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.

Multimodality functional imaging using DW-MRI and 18F-FDG-PET/CT during radiation therapy for human papillomavirus negative head and neck squamous cell carcinoma: Meixoeiro Hospital of Vigo Experience

AIM To noninvasively investigate tumor cellularity measured using diffusion-weighted magnetic resonance imaging(DW-MRI) and glucose metabolism measured by 18 Flabeled fluorodeoxyglucose positron emission tomography/computed tomography(18F-FDG-PET/CT) during radiation therapy(RT) for human papillomavirus negative(HPV-) head and neck squamous cell carcinoma(HNSCC).METHODS In this prospective study, 6 HPV- HNSCC patients underwent a total of 34 multimodality imaging examinations(DW-MRI at 1.5 T Philips MRI scanner [(n = 24) pre-, during-(2-3 wk), and post-treatment(Tx), and 18F-FDG PET/CT pre- and post-Tx(n = 10)]. All patients received RT. Monoexponential modeling of the DW-MRI data yielded the imaging metric apparent diffusion coefficient(ADC) and the mean of standardized uptake value(SUV) was measured from 18F-FDG PET uptake. All patients had a clinical follow-up as the standard of care and survival status was documented at 1 year.RESULTS There was a strong negative correlation between the mean of pretreatment ADC(ρ =-0.67, P = 0.01) and the pretreatment 18F-FDG PET SUV. The percentage(%) change in delta(?) ADC for primary tumors and neck nodal metastases between pre- and Wk2-3 Tx were as follows: 75.4% and 61.6%, respectively, for the patient with no evidence of disease, 27.5% and 32.7%, respectively, for those patients who were alive with disease, and 26.9% and 7.31%, respectively, for those who were dead with disease.CONCLUSION These results are preliminary in nature and are indicative, and not definitive, trends rendered by the imaging metrics due to the small sample size of HPV- HNSCC patients in a Meixoeiro Hospital of Vigo Experience.

Prognostic value of baseline FDG uptake on PET-CT in esophageal carcinoma

AIM: To evaluate the influence of baseline maximum standardized uptake value(SUVmax) on survival in a cohort of patients, undergoing positron emission tomography-computed tomography(PET-CT) scan for esophageal carcinoma. METHODS: The pre-treatment SUVmax numeric reading was determined in patients with confirmed esophageal or junctional cancer having PET-CT scan during the time period 1st January 2007 until 31 st July 2012. A minimum follow up of 12 mo was required. Patients were subdivided into quartiles according to SUVmax value and the influence of SUVmax on survival was assessed using univariate and multivariate analysis. The following pre-treatment factors were investigated: patient characteristics, tumor characteristics and planned treatment. RESULTS: The study population was 271 patients(191male) with esophageal or junctional carcinoma. The median age was 65 years(range 40-85) and histologic subtype was adenocarcinoma in 197 patients and squamous carcinoma in 74 patients. The treatment intent was radical in 182 and palliative in 89 patients. SUVmax was linked to histologic subtype(P = 0.008), tumor site(P = 0.01) and Union for International Cancer Control(UICC) stage(P < 0.001). On univariate analysis, prognosis was significantly associated with SUVmax(P = 0.001), T-stage(P < 0.001) and UICC stage(P < 0.001). On multivariate analysis, only T-stage and UICC stage remained significant. CONCLUSION: Pretreatment SUVmax was not a useful marker in isolation for determining prognosis of patients with esophageal carcinoma.

Positron emission tomography/computed tomography findings of multiple cystic lymphangiomas in an adult: A case report

BACKGROUND Lymphangioma is a rare benign cystic tumor believed to be a proliferation of heterotopic lymphocytes.It is caused by congenital lymphatic dysplasia or other acquired factors related to surgery,trauma,infection,or cancer.In this article,we present the case of an adult patient who underwent multi-modal imaging and whose condition was finally confirmed to be multiple cystic lymphangiomas by pathological examination.CASE SUMMARY A 61-year-old man was referred to our hospital for having suffered from painless gross hematuria for 2 wk.Multiple masses rising from the retroperitoneum and pelvis were found incidentally by urinary ultrasonography.Contrast-enhanced abdominal-pelvic computed tomography showed multiple well-defined hypodense cystic lesions without enhancement.The lesions showed no uptake on F-18-fluorodeoxyglucose positron emission tomography/computed tomography images.Exploratory laparotomy was performed,and the case was confirmed as multiple cystic lymphangiomas.CONCLUSION When retroperitoneal and pelvic masses are found,clinicians should always consider cystic lymphangioma when making a differential diagnosis.

