Combined CT colonography and 18F-FDG PET of colon polyps: potential technique for selective detection of cancer and precancerous lesions

Assessment of water enema PET/CT: an effective imaging technique for the diagnosis of incidental colorectal 18F-FDG uptake

BACKGROUND

To validate the feasibility of water enema PET/CT (WE-PET/CT) in incidental colorectal 18F-FDG uptake and improve the accuracy of diagnosing colorectal neoplastic lesions.

METHODS

We retrospectively analysed the electronic records of 338 patients undergoing common PET/CT and WE-PET/CT at our hospital. PET/CT results were correlated with colonoscopy pathology and follow-up results. The ROC contrast curve was plotted to evaluate the accuracy of SUVmax on common PET/CT and WE-PET/CT for detecting neoplastic lesions. SUVmax and the median retention indexes (RIs) of cancerous, precancerous, and benign lesions and physiologic uptake were compared.

RESULTS

The sensitivity, specificity and accuracy of diagnosing neoplastic lesions with common PET/CT were 84.0%, 78.3% and 80.2%, respectively. The corresponding results with WE-PET/CT were 95.8%, 96.5% and 96.2%. The AUC of SUVmax on WE-PET/CT was significantly higher than that on common PET/CT (0.935 vs. 0.524, p < 0.001). The median SUVmax on WE-PET/CT was significantly higher than that on common PET/CT in cancerous and precancerous lesions, and significantly decreased in benign lesions and physiologic uptake (p < 0.001). The RI was significantly different between cancerous lesions and physiologic uptake, between precancerous lesions and physiologic uptake, between benign lesions and physiologic uptake, and between cancerous and benign lesions (p < 0.05).

CONCLUSIONS

WE-PET/CT is a noninvasive, well-tolerated and effective technique for diagnosing incidental colorectal 18F-FDG uptake. It is helpful for a timely colonoscopy and can effectively avoid an unnecessary colonoscopy for incidental colorectal 18F-FDG uptake.

PET/CT Integrated With CT Colonography in Preoperative Obstructive Colorectal Cancer by Incomplete Optical Colonoscopy: A Prospective Study

AIM

The aim of this study was to evaluate if integrating whole-body PET/CT with CT colonography (PET/CTC) improves the preoperative diagnosis of obstructive colorectal cancer (CRC).

METHODS

We prospectively included 47 consecutive patients (18 women and 29 men; mean age, 71 ± 14 years) suspected of having CRC by optical colonoscopy, which was not completed due to obstructive masses. To perform PET/CTC, a small caliber Foley catheter was inserted to distend the colon with CO2 insufflations. Polyps measuring 10 mm or larger were considered as high risk of malignancy. All findings were histologically confirmed.

RESULTS

Colorectal cancer was localized in the sigmoid (n = 21), rectum (n = 7), rectosigmoid junction (n = 5), ascending (n = 7), descending (n = 5), and transverse (n = 2) colon. All tumors showed FDG uptake (mean ± SD SUVmax, 20.02 ± 9.9) including one synchronic tumor (SUVmax, 10.46). Forty-seven polyps were histologically confirmed as smaller than 10 mm (n = 35) and 10 mm or larger (n = 12). All 12 polyps 10 mm or larger showed FDG uptake (SUVmax range, 3.08-19.5), but only one smaller than 10 mm could be identified by PET. Pathological lymph nodes were diagnosed in 17/47 cases after surgical removal with a sensitivity and specificity for CTC and PET/CTC of 71% and 97% and 59% and 100%, respectively. Liver metastases were confirmed in 9 patients and in 4/9 along with lung metastases (n = 2) or implants (n = 2), showing a sensitivity and specificity for CTC of 89% and 100% and both 100% for PET/CTC.

CONCLUSIONS

PET/CTC is a reliable technique for staging CRC and diagnosing synchronous tumors. In this series, PET/CTC was not able to identify small polyps but showed potential use for ruling out 10 mm or larger polyps at high risk of malignancy.

Focal colorectal uptake in (18)FDG-PET/CT: maximum standard uptake value as a trigger in a semi-automated screening setting

BACKGROUND

Focal colorectal uptake in (18)FDG-PET/CT may be associated with a malignancy and can be quantified. This provides the basis for an automatic trigger threshold above which cases are flagged for colonoscopic evaluation and below which for individual assessment.

