Evaluation of the effects of oral water and low-density barium sulphate suspension on bowel appearance on FDG-PET/CT

Comprehensive literature review of oral and intravenous contrast-enhanced PET/CT: a step forward?

The integration of diagnostic CT scans into PET/CT facilitates a comprehensive single examination, presenting potential advantages for patients seeking a thorough one-shot check-up. The introduction of iodinated contrast media during PET scanning raises theoretical concerns about potential interference with uptake quantification, due to the modification of tissue density on CT. Nevertheless, this impact appears generally insignificant for clinical use, compared to the intrinsic variability of standardized uptake values. On the other hand, with the growing indications of PET, especially 18F-FDG PET, contrast enhancement increases the diagnostic performances of the exam, and provides additional information. This improvement in performance achieved through contrast-enhanced PET/CT must be carefully evaluated considering the associated risks and side-effects stemming from the administration of iodinated contrast media. Within this article, we present a comprehensive literature review of contrast enhanced PET/CT, examining the potential impact of iodinated contrast media on quantification, additional side-effects and the pivotal clinically demonstrated benefits of an all-encompassing examination for patients. In conclusion, the clinical benefits of iodinated contrast media are mainly validated by the large diffusion in PET protocols. Contrary to positive oral contrast, which does not appear to offer any major advantage in patient management, intravenous iodine contrast media provides clinical benefits without significant artifact on images or quantification. However, studies on the benefit-risk balance for patients are still lacking.

The role of PET imaging in inflammatory bowel diseases: state-of-the-art review

Inflammatory bowel diseases (IBD), i.e. Crohn disease and ulcerative colitis, are autoimmune processes of undetermined origin characterized by the chronic inflammation of the digestive tract. There is no single gold-standard to diagnose IBD which is therefore carried out through the combination of endoscopy, biopsy, radiological and biological investigations; and the development of non-invasive technique allowing the assessment and monitoring of these diseases is necessary. In this state-of-the-art review of the literature, we present the results of PET imaging studies for the diagnosis and staging of IBD (suspected or known), response evaluation to treatment and evaluation of one the main complication, i.e. strictures; explain the reasons why this examination is currently not considered in the IBD guidelines, e.g. radiation exposure, lack of standardization and not validated performances; and finally discuss the perspectives that could possibly allow it to find a place in the future, e.g. digital PET-CT, dynamic PET images acquisition, new radiopharmaceuticals, use of radiomics and use of artificial intelligence for automatically characterize and quantify digestive [¹⁸F]FDG uptake.

Lower Gastrointestinal Tract Applications of PET/Computed Tomography and PET/MR Imaging

This article discusses the role of PET/CT and PET/MR imaging in the evaluation of inflammatory and malignant disorders of the lower gastrointestinal tract. This includes a review of the current literature and a discussion of new and emerging research.

Usefulness of dual-time point imaging after carbonated water for the fluorodeoxyglucose positron emission imaging of peritoneal carcinomatosis in colon cancer

BACKGROUND

Fluorodeoxygluose (FDG) positron emission/computed tomography (PET/CT) is emerging as a useful tool for the diagnosis of peritoneal carcinomatosis (PC). In this study, we assessed whether dual-time point imaging can improve the accuracy of FDG PET/CT for the diagnosis of PC after colon rectal cancer (CRC).

METHODS

Thirty-nine patients with past history of CRC were evaluated. Whole-Body PET/CT scan was acquired 1 hour after tracer injection. If one or more focal areas of increased FDG uptake (standardized uptake value, SUV max>2.5) were found in the abdomen, 1 L of carbonated water was orally administered to patients and a delayed scan of the abdominal region was acquired at 2 hours. The SUV max and the mean Delta (Δ) SUV were calculated. The scintigraphic results were compared with the results of colonoscopy and histology and with the clinical follow-up.