Early evaluation for treatment efficacy of 5-fluorouracil and hyperthermia on HCT-116 colon cancer cells by fluorine-18-fluorodeoxyglucose uptake

Backgroud Fluorine-18-fluorodeoxyglucose （18F-FDG） positron emission tomography imaging can be used to assess the treatment efficacy of chemotherapy and prognosis.The aim of this study was to determine the uptake rate of 18F-FDG in colon cancer HCT-116 cells,and to evaluate the treatment efficacy of chemotherapy,hyperthermia and thermo-chemotherapy through the uptake inhibition rate of 18F-FDG.Methods The uptake rate of 18F-FDG in HCT-116 ceils was determined at various experimental conditions.The inhibition rate of cell growth,uptake rate of 18F-FDG and uptake inhibition rate of l8F-FDG in HCT-116 cells treated with 5-fluorouracil （5-FU） at various concentrations were determined.In HCT-116 cells subjected to chemotherapy （5-FU,100 μg/ml）,hyperthermia （43℃,40 minutes） and thermo-chemotherapy for 24 hours,the inhibition rate of cell growth and uptake inhibition rate of 18F-FDG were determined; early apoptosis,the morphology and ultrastructure of HCT-116 cells were examined; and the contents of glucose and lactate dehydrogenase （LDH） in the cell culture medium of HCT-116 cells were determined.One-way analysis of variance （ANOVA） and correlation analyses were conducted by using SPSS 16.0 software.Results The uptake rate of 18F-FDG in HCT-116 cells was （44.25±2.19）%.Under the condition of adding 5-FU at various concentrations for 24 hours,the uptake rate of 18F-FDG was negatively correlated with 5-FU dosage （r=-0.879,P 〈0.01）; the inhibition rate of cell growth revealed a positive correlation with the uptake inhibition rate of 18F-FDG （r=0.831,P 〈0.01）.In HCT-116 cells subjected to hyperthermia,chemotherapy,and thermo-chemotherapy for 24 hours,the uptake inhibition rates of 18F-FDG were （12.94±2.80）%,（28.25±4.59）%,and （21.60±3.68）%,respectively.The early apoptotic rates of HCT-116 cells were （9.80±0.16）%,（19.80±2.40）%,and （15.70±1.80）%,respectively.Moreover,the contents of glucose and LDH in cell culture medium of HCT-116 cells after treatments were higher than those before treatment.Conclusion The uptake inhibition rate of 18F-FDG can be used for early evaluation of hyperthermia and 5-FU treatment efficacy on cancer cells although hyperthermia （43℃,40 minutes） does not reveal the synergistic effect on 5-FU at the low dosage.

Differentiating gastric cancer and gastric lymphoma using texture analysis(TA)of positron emission tomography(PET)

Background:Texture analysis(TA)can quantify intra-tumor heterogeneity using standard medical images.The present study aimed to assess the application of positron emission tomography(PET)TA in the differential diagnosis of gastric cancer and gastric lymphoma.Methods:The pre-treatment PET images of 79 patients(45 gastric cancer,34 gastric lymphoma)between January 2013 and February 2018 were retrospectively reviewed.Standard uptake values(SUVs),first-order texture features,and second-order texture features of the grey-level co-occurrence matrix(GLCM)were analyzed.The differences in features among different groups were analyzed by the two-way Mann-Whitney test,and receiver operating characteristic(ROC)analysis was used to estimate the diagnostic efficacy.Results:InertiaGLCM was significantly lower in gastric cancer than that in gastric lymphoma(4975.61 vs.11,425.30,z=-3.238,P=0.001),and it was found to be the most discriminating texture feature in differentiating gastric lymphoma and gastric cancer.The area under the curve(AUC)of inertiaGLCM was higher than the AUCs of SUVmax and SUVmean(0.714 vs.0.649 and 0.666,respectively).SUVmax and SUVmean were significantly lower in low-grade gastric lymphoma than those in high grade gastric lymphoma(3.30 vs.11.80,2.40 vs.7.50,z=-2.792 and-3.007,P=0.005 and 0.003,respectively).SUVs and first-order greylevel intensity features were not significantly different between low-grade gastric lymphoma and gastric cancer.EntropyGLCM12 was significantly lower in low-grade gastric lymphoma than that in gastric cancer(6.95 vs.9.14,z=-2.542,P=0.011)and had an AUC of 0.770 in the ROC analysis of differentiating low-grade gastric lymphoma and gastric cancer.Conclusions:InertiaGLCM and entropyGLCM were the most discriminating features in differentiating gastric lymphoma from gastric cancer and low-grade gastric lymphoma from gastric cancer,respectively.PET TA can improve the differential diagnosis of gastric neoplasms,especially in tumors with similar degrees of fluorodeoxyglucose uptake.