PURPOSE

To determine the lowest maximum standard uptake (SUVmax) in colorectal cancer that could be used as a threshold to trigger endoscopic evaluation and to evaluate whether the SUVmax needs to be further normalised to a priori known extrinsic factors.

METHODS

The SUVmax was measured in 54 colorectal carcinomas and correlated with gender, age, blood glucose level, injected activity, body mass index and time to scan using t test or correlation coefficients (Pearson or Spearman, according to distribution).

RESULTS

There was no correlation between SUVmax and any of the extrinsic factors mentioned above. The lowest SUVmax value was 5 [mean ± SD (range): 11.1 ± 4.8 (5.0-24.6)].

CONCLUSION

In contrast to most other screening techniques, semi-automation in colorectal screening seems possible with PET/CT. This opens the door for further study into the feasibility of automated screening. Independent from extrinsic factors, an SUVmax ≥5.0 in a focal colorectal uptake in (18)FDG-PET/CT should automatically trigger for endoscopic evaluation, if not contraindicated. Cases with SUVmax <5 should be assessed individually before referral for endoscopy. Thus, more interpretation time could be spent on those cases with a lower uptake and more ambiguous diagnosis.

Virtual gastrointestinal colonoscopy in combination with large bowel endoscopy: Clinical application

Although colorectal cancer (CRC) has no longer been the leading cancer killer worldwide for years with the exponential development in computed tomography (CT) or magnetic resonance imaging, and positron emission tomography/CT as well as virtual colonoscopy for early detection, the CRC related mortality is still high. The objective of CRC screening is to reduce the burden of CRC and thereby the morbidity and mortality rates of the disease. It is believed that this goal can be achieved by regularly screening the average-risk population, enabling the detection of cancer at early, curable stages, and polyps before they become cancerous. Large-scale screening with multimodality imaging approaches plays an important role in reaching that goal to detect polyps, Crohn’s disease, ulcerative colitis and CRC in early stage. This article reviews kinds of presentative imaging procedures for various screening options and updates detecting, staging and re-staging of CRC patients for determining the optimal therapeutic method and forecasting the risk of CRC recurrence and the overall prognosis. The combination use of virtual colonoscopy and conventional endoscopy, advantages and limitations of these modalities are also discussed.

(18)F-FDG PET/CT findings of obstructive colitis proximal to colorectal cancer

PURPOSE

This study was performed to determine the frequency and patterns of obstructive colitis (OC) seen on F-FDG PET/CT scan of patients with adenocarcinoma of the colon and rectum.

PATIENTS AND METHODS

Preoperative PET/CT scans and surgical records of 308 patients with surgically proven colorectal adenocarcinoma were retrospectively reviewed for the presence of colon obstruction and OC proximal to the colorectal adenocarcinoma. The distributions, patterns, and SUVmax of OC were evaluated on PET/CT. Abdominal CT, colonoscopic finding, and histopathologic findings of surgical specimen were also reviewed.

RESULTS

Of 308 patients, PET/CT scans of 29 (9.4%) showed OC. The mean SUVmax of OC was 3.6 ± 2.2 (range, 1.6-12.3). Obstructive colitis was contiguous to the tumor in 23 patients (79.3%) and noncontiguous in 6 (20.7%). Obstructive colitis was diffuse in 25 patients (86%) and patchy in 4 (14%). It was segmental in 16 patients (55%) and pancolonic in 13 (45%). Twenty-three of 29 patients (79.3%) showed proximal wall thickening to colon cancer on abdominal CT performed about 3 days before PET/CT.The patients with OC on PET/CT was significantly associated with annular (P = 0.017), large-sized (P < 0.001), and advanced colon cancer (P < 0.001). However, there was no association between tumor size and SUVmax of OC.Ten proximal polyps were detected in 7 of 29 patients (24.1%) on colonoscopy and surgical specimen. Of these, 1 proximal polyp was removed before PET/CT scan, whereas the remaining 9 were not detected on PET/CT scan.

CONCLUSIONS

Obstructive colitis is predominantly diffuse and contiguous with the obstructing adenocarcinoma. Colorectal cancer with OC tends to show annular shape and larger tumor size. Obstructive colitis may lower the possibility of detection of synchronous proximal colonic lesion by PET/CT.

