The Role of 18F-FDG PET/CT in the evaluation of Ascites of Undetermined Origin

TAFRO Syndrome on 18F-FDG-PET/CT: An Appealing Diagnostic Tool

TAFRO syndrome (TS) is a recently recognized and heterogenous systemic disease characterized by a confluence of symptoms: thrombocytopenia (T), anasarca (A), fever (F), reticulin myelofibrosis (R), and organomegaly (O). First described in Japan in 2010, the pathogenesis remains unclear and includes various clinical conditions such as malignancies, rheumatologic disorders, infections, and "Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal plasma cell disorder, and Skin changes" (POEMS) syndrome. Due to its heterogeneous presentation and potential life-threatening delays in diagnosis, accurate diagnosis is crucial. According to the literature, no specific imaging modality has been recommended for the work-up of patients with suspected TS. Here, we report a case of TS and its management using 18F-FDG-PET/CT imaging as an attractive complementary diagnostic tool.

Added value of regional 18F-FDG PET/MRI-assisted whole-body 18F-FDG PET/CT in malignant ascites with unknown primary origin

BACKGROUND

Comparing to PET/CT, integrative PET/MRI imaging provides superior soft tissue resolution. This study aims to evaluate the added value of regional delayed 18F-FDG PET/MRI-assisted whole-body 18F-FDG PET/CT in diagnosing malignant ascites patients.

RESULTS

The final diagnosis included 22 patients with ovarian cancer (n = 11), peritoneal cancer (n = 3), colon cancer (n = 2), liver cancer (n = 2), pancreatic cancer (n = 2), gastric cancer (n = 1), and fallopian tube cancer (n = 1). The diagnosis of the primary tumor using whole-body PET/CT was correct in 11 cases. Regional PET/MRI-assisted whole-body PET/CT diagnosis was correct in 18 cases, including 6 more cases of ovarian cancer and 1 more case of fallopian tube cancer. Among 4 cases that were not diagnosed correctly, 1 case had the primary tumor outside of the PET/MRI scan area, 2 cases were peritoneal cancer, and 1 case was colon cancer. The diagnostic accuracy of regional PET/MRI-assisted whole-body PET/CT was higher than PET/CT alone (81.8% vs. 50.0%, κ 2 = 5.14, p = 0.023). The primary tumor conspicuity score of PET/MRI was higher than PET/CT (3.67 ± 0.66 vs. 2.76 ± 0.94, P < 0.01). In the same scan area, more metastases were detected in PET/MRI than in PET/CT (156 vs. 86 in total, and 7.43 ± 5.17 vs. 4.10 ± 1.92 per patient, t = 3.89, P < 0.01). Lesion-to-background ratio in PET/MRI was higher than that in PET/CT (10.76 ± 5.16 vs. 6.56 ± 3.45, t = 13.02, P < 0.01).

CONCLUSION

Comparing to whole-body PET/CT alone, additional delayed regional PET/MRI with high soft tissue resolution is helpful in diagnosing the location of the primary tumor and identifying more metastases in patients with malignant ascites. Yet larger sample size in multicenter and prospective clinical researches is still needed.

The Value of 18F-FDG PET/CT in the Diagnosis of Tuberculous Pleurisy and in the Differential Diagnosis between Tuberculous Pleurisy and Pleural Metastasis from Lung Adenocarcinoma

Objectives

This study aims to investigate the diagnostic value of 18F-FDG PET/CT in tuberculous pleurisy (TBP) and the differential diagnostic value of 18F-FDG PET/CT between TBP and pleural metastasis from lung adenocarcinoma (PMLAC).

Materials and Methods

The features of pleura on PET and hybrid CT were retrospectively studied in 20 patients with TBP and 32 patients with PMLAC. The ROC curve was used to evaluate the diagnostic effectiveness of these indices for TBP and PMLAC, and binary logistic regression analysis was conducted to identify independent predictors of TBP and PMLAC.

