Imaging Gallbladder Lesions: What Can Positron Emission Tomography/Computed Tomography Add to the Conventional Imaging Approach?

OBJECTIVE: Incidental gallbladder lesions are common in imaging studies, although it is not always easy to discriminate benign lesions from gallbladder cancer with conventional imaging procedures. The present study aims to assess the capacity of positron emission tomography/computed tomography (PET/CT) with 2-[ 18 F]FDG to distinguish between benign and malignant pathology of the gallbladder, compared with conventional imaging techniques (contrast-enhanced CT or magnetic resonance imaging). METHODS: Positron emission tomography/CT and conventional imaging studies of 53 patients with gallbladder lesions were evaluated and visually classified as benign, malignant, or inconclusive. Agreement between PET/CT and conventional imaging was determined, and imaging findings were correlated with histology or follow-up. Positron emission tomography/CT images were also analyzed semiquantitatively (SUV max and maximum tumor-to-liver ratio [TLR max ]). The presence of adenopathies and distant metastases was assessed and compared between both imaging procedures. RESULTS: According to histology or follow-up, 33 patients (62%) had a malignant process and 20 (38%) had benign lesions. Positron emission tomography/CT and conventional imaging showed a moderate agreement ( κ = 0.59). Conventional imaging classified more studies as inconclusive compared with PET/CT (17.0% and 7.5%, respectively), although both procedures showed a similar accuracy. Malignant lesions had significantly higher SUV max and, especially, TLR max (0.89 and 2.38 [ P = 0.00028] for benign and malignant lesions, respectively). Positron emission tomography/CT identified more pathologic adenopathies and distant metastases, and patients with regional or distant spread had higher SUV max and TLR max in the gallbladder. CONCLUSIONS: Positron emission tomography/CT is accurate to distinguish between benign and malignant pathology of the gallbladder, with a similar performance to conventional imaging procedures but with less inconclusive results. Malignant lesions present higher SUV max and TLR max values.

Usefulness of 18F-FDG PET-CT for assessing large-vessel involvement in patients with suspected giant cell arteritis and negative temporal artery biopsy.

OBJECTIVE: To investigate the usefulness of 18F-FDG PET-CT for assessing large-vessel (LV) involvement in patients with suspected giant cell arteritis (GCA) and a negative temporal artery biopsy (TAB). METHODS: A retrospective review of our hospital databases was conducted to identify patients with suspected GCA and negative TAB who underwent an 18F-FDG PET-CT in an attempt to confirm the diagnosis. The gold standard for GCA diagnosis was clinical confirmation after a follow-up period of at least 12 months. RESULTS: Out of the 127 patients included in the study, 73 were diagnosed with GCA after a detailed review of their medical records. Of the 73 patients finally diagnosed with GCA, 18F-FDG PET-CT was considered positive in 61 cases (83.5%). Among the 54 patients without GCA, 18F-FDG PET-CT was considered positive in only eight cases (14.8%), which included 1 case of Erdheim-Chester disease, 3 cases of IgG4-related disease, 1 case of sarcoidosis, and 3 cases of isolated aortitis. Overall, the diagnostic performance of 18F-FDG PET-CT for assessing LV involvement in patients finally diagnosed with GCA and negative TAB yielded a sensitivity of 83.5%, specificity of 85.1%, and a diagnostic accuracy of 84% with an area under the ROC curve of 0.844 (95% CI: 0.752 to 0.936). The sensitivity was 89% in occult systemic GCA and 100% in extracranial LV-GCA. CONCLUSION: Our study confirms the utility of 18F-FDG PET-CT in patients presenting with suspected GCA and a negative TAB by demonstrating the presence of LV involvement across different subsets of the disease.

Differences in glucose metabolic activity in liver metastasis separates two groups of metastatic uveal melanoma patients with different prognosis.