Differentiation of incidental intestinal activities at PET/CT examinations with a new sign: peristaltic segment sign

PURPOSE

The aim of this study was to present the effect of the peristaltic segment sign for the differential diagnosis between malignant, physiological and gastrointestinal focal fluorodeoxyglucose (FDG) uptakes as an alternative method to maximum standardized uptake value (SUVmax).

MATERIALS AND METHODS

Gastrointestinal tract (GIT) sections of 823 FDG positron emission tomography/computed tomography (FDG-PET/CT) performed in our center were reviewed retrospectively. Images of these cases that have been reported for positive intestinal focal FDG uptake areas were included. Through the sectional images, any accompanying short segment expanded with air just after or before the uptake area was marked as "positive peristaltism sign". The cases were confirmed with endoscopy plus biopsy (n:42), endoscopy (n:5), laparotomy (n:1), transabdominal biopsy (n:1), enteroclysis (n:1), CT-colonoscopy (n:5), rectal contrast enhanced CT (n:4). Distinguishing features of the sign were analyzed statistically compared to the conventional method for differentiation of malignity.

RESULTS

Localized FDG uptake was reported in 59 of 823 cases. A SUVmax greater than 2.5 with intestinal wall thickening allowed the diagnosis of malignity with sensitivity 33%, specificity 65%, positive predictive value 69% and negative predictive value 46%. The peristaltic segment sign, considered as a benign finding, increased the statistical values to 68%, 80%, 82% and 65%, respectively.

CONCLUSION

In case of gastrointestinal increased focal FDG uptake, the new parameter of peristaltic segment sign may differentiate the physiologic uptakes from the malignant ones more accurately than the conventional SUVmax.

Positron emission tomography for benign and malignant disease

Functional imaging using radiolabeled probes that specifically bind and accumulate in target tissues has improved the sensitivity and specificity of conventional imaging. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) has shown improved diagnostic accuracy in differentiating benign from malignant lesions in the setting of solitary pulmonary nodules. FDG-PET has become useful in preoperative staging of patients with lung cancer, and is being tested with many other malignancies for its ability to change patient management. This article provides an overview of the current status of FDG-PET and presents the challenges of moving toward routine use.

Incidental finding of focal FDG uptake in the bowel during PET/CT: CT features and correlation with histopathologic results

OBJECTIVE

The purpose of this study was to identify and characterize the clinically significant lesions associated with incidental detection of focal uptake of (18)F-FDG in the bowel at PET/CT.

MATERIALS AND METHODS

Among 2,250 consecutively registered patients with various nongastrointestinal malignant diseases who underwent FDG PET/CT as part of their care, patients with the incidental finding of focal bowel uptake of FDG were included in the study. All patients underwent an endoscopic or surgical procedure for characterization of the lesions. The location, intensity of uptake, and appearance of the lesions on PET/CT images were recorded and compared with the endoscopic and surgical pathologic results.

RESULTS

Twenty-one of 25 foci of intense uptake in the bowel were associated with endoscopic or surgical abnormalities (positive predictive value, 84%). Seven lesions were malignant (two primary, five secondary); 13 were premalignant (nine tubovillous adenoma, four tubular adenoma); and one lesion was benign (hyperplastic polyp). Eleven lesions detected with endoscopy were not FDG avid, and all 11 were smaller than 1 cm in diameter. There was no statistically significant difference in the maximum standardized uptake values of the benign and malignant lesions.

CONCLUSION

The incidental finding of focal FDG uptake in the bowel justifies further investigation of these foci and should not be dismissed as physiologic uptake. Premalignant lesions, such as adenoma, are often found, and early treatment may prevent the development of carcinoma.

Nonlaxative PET/CT colonography: feasibility, acceptability, and pilot performance in patients at higher risk of colonic neoplasia

CT colonography without bowel preparation is a safer and better-tolerated alternative to full laxation protocols, but comparative sensitivity and specificity are potentially reduced. Uptake of (18)F-FDG by colonic neoplasia is well described, and combining PET with nonlaxative CT colonography could improve accuracy. The purpose was to prospectively test the technical feasibility and acceptability of combined nonlaxative PET/CT colonography in patients at higher risk of colorectal neoplasia and to provide pilot data on diagnostic performance.

