Focal incidental colorectal fluorodeoxyglucose uptake:Should it be spotlighted?

Fluorine-18 fluorodeoxyglucose(F-18 FDG)positron emission tomography/computed tomography(PET/CT)has emerged as a cornerstone in cancer evaluation imaging,with a well-established history spanning several years.This imaging modality,encompassing the examination of the body from the base of the skull to the upper thighs,comprehensively covers the chest and abdominopelvic regions in a singular scan,allowing for a holistic assessment of nearly the entire body,including areas of marginal interest.The inherent advantage of this expansive scan range lies in its potential to unveil unexpected incidental abnormal hypermetabolic areas.The identification of incidental focal FDG uptake within colorectal regions during PET/CT scans is not an uncommon occurrence,albeit fraught with challenges associated with non-specific FDG uptake.The presence of benign colorectal lesions or physiological uptake poses a particular obstacle,as these may manifest with FDG uptake levels that mimic malignancy.Consequently,physicians are confronted with a diagnostic dilemma when encountering abnormal FDG uptake in unexpected colorectal areas.Existing studies have presented divergent results concerning these uptakes.Standardized uptake value and its derivatives have served as pivotal metrics in quantifying FDG uptake in PET images.In this article,we aim to succinctly explore the distinctive characteristics of FDG,delve into imaging findings,and elucidate the clinical significance of incidental focal colorectal uptake.This discussion aims to contribute valuable insights into the nuanced interpretation of such findings,fostering a comprehensive understanding.

Unexpected focal fluorodeoxyglucose uptake in main organs;pass through or pass by?

Since the inception of fluorine-18 fluorodeoxyglucose(F-18 FDG),positron emission tomography/computed tomography(PET/CT)utilizing F-18 FDG has become widely accepted as a valuable imaging modality in the field of oncology,with global prevalence in clinical practice.Given that a single Torso PET/CT scan encompasses the anatomical region from the skull base to the upper thigh,the detection of incidental abnormal focal hypermetabolism in areas of limited clinical interest is both feasible and not uncommon.Numerous investigations have been undertaken to delineate the distinctive features of these findings,yet the outcomes have proven inconclusive.The incongruent results of these studies present a challenge for physicians,leaving them uncertain about the appropriate course of action.This article provides a succinct overview of the characteristics of fluorodeoxyglucose,followed by a comprehensive discussion of the imaging findings and clinical significance associated with incidental focal abnormal F-18 FDG activity in several representative organs.In conclusion,while the prevalence of unrecognized malignancy varies across organs,malignancies account for a substantial proportion,ranging from approximately one-third to over half,of incidental focal uptake.In light of these rates,physicians are urged to exercise vigilance in not disregarding unexpected uptake,facilitating more assured clinical decisions,and advocating for further active evaluation.

Appearance of aseptic vascular grafts after endovascular aortic repair on[(18)F]fluorodeoxyglucose positron emission tomography/computed tomography