BACKGROUND: Uveal melanoma metastasizes to the liver. We aimed to explore the metabolic activity of liver metastases (LM) as a biomarker for survival. METHODS: We analyzed newly diagnosed patients with metastatic UM (MUM) with LM detected by liver-directed imaging and had undergone a PET/CT at diagnosis. FINDINGS: 51 patients were identified between 2004 and 2019. Median age was 62 years, 41% male and 22% ECOG ≥1. LDH, ALP, and GGT were elevated in 49%, 37%, and 57% of patients. Median LM SUVmax was 8.5 (3-42.2). Same size lesions presented a wide range of metabolic activity. Median OS was 17.3 m (95% CI:10.6-23.9). Patients with SUVmax ≥8.5 had an OS of 9.4 m (95% CI:6.4-12.3), whereas patients with SUVmax <8.5 had an OS of 38.4 m (95% CI:21.4-55.5; p < 0.0001, HR = 2.9). We observed similar results when studying M1a disease separately. Multivariate analysis showed SUVmax as an independent prognostic factor for the whole population and those with M1a disease. INTERPRETATION: Increased metabolic activity of LM seems to be an independent predictor of survival. MUM is a heterogeneous disease and metabolic activity probably reflects a different intrinsic behavior.

Brain metabolic changes in patients with disseminated malignant melanoma under immunotherapy.

Although there is evidence that chemotherapy can have side effects on metabolism and brain function, there are few studies on the occurrence of these side effects with immunotherapy. The present study was conducted to assess whether brain metabolic changes occur in patients with malignant melanoma under immunotherapy. Thirty-nine patients after surgical intervention and with a diagnosis of malignant melanoma were retrospectively included and were divided into two groups: one group under the first-line therapy with anti-programmed cell death-1 ± anti-cytotoxic T lymphocyte antigen-4 monoclonal antibodies and the other group without any treatment after surgery, which served as a control. Basal and follow-up whole body and brain 2-[ 18 F]fluoro-2-deoxy-D-glucose ( 18 F]FDG) PET/computed tomography (CT) studies were performed. Changes in brain glucose metabolism after treatment initiation of the immunotherapy group were compared with the findings in the control group. In addition, longitudinal regression analysis to investigate whether the time under immunotherapy influenced the changes of brain metabolism was performed. None of the patients presented cognitive impairment or other neurological alterations between basal and follow-up brain [ 18 F]FDG PET/CT examinations. The statistical analysis revealed a significant relative SUV (SUVr)-loss in the left frontal region in patients of the immunotherapy group compared with the control group, with radjusted = -0.62 and P = 0.008. Severity of SUVr-loss was correlated with duration of treatment. Patients with disseminated malignant melanoma receiving immunotherapy may present a decrease of brain metabolism in the left frontal region, which is related with time-under-treatment, without any clinical evidence of neurological disorder.

Assessing dynamic change in muscle during treatment of patients with cancer: Precision testing standards.

BACKGROUND: Computed tomography images acquired during routine cancer care provide an opportunity to determine body composition with accuracy and precision. Quantification of skeletal muscle is of interest owing to its association with clinical outcomes. However, the standards of precision testing considered mandatory in other areas of radiology are lacking from the literature in this area. We aim to describe the change in skeletal muscle over time at different anatomical levels using the precision error. METHODS: Thirty-eight male patients with squamous cell carcinoma of the head and neck were evaluated at two time points encompassing their treatment plan. Precision testing consisted of analyzing the cross-sectional area (CSA) of the skeletal muscle and total adipose tissue of 76 CT studies (38 images at baseline repeated twice and 38 follow-up images repeated twice) measured by a skilled observer. The % coefficient of variation (%CV), the root-mean-square standard deviation (RMS SD) and the corresponding 95% least significant change (LSC) were calculated for four anatomical levels: upper arm, thigh, chest and abdomen. RESULTS: The median time between scans was 223.6 (SD 31.2) days. Precision error (% CV) for total skeletal muscle cross sectional area was 0.86% for upper arm, 0.26% for thigh, 0.39% for chest and 0.63% for abdomen. The corresponding LSC values in upper arm, thigh, chest and abdomen were 2.4%, 0.7%, 1.1% and 1.8%, respectively. Based on the LSC for RMS SD, patients were classified in two categories according to muscle cross-sectional area: stable (i.e within LSC value) or gained and loss. To compare the four anatomical levels, the proportion of patients with muscle loss exceeding the LSC value was 74.3% for arm, 86.2% for thigh, 82.9% for chest and 76.3% for abdomen. For these same anatomic regions, the mean muscle loss for those patients classified below the LSC was 14.6% (SD 9.3), 13.4% (SD 7.8), 11.9% (SD 6.5) and 11.6% (SD 5.5), respectively. Only the loss of muscle area was significantly higher in thigh (p = 0.023), using L3 as the reference level. CONCLUSIONS: We recommend the uniform use of a standard precision test when reporting muscle change over time. LSC values vary from 0.7 to 2.4% depending on anatomic site; with the lowest precision error to detect change in the thigh. Based on this analysis, muscle wasting appears to be systemic and while present in limbs and trunk is significantly higher in the thigh than in the chest, abdomen or upper arm.