Results

There were significant differences in pleural 18F-FDG uptake pattern on PET (P=0.001), pleural morphology pattern on CT (P=0.002), the maximum diameter of the pleural nodule (P=0.001), and interlobular fissure nodule (P=0.001) between TBP and PMLAC groups. The diffused pleural FDG uptake type on PET (odds ratio (OR) = 6.0, 95% CI 2.216–16.248, P=0.001) and the lamellar pleural thickening type on CT (OR = 4.4, 95% CI 2.536–7.635, P=0.001) were independent predictors of TBP, with 60% and 55% sensitivity, 96.6% and 90.6% specificity, and 82.7% and 77.0% accuracy. The combined diagnostic sensitivity, specificity, and accuracy for TBP were 70%, 87.5%, and 80.8%. The mixed pleural FDG uptake type on PET (OR = 5.106, 95% CI 2.024–12.879, P=0.001), the mixed pleural thickening type on CT (OR = 2.289, 95% CI 1.442–3.634, P=0.001), and the maximum diameter of the pleural nodule (OR = 1.027, 95% CI 1.012–1.042, P=0.001) were independent predictors of PMLAC, with 78.1%, 71.9%, and 87.5% sensitivity, 85%, 80%, and 85% specificity, and 80.8%, 75%, and 86.5% accuracy. The combined diagnostic sensitivity, specificity, and accuracy for PMLAC were 96.9%, 85%, and 90.4%.

Conclusions

18F-FDG PET/CT is of great clinical value in the diagnosis of TBP and in the differential diagnosis between TBP and PMLAC.

Diagnostic Accuracy of Different Computed Tomography Signs for Differentiating Between Malignant and Cirrhotic Ascites Keeping Ascitic Fluid Cytology as Gold Standard

Objective

The goal of this research was to define the diagnostic precision of CT signs to distinguish malignant ascites from cirrhotic ascites. Ascitic fluid cytology was kept as the gold standard.

Study design

This research was a prospective cross-sectional study.

Place and duration of the study

Participants’ recruitment started on July 15, 2021, and the whole study lasted about three months till October 15, 2021, at the Radiology Department of Pakistan Institute of Medical Sciences, Islamabad.

Patients and methods

A total of 80 patients were included in the research and divided into two groups grounded on the cirrhotic or malignant etiology of the ascites based on their fluid cytology. Ascites volume, relative spread between the lesser sac and greater peritoneal cavity, the wall thickness of gallbladder, density of ascites, parietal peritoneum thickness and degree of its enhancement, and presence of septa and loculations were some of the major CT signs studied.

Results

The average age of patients included in this study was 36.2 ± 6.67 years (range 29-49 years). Of the 80 patients, 50 (62.5 %) were men, and 30 (37.5 %) were women. CT signs associated with the malignant ascites reported in this study were fluid present in the lesser sac (p = 0.03), peritoneal thickening and degree of its enhancement (p = 0.05), increased ascites density (p= 0.001), and presence of septa and loculations (63.6 % of malignant ascites). However, gallbladder wall thickness did not show any variation between both groups.

Conclusion

We conclude that in the diagnosis of malignant ascites, CT scan imaging can play a vital role. This research approves and testifies the benefits of indirect signs such as the spread of ascites, increased density of ascites, thickening and enhancement of parietal peritoneum, and ascitic fluid complexity in pointing out malignancy as a cause of ascites.

Variants and Pitfalls in PET/CT Imaging of Gastrointestinal Cancers

In the past two decades, PET/CT has become an essential modality in oncology increasingly used in the management of gastrointestinal (GI) cancers. Most PET/CT tracers used in clinical practice show some degree of GI uptake. This uptake is quite variable and knowledge of common patterns of biodistribution of various radiotracers is helpful in clinical practice. 18F-Fluoro-Deoxy-Glucose (FDG) is the most commonly used radiotracer and has quite a variable uptake within the bowel. 68Ga-Prostate specific membrane antigen (PSMA) shows intense uptake within the proximal small bowel loops. 11C-methyl-L-methionine (MET) shows high accumulation within the bowels, which makes it difficult to assess bowel or pelvic diseases. One must also be aware of technical artifacts causing difficulties in interpretations, such as high attenuation oral contrast material within the bowel lumen or misregistration artifact due to patient movements. It is imperative to know the common variants and benign diseases that can mimic malignant pathologies. Intense FDG uptake within the esophagus and stomach may be a normal variant or may be associated with benign conditions such as esophagitis, reflux disease, or gastritis. Metformin can cause diffuse intense uptake throughout the bowel loops. Intense physiologic uptake can also be seen within the anal canal. Segmental bowel uptake can be seen in inflammatory bowel disease, radiation, or medication induced enteritis/colitis or infection. Diagnosis of appendicitis or diverticular disease requires CT correlation, as normal appendix or diverticulum can show intense uptake. Certain malignant pathologies are known to have only low FDG uptake, such as early-stage esophageal adenocarcinoma, mucinous tumors, indolent lymphomas, and multicystic mesotheliomas. Response assessment, particularly in the neoadjuvant setting, can be limited by post-treatment inflammatory changes. Post-operative complications such as abscess or fistula formation can also show intense uptake and may obscure underlying malignant pathology. In the absence of clinical suspicion or rising tumor marker, the role of FDG PET/CT in routine surveillance of patients with GI malignancy is not clear.