BACKGROUND Diagnosis of prosthetic vascular graft infection with[(18)F]fluorodeoxyglucose positron emission tomography/computed tomography(18F-FDG PET/CT)allows for early detection of functional changes associated with infection,based on increased glucose utilization by activated macrophages and granulocytes.Aseptic vascular grafts,like all foreign bodies,can stimulate an inflammatory response,which can present as increased activity on 18F-FDG PET/CT.Consequently,distinguishing aseptic inflammation from graft infection,though important,can be difficult.In the case of endovascular aneurysm repair(EVAR),a minimally invasive procedure involving the transfemoral insertion of an endoprosthetic stent graft,the normal postoperative appearance of these grafts on 18F-FDG PET/CT can vary over time,potentially confounding study interpretation.AIM To investigate the visual,semiquantitative,and temporal characteristics of aseptic vascular grafts in patients status post EVAR.METHODS In this observational retrospective cohort study,patients with history of EVAR who underwent 18F-FDG PET/CT for indications other than infection were identified retrospectively.All patients were asymptomatic for graft infection-no abdominal pain,fever of unknown origin,sepsis,or leukocytosis-at the time of imaging and for≥2 mo after each PET/CT.Imaging studies such as CT for each patient were also reviewed,and any patients with suspected or confirmed vascular graft infection were excluded.One hundred two scans performed on 43 patients(34 males;9 females;age=77±8 years at the time of the final PET/CT)were retrospectively reviewed.All 43 patients had an abdominal aortic(AA)vascular graft,40 patients had a right iliac(RI)limb graft,and 41 patients had a left iliac(LI)limb graft.Twentytwo patients had 1 PET/CT and 21 patients had from 2 to 9 PET/CTs.Grafts were imaged between 2 mo to 168 mo(about 14 years)post placement.Eight grafts were imaged within 6 mo of placement,including three that were imaged within three months of placement.The mean interval between graft placement and PET/CT for all 102 scans was 51±39 mo.PET/CT data was reconstructed with region-of-interest analysis of proximal,mid and distal portions of the grafts and background ascending aorta.Maximum standardized uptake value(SUVmax)was recorded for each region.SUVmax-to-background uptake ratios(URs)were calculated.Visual assessment was performed using a 2-pattern grading scale:Diffuse(homogeneous uptake less than liver uptake)and focal(one or more areas of focal uptake in any part of the graft).Statistical analysis was performed.RESULTS In total,there were 306 AA grafts,285 LI grafts,282 RI grafts,and 306 ascending aorta background SUVmax measurements.For all 102 scans,mean SUVmax values for AA grafts were 2.8-3.0 along proximal,mid,and distal segments.Mean SUVmax values for LI grafts and RI grafts were 2.7-2.8.Mean SUVmax values for background were 2.5±0.5.Mean URs were 1.1-1.2.Visual analysis of the scans reflected results of quantitative analysis.On visual inspection,98%revealed diffuse,homogeneous 18F-FDG uptake less than liver.Graft URs and visual pattern categories were significantly associated for AA graft URs(F-ratio=21.5,P<0.001),LI graft URs(F-ratio=20.4,P<0.001),and RI graft URs(F-ratio=30.4,P<0.001).Thus,visual patterns of 18F-FDG uptake corresponded statistically significantly to semiquantitative URs.The age of grafts showing focal patterns was greater than grafts showing diffuse patterns,87±89 vs 50±37 mo,respectively(P=0.02).URs were significantly associated with graft age for AA grafts(r=0.19,P=0.001).URs were also significantly associated with graft age for LI grafts(r=0.25,P<0.0001),and RI grafts(r=0.31,P<0.001).Quartiles of similar numbers of graft(n=25-27)grouped by graft age indicated that URs were significantly higher for 4th quartile vs 2nd quartile URs(F-ratio=19.5,P<0.001).When evaluating URs,graft SUVmax values within 10%-20%of the ascending aorta SUVmax is evident in aseptic grafts,except for grafts in the oldest quartiles.In this study,grafts in the oldest quartiles(>7 years post EVAR)showed SUVmax up to 30%higher than the ascending aorta SUVmax.CONCLUSION Characteristics of an aseptic vascular stent graft in the aorta and iliac vessels on 18F-FDG PET/CT include graft SUVmax values within 10%-20%of the ascending aorta background SUVmax.The SUVmax of older aseptic grafts can be as much as 30%above background.The visual uptake pattern of diffuse,homogeneous uptake less than liver was seen in 98%of aseptic vascular grafts,making this pattern particularly reassuring for clinicians.

Role of 18F-fluorodeoxyglucose positron emission tomography imaging in surgery for pancreatic cancer

AIM： To evaluate the role of positron emission tomography using 18F-fluorodeoxyglucose （FDG-PET） in the surgical management of patients with pancreatic cancer, including the diagnosis, staging, and selection of patients for the subsequent surgical treatment. METHODS： This study involved 53 patients with proven primary pancreatic cancer. The sensitivity of diagnosing the primary cancer was examined for FDG-PET CT, cytological examination of the bile or pancreatic juice, and the serum levels of carcinoembrionic antigens （CEA） and carbohydrate antigen 19-9 （CA29-9）. Next, the accuracy of staging was compared between FDG-PET and CT. Finally, FDG-PET was analyzed semiquantitatively using the standard uptake value （SUV）. The impact of the SUV on patient management was evaluated by examining the correlations between the SUV and the histological findings of cancer. RESULTS： The sensitivity of FDG-PET, CT, cytological examination of the bile or pancreatic juice, and the serum levels of CEA and CA19-9 were 92.5%, 88.7%, 46.4%, 37.7% and 69.8%, respectively. In staging, FDG-PET was superior to CT only in diagnosing distant disease （bone metastasis）. For local staging, the sensitivity of CT was better than that of FDG-PEr. The SUV did not correlate with the pTNM stage, grades, invasions to the vessels and nerve, or with the size of the tumor. However, there was a statistically significant difference （4.6 ± 2.9 vs 7.8 ± 4.5, P = 0.024） in the SUV between patients with respectable and unresectable disease. CONCLUSION： FDG-PET is thus considered to be useful in the diagnosis of pancreatic cancer. However, regarding the staging of the disease, FDG-PET is not considered to be a sufficiently accurate diagnostic modality. Although the SUV does not correlate with the patho-histological prognostic factors, it may be useful in selecting patients who should undergo subsequent surgical treatment.

Xanthogranulomatous cholecystitis mimicking gallbladder carcinoma with a false-positive result on fluorodeoxyglucose PET

Recently, several reports have demonstrated that fluorine-18 fluorodeoxyglucose positron emission tomography （FDG-PET） is useful in differentiating between benign and malignant lesions in the gallbladder. However, there is a limitation in the ability of FDG-PET to differentiate between inflammatory and malignant lesions. We herein present a case of xanthogranulomatous cholecystitis misdiagnosed as gallbladder carcinoma by ultrasonography and computed tomography. FDG-PET also showed increased activity. In this case, FDG-PET findings resulted in a false-positive for the diagnosis of gallbladder carcinoma.