RESULTS

Thirteen out of the 39 patients did not show any significant area of FDG uptake at the whole-body scan. The remaining 26 patients showed an overall number of 27 sites of focal increased uptake, showing a mean SUV max of 6.5+3.3. Late scan of the abdomen showed vanishing spots in 11 cases. Focal and increasing FDG uptake was found in 15 subjects (for an overall number of 16 sites) with SUV max of 15.6+4 and mean Δ SUV of +26.3%±7.5%. In these cases, final diagnosis was PC in 10 patients (according to cytology or histology) and dysplastic polyp in 5 cases. No significant difference in Δ SUV was found between patients with PC and those with polypoid formations.

CONCLUSIONS

According to our results, dual-time point imaging after carbonated water may increase the accuracy of FDG PET/CT for the imaging of PC in patients affected by CRC.

Utility of positron emission tomography/CT in the evaluation of small bowel pathology

We describe the management principles and different roles of positron emission tomography (PET)/CT in the evaluation of patients with small bowel tumours (adenocarcinoma, gastrointestinal stromal tumour, lymphoma, metastases) from initial staging, monitoring response to treatment, to detection of recurrent disease. We also discuss the various non-malignant aetiologies of small bowel fludeoxyglucose (FDG) PET uptake, and other pitfalls in FDG PET/CT interpretation. Awareness of the imaging appearances of small bowel tumours, patterns of disease spread and potential PET/CT interpretation pitfalls are of paramount importance to optimise diagnostic accuracy.

Utility of negative oral contrast (milk with 4% fat) in PET-CT studies

AIMS

The aim of this study was to evaluate whether low-attenuation oral contrast agent (milk with 4% fat) in PET-CT gastrointestinal studies(GIT) improves the diagnostic accuracy.

JUSTIFICATION FOR THE STUDY

Traditional high-contrast oral agents like iodine solutions, and barium suspensions which due to overcorrection problems in PET-CT interpretation lowers the accuracy of diagnosis. Traditional low-attenuation oral contrast agents are water, air, fat containing agents used with 12.5% corn oil and polyethylene glycol. Volumen is a 0.1% barium suspension and has found favor in visualization of mural features as well as for GIT distension. Milk with 4% fat content has also been tested out in radiological studies and found to be as effective as Volumen. As the former is more easily available, palatable, and acceptable especially, by children it needed to be tested in the visualization of the GIT in the PET-CT scenario.

MATERIALS AND METHODS

Total of 112 patients were divided into 3 groups. Group I: No intervention (18 subjects) Group II: Water (55 subjects): All these patients had 500-750 ml of water 5-10 min before PET examination. Group III: Milk (39 subjects) 500 ml of milk (4% fat content with no additives) was given 40-45 min after 18F-Fluorodeoxyglucose (FDG) injection and another 500 ml 5 min before scan was started. For patients intolerant to milk the same procedure was carried out with soya milk. Group IV comparison with data with Volumen.

RESULTS

CRITERIA FOR EVALUATION OF GUT DISTENSION ON CT IMAGES: (0) No distension, (1) 1 cm distension, (2) 1-2 cm distension, (3) >2 cm distension. For the study analysis, % of patients with criteria 2 and 3 were considered as good visualization. Stomach distension was16%, 47%, 88%, 75% in Gr1-4 respectively, Duodenum-11%, 27% 88%, 86%, Jejunum-33%, 49%, 89%, 76%(*) Ileum-40%, 77%, 82%, 80%(*) and Colon-55%, 58%, 7 4%. Visualization of bowel wall with enhancement of stomach, duodenum, jejunum, and ileum and proximal colon was significantly better with milk than with water or no intervention. Intensity of FDG uptake was mild to moderate with no overcorrection in normal bowel loops and in patients with GIT lesions. Gaseous distension was not increased with milk as an oral contrast agent. Images of patients with bowel tumor was well-delineated with milk administration as the FDG uptake ratio of tumor to gut was high.

CONCLUSION

Distension and visualization of the stomach, duodenum, jejunum, and proximal bowel was significantly improved with milk as a low-attenuation contrast agent. Intensity of FDG uptake was not significantly increased in normal gut and delineation of tumor with increased FDG uptake was improved as overcorrection was minimal.

High incidence of peritoneal implants in recurrence of intra-abdominal cancer revealed by 18F-FDG PET/CT in patients with increased tumor markers and negative findings on conventional imaging

OBJECTIVE

The aim of this prospective study was to investigate the role of 18F-fluorodeoxyglucose (18F-FDG) PET/CT in the diagnosis of recurrent intra-abdominal cancer in patients with increased tumor markers and negative findings on conventional imaging studies.