Visual PET/CT scoring of mesenteric fdg uptake to differentiate between tuberculous peritonitis and peritoneal carcinomatosis

PURPOSE

We aimed to differentiate tuberculous peritonitis (TBP) from peritoneal carcinomatosis (PC) using a visual positron-emission tomography/computed tomography (PET/CT) scoring system based on mesenteric fluorodeoxyglucose (FDG) uptake.

METHODS

PET/CT scans from 31 patients with TBP and 92 patients with PC were retrospectively reviewed. A visual PET/CT scoring system for mesenteric FDG uptake was used according to the following characteristics: FDG uptake intensity (low = 0, moderate = 1, high = 2), FDG uptake deposits (uniform = 0, irregular = 1, ascitic = 2), FDG uptake focality (diffuse = 0, segmental = 1, focal = 2), nodularity on the corresponding CT (nonnodular = 0, micronodular = 1, macronodular = 2) and mesenteric lymphadenopathy (absent = 0, lymphadenopathy without FDG uptake = 1, lymphadenopathy with FDG uptake = 2). The FDG uptake intensity, deposits, focality, nodularity and mesenteric lymphadenopathy scores between TBP and PC were compared using chi-square tests. The diagnostic performance of this scoring system for differentiating TBP from PC was analyzed using a receiver operating characteristic (ROC) curve. P < 0.05 was considered statistically significant.

RESULTS

Twenty-four patients with TBP (77.4%) and 56 patients with PC (60.9%) had mesenteric FDG uptake (P = 0.095) and were included for evaluation with the visual PET/CT scoring system. PC lesions scored higher than TBP lesions in FDG uptake deposits (P < 0.001), focality (P < 0.001) and nodularity (P < 0.001). No significant differences were observed between PC and TBP lesions in FDG uptake intensity (P = 0.396) and lymphadenopathy (P = 0.074). The total score that combined deposits, focality and nodularity had significant value for differentiating TBP from PC (area under the curve (AUC) = 0.869, P < 0.001), and a cutoff > 1 had a sensitivity (the accuracy for diagnosis of PC) of 80.4% and a specificity (the accuracy for diagnosis of TBP) of 75.0%.

CONCLUSION

A visual PET/CT scoring system based on mesenteric FDG uptake performed well in differentiating between TBP and PC.

Value of 18F-FDG PET/CT Combined With Tumor Markers in the Evaluation of Ascites

OBJECTIVE

The purpose of this study is to investigate the value of ¹⁸F-FDG PET/CT combined with assessment of tumor markers in serum or ascites for the diagnosing and determining the prognosis of benign and malignant ascites.

MATERIALS AND METHODS

Patients with ascites of unknown cause who underwent evaluation with FDG PET/CT were included in this retrospective study. The maximum standardized uptake value (SUV_max) and levels of the tumor markers carbohydrate antigen-125 (CA-125) and carcinoembryonic antigen (CEA) in serum and ascites were recorded. The diagnostic values of FDG PET/CT, CEA and CA-125 levels in serum or ascites, and the combination of imaging plus tumor marker assessment were evaluated. Factors that were predictive of survival were also analyzed.

RESULTS

A total of 177 patients were included. Malignant ascites was eventually diagnosed in 104 patients, and benign ascites was diagnosed in the remaining 73 patients. With the use of FDG PET/CT, 44 patients (42.3%) were found to have primary tumors. The sensitivity, specificity, and accuracy of FDG PET/CT were 92.3%, 83.6%, and 88.7%, respectively. CA-125 levels in serum and ascites showed much better sensitivity than did CEA levels, but they showed significantly lower specificity. If the combination of tumor markers and FDG PET/CT was analyzed, the sensitivity, specificity, and accuracy of tumor markers in serum were 96.6%, 78.1%, and 88.7%, and those of tumor markers in ascites were 97.7%, 80.0%, and 90.4%, respectively. Sex may be an important factor affecting survival time (hazard ratio, 0.471; p = 0.004), but age, CEA level, and FDG PET/CT findings could not predict survival.

