrum of benign musculoskeletal disorders associated with focal FDG uptake may be detected in cancer patients. This incidental uptake usually does not seem to be a clinically significant finding, but it can affect quality of life.