Emerging role of ^(18)F-fluorodeoxyglucose positron emission tomography for guiding management of hepatocellular carcinoma

Hepatocellular carcinoma(HCC) is one of major causes of cancer mortality worldwide. For decades, ^(18)F-fluorodeoxyglucose(FDG) positron emission tomography(PET) has been widely used for staging, predicting prognosis, and detecting cancer recurrence in various types of malignant diseases. Due to low sensitivity of FDG PET for detecting intrahepatic HCC lesions, the clinical value of FDG PET in HCC patients has been limited. However, recent studies with diverse analytic methods have shown that FDG PET has promising role in aiding management of HCC patients. In this review, we will discuss the clinical role of FDG PET for staging, predicting prognosis, and evaluating treatment response in HCC. Further, we will focus on recent clinical studies regarding implication of volumetric FDG PET parameters, the significance of FDG uptake in HCC for selecting treatment and predicting treatment response, and the use of radiomics of FDG PET in HCC.

Prognostic value and clinical correlations of18-fluorodeoxyglucose metabolism quantifiers in gastriccancer

AIM： To investigate the correlations of pre-treatmentpositron emission tomography-computer tomography（PET-CT） metabolic quantifiers with clinical data ofunstratified gastric cancer （GC） patients.METHODS： Forty PET-CT scans utilising 18-fluorodeoxyglucosein patients who received no prior treatmentwere analysed. Analysis involved measurements ofmaximum and mean standardised uptake volumes（SUV）, coefficient of variation （COV）, metabolictumour volumes and total lesion glycolysis of differentthresholds above which the tumor volumes wereidentified. The threshold values were： SUV absolutevalue of 2.5, 30% of SUVmax, 40% of SUVmax,and liver uptake-based （marked 2.5, 30, 40 and liv,respectively）. Clinical variables such as age, sex,clinical stage, performance index, weight loss, tumorhistological type and grade, and CEA and CA19.9 levelswere included in survival analysis. Patients receivedvarious treatment modalities appropriate to theirdisease stage and the outcome was defined by time tometastasis （TTM） and overall survival （OS）. Clinical andmetabolic parameters were evaluated by analysis of variance, receiver operating characteristics, univariateKaplan-Meier, and multivariate Cox models. P 〈 0.05was considered statistically significant.RESULTS： Significant differences were observedbetween initially disseminated and non-disseminatedpatients in mean SUV （6.05 vs 4.13, P = 0.008）, TLG2.5（802 cm3 vs 226 cm3; P = 0.031）, and TLG30 （436 cm3vs 247 cm3, P = 0.018）. Higher COV was associatedwith poor tumour differentiation （0.47 for G3 vs0.28 for G1 and G2; P = 0.03）. MTV2.5 was positivelycorrelated to patient weight loss （〈 5%, 5%-10%and 〉 10%： 40.4 cm3 vs 123.6 cm3 vs 181.8 cm3,respectively, P = 0.003）. In multivariate Cox analysis,TLG30 was prognostic for OS （HR = 1.001, 95%CI：1.0009-1.0017; P = 0.047） for the whole group ofpatients. In the same model yet only including patientswithout initial disease dissemination TLG30 （HR = 1.009,95%CI： 1.003-1.014; P = 0.004） and MTV2.5 （HR = 1.02,95%CI： 1.002-1.036; P = 0.025） were prognostic forOS; for TTM TLG30 was the only significant prognosticvariable （HR = 1.006, 95%CI： 1.001-1.012; P = 0.02）.CONCLUSION： PET-CT in GC may represent a valuablediagnostic and prognostic tool that requires furtherevaluation in highly standardised environments such asrandomised clinical trials.

Nomogram using F-18 fluorodeoxyglucose positron emission tomography/computed tomography for preoperative prediction of lymph node metastasis in gastric cancer