CONCLUSION

FDG PET/CT combined with assessment of tumor markers, especially CEA, increased the efficacy of diagnosis of ascites of unknown causes. Male sex conferred a poorer prognosis, whereas age, CEA level, and FDG uptake had no predictive significance in patients with malignant ascites.

Tuberculosis

Tuberculosis (TB) is currently the world's leading cause of infectious mortality. Imaging plays an important role in the management of this disease. The complex immune response of the human body to Mycobacterium tuberculosis results in a wide array of clinical manifestations, making clinical and radiological diagnosis challenging. ¹⁸F-FDG-PET/CT is very sensitive in the early detection of TB in most parts of the body; however, the lack of specificity is a major limitation. ¹⁸F-FDG-PET/CT images the whole body and provides a pre-therapeutic metabolic map of the infection, enabling clinicians to accurately assess the burden of disease. It enables the most appropriate site of biopsy to be selected, stages the infection, and detects disease in previously unknown sites. ¹⁸F-FDG-PET/CT has recently been shown to be able to identify a subset of patients with latent TB infection who have subclinical disease. Lung inflammation as detected by ¹⁸F-FDG-PET/CT has shown promising signs that it may be a useful predictor of progression from latent to active infection. A number of studies have identified imaging features that might improve the specificity of ¹⁸F-FDG-PET/CT at some sites of extrapulmonary TB. Other PET tracers have also been investigated for their use in TB, with some promising results. The potential role and future perspectives of PET/CT in imaging TB is considered. Literature abounds on the very important role of ¹⁸F-FDG-PET/CT in assessing therapy response in TB. The use of ¹⁸F-FDG for monitoring response to treatment is addressed in a separate review.

PET/CT for differentiating between tuberculous peritonitis and peritoneal carcinomatosis: The parietal peritoneum

OBJECTIVES

Tuberculous peritonitis (TBP) mimics peritoneal carcinomatosis (PC). We aimed to investigate the discriminative use of PET/CT findings in the parietal peritoneum.

MATERIALS AND METHODS

Parietal peritoneal PET/CT findings from 76 patients with TBP (n = 25) and PC (n = 51) were retrospectively reviewed. The lesion locations were noted as right subdiaphragmatic, left subdiaphragmatic, right paracolic gutters, left paracolic gutters, and pelvic regions. The distribution characteristic consisted of a dominant distribution in the pelvic and/or right subdiaphragmatic region (susceptible area for peritoneal implantation, SAPI) (SAPI distribution), a dominant distribution in the remaining regions (less-susceptible area for peritoneal implantation, LSAPI) (LSAPI distribution), or a uniform distribution. PET morphological patterns were classified as F18-fluorodeoxyglucose (F-FDG) uptake in a long beaded line (string-of-beads F-FDG uptake) or in a cluster (clustered F-FDG uptake) or focal F-FDG uptake. CT patterns included smooth uniform thickening, irregular thickening, or nodules.

RESULTS

More common findings in the parietal peritoneum corresponding to TBP as opposed to PC were (a) ≥4 involved regions (80.0% vs 19.6%), (b) uniform distribution (72.0% vs 5.9%), (c) string-of-beads F-FDG uptake (76.0% vs 7.8%), and (d) smooth uniform thickening (60.0% vs 7.8%) (all P < 0.001), whereas more frequent findings in PC compared with TBP were (a) SAPI distribution (78.4% vs 28.0%), (b) clustered F-FDG uptake (56.9% vs 20.0%), (c) focal F-FDG uptake (21.6% vs 4.0%), (d) irregular thickening (51.0% vs 12.0%), and (e) nodules (21.6% vs 4.0%) (P < 0.001, P < 0.05, P > 0.05, P < 0.05, P > 0.05, respectively).

CONCLUSION

Our data show that PET/CT findings in the parietal peritoneum are useful for differentiating between TBP and PC.