Mediastinal Recurrence of Uterine Cervix Cancer on 18F-FDG PET/CT.

ABSTRACT: We report the case of a 64-year-old woman with a mediastinal relapse of a uterine cervix cancer with positive human papillomavirus, an unusual site of recurrence. She consulted because of solid and liquid dysphagia of sudden appearance. Endoscopic study and non-contrast-enhanced CT showed intraluminal esophageal stenosis with a retrograde esophageal distension. 18F-FDG PET/CT demonstrated an infiltrating hypermetabolic lesion in posterior mediastinum, middle and lower esophagus, and stomach, with no signs of local or regional relapse of the uterine neoplasm.

2-[18F]FDG PET/CT as a Predictor of Microvascular Invasion and High Histological Grade in Patients with Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) generally presents a low avidity for 2-deoxy-2-[18F]fluoro-d-glucose (FDG) in PET/CT although an increased FDG uptake seems to relate to more aggressive biological factors. To define the prognostic value of PET/CT with FDG in patients with an HCC scheduled for a tumor resection, forty-one patients were prospectively studied. The histological factors of a poor prognosis were determined and FDG uptake in the HCC lesions was analyzed semi-quantitatively (lean body mass-corrected standardized uptake value (SUL) and tumor-to-liver ratio (TLR) at different time points). The PET metabolic parameters were related to the histological characteristics of the resected tumors and to the evolution of patients. Microvascular invasion (MVI) and a poor grade of differentiation were significantly related to a worse prognosis. The SULpeak of the lesion 60 min post-FDG injection was the best parameter to predict MVI while the SULpeak of the TLR at 60 min was better for a poor differentiation. Moreover, the latter parameter was also the best preoperative variable available to predict any of these two histological factors. Patients with an increased TLRpeak60 presented a significantly higher incidence of poor prognostic factors than the rest (75% vs. 28.6%, p = 0.005) and a significantly higher incidence of recurrence at 12 months (38% vs. 0%, p = 0.014). Therefore, a semi-quantitative analysis of certain metabolic parameters on PET/CT can help identify, preoperatively, patients with histological factors of a poor prognosis, allowing an adjustment of the therapeutic strategy for those patients with a higher risk of an early recurrence.

Adequacy of nutritional support using computed tomography (CT) in patients with head and neck cancer (HNC) during chemo-radiotherapy (CRT).

We assessed forty HNC patients receiving treatment with curative intent. Specific quantitative muscle and fat changes were evaluated using CT. Nutrition support was provided according to ESPEN guidelines, with adjusted body weight (ABW) in overweight/obese patients used to define their nutritional targets. Linear regression models were used to evaluate clinical predictors of tissue loss. Mean overall losses were body weight (-10.5%), and CT-defined muscle (-8.4%) and fat mass (-24.8%), p < 0.001. A subset of 20 patients had high muscle loss (-14.7%) with concurrent negative energy balance as reflected by considerable fat loss (-29.7%); those tended to have higher baseline body mass index (26.2 vs. 23.3 kg/m2, p = 0.063). In multivariate regression, only ABW independently predicted muscle loss (p < 0.001) and fat loss (p = 0.002). Nutrition support according to guidelines was appropriate for a subset of patients. ABW use to set nutrition targets in overweight/obese patients would appear to be insufficient, based on large tissue losses.

Hibernoma as an incidental finding in the 18F-FDG PET/CT of a patient with melanoma.