BACKGROUND Lymph node(LN)metastasis is an important prognostic factor in patients with gastric cancer(GC).However,the evaluation of LN metastasis status in the preoperative setting is not accurate.Therefore,precise preoperative prediction of LN metastasis status is crucial for optimal treatment in patients with GC.AIM To develop a preoperative nomogram for LN metastasis using F-18 fluorodeoxyglucose(F-18 FDG)positron emission tomography/computed tomography(PET/CT)and preoperative laboratory test findings in GC.METHODS In this study,the data of 566 GC patients who underwent preoperative F-18 FDG PET/CT and subsequent surgical resection were analyzed.The LN metastasis prediction model was developed in the training cohort and validated in the internal validation cohort.Routine preoperative laboratory tests,including albumin and carbohydrate antigen(CA)19-9 were performed in all patients.Univariate and multivariable logistic regression was performed to validate the preoperative predictive indicators for LN metastasis.RESULTS Of the 566 patients,232(41%)had confirmed histopathologic LN metastasis.Univariate logistic regression revealed that the tumor location,blood hemoglobin,serum albumin levels,neutrophil to lymphocyte ratio,platelet to lymphocyte ratio,CA 19-9,maximum standardized uptake value(SUVmax)of the primary tumor(T_SUVmax),and SUVmax of LN(N_SUVmax)were significantly associated with LN metastasis.In multivariate analysis,T_SUVmax(OR=1.08;95%CI:1.02–1.15;P=0.011)and N_SUVmax(OR=1.49;95%CI:1.19–1.97;P=0.002)were found to be significant predictive factors for LNmetastasis.The LN metastasis prediction model using T_SUVmax,N_SUVmax,serum albumin,and CA 19-9 yielded an area under the curve(AUC)of 0.733(95%CI:0.683–0.784,P=0.025)in the training cohort and AUC of 0.756(95%CI:0.678–0.833,P<0.001)in the test cohort.CONCLUSION T_SUVmax and N_SUVmax measured by preoperative F-18 FDG PET/CT are independent predictive factors for LN metastasis in GC.

Application of fluorodeoxyglucose positron emission tomography in the management of head and neck cancers

The use of fluorodeoxyglucose positron emission to-mography(FDG PET) scan technology in the manage-ment of head and neck cancers continues to increase. We discuss the biology of FDG uptake in malignant lesions and also discuss the physics of PET imaging. The various parameters described to quantify FDG up-take in cancers including standardized uptake value, metabolic tumor volume and total lesion glycolysis are presented. PET scans have found a significant role in the diagnosis and staging of head and neck cancers. They are also being increasingly used in radiation ther-apy treatment planning. Many groups have also used PET derived values to serve as prognostic indicators of outcomes including loco-regional control and overall survival. FDG PET scans are also proving very useful in assessing the efficacy of treatment and management and follow-up of head and neck cancer patients. This review article focuses on the role of FDG-PET com-puted tomography scans in these areas for squamous cell carcinoma of the head and neck. We present the current state of the art and speculate on the future applications of this technology including protocol de-velopment, newer imaging methods such as combinedmagnetic resonance and PET imaging and novel ra-diopharmaceuticals that can be used to further study tumor biology.

^(18)F-fluorodeoxyglucose PET/CT findings of a solitary primary hepatic lymphoma:A case report

Primary hepatic lymphoma is extremely rare,and only a few cases have been described on positron emission tomography(PET) or PET/computed tomography(PET/CT) imaging in the English literature.We report a case of a 55-year-old woman who presented with low-grade fever and weight loss of three months.On CT scanning,a mass was identified which appeared to be a hypoattenuating lesion,on ultrasonographic imaging,the mass was hypoechoic,therefore,liver abscess or hepatic metastasis from a gastrointestinal primary was initially suspected.Tumor markers such as alpha-fetoprotein,carcinoembryonic antigen and carbohydrate antigen 19-9 were within normal limits.PET/CT demonstrated a large abnormal ring-like hypermetabolic focus in the right liver lobe.The lesion was resected and the histo-pathological findings were consistent with lymphoma.The patient was discharged two weeks after surgery and did not receive any further treatment.After 25 mo follow-up,she is in good health.18F-fluorodeoxyglucose PET/CT is useful in confirming the diagnosis of primary hepatic lymphoma by demonstrating no other foci with high uptake in other parts of the body.

Fluorodeoxyglucose uptake in absence of CT abnormality on PET-CT: What is it?

The purpose of this article is to provide a pictorial review of the findings and interpretative pitfalls about focal fluorodeoxyglucose(FDG)uptake in the absence of corresponding computer tomography(CT)lesion or abnormality on an integrated positron emission tomography(PET)-CT.The integrated CT images in the PET-CT scanner allow correct co-registration and fused imaging of anatomical and functional data.On FDG PET-CT imaging,a real pathologic process often demonstrates abnormal uptake associated with a visible corresponding CT lesion or abnormality.When focal uptake is seen on PET imaging but no corresponding anatomic abnormality is visualized on the integrated CT,one should always be aware of possible mis-registration or mismatch of the PET and CT images due to the patient’s respiratory or body motion.While most of the hot spots in the absence of corresponding anatomic abnormalities are artefactual or secondary to benign etiologies,some may represent small sized or early staged neoplasm or metastases,especially in the gastrointestinal tract and skeletons.Caution should be exercised to simply diagnose a pathology based on the presence of the uptake only,or exclude the disease based on the absence of anatomic abnormality.