Acute Cholecystitis with Significantly Elevated Levels of Serum Carbohydrate Antigen 19-9

Serum carbohydrate antigen 19-9 (CA 19-9), a marker of malignant tumors, is generally slightly elevated in benign conditions. We report a case of acute cholecystitis with a significantly elevated level of serum CA 19-9 based on positron emission tomography (PET)-computed tomography (CT) findings. A 65-year-old woman presented with abdominal pain and fever. A CT image revealed an enlarged gallbladder without tumor shadows. The C-reactive protein (CRP) level was elevated to 7.66 mg/dl. Moreover, the serum CA 19-9 level was significantly elevated to 19,392 U/ml. We started antibiotic treatment, because we suspected acute cholecystitis, but still, we could not ignore the possible presence of malignant tumors. After 11 days of antibiotic treatment, serum CRP and CA 19-9 levels decreased to 0.11 mg/dl and 1,049 U/ml, respectively. There was an accumulation of fluorine 18-labeled fluorodeoxyglucose (maximum standardized uptake value, 9.3) without tumor shadows in the liver, near the gallbladder, on the PET-CT examination. We considered the possibility that the inflammation had spread from the gallbladder to the liver, made a diagnosis of acute cholecystitis, and performed a cholecystectomy 33 days after treatment initiation. The serum CA 19-9 level decreased to 45 U/ml after the surgery. One year after the surgery, the patient was alive, and the serum CA 19-9 level was 34 U/ml. Acute cholecystitis with a significantly high elevation of the serum CA 19-9 level is rare. In such cases, it is important to confirm the change in the serum CA 19-9 level over time after antibiotic treatment and perform imaging studies to distinguish between inflammation and malignancy.

The Role of ¹⁸F-FDG PET/CT in the Evaluation of Peritoneal Thickening of Undetermined Origin

The aim of this study was to assess the value of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) for the differentiation of peritoneal thickening of undetermined origin. This retrospective study included 103 patients (44 men and 59 women, age 59.2 ± 14.8 years) who had undergone 18F-FDG PET/CT for the evaluation of peritoneal thickening of undetermined origin. All 18F-FDG PET/CT images were visually interpreted, and the maximal standardized uptake values (SUVmax) were measured. We compared the role of 18F-FDGPET/CT with that of CT alone in detecting peritoneal thickening of undetermined origin. We also compared the differences between malignant and tuberculous peritoneal thickening in PET/CT parameters and clinical characteristics. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy in detecting the primary cause of the peritoneal thickening were 76.2%, 78.9%, 94.1%, 42.9%, and 81.2%, respectively, for 18F-FDG PET/CT, and 58.3%, 84.2%, 94.2%, 31.4%, and 63.1%, respectively, for CT imaging. Malignant peritoneal thickening had significantly higher SUVmax than nontuberculous benign peritoneal thickening. However, tuberculous peritoneal thickening also had a high SUVmax. There were some factors that were significantly different between patients with tuberculous peritoneal thickening and those with malignant peritoneal thickening in our study; these included age, pattern of peritoneal thickening, and presence of ascites. 18F-FDG PET/CT is useful for detecting the underlying cause of peritoneal thickening. Special attention should be paid to peritoneal tuberculosis, which has a high SUVmax and may mimic malignant peritoneal thickening. Multiple PET/CT parameters which were different in patients with tuberculous and malignant causes could be taken into consideration to make the differential diagnosis.

18F-FDG PET/CT in differentiating malignant from benign origins of obstructive jaundice

BACKGROUND

The various origins of obstructive jaundice make the diagnosis of the disease difficult. This study was undertaken to evaluate the role of 18F-FDG PET/CT in differentiating malignant from benign origins of obstructive jaundice and to quantify the added value of 18F-FDG PET/CT over conventional imaging (enhanced CT and/or MRI).

METHODS

Eighty-five patients with obstructive jaundice who underwent 18F-FDG PET/CT within 2 weeks after enhanced CT and/or MRI were reviewed retrospectively. All 18F-FDG PET/CT images were independently evaluated by 2 nuclear medicine physicians who were unaware of other imaging data; differences were resolved by consensus of the physicians. All conventional imaging interpretations, according to the medical records, were reviewed by 2 radiologists to determine the potential value. Final diagnoses were based on histological or surgical findings.