METHODS

Fifty-six patients (median age, 64 y; 30 women) at high risk of colonic neoplasia underwent nonlaxative PET/CT colonography with barium fecal tagging within 2 wk of scheduled colonoscopy. Colonic segmental distension was graded 1 (poor) to 3 (good). A radiologist, experienced in CT colonography, and nuclear medicine physician in consensus analyzed the datasets. The diagnostic performance for standalone CT colonography and combined PET/CT colonography was compared with the reference colonoscopy. Patient experience for 25 items (each scored from 1 to 7) pertaining to satisfaction, worry, and physical discomfort was canvassed after both PET/CT colonography and colonoscopy.

RESULTS

Distension was good in 298 of 334 segments (89%; 95% confidence interval [CI], 85%-92%). Patients experienced more physical discomfort during colonoscopy (median, 4; interquartile range [IQR], 2-7) than during PET/CT colonography (median, 5; IQR, 3-7; P = 0.03) and were more willing to undergo PET/CT colonography again (36/43 [84%; 95% CI, 73%-95%] vs. 31/43 [72%; 95% CI, 59%-86%]; P = 0.001). Twenty-one patients had 54 polyps according to colonoscopy (10 with at least 1 polyp >or=6 mm and 8 with at least 1 polyp >or=10 mm). Of 14 polyps 6 mm or greater, 12 (86%; 95% CI, 67%-100%) were (18)F-FDG-avid, including all those 10 mm or greater (mean standardized uptake value, 10.1). CT colonography sensitivity for polyps 6 mm or larger was 92.9% (95% CI, 79.4%-100%) and was not improved by the addition of PET. However, combined PET/CT colonography review improved per-patient positive predictive value for a polyp 10 mm or greater from 73% (95% CI, 39-92) to 100% (95% CI, 60-100).

CONCLUSION

In this feasibility study, simultaneous PET acquisition during nonlaxative CT colonography is technically feasible, is well tolerated, and potentially improves specificity.

Positron emission tomography for the detection of colorectal adenomas

BACKGROUND

(18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) has been reported to detect colorectal adenomas.

AIMS

This study aimed at evaluating the sensitivity of (18)F-FDG PET with computed tomography image fusion (PET/CT) for detecting colorectal adenomas.

METHODS

We retrospectively compared the results of 92 (18)F-FDG PET/CT studies followed by colonoscopy. Colonoscopy and histology were considered as the gold standard.

RESULTS

One hundred fifty-seven lesions were observed. All the 12 malignancies were identified by (18)F-FDG PET/CT but only 27 out of 119 resected adenomas (sensitivity 22.7%) and none of the hyperplastic polyps were detected. At the univariate and multivariate analyses there was a significant statistical association between adenomas sized more than 10mm, presence of villous component and high-grade dysplasia and the ability of (18)F-FDG PET/CT to detect adenomas. (18)F-FDG PET/CT showed an overall sensitivity of 29.8%, a specificity of 81.1%, a positive predictive value (PPV) of 84.8% and a negative predictive value (NPV) of 24.6% for the neoplastic colorectal lesions globally considered.

CONCLUSION

(18)F-FDG PET/CT has a low sensitivity for detecting adenomas. However, because of the specificity and PPV of the technique for neoplastic colorectal lesions, the presence of a focal colorectal FDG uptake justifies the patient undergoing colonoscopy.

PET/CT colonography: a novel non-invasive technique for assessment of extent and activity of ulcerative colitis

PURPOSE

Extent of involvement and activity of ulcerative colitis (UC) is best evaluated by colonoscopy. Colonoscopy however carries risk during acute exacerbation. We investigated the utility of PET/CT colonography for assessment of extent and activity of UC.

METHODS

Within a 1-week window, 15 patients with mild to moderately active UC underwent colonoscopy and PET/CT colonography 60 min after injection of 10 mCi of (18)F-fluorodeoxyglucose (FDG). PET activity score based on the amount of FDG uptake and endoscopic mucosal activity in seven colonic segments of each patient was recorded. The mean maximum standardized uptake value (SUV(max)) of seven segments was compared with activity in liver. A PET activity grade of 0, 1, 2 or 3 was assigned to each region depending upon their SUV(max) ratio (colon segment to liver).