Despite being benign tumors, hibernomas show intense fluorine-18-fluorodeoxyglucose uptake, as they are derived from brown fat, which is frequently seen as hypermetabolic fatty areas on PET/CT. We present the case of a patient with cutaneous melanoma, diagnosed with a cervical hibernoma mimicking a metastatic lymph node at fluorine-18-fluorodeoxyglucose PET/CT. Being aware of the metabolic behavior and radiologic appearance of this entity may prevent reporting false-positive lesions, especially in an oncologic setting.

Comparison of different automatic methods for the delineation of the total metabolic tumor volume in I-II stage Hodgkin Lymphoma.

Total metabolic tumor volume (TMTV) is a promising quantitative biomarker for therapy assessment and prognosis in Hodgkin Lymphoma affected patients that allows prediction of patient outcome. The aim of this study was to evaluate the TMTV reproducibility between different sources of variability in tumor delimitation such as SUV-based thresholds (2.5, 41% and 50%) and software tools (Beth Israel plugin (BI) and LIFEx). Effect of contouring procedure both including single and multiple regions of interest was also studied in patients with multiple lesions, and optimal cut-offs for each studied method were displayed to compare the effect on prognosis. Strong alikeness in TMTV was found for 2.5 under software choice. Best accuracy in contouring compared to visual assessment of the disease was found for BI multiple ROI and LIFEx single ROI drawing. Similar cut-offs were found between both software for all considered thresholds, but best resemblance and highest cut-off due to an overestimation of the TMTV was found for 2.5 SUV. Our findings suggest that optimal reproducibility in TMTV is found for SUV > 2.5 threshold under choice of contouring methodology or software tool, meaning that overestimation of the TMTV threshold using 2.5 looks to be preferable than underestimation with 41% and 50%.

Image quality evaluation in a modern PET system: impact of new reconstructions methods and a radiomics approach.

The present work investigates the influence of different biological and physical parameters on image quality (IQ) perception of the abdominal area in a modern PET scanner, using new reconstruction algorithms and testing the utility of a radiomics approach. Scans of 112 patients were retrospectively included. Images were reconstructed using both OSEM + PSF and BSRM methods, and IQ of the abdominal region was subjectively evaluated. First, 22 IQ related parameters were obtained (including count rate and biological or mixed parameters) and compared to the subjective IQ scores by means of correlations and logistic regression. Second, an additional set of radiomics features was extracted, and a model was constructed by means of an elastic-net regression. For the OSEM + PSF and especially for the BSRM reconstructions, IQ parameters presented only at best moderated correlations with the subjective IQ. None of the studied parameters presented a good predictive power for IQ, while a simple radiomics model increased the performance of the IQ prediction. These results suggest the necessity of changing the standard parameters to evaluate IQ, particularly when a BSRM algorithm is involved. Furthermore, it seems that a simple radiomics model can outperform the use of any single parameter to assess IQ.

Diagnostic Accuracy of 18F-FDG PET/CT in Patients With Biochemical Evidence of Recurrent, Residual, or Metastatic Medullary Thyroid Carcinoma.

OBJECTIVE: Medullary thyroid carcinoma (MTC) is a rare malignancy. Location of residual, recurrent, or metastatic disease is crucial to treatment management and outcome. We aimed to evaluate the use of F-FDG PET/CT in localizing MTC foci in patients with biochemical relapse. METHODS: This is a retrospective cohort study. Review of 51 FDG PET/CT studies of 45 patients referred to restage MTC due to increased calcitonin (Ctn) and carcinoembryonic antigen (CEA) values at follow-up. FDG PET/CT diagnostic accuracy was determined through a patient-based analysis, using histology as criterion standard when available, or other imaging studies and clinical follow-up otherwise (mean, 4 years). RESULTS: There were 25 positive scans. Sensitivity, specificity, positive and negative predictive values, diagnostic accuracy, and positive likelihood ratio were 66.7%, 83.3%, 88.0%, 57.7%, 72.5%, and 4.0, respectively. Using a Ctn cutoff of 1000 pg/mL, sensitivity increased to 76.9%. There were significant differences of Ctn and CEA values between positive and negative FDG PET/CT (P < 0.05). Regarding true-positive studies, average SUVmax comparing locoregional and metastatic disease was at the limit of significance (P = 0.046). CONCLUSIONS: PET/CT can be useful to restage patients with biochemical relapse of MTC, with a better performance in higher Ctn levels. Its high positive predictive value (88%) may impact in the therapeutic management, although its low negative predictive value (57.7%) makes strict follow-up mandatory in examinations without pathologic findings.