RESULTS

Sixty-six patients were diagnosed with malignancies, and 19 patients with benign lesions. The maximum standardized uptake values for malignant and benign lesions causing biliary obstruction were 8.2+/-4.4 and 4.0+/-5.0, respectively (P<0.05). The sensitivity, specificity, and overall accuracy for differentiating malignant from benign origins with 18F-FDG PET/CT were 86.4% (57/66), 73.7% (14/19), and 83.5% (71/85), respectively. 18F-FDG PET/CT in conjunction with conventional imaging changed the sensitivity, specificity, and overall accuracy of conventional imaging alone from 75.8% (50/66) to 95.5% (63/66) (P<0.05), 68.4% (13/19) to 57.9% (11/19) (P>0.05), and 74.1% (63/85) to 87.1% (74/85) (P<0.05), respectively.

CONCLUSIONS

18F-FDG PET/CT is of great value in differentiating malignant from benign origins of obstructive jaundice and is a useful adjuvant to conventional imaging. 18F-FDG PET/CT should be recommended for further etiological clarification.

Use of (18)F-FDG PET/CT to locate primary malignancies in patients with hepatic cirrhosis and malignant ascites

OBJECTIVE

Ascites in patients with hepatic cirrhosis is caused by cirrhosis in most cases. For most malignant ascites, the primary malignancy could be readily identified using conventional imaging methods, e.g., computed tomography (CT) and magnetic resonance imaging (MRI). However, in a small fraction of the patients, the primary malignancy remains occult even with these examinations. In this retrospective study, we assessed the usefulness of (18)F-FDG PET/CT in patients with hepatic cirrhosis and malignant ascites of otherwise unknown origin.

METHODS

Twenty-eight patients with malignant ascites of unknown primary sites after CT, MRI and ultrasound during the period of five years between January 2008 and December 2012 had received (18)F-FDG PET/CT. Medical records of these patients were reviewed and analyzed.

RESULTS

Elevated (18)F-FDG absorption was found in 23 of 28 cases in the following sites: gastrointestinal tract (n=10, 43.5%), prostate (n=5, 21.7%), peritoneum (n=4, 13.3%), and ovary (n=4, 13.3%). Cancer was confirmed by pathology in 20 cases after open or laparoscopic surgeries. Five patients were found to have benign ascites, among which, 3 were found to be false positive due to tuberculosis. SUV values were significantly higher for tumors than for benign lesions (mean values, 6.95 vs. 2.94; P=0.005).

CONCLUSIONS

The (18)F-FDG PET/CT can be as a powerful imaging tool in identifying tissue origin in liver cirrhosis patients suspected of cancers or with cancers of unknown primary sites.

The clinical value of 18F-FDG PET/CT in the evaluation of bone metastases undetermined origin

PURPOSE

To evaluate the clinical value of (18)F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT) in detection of primary lesions of bone metastases.

METHODS

The PET/CT scans of 77 patients with bone metastases undetermined origin were retrospectively reviewed. The results of clinical information were collected.

RESULTS

Forty-four suspected primary tumors were found on the PET/CT images in 77 patients of bone metastases, including 40 patients with the primary tumor confirmed, and 4 patients false-positive. In 37 patients, no primary lesions were detected, including one patient false-negative (signet-ring cell carcinoma). The sensitivity, specificity, and accuracy was 97.6%, 88.9%,and 93.5% respectively. The primary lesions of 51.9% patients could be diagnosed by PET/CT.

CONCLUSION

PET/CT is helpful in detecting the primary lesions of bone metastases.

Peritoneal carcinomatosis in patients with ovarian cancer: enhanced CT versus 18F-FDG PET/CT

PURPOSE

The study aimed to evaluate the efficacy of PET/CT in detecting peritoneal carcinomatosis in patients with ovarian cancer and to compare the diagnostic accuracy of FDG PET/CT with that of enhanced abdominal CT.

METHODS

The medical records of 46 consecutive patients with ovarian cancer were reviewed, and the presence of peritoneal tumor on (18)F-FDG PET/CT and enhanced abdominal CT scans was also assessed. Imaging results were compared with the pathologic findings obtained by surgery.

