TORONTO - Can the amount of MRI and CT contrast residuals found in hospital wastewater be reduced? Yes, according to research presented on 2 June at the International Society for Magnetic Resonance in Medicine (ISMRM) meeting in Toronto.
The findings were part of a poster session for the International Society of MRI Radiographers & Technologists (ISMRT) and were presented by Moreno Zanardo, PhD, of the Università degli Studi di Milano in Italy. A new study called Greenwater will monitor over a 12-month period the quantity of retrievable iodinated (ICAs) and gadolinium-based contrast agents (GBCAs) from urine collected from outpatients within an hour from contrast agent administration.
Both GBCAs and ICAs are eliminated from patients' bodies through the urine and are not metabolized; their excretion after intravenous administration in patients undergoing CT or MRI exams could allow for recovery of the contrast waste via collecting patients' urine and its disposal in an intentional way.
"ICAs and GBCAs relatively rapid excretion profile after intravenous administration in humans could allow for a considerable recovery by specific targeting of hospital sewage, for example if outpatients being administered ICAs or GBCAs could be kept in the facility long enough to allow for the urinary excretion of a sizable quantity of these contrast agents in monitored sewers," the group noted in its poster abstract.
The team conducted an initial phase of the study that included 130 adult patients who underwent contrast-enhanced MRI or a contrast-enhanced CT for any reason. Participants had to be willing to stay 60 minutes after the exam to provide the urine sample (collected in designated canisters). The researchers quantified urinary iodine and gadolinium using spectroscopy and also assessed patients' "environmental awareness" about the environmental impact of ICAs and GBCAs.
Of the total patient cohort for this initial phase of the project, 74 underwent MR and 56 CT imaging. Most of these patients (45%) were referred to imaging for cardiac indications, while 36% were referred for neurological workup and 18% for other reasons. Median volume of gadolinium injected per patient was 1.2 mol, median volume of iodine was 22.2 g, and median volume of urine collected was 100 mL.
The group found that GBCA waste recovered per patient through urine was 13.9% of the total fluid; ICA waste recovered was 53.3%.
Zanardo's group reported that patients' acceptance rate for participating in the study was high, over 90%, "indicating a high ... 'green' awareness and interest for a sustainable radiology," it noted.
"Urine samples displayed sufficient volumes to allow patient-by-patients analyses for building a model to predict the amount of iodine and gadolinium retrievable using this approach," the investigators wrote.
Zanardo and colleagues also published their study results on 4 May in European Radiology Experimental.
Disclaimer: The study is funded by Bracco Imaging.
![Examples of ultrasound findings and techniques. (A) Images in a 39-year-old male patient with a mass in the left thigh. The mass is heterogeneous on the B-mode US image (compared with the patient in D) and showed increased microvascularity (superb microvascular imaging [SMI]) and shear-wave elastography (SWE) values. Undifferentiated pleomorphic sarcoma was diagnosed at biopsy (with pleomorphic rhabdomyosarcoma in surgical specimen). (B) Images in an 18-year-old male patient with a mass in the left leg. The mass is hypoechoic on the B-mode image, with no other findings suggestive of malignancy. The lesion is in contact with the cortex of the tibia, which is slightly irregular. CT revealed a doubtful anteromedial tibial erosion. The microvascular study demonstrated high vascularization, suggestive of malignancy. Periosteal Ewing sarcoma was diagnosed with both histologic and immunohistochemical confirmation. (C) Images in a 69-year-old female patient with a lump growing on the outside of the left leg. Multiple SWE examinations were performed (please note the high values obtained in the measurements, whereas the color map highlights the stiffness relative to adjacent tissues). SMI showed areas of increased vascularization to target for sampling. Undifferentiated spindle cell sarcoma was diagnosed at biopsy, with residual leiomyosarcoma in the surgical specimen after neoadjuvant therapy. (D) Images in a 56-year-old female patient with a mass in the right thigh. The mass is heterogeneous at both B-mode ultrasound (similar to patient A) and MRI (coronal T2-weighted spectral attenuated inversion recovery [SPAIR]; T1-weighted pre-contrast and postcontrast imaging), which even shows uptake after the administration of paramagnetic contrast material, which is traditionally suggestive of malignancy. Low values at SMI and elastography are suggestive of benignity. Spindle cell lipoma was diagnosed at biopsy, with atypical spindle cell lipomatous tumor in the surgical specimen.](https://img.auntminnieeurope.com/mindful/smg/workspaces/default/uploads/2026/08/images-radiol250278fig2.APCFLSvX6p.jpg?auto=format%2Ccompress&fit=crop&h=100&q=70&w=100)
![Examples of ultrasound findings and techniques. (A) Images in a 39-year-old male patient with a mass in the left thigh. The mass is heterogeneous on the B-mode US image (compared with the patient in D) and showed increased microvascularity (superb microvascular imaging [SMI]) and shear-wave elastography (SWE) values. Undifferentiated pleomorphic sarcoma was diagnosed at biopsy (with pleomorphic rhabdomyosarcoma in surgical specimen). (B) Images in an 18-year-old male patient with a mass in the left leg. The mass is hypoechoic on the B-mode image, with no other findings suggestive of malignancy. The lesion is in contact with the cortex of the tibia, which is slightly irregular. CT revealed a doubtful anteromedial tibial erosion. The microvascular study demonstrated high vascularization, suggestive of malignancy. Periosteal Ewing sarcoma was diagnosed with both histologic and immunohistochemical confirmation. (C) Images in a 69-year-old female patient with a lump growing on the outside of the left leg. Multiple SWE examinations were performed (please note the high values obtained in the measurements, whereas the color map highlights the stiffness relative to adjacent tissues). SMI showed areas of increased vascularization to target for sampling. Undifferentiated spindle cell sarcoma was diagnosed at biopsy, with residual leiomyosarcoma in the surgical specimen after neoadjuvant therapy. (D) Images in a 56-year-old female patient with a mass in the right thigh. The mass is heterogeneous at both B-mode ultrasound (similar to patient A) and MRI (coronal T2-weighted spectral attenuated inversion recovery [SPAIR]; T1-weighted pre-contrast and postcontrast imaging), which even shows uptake after the administration of paramagnetic contrast material, which is traditionally suggestive of malignancy. Low values at SMI and elastography are suggestive of benignity. Spindle cell lipoma was diagnosed at biopsy, with atypical spindle cell lipomatous tumor in the surgical specimen.](https://img.auntminnieeurope.com/mindful/smg/workspaces/default/uploads/2026/08/images-radiol250278fig2.APCFLSvX6p.jpg?auto=format%2Ccompress&dpr=2&fit=crop&h=167&q=70&w=250)
