Oral contrast agents lead to underestimation of dose calculation in volumetric-modulated arc therapy planning for pelvic irradiation

Background:The effects of oral contrast agents(OCAs)on dosimetry have not been studied in detail.Therefore,this study aimed to examine the influence of OCAs on dose calculation in volumetric-modulated arc therapy plans for rectal cancer.Methods:From 2008 to 2016,computed tomography(CT)images were obtained from 33 rectal cancer patients administered OCA with or without intravenous contrast agent(ICA)and 14 patients who received no contrast agent.CT numbers of organs at risk were recorded and converted to electronic densities.Volumetric-modulated arc therapy plans were designed before and after the original densities were replaced with non-enhanced densities.Doses to the planned target volume(PTV)and organs at risk were compared between the plans.Results:OCA significantly increased the mean and maximum densities of the bowels,while the effects of ICA on these parameters depended on the blood supply of the organs.With OCA,the actual doses for PTV were significantly higher than planned and doses to the bowel increased significantly although moderately.However,the increase in the volume receiving a high-range doses was substantial the absolute change of intestine volume receiving≥52 Gy:1.46[0.05-3.99,cubic centimeter range:-6.74 to 128.12],the absolute change of colon volume receiving≥50 Gy:0.34[0.01-1.53 cc,range:-0.08 to 3.80 cc].Dose changes due to ICA were insignificant.Pearson correlation showed that dose changes were significantly correlated with a high intestinal volume within or near the PTV(ρ>0.5,P<0.05)and with the density of enhanced intestine(ρ>0.3,P<0.05).Conclusions:Contrast agents applied in simulation cause underestimation of doses in actual treatment.The overdose due to ICA was slight,while that due to OCA was moderate.The bowel volume receiving≥50Gy was dramatically increased when OCA within the bowel was absent.Physicians should be aware of these issues if the original plan is barely within clinical tolerance or if a considerable volume of enhanced intestine is within or near the PTV.

Contrast-enhanced ultrasound using SonoVue mixed with oral gastrointestinal contrast agent to evaluate esophageal hiatal hernia: Report of three cases and a literature review

BACKGROUND Due to a thicker abdominal wall in some patients,ultrasound artifacts from gastrointestinal gas and surrounding tissues can interfere with routine ultrasound examination,precluding its ability to display or clearly show the structure of a hernial sac(HS)and thereby diminishing diagnostic performance for esophageal hiatal hernia(EHH).Contrast-enhanced ultrasound(CEUS)imaging using an oral agent mixture allows for clear and intuitive identification of an EHH sac and dynamic observation of esophageal reflux.CASE SUMMARY In this case series,we report three patients with clinically-suspected EHH,including two females and one male with an average age of 67.3±16.4 years.CEUS was administered with an oral agent mixture(microbubble-based SonoVue and gastrointestinal contrast agent)and identified a direct sign of supradiaphragmatic HS(containing the hyperechoic agent)and indirect signs[e.g.,widening of esophageal hiatus,hyperechoic mixture agent continuously or intermittently reflux flowing back and forth from the stomach into the supradiaphragmatic HS,and esophagus-gastric echo ring(i.e.,the“EG”ring)seen above the diaphragm].All three cases received a definitive diagnosis of EHH by esophageal manometry and gastroscopy.Two lesions resolved upon drug treatment and one required surgery.The recurrence rate in follow-up was 0%.The data from these cases suggest that the new non-invasive examination method may greatly improve the diagnosis of EHH.CONCLUSION CEUS with the oral agent mixture can facilitate clear and intuitive identification of HS and dynamic observation of esophageal reflux.

Oral Gd-DTPA as a negative gastrointestinal contrast agent in magnetic resonance cholangiopancreatography

Objective: To evaluate the value of oral Gd-DTPA as a negative contrast agent during magnetic resonance cholangiopancreatography (MRCP) to eliminate the high signals of the gastrointestinal tract. Methods: To select the optimal concentration of oral Gd-DTPA for MRCP, a phantom study was performed followed by clinical trial in 15 cases undergoing MRCP before and after oral Gd-DTPA (in a total volume of 250 ml 1∶5 diluted Gd-DTPA, 1.488 g/L). MRCP images were acquired using two-dimensional single slice fast spin-echo (SSTSE) sequence and half-Fourier acquisition single slice fast spin-echo (HASTE) sequence. Results: The phantom study showed that the 1∶5 diluted oral Gd-DTPA was best in decreasing the signal intensity both in T2-weighted imaging (59.5%) and in HASTE sequence (82.45%). The high signal intensity of the stomach and intestinal fluid was completely suppressed in all the cases. The depictions of the common bile duct and pancreatic duct were markedly improved by using the oral contrast agent (P<0.05). Conclusion: Oral Gd-DTPA is effective and safe for eliminating the high signal of the gastrointestinal tract to improve the depiction of the biliary system by MRCP.