RESULTS

The extent of disease was left-sided colitis in five and pancolitis in ten. The mean Ulcerative Colitis Disease Activity Index (UCDAI) was 7.6. The number of segments involved as per colonoscopic evaluation and PET/CT colonography was 67 and 66, respectively. There was a good correlation for extent evaluation between the two modalities (kappa 55.3%, p = 0.02). One patient had grade 0 PET activity, nine had grade 2 and five had grade 3 PET activity. In six patients, there was one to one correlation between PET activity grades with that of endoscopic grade. One patient showed activity in the sacroiliac joint suggesting active sacroiliitis.

CONCLUSION

PET/CT colonography is a novel non-invasive technique for the assessment of extent and activity of the disease in patients with UC.

Functional imaging of colorectal cancer: positron emission tomography, magnetic resonance imaging, and computed tomography

In the past 10 years, overall survival and disease-free survival of patients with colorectal cancer (CRC) has improved substantially because of a combination of factors: (1) more accurate staging as a result of advances in imaging technology; (2) refinements in surgical technique; (3) 'curative' metastasectomy for patients with limited metastatic disease; (4) improvements in radiation therapy planning and greater precision of radiation therapy delivery; and (5) increasing chemotherapeutic options, including antiangiogenic and vascular targeting drugs. In this era of 'personalized medicine,' the increasingly individualized treatment of patients with CRC has highlighted the need for functional imaging techniques in addition to conventional anatomic-based imaging. This review discusses the contribution of positron emission tomography to the clinical management of CRC. In addition, evolving techniques such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), DCE computed tomography (perfusion CT), diffusion-weighted MRI, and blood oxygenation level-dependent MRI that might have a future role will be covered.

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

The first aim of our study was to compare the role of (18)F-FDG PET/CT with that of CT alone in detecting the primary cause of ascites. A secondary aim was to compare the value of (18)F-FDG PET/CT with that of CT alone in detecting abdominal cavity metastasis. Finally, we analyzed the receiver-operating-characteristic (ROC) curves of maximal standardized uptake values (SUVmax), serum carcinoembryonic antigen, CA19-9, and CA12-5 for differential diagnostic abilities.

METHODS

The (18)F-FDG PET/CT scans of 40 patients with ascites of undetermined origin, including 30 patients with malignant diseases and 10 with benign lesions, were reviewed for the presence of ascites. Among the 40 patients, 34 had received their diagnosis by pathologic examination and 6 by clinical follow-up. We also assessed the (18)F-FDG PET/CT scans of 20 healthy volunteers for comparison. All (18)F-FDG PET/CT images were visually interpreted, and the SUVmax was measured. We compared the mean diameter of true-positive lesions with that of false-negative lesions. The diagnostic abilities of SUVmax, serum carcinoembryonic antigen, CA19-9, and CA12-5 were compared using the ROC curve.

RESULTS

The sensitivity, specificity, and accuracy of PET/CT in detecting the primary cause of ascites were 63.3% (19/30), 70.0% (7/10), and 65.0% (26/40), respectively, and those of CT alone were 36.7% (11/30), 80% (8/10), and 47.5% (19/40), respectively (sensitivity, P < 0.05). The sensitivity of PET/CT was higher than that of CT alone for detecting abdominal cavity metastasis (86.4% vs. 27.3%, P < 0.01). The SUVmax in patients with malignant primary and metastatic lesions was significantly higher than that in healthy volunteers and in patients with benign ascites (P < 0.05). The mean maximal diameter of false-negative lesions was significantly smaller than that of true-positive lesions (P < 0.05). In ROC analysis, the areas under the curve of SUVmax, serum carcinoembryonic antigen, CA19-9, and CA12-5 were 0.803 (P < 0.01), 0.773 (P < 0.05), 0.552 (P > 0.05), and 0.220 (P < 0.01), respectively.

CONCLUSION

(18)F-FDG PET/CT assisted in detecting the original cause of ascites. The differential diagnostic ability of (18)F-FDG PET/CT was superior to that of CT alone, tumor markers, and cytology. More attention should be paid to peritoneal tuberculosis, which can markedly accumulate (18)F-FDG and mimic peritoneal carcinoma.