Phantom, clinical, and texture indices evaluation and optimization of a penalized-likelihood image reconstruction method (Q.Clear) on a BGO PET/CT scanner.

INTRODUCTION: The aim of this study was to evaluate the behavior of a penalized-likelihood image reconstruction method (Q.Clear) under different count statistics and lesion-to-background ratios (LBR) on a BGO scanner, in order to obtain an optimum penalization factor (ß value) to study and optimize for different acquisition protocols and clinical goals. METHODS: Both phantom and patient images were evaluated. Data from an image quality phantom were acquired using different Lesion-to-Background ratios and acquisition times. Then, each series of the phantom was reconstructed using ß values between 50 and 500, at intervals of 50. Hot and cold contrasts were obtained, as well as background variability and contrast-to-noise ratio (CNR). Fifteen 18 F-FDG patients (five brain scans and 10 torso acquisitions) were acquired and reconstructed using the same ß values as in the phantom reconstructions. From each lesion in the torso acquisition, noise, contrast, and signal-to-noise ratio (SNR) were computed. Image quality was assessed by two different nuclear medicine physicians. Additionally, the behaviors of 12 different textural indices were studied over 20 different lesions. RESULTS: Q.Clear quantification and optimization in patient studies depends on the activity concentration as well as on the lesion size. In the studied range, an increase on ß is translated in a decrease in lesion contrast and noise. The net product is an overall increase in the SNR, presenting a tendency to a steady value similar to the CNR in phantom data. As the activity concentration or the sphere size increase the optimal ß increases, similar results are obtained from clinical data. From the subjective quality assessment, the optimal ß value for torso scans is in a range between 300 and 400, and from 100 to 200 for brain scans. For the recommended torso ß values, texture indices present coefficients of variation below 10%. CONCLUSIONS: Our phantom and patients demonstrate that improvement of CNR and SNR of Q.Clear algorithm which depends on the studied conditions and the penalization factor. Using the Q.Clear reconstruction algorithm in a BGO scanner, a ß value of 350 and 200 appears to be the optimal value for 18F-FDG oncology and brain PET/CT, respectively.

Low-Dose PET/CT and Full-Dose Contrast-Enhanced CT at the Initial Staging of Localized Diffuse Large B-Cell Lymphomas.

Computed tomography (CT) has been used as the reference imaging technique for the initial staging of diffuse large B-cell lymphoma until recent days, when the introduction of positron emission tomography (PET)/CT imaging as a hybrid technique has become of routine use. However, the performance of both examinations is still common. The aim of this work was to compare the findings between low-dose 2-deoxy-2-((18)F)fluoro-d-glucose ((18)F-FDG) PET/CT and full-dose contrast-enhanced CT (ceCT) in 28 patients with localized diffuse large B-cell lymphoma according to PET/CT findings, in order to avoid the performance of ceCT. For each technique, a comparison in the number of nodal and extranodal involved regions was performed. PET/CT showed more lesions than ceCT in both nodal (41 vs. 36) and extranodal localizations (16 vs. 15). Disease staging according to both techniques was concordant in 22 patients (79%) and discordant in 6 patients (21%), changing treatment management in 3 patients (11%). PET/CT determined a better staging and therapeutic approach, making the performance of an additional ceCT unnecessary.

Relationship of promising methods in the detection of anthracycline-induced cardiotoxicity in breast cancer patients.