RESULTS

Pathologic results were positive for peritoneal carcinomatosis in 26 patients and negative in 20 patients. PET/CT correctly detected 25 of 26 patients with peritoneal carcinomatosis and enhanced abdominal CT correctly detected 23 of 26 patients. Sensitivity and specificity for the diagnosis of peritoneal carcinomatosis were 96.2% and 90%, respectively, for PET/CT and 88.5% and 65%, respectively, for enhanced abdominal CT. The accuracy of PET/CT was statistically higher than that of enhanced abdominal CT (93.5% vs 78.3%, P = 0.039). Four distinctly abnormal PET/CT findings of single nodular, multiple nodular, diffuse, and mixed FDG uptakes were identified and corresponded to pathologic findings.

CONCLUSIONS

(18)F-FDG PET/CT imaging is efficient in the diagnosis of peritoneal carcinomatosis and its performance is superior to that of enhanced abdominal CT.

Ascites metabolism measurement enhanced the diagnostic value and accuracy of prognostic evaluation in 18F-FDG PET/CT studies in malignant ascites patients

OBJECTIVE

This study aimed to evaluate the role of ascites metabolism measurement in (18)F-fluorodeoxyglucose ((18)F-FDG) PET/computed tomography (CT) for auxiliary diagnosis and prognostic evaluation of malignant ascites.

MATERIALS AND METHODS

This was a retrospective study on 55 patients, including 36 with malignant ascites and 19 with benign ascites of undetermined origin, before they underwent their first (18)F-FDG PET/CT scan. The χ(2) -test was used to compare the diagnostic efficiencies among (18)F-FDG PET/CT ascites metabolism measurement, tumor localization, and ascites cytology examination. The standard uptake values of ascites and of the normal liver were measured, respectively, and their ratio, denoted as T/NT, was calculated for each patient. The receiver-operating characteristic curve was used to analyze the diagnostic efficiency of the ascites T/NT, ascites carcinoembryonic antigen, ascites CA1(25), and ascites CA(199), and the linear regression was used to analyze the relationship between the ascites T/NT and the survival time of patients.

RESULTS

The metabolic level of malignant ascites was high. The sensitivity and accuracy of ascites metabolism measurement were higher than those of ascites cytology examination (χ(2) =6.98, 4.58; all P's<0.05). The specificity of ascites metabolism measurement was higher than that of (18)F-FDG PET/CT tumor localization (χ(2) =5.70, P<0.05). The T/NT value of malignant ascites (0.68 ± 0.17) was higher than that of benign ascites (0.38 ± 0.10) (t=7.21, P<0.05). The area under the receiver-operating characteristic curve of ascites T/NT was larger than those of ascites carcinoembryonic antigen, CA(125), and CA(199). There was a negative correlation between the ascites T/NT and the survival of patients with malignant ascites (r=-0.647, P<0.01).

CONCLUSION

Ascites metabolism measurement has an important auxiliary diagnostic value in (18)F-FDG PET/CT for ascites patients. The ascites T/NT may be a good index for prognostic evaluation of malignant ascites.

18F-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography fused imaging in malignant mesothelioma patients: looking from outside is not enough

Malignant mesothelioma (MM) is an uncommon neoplasm with a poor prognosis usually associated with asbestos exposure. 18F-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET)/computed tomography (CT) has become an invaluable tool for the diagnosis, staging, and prognosis of this severe disease as it combines both anatomic and functional information in a single imaging procedure, allowing for improved management of this disease. For many authors, 18F-FDG-PET/CT is the cornerstone of the pre-therapeutic evaluation of mesothelioma patients, particularly when multimodal therapy (including extra-pleural pneumonectomy or omentectomy) is considered. However, while characteristic patterns have been reported as predictive of macroscopic pleural or peritoneal involvement, false negative findings are possible, both for pleural and peritoneal mesothelioma, during the initial diagnosis or during the patient's surveillance as illustrated by this report of three cases of suspected MM with negative PET/CT. This report highlights the limitations of PET/CT in the diagnostic evaluation of MM and the importance of histopathological confirmation by thoracoscopy and/or laparoscopy, which remain the most important diagnostic procedures in MM.

High 18F-FDG uptake in microscopic peritoneal tumors requires physiologic hypoxia

The objective of this study was to examine (18)F-FDG uptake in microscopic tumors grown intraperitoneally in nude mice and to relate this to physiologic hypoxia and glucose transporter-1 (GLUT-1) expression.