Characterization of focal hypermetabolic thyroid incidentaloma: An analysis with F-18 fluorodeoxyglucose positron emission tomography/computed tomography parameters

BACKGROUND Incidentally found thyroid tumor(thyroid incidentaloma,TI)on F-18 fluorodeoxyglucose(FDG)positron emission tomography-computed tomography(PETCT)is reported in 2.5%-5%of patients being investigated for non-thyroid purposes.Up to 50%of these cases have been diagnosed to be malignant by cytological/histological results.Ultrasonography(US)and fine-needle aspiration cytology are recommended for thyroid nodules with high FDG uptake(hypermetabolism)that are 1 cm or greater in size.It is important to accurately determine whether a suspicious hypermetabolic TI is malignant or benign.AIM To distinguish malignant hypermetabolic TIs from benign disease by analyzing F-18 FDG PET-CT parameters and to identify a cut-off value.METHODS Totally,12761 images of patients who underwent F-18 FDG PET-CT for nonthyroid purposes at our hospital between January 2016 and December 2020 were retrospectively reviewed,and 339 patients[185 men(mean age:68±11.2)and 154 women(mean age:63±15.0)]were found to have abnormal,either focal or diffuse,thyroid FDG uptake.After a thorough review of their medical records,US,and cytological/histological reports,46 eligible patients with focal hypermetabolic TI were included in this study.The TIs were categorized as malignant and benign according to the cytological/histological reports,and four PET parameters[standardized uptake value(SUV)max,SUV_(peak),SUV_(mean),and metabolic tumor volume(MTV)]were measured on FDG PET-CT.Total lesion glycolysis(TLG)was calculated by multiplying the SUV_(mean) by MTV.Both parametric and non-parametric methods were used to compare the five parameters between malignant and benign lesions.Receiver operating characteristic(ROC)curve analysis was performed to identify a cut-off value.RESULTS Each of the 46 patients[12 men(26.1%;mean age:62±13.1 years)and 34 women(73.9%;mean age:60±12.0 years)]with focal hypermetabolic TIs had one focal hypermetabolic TI.Among them,26(56.5%)were malignant and 20(43.5%)were benign.SUV_(max),SUV_(peak),SUV_(mean),and TLG were all higher in malignant lesions than benign ones,but the difference was statistically significant(P=0.012)only for SUV_(max).There was a positive linear correlation(r=0.339)between SUV_(max) and the diagnosis of malignancy.ROC curve analysis for SUV_(max) revealed an area under the curve of 0.702(P<0.05,95%confidence interval:0.550-0.855)and SUV_(max) cut-off of 8.5 with a sensitivity of 0.615 and a specificity of 0.789.CONCLUSION More than half of focal hypermetabolic TIs on F-18 FDG PET-CT were revealed as malignant lesions,and SUV_(max) was the best parameter for discriminating between malignant and benign disease.Unexpected focal hypermetabolic TIs with the SUV_(max) above the cut-off value of 8.5 may have a greater than 70%chance of malignancy;therefore,further active assessment is required.

Clinical significance of prostate 18F-labelled fluorodeoxyglucose uptake on positron emission tomography/computed tomography:A five-year review

AIM To determine the significance and need for investigation of incidental prostatic uptake in men undergoing ^(18)F-labelled fluorodeoxyglucose(^(18)F-FDG) positron emission tomography/computed tomography(PET/CT) for other indications.METHODS Hospital databases were searched over a 5-year period for patients undergoing both PET/CT and prostate magnetic resonance imaging(MRI). For the initial analysis, the prostate was divided into six sectors and suspicious or malignant sectors were identified using MRI and histopathology reports respectively. Maximum and mean ^(18)F-FDG standardised uptake values were measured in each sector by an investigator blinded to the MRI and histopathology findings. Two agematched controls were selected per case. Results were analysed using a paired t-test and one-way ANOVA. For the second analysis, PET/CT reports were searched for prostatic uptake reported incidentally and these patients were followed up. RESULTS Over a 5-year period, 15 patients underwent both PET/CT and MRI and had biopsy-proven prostate cancer.Malignant prostatic sectors had a trend to higher ^(18)F-FDG uptake than benign sectors, however this was neither clinically nor statistically significant(3.13 ±0.58 vs 2.86 ± 0.68, P > 0.05). ^(18)F-FDG uptake showed no correlation with the presence or histopathological grade of tumour. ^(18)F-FDG uptake in cases with prostate cancer was comparable to that from age-matched controls. Forty-six(1.6%) of 2846 PET/CTs over a 5-year period reported incidental prostatic uptake. Of these, 18(0.6%) were investigated by PSA, 9(0.3%)were referred to urology, with 3(0.1%) undergoing MRI and/or biopsy. No cases of prostate cancer were diagnosed in patients with incidental ^(18)F-FDG uptake in our institute over a 5-year period.CONCLUSION ^(18)F-FDG uptake overlaps significantly between malignant and benign prostatic conditions. Subsequent patient management was not affected by the reporting of incidental focal prostatic uptake in this cohort.

