Reply to Letter to Editor: Abdominal CT: a radiologist-driven adjustment of the dose of iodinated contrast agent approaches a calculation per lean body weight

Reducing contrast agent residuals in hospital wastewater: the GREENWATER study protocol

The potential enviromental impact of iodinated (ICAs) and gadolinium-based contrast agents (GBCAs) have recently come under scrutiny, considering the current nonselective wastewater treatment. However, their rapid excretion after intravenous administration could allow their potential recovery by targeting hospital sewage. The GREENWATER study aims to appraise the effective quantities of ICAs and GBCAs retrievable from patients' urine collected after computed tomography (CT) and magnetic resonance imaging (MRI) exams, selecting ICA/GBCA per-patient urinary excretion and patients' acceptance rate as study endpoints. Within a prospective, observational, single-centre, 1-year framework, we will enrol outpatients aged ≥ 18 years, scheduled to perform contrast-enhanced CT or MRI, willing to collect post-examination urine in dedicated canisters by prolonging their hospital stay to 1 h after injection. Collected urine will be processed and partially stored in the institutional biobank. Patient-based analysis will be performed for the first 100 CT and 100 MRI patients, and then, all analyses will be conducted on the pooled urinary sample. Quantification of urinary iodine and gadolinium will be performed with spectroscopy after oxidative digestion. The evaluation of the acceptance rate will assess the "environmental awareness" of patients and will aid to model how procedures to reduce ICA/GBCA enviromental impact could be adapted in different settings. Key points • Enviromental impact of iodinated and gadolinium-based contrast agents represents a growing point of attention.• Current wastewater treatment is unable to retrieve and recycle contrast agents.• Prolonging hospital stay may allow contrast agents retrieval from patients' urine.• The GREENWATER study will assess the effectively retrievable contrast agents' quantities.• The enrolment acceptance rate will allow to evaluate patients' "green sensitivity".

Lean body weight versus total body weight to calculate the iodinated contrast media volume in abdominal CT: a randomised controlled trial

Objectives

Iodinated contrast media (ICM) could be more appropriately dosed on patient lean body weight (LBW) than on total body weight (TBW).

Methods

After Ethics Committee approval, trial registration NCT03384979, patients aged ≥ 18 years scheduled for multiphasic abdominal CT were randomised for ICM dose to LBW group (0.63 gI/kg of LBW) or TBW group (0.44 gI/kg of TBW). Abdominal 64-row CT was performed using 120 kVp, 100–200 mAs, rotation time 0.5 s, pitch 1, Iopamidol (370 mgI/mL), and flow rate 3 mL/s. Levene, Mann–Whitney U, and χ² tests were used. The primary endpoint was liver contrast enhancement (LCE).

Results

Of 335 enrolled patients, 17 were screening failures; 44 dropped out after randomisation; 274 patients were analysed (133 LBW group, 141 TBW group). The median age of LBW group (66 years) was slightly lower than that of TBW group (70 years). Although the median ICM-injected volume was comparable between groups, its variability was larger in the former (interquartile range 27 mL versus 21 mL, p = 0.01). The same was for unenhanced liver density (IQR 10 versus 7 HU) (p = 0.02). Median LCE was 40 (35–46) HU in the LBW group and 40 (35–44) HU in the TBW group, without significant difference for median (p = 0.41) and variability (p = 0.23). Suboptimal LCE (< 40 HU) was found in 64/133 (48%) patients in the LBW group and 69/141 (49%) in the TBW group, but no examination needed repeating.

Conclusions

The calculation of the ICM volume to be administered for abdominal CT based on the LBW does not imply a more consistent LCE.

Technique and protocols for cardiothoracic time-resolved contrast-enhanced magnetic resonance angiography sequences: a systematic review

AIM

To review contrast medium administration protocols used for cardiothoracic applications of time-resolved, contrast-enhanced magnetic resonance angiography (MRA) sequences.

MATERIALS AND METHODS

A systematic search of the literature (Medline/EMBASE) was performed to identify articles utilising time-resolved MRA sequences, focusing on type of sequence, adopted technical parameters, contrast agent (CA) issues, and acquisition workflow. Study design, year of publication, population, magnetic field strength, type, dose, and injection parameters of CA, as well as technical parameters of time-resolved MRA sequences were extracted.

RESULTS

Of 117 retrieved articles, 16 matched the inclusion criteria. The study design was prospective in 9/16 (56%) articles, and study population ranged from 5 to 185 patients, for a total of 506 patients who underwent cardiothoracic time-resolved MRA. Magnetic field strength was 1.5 T in 13/16 (81%), and 3 T in 3/16 (19%) articles. The administered CA was gadobutrol (Gadovist) in 6/16 (37%) articles, gadopentetate dimeglumine (Magnevist) in 5/16 (31%), gadobenate dimeglumine (MultiHance) in 2/16 (13%), gadodiamide (Omniscan) in 2/16 (13%), gadofosveset trisodium (Ablavar, previously Vasovist) in 1/16 (6%). CA showed highly variable doses among studies: fixed amount or based on patient body weight (0.02-0.2 mmol/kg) and was injected with a flow rate ranging 1-5 ml/s. Sequences were TWIST in 13/16 (81%), TRICKS in 2/16 (13%), and CENTRA 1/16 articles (6%).

CONCLUSION

Time-resolved MRA sequences were adopted in different clinical settings with a large spectrum of technical approaches, mostly in association with different CA dose, type, and injection method. Further studies in relation to specific clinical indications are warranted to provide a common standardised acquisition protocol.