PURPOSE: It remains challenging to identify patients at risk of anthracycline-induced cardiotoxicity. To better understand the different risk-stratifying approaches, we evaluated (123)I-metaiodobenzylguanidine ((123)I-mIBG) scintigraphy and its interrelationship with conventional echocardiography, 2D strain imaging and several biomarkers. METHODS: We performed (123)I-mIBG scintigraphy, conventional and strain echocardiography and biomarker (NT-proBNP, TNF-α, galectin-3, IL-6, troponin I, ST-2 and sFlt-1) assessment in 59 breast cancer survivors 1 year after anthracycline treatment. Interobserver and intermethod variability was calculated on planar and SPECT (123)I-mIBG scintigraphy, using the heart/mediastinum (H/M) ratio and washout (WO). Pearson's r and multivariate analyses were performed to identify correlations and independent predictors of (123)I-mIBG scintigraphy results. RESULTS: Delayed planar anterior whole-heart ROI (WH) H/M ratios and WO were the most robust (123)I-mIBG parameters. Significant correlations were observed between (123)I-mIBG parameters and several conventional echo parameters, global longitudinal and radial strain (GLS and GRS) and galectin-3. The highest Pearson's r was observed between delayed H/M ratio and GRS (Pearson's r 0.36, p = 0.01). Multivariate analysis showed that GRS was the only independent predictor of the delayed WH H/M ratio (p = 0.023). CONCLUSION: The delayed planar H/M ratio is the most robust (123)I-mIBG parameter. It correlates with several conventional echocardiographic parameters, GLS, GRS and galectin-3. Of these, only GRS predicts the H/M ratio.

Bone marrow evaluation in initial staging of lymphoma: 18F-FDG PET/CT versus bone marrow biopsy.

PURPOSE: The evaluation of bone marrow infiltration (BMI) is of crucial importance in the staging of lymphoma. Although bone marrow biopsy (BMB) is the reference standard for the evaluation of BMI, it has limitations. PET/CT has become an excellent tool in staging of lymphoma, and bone marrow uptake is correlated with the involvement of lymphoma. The aim of this study was to assess the utility of PET/CT and its concordance with BMB in the detection of BMI in patients with diffuse large B-cell lymphoma (DLBCL) and Hodgkin lymphoma (HL). PATIENTS AND METHODS: One hundred forty-seven patients with DLBCL (84) and HL (63) were referred for a PET/CT and a BMB (unilateral) at the initial staging. The reference standard was BMB. RESULTS: Bone marrow infiltration was detected by PET/CT in 39 (26%) and by BMB in 21 (14%) cases. There was concordance between PET/CT and BMB in 128 patients (87%) (74 DLBCL, 54 HL), 21 with positive PET/CT and BMB results and 107 with negative PET/CT and BMB results. Discordant results were observed in 19 patients (14%); 18 of them with positive PET/CT and negative standard BMB results (not performed in active sites). The sensitivity, specificity, accuracy, as well as positive and negative predictive values of FDG-PET/CT for the detection of BMI were 95%, 86%, 87%, 54%, and 99%, respectively. CONCLUSIONS: PET/CT detects more bone marrow involvement in DLBCL and HL compared with BMB. Its good concordance with BMB makes it a complementary technique, as it helps select the biopsy site in cases with negative results.

Lymphoscintigraphy in oral squamous cell carcinoma sentinel node biopsy and its role in the surgical planning.

AIM: The purpose of this study was to analyze the influence of different lymphatic pathways on surgical planning and the reliability of sentinel lymph node (SLN) biopsy to predict regional recurrence in patients with clinically N0 oral squamous cell carcinoma (OSCC). METHODS: Twenty-five patients with cT1/T2 N0 OSCC underwent a lymphoscintigraphy and an SLN biopsy. Elective neck dissection was performed at the validation stage and in patients with metastatic SLN. Scintigraphic and surgical SLN detection, pathologic status of SLN and of elective neck dissection, and regional recurrence in patients with negative SLN (pN0(sn)) were all analyzed. RESULTS: Scintigraphic and surgical detection were 96% and 100%, respectively, with 68% of negative SLN. Lymphoscintigraphy modified surgery in 32% of patients. In pN0(sn) patients, the free-of-disease survival rate was 88%. CONCLUSIONS: These results support the reliability of sentinel node biopsy in OSCC. Presurgical lymphoscintigraphy is essential, because it can modify the surgical procedure.

Utilidad de la PET/TC en la enfermedad por IgG4 / Usefulness of PET/CT in IgG4-related disease

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