F-18 fluorodeoxyglucose positron emission tomography/computed tomography image of gastric mucormycosis mimicking advanced gastric cancer: A case report

BACKGROUND Mucormycosis is a very rare fungal infection,and its prognosis is poor.Most common sites of infection are the sinuses,lung,or skin,and gastric involvement is uncommon.The standard antifungal therapy is the treatment of choice for gastric mucormycosis.However,the symptoms of gastric mucormycosis are varied and the early diagnosis is not easy.CASE SUMMARY I report a 53-year-old alcoholic man,who was admitted due to epigastric pain.The upper gastrointestinal endoscopy revealed a huge ulcer lesion in the stomach,which was suspected to be gastric cancer.F-18 fluorodeoxyglucose positron emission tomography/computed tomography(F-18 FDG PET/CT)showed diffusely intense FDG uptake at the ulcer lesion of the stomach,and several enlarged hypermetabolic lymph nodes were noted at the left gastric chain.Although,endoscopy and F-18 FDG PET/CT findings suggested advanced gastric cancer with regional lymph node metastases,there was no cancer cells in the biopsy results and multiple fungal hyphae were noted in the periodic acid-Schiff stained image.CONCLUSION He was diagnosed with gastric mucormycosis and successfully underwent amphotericin B and posaconazole treatment.

Significance of incidental focal fluorine-18 fluorodeoxyglucose uptake in colon/rectum,thyroid,and prostate:With a brief literature review

BACKGROUND Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography(F-18 FDG PET/CT),a functional imaging method,is usually performed on the entire torso,and regions of unexpected suspicious focal hypermetabolism are not infrequently observed.Among the regions,colon,thyroid,and prostate were found to be the common organs in a recent umbrella review.Some studies reported that a high rate of malignancy was shown in incidentally identified focal hypermetabolic regions and suggested that further examinations should not be ignored.AIM To investigate the malignancy rate of incidental focal FDG uptake,useful PET parameters and their cutoffs in discrimination between malignant and benign lesions.METHODS Retrospectively,the final reports of 16510 F-18 FDG PET/CT scans performed at our hospital between January 2016 and March 2022 were reviewed to identify incidentally observed FDG uptake in the colon/rectum,thyroid,and prostate.The scans of patients with current or prior malignancies at each corresponding location,without the final reports of histopathology or colonoscopy(for colon and rectum)for the corresponding hypermetabolic regions,or with diffuse(not focal)hypermetabolism were excluded.Finally,88 regions of focal colorectal hypermetabolism in 85 patients(48 men and 37 women with mean age 67.0±13.4 years and 63.4±15.8 years,respectively),48 focal thyroid uptakes in 48 patients(12 men and 36 women with mean age 62.2±13.1 years and 60.8±12.4 years,respectively),and 39 focal prostate uptakes in 39 patients(mean age 71.8±7.5 years)were eligible for this study.For those unexpected focal hypermetabolic regions,rates of malignancy were calculated,PET parameters,such as standardized uptake value(SUV),capable of distinguishing between malignant and benign lesions were investigated,and the cutoffs of those PET parameters were determined by plotting receiver operating characteristic curves.RESULTS In the colon and rectum,29.5%(26/88)were malignant and 33.0%(29/88)were premalignant lesions.Both SUVmax and SUVpeak differentiated malignant/premalignant from benign lesions,however,no parameters could distinguish malignant from premalignant lesions.Higher area under the curve was shown with SUVmax(0.752,95%CI:0.649-0.856,P<0.001)and the cutoff was 7.6.In the thyroid,60.4%(29/48)were malignant.The majority were well-differentiated thyroid cancers(89.7%,26/29).The results of BRAF mutation tests were available for 20 of the 26 welldifferentiated thyroid cancers and all 20 had the mutation.Solely SUVmax differentiated malignant from benign lesions and the cutoff was 6.9.In the prostate,56.4%(22/39)were malignant.Only SUVmax differentiated malignant from benign lesions and the cutoff was 3.8.Overall,among the 175 focal hypermetabolic regions,60.6%(106/175)were proven to be malignant and premalignant(in colon and rectum)lesions.CONCLUSION Approximately 60%of the incidentally observed focal F-18 FDG uptake in the colon/rectum,thyroid,and prostate were found to be malignant.Of the several PET parameters,SUVmax was superior to others in distinguishing between malignant/premalignant and benign lesions.Based on these findings,incidental focal hypermetabolism should not be ignored and lead physicians to conduct further investigations with greater confidence.