PET/CT imaging in the diagnosis, staging, and follow-up of colorectal cancer

Colorectal cancer is a common malignancy that afflicts many in the western world. Imaging studies are frequently used to evaluate patients in the screening, staging and surveillance of colorectal cancer. Cross sectional imaging studies such as ultrasound, computed tomography and magnetic resonance imaging provide anatomic and morphologic information about tumor and patterns of spread. Positron emission tomography (PET) differs in that it provides information about tumor metabolism.[(18)F]Fluorodeoxyglucose PET has been clinically used for the evaluation of patients with a wide variety of cancers since most malignancies, including colorectal cancer, typically show increased glucose metabolism. This review present the positron emission tomography/computed tomography imaging findings that may be encountered in the diagnosis, staging and follow-up of patients with colorectal cancer.

PET-CT in oncology: making the most of CT

Combined positron emission tomography–computed tomography (PET-CT) has made a significant impact on cancer imaging. The use of CT to map tissue attenuation for correction of PET images and the ability to co-register the functional information provided by PET with the anatomical data afforded by CT, has resulted in demonstrable improvements in diagnostic accuracy. However, attenuation correction and anatomical localisation may not represent the full benefits of integrating CT with PET. The use of CT acquisition techniques for patient positioning and the use of contrast media can improve diagnostic performance, and incorporation of CT image processing techniques such as perfusion CT, 3D imaging and computer-assisted diagnosis offers new applications. The interpretation of PET-CT images can be improved by fully integrating the morphological appearances on CT into image analysis. Better utilisation of the CT component of PET-CT could further enhance the benefits of PET-CT in oncology but will have implications for manufacturers and purchasers of PET-CT equipment and analysis software. Furthermore, specialists working in PET-CT will need CT competencies beyond knowledge of cross-sectional anatomy. CT continues to exhibit rapid evolution and these advances will inevitably impact on the practice of PET-CT.

PET/CT colonography in patients with colorectal polyps: a feasibility study

PURPOSE

To examine: (1) the feasibility of PET/CT colonography (PET/CTc) in patients with colorectal polyps; (2) the impact of metabolic information on CTc interpretation and, conversely, the impact of morphological information on PET characterisation of focal colorectal uptake.

METHODS

Ten patients with colorectal polyps underwent PET/CTc, followed within 3 h by therapeutic conventional colonoscopy (CC). A radiologist and a nuclear medicine physician analysed the PET/CTc images. The agreement of morphological and metabolic information in the colon and rectum was evaluated. The sensitivity and specificity of PET, CT and PET/CT were calculated for colorectal polyps.

RESULTS

Seventeen polypoid lesions were identified at CC: six< or =5 mm, six between 6 and 9 mm, and five > or =10 mm (four hyperplastic polyps, 11 tubular adenomas, one adenocarcinoma and one submucosal lipoma). A total of 20 scans (supine and prone) were performed in the ten patients: the agreement of morphological and metabolic information was excellent in 17 scans, good in two and moderate in one. PET/CTc showed a sensitivity of 91% for lesions > or =6 mm and a specificity of 100%. The metabolic information did not disclose any further polyps missed on CTc. The morphological information permitted correct classification of all eight instances of focal radiotracer uptake.

CONCLUSION

PET/CTc is a feasible study. Adding a colonographic protocol to PET/CT images seems to allow correct characterisation of all cases of colorectal focal radiotracer uptake. The metabolic information does not seem to increase the accuracy of CTc.

Update on Colorectal Cancer Imaging

Colorectal cancer remains a leading cancer killer worldwide. The disease is both curable and preventable, and yet the importance of widespread screening is only now starting to be appreciated. This article reviews the variety of diagnostic tests, imaging procedures and endoscopic examinations available to detect colorectal cancer and polyps in their early stage and also presents details on various screening options. The critical role of the radiologist is elaborated on including accurate assessment of the tumor extent within the bowel wall and beyond and the detection of lymph node and distant metastases. Staging with CT, MR imaging, endorectal ultrasound, and positron emission tomography are of paramount importance in determining the most appropriate therapy and the risk of tumor recurrence and overall prognosis.