METHODS

Seventy-three patients (30 men; age 61.1 ± 11.5 years) with intra-abdominal cancer (colorectal, n=32; ovarian, n=18; gastric, n=7; pancreatic, n=7; cervical, n=4; endometrial, n=3; duodenal, n=1; and small bowel, n=1) and increasing levels of tumor markers during follow-up and negative CT, MRI or both underwent 125 18F-FDG PET/CT examinations. The final diagnosis was confirmed by histopathological findings in 22 patients, clinical follow-up (median of 12 months) in 13 patients,and repeated imaging with 18F-FDG PET/CT examinations in 38 patients.

RESULTS

Of 73 cancer patients, 18F-FDG PET/CT identified recurrent disease in 52 patients and ruled out in 21 patients. 18F-FDG PET/CT scan was true positive (TP) in 49 patients, false positive in three patients, false negative in four patients, and true negative in 17 patients. In our study, the 18F-FDG-PET/CT scan had a sensitivity of 92.4%, a specificity of 85%, and an accuracy of 91%. Fourteen of 49 TP studies (28.5%) showed peritoneal implants only. Moreover, peritoneal implants were detected in additional nine of 49 TP studies (18.3%) presented with multiple lesions. Thus, half of the true-positive examination revealed peritoneal implants that CT or MRI had not depicted.

CONCLUSION

The results of this study indicate a high incidence of peritoneal implants revealed by 18F-FDG PET/CT in the diagnosis of recurrent intra-abdominal cancer in patients with increasing tumor markers and negative findings on conventional imaging studies.

Management of patients following detection of unsuspected colon lesions by PET imaging

Positron emission tomography (PET) is a well-established and integral component of multimodality imaging in oncology. However, the expanded use of PET in oncological and also non-oncological imaging (such as in assessing inflammatory conditions) has identified more lesions or tumors at unsuspected locations, such as in the large bowel during examination of patients not known to have colorectal disease. We review the clinical significance of colon lesions that were discovered incidentally by PET imaging and management strategies for gastroenterologists.

Molecular imaging in oncology: the acceptance of PET/CT and the emergence of MR/PET imaging

In the last decade, PET-only systems have been phased out and replaced with PET-CT systems. This merger of a functional and anatomical imaging modality turned out to be extremely useful in clinical practice. Currently, PET-CT is a major diagnostic tool in oncology. At the dawn of the merger of MRI and PET, another breakthrough in clinical imaging is expected. The combination of these imaging modalities is challenging, but has particular features such as imaging biological processes at the same time in specific body locations.

MDCT appearance of the appendix: how does the low-density barium sulfate oral contrast agent affect it?

We compared the effect of low-density barium sulfate neutral oral contrast agent on the diameter of normal appendix and its luminal content versus that of water on multidetector-row CT. CT scans of 24 patients who had been imaged on two separate occasions for the evaluation of pancreatic pathology, once with water and subsequently with low-density barium sulfate as the neutral oral contrast agent were evaluated (total of 48 scans). Studies were randomized and reviewed in consensus on a workstation in the stack mode by two radiologists blinded to the type of oral contrast. The appendix was measured at baseline and 10 days later to obtain an average diameter. Results of the water and low-density barium sulfate groups were compared using paired t test. Contents of the appendiceal lumen were also noted (gas, fluid, mixed, and collapsed appendix). The average diameter of the appendix for scans obtained with water and low-density barium sulfate was 4.09 ± 0.87 mm (median, 4.22 mm; range, 2.50-5.65 mm) and 4.13 ± 0.93 mm (median, 4 mm, range, 2.2-5.65 mm), respectively. This difference was not statistically significant (P = 0.69). There was no statistically significant difference in the appendiceal content when water or low-density barium sulfate were used as oral contrast (χ (2) = 4.25, P = 0.89). Low-density barium sulfate does not affect appendiceal content or diameter and, therefore, should not adversely affect evaluation of the appendix on multidetector row CT.