Assessment of incidental focal colorectal uptake by analysis of fluorine-18 fluorodeoxyglucose positron emission tomography parameters

BACKGROUND Colon and rectal cancers are among the top five cancers worldwide in terms of their incidence and mortality rates.As the treatment options for cure include surgery even in specific advanced-stage cases,the early detection of lesions is important for applying active treatment methods.Fluorine-18 fluorodeoxyglucose(F-18 FDG)positron emission tomography/computed tomography(PET/CT)is an established imaging study for many types of cancers;however,physiologic uptake in the gastrointestinal tract is a frequent finding and may interfere with lesion identification.Nevertheless,as unexpectedly observed focal colorectal F-18 FDG uptake may harbor malignant lesions,further examination must not be avoided.AIM To assess the clinical implications of unexpected focal colorectal F-18 FDG uptake by analyzing FDG PET parameters.METHODS A total of 15143 F-18 FDG PET/CT scans performed at our hospital between January 2016 and September 2021 were retrospectively reviewed to identify incidentally observed focal colorectal FDG uptake.Finally,83 regions showing focal colorectal FDG uptake with final histopathological reports from 80 patients(45 men and 35 women with mean ages of 66.9±10.7 years and 63.7±15.3 years,respectively)were eligible for inclusion in the present study.Each focal hypermetabolic colorectal region was classified as malignant,premalignant,or benign according to the histopathological report.PET parameters such as maximum and peak standardized uptake value(SUVmax and SUVpeak),metabolic tumor volume(MTV),mean SUV of the metabolic tumor volume(mSUVmtv),and total lesion glycolysis(TLG)were measured or calculated for the corresponding hypermetabolic regions.Parametric and nonparametric statistical comparisons of these parameters were performed among the three groups.Receiver operating characteristic curves were plotted to identify cut-off values.RESULTS The detection rate of incidental focal colorectal uptake was 0.53%(80/15,143).Of the 83 regions with unexpected focal colorectal hypermetabolism,28.9%(24/83)were malignant,32.5%(27/83)were premalignant,and 38.6%(32/83)were benign.Overall,61.4% of the regions had malignant or premalignant lesions.SUVmax,SUVpeak,and mSUVmtv differentiated malignant and/or premalignant lesions from benign lesions with statistical significance(P<0.05).mSUVmtv3.5 differentiated malignant from benign lesions,with the largest area under the curve(AUC)of 0.792 and a cut-off of 4.9.SUVmax showed the largest AUC of 0.758 with a cut-off value of 7.5 for distinguishing between premalignant and benign lesions.Overall,SUVmax with a cut-off value of 7.6(AUC:0.770,95% confidence interval(CI):0.668-0.872;sensitivity,0.686;specificity,0.688)was a superior parameter for distinguishing between malignant/premalignant and benign lesions or physiologic uptake.No parameters differentiated malignant from premalignant lesions.Moderate or weak positive correlations were observed between the long diameter of the malignant lesions and PET parameters such as SUVpeak and some mSUVmtv.CONCLUSION Approximately two-thirds(61.4%)of incidental focal hypermetabolic colorectal regions were malignant/premalignant lesions,for which SUVmax was an independent diagnostic parameter.Unexpected suspicious focal colorectal FDG uptake should not be avoided and consideration for further evaluation is strongly recommended not to miss the two-thirds.

Incidental anal ^18fluorodeoxyglucose uptake:Should we further examine the patient?

BACKGROUND There are no studies on incidental anal ^18F-fluorodeoxyglucose(^18FDG)uptake.AIM To assess the rate and aetiologies of incidental anal ^18FDG uptake and to evaluate the correlation between ^18FDG positron-emission tomography/computed tomography(PET/CT)parameters and the diagnosis of an anorectal disease.METHODS The data from patients with incidental anal ^18FDG uptake were retrospectively analysed.Patients who underwent anorectal examinations were identified and compared to those who did not undergo examinations.Patients who were offered treatment were then identified and compared to those who did not receive treatment.RESULTS Among the 43020^18FDG PET/CT scans performed,197^18FDG PET/CT scans of 146 patients(0.45%)reported incidental anal uptake.Among the 134 patients included,48(35.8%)patients underwent anorectal examinations,and anorectal diseases were diagnosed in 33(69.0%)of these patients and treated in ^18/48(37.5%)patients.Among the examined patients,those with a pathology requiring treatment had significantly smaller metabolic volumes(MV)30 and MV41 values and higher maximal and mean standardized uptake value measurements than those who did not require treatment.CONCLUSION Incidental anal ^18FDG uptake is rare,but a reliable anorectal diagnosis is commonly obtained when an anorectal examination is performed.The diagnosis of an anorectal disease induces treatment in more than one-third of the patients.These data should encourage practitioners to explore incidental anal ^18FDG uptake systematically.

Findings of ¹⁸F-Fluorodeoxyglucose Positron-Emission Tomography in Methotrexate-Related Lymphoproliferative Disorder

Introduction: The use of methotrexate (MTX) for rheumatoid arthritis (RA) is increasing. However, the immune suppression state leads to the occurrence of lymphoproliferative disorder (MTX-LPD). The purpose of this study was to describe the findings of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in MTX-LPD patients, and compare it with non-MTX-related malignant lymphoma (ML). Materials and Methods: We retrospectively reviewed 11 MTX-LPD patients (9 female, mean age 68.3 years) and 21 ML patients (7 female, mean age 60.6 years) with a histopathological diagnosis. FDG-PET imaging was performed using a standard oncology procedure. We assessed the disease distribution based on FDG-PET images and measured the maximum standardized up take values (SUVmax) for each region. Results: Mean values of SUVmax in MTX-LPD and ML were 14.6 and 17.2, respectively (p = 0.49). In MTX-LPD, 55 lesions met the Cotswold classification, consisting of 37 nodal and 18 extranodal lesions. In ML, 82 lesions were found, consisting of 68 nodal and 14 extranodal lesions. MTX-LPD showed a higher incident of the involvement in extranodal lesions throughout the whole body (p < 0.001). Conclusion: Because this disease occurs widely throughout the whole body, we need to pay attention to the less frequent sites as well when performing PET imaging in patients with MTX-LPD.

Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography for Osteochondromas Utilizing a Triple-Time Point Protocol

Purpose: The purpose of this study was to assess solitary osteochondroma and hereditary multiple osteochondral exostoses (HMOCE) utilizing FDG PET and a triple time point protocol. Methods: Seven patients were consented and recruited for PET evaluation of presumed benign osteochondroma. Following injection of 15 mCi of FDG, the lesion(s) of interest was imaged with PET-CT at 45 minutes post injection, whole body at 50 minutes post, and lesion of interest at 95 minutes post injection. A maximum standardized uptake value (SUVmax) was obtained for the lesion(s) of interest at each time point, and an SUVΔ was calculated for each lesion of interest from the first time point to the third time point. Results: 16 lesions from 7 patients were included in the study. Mean SUVmax for all 3 time points was 1.04 with a standard deviation of 0.50 (range 0.3 - 2.2). The mean SUV was 0.096 with a range of 0 - 0.4. Among the 3 patients with histologically confirmed osteochondromas, mean SUVmax was 0.67, with standard deviation of 0.23 and range of 0.3 to 1.0. The mean SUVΔ13 was 0.081 (range 0 - 0.4), mean SUVΔ12 was 0.10 (0 - 0.3), and mean SUVΔ23 was 0.11 (range 0 - 0.4) (p = 0.74). Conclusion: Benign lesions were found to not have progressively increasing uptake on multiple time point FDG PET. Until chondrosarcomas are evaluated using triple time point 18FDG PET, its applicability in the evaluation of osteochondroma versus malignant change remains uncertain.

Imaging of atherosclerotic aorta of rabbit model by detection of plaque inflammation with fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography

Abstract：Background Atherosclerotic plaque rupture is the primary mechanism of thrombosis which plays a key role in the onset of acute coronary syndromes. Detection of these plaques prone to rupture （vulnerable plaque） could be clinically significant for prevention of cardiac events. It has been shown that high metabolism cells have a high uptake of fluorine-18 fluorodeoxyglucose （18F-FDG）. The objective of this study was to investigate the correlation of FDG uptake and the immuno-histochemistry parameters of plaques, and the effect of atorvastatin on vulnerable atherosclerotic plaque in a rabbit model.Methods Ten male New Zealand White rabbits were divided into three groups as follows： （1） normal control group （n=2,C group）： the animals were fed a standard diet at 120 g/d and were given water ad labium; （2） atherosclerosis group （n=4,As group）： animals were fed with high fat diet for 5 months after aortic endothelia damage; （3） treatment group （atherosclerosis ＋ atorvastatin, n=4, Statin group）： animals were fed with high fat diet for 5 months and then changed into normal chow plus atorvastatin （2.5 mg·d-1·kg-1） treatment for another 4 months. Then these four rabbits were imaged with fluorine-18 fluorodexyglucose positron emission tomography/computed tomography （PET/CT） and sacrificed for pathohistologic studies. FDG uptake by the aorta was expressed as target-to-background ratio （TBR）. Maximal standardized uptake value （SUV） was measured over the thoracic and abdominal aortas. The aortic smooth muscle cell （SMC） number, CD-14 antibody positive cell （macrophage） number and the ratio of the thickness of fibrous cap to the thickness of lipid core （cap-to-core ratio） in atherosclerotic plaques were analyzed.Results As group showed significantly higher uptake of FDG than C group （SUVs： 0.746±0.172 vs. 0.286±0.073, P 〈0.001）. After 4 months of atorvastatin treatment and the modification of diet, SUVs decreased significantly （Statin group：0.550±0.134, compared to As group, P 〈0.001）. However, no marked difference was found in TBR, the number of macrophages, the number of SMC and the cap-to-core ratio in the aortic segments between Statin group and As group.The correlation of aortic FDG uptake with SMC assessed by histopathology was negatively significant （r=0.57, P〈0.001）. When aortic FDG uptake was expressed as TBR, it correlated significantly （r=0.69, P 〈0.001） with the macrophage number, and also correlated significantly （r=0.78, P 〈0.001） with the cap-to-core ratio.Conclusion 18F-FDG PET/CT might serve as a useful non-invasive imaging technique for detection of atherosclerotic plaque and potentially permit monitoring of relative changes in inflammation within the atherosclerotic lesion.