METHODS

Human colon cancer HT29 and HCT-8 cells were injected intraperitoneally into nude mice to generate disseminated tumors of varying sizes. After overnight fasting, animals, breathing either air or carbogen (95% O(2) + 5% CO(2)), were intravenously administered (18)F-FDG together with the hypoxia marker pimonidazole and cellular proliferation marker bromodeoxyuridine 1 h before sacrifice. Hoechst 33342, a perfusion marker, was administered 1 min before sacrifice. After sacrifice, the intratumoral distribution of (18)F-FDG was assessed by digital autoradiography of frozen tissue sections. Intratumoral distribution was compared with the distributions of pimonidazole, GLUT-1 expression, bromodeoxyuridine, and Hoechst 33342 as visualized by immunofluorescent microscopy.

RESULTS

Small tumors (diameter, <1 mm) had high (18)F-FDG accumulation and were severely hypoxic, with high GLUT-1 expression. Larger tumors (diameter, 1-4 mm) generally had low (18)F-FDG accumulation and were not significantly hypoxic, with low GLUT-1 expression. Carbogen breathing significantly decreased (18)F-FDG accumulation and tumor hypoxia in microscopic tumors but had little effect on GLUT-1 expression.

CONCLUSION

There was high (18)F-FDG uptake in microscopic tumors that was spatially associated with physiologic hypoxia and high GLUT-1 expression. This enhanced uptake was abrogated by carbogen breathing, indicating that in the absence of physiologic hypoxia, high GLUT-1 expression, by itself, was insufficient to ensure high (18)F-FDG uptake.

Diagnosis of patients with peritoneal diseases: an analysis of 42 cases

AIM: To evaluate the clinical value of different methods for diagnosis of peritoneal diseases.

METHODS: A total of 42 patients with peritoneal diseases were included in the study. Measurement of serum tumor markers and computed tomography (CT) were performed in all patients, peritoneocentesis in 40 patients, positron emission tomography (PET)/CT in 9 patients, and ultrasound-guided percutaneous peritoneal biopsy in 13 patients. The sensitivity, specificity and accuracy of each method and the causes of peritoneal diseases were analyzed.

RESULTS: The sensitivity of measurement of serum tumor markers (CEA, CA153, CA19-9, CA242 and CA125) in the diagnosis of metastatic peritoneal tumors was 14.8%, 18.5%, 29.6%, 22.2% and 100%, and the specificity was 80.0%, 93.3%, 93.3%, 93.3% and 0%, respectively. The sensitivity and specificity of exfoliative cytologic examination in the diagnosis of carcinous ascites were 36% and 100%, respectively. The sensitivity and specificity of ascites adenosine deaminase (ADA) in the diagnosis of tuberculous ascites were 92.3% and 92.5%, respectively. The accuracy of CT, PET/CE and percutaneous peritoneal biopsy was 19%, 78% and 85%, respectively.

CONCLUSION: Serum tumor marker measurement, exfoliative cytologic examination and ascites ADA can help differentiate between carcinous and inflammatory peritoneal diseases. The accuracy of PET/CT and percutaneous peritoneal biopsy is higher than that of CT.

Intestinal tuberculosis

PURPOSE OF REVIEW

Intestinal tuberculosis (TB) is increasing due partly to the HIV pandemic. Its clinical presentation mimics inflammatory conditions such as Crohn's disease and malignancies, which are becoming more prevalent, so the diagnosis is problematic.

RECENT FINDINGS

Greater awareness of intestinal TB is needed, both in countries where TB is endemic and developed countries with immigrant populations. Some strains of Mycobacterium tuberculosis are associated with more extrapulmonary disease and greater dissemination, thereby exacerbating the rise in HIV-associated extrathoracic TB. Recent retrospective and prospective studies are leading to the development of diagnostic algorithms. A wide range of imaging techniques is available for sampling and diagnosis. New biochemical, immunological and molecular diagnostic methods are being developed but must be standardized and validated. Developments in drug delivery will facilitate oral therapy even in patients suffering from malabsorption.

SUMMARY

There is an increasing consensus on the risk factors and clinical presentations of intestinal TB. Imaging techniques, coupled with fine needle biopsies, are useful aids to diagnosis, but most important is a greater awareness of the condition by clinicians.