Feasibility of Computed Tomography Pulmonary Angiography with Low Flow Rates

Abstract

Computed tomography pulmonary angiography (CTPA) is the imaging test of choice in suspected pulmonary embolism. High flow rates for the administration of contrast medium are recommended, but these cannot be achieved in a number of patients due to poor peripheral venous access or when using certain central venous catheters. This small feasibility study has examined the CTPA data in a set of 22 patients in whom contrast medium was given at low flow rates (2.0 or 2.5 mL/s). Subjectively, all but one of the patients was judged to be diagnostic. Objectively, enhancement values ≥200 HU were reached in 92% of the examined central vessels (pulmonary trunk, main pulmonary arteries, and lobar arteries). In conclusion, even with a low injection rate CTPA is of diagnostic value in most patients.

Incidence of transient interruption of contrast (TIC) – A retrospective single-centre analysis in CT pulmonary angiography exams acquired during inspiratory breath-hold with the breathing command: “Please inspire gently!”

“…catheters. It can be argued that flow rates have an effect on the incidence of TIC, albeit data has been published on sufficiently diagnostic CTPA image quality in 95% of patients at flow rates as low as 2.0 and 2.5 mL/s [15].…”

An audit of the adequacy of contrast enhancement in CT pulmonary angiograms in a South African tertiary academic hospital setting

“…The recommended minimum flow rate for general CT angiograms is 3 mL/s, 14 while a flow rate of 4 mL/s or higher has been recommended for CTPAs internationally. 13,18,19,20 Flow rates of 3 mL/s have been safely achieved with 22 G IV cannulae; 21 thus the use of 22 G cannulas can, in theory, still be sufficient. Power injectors have a predetermined pressure limit that can be exceeded in cases of access vein size and IV cannula size mismatch, and this will lead to an automatic decrease in the flow rate.…”

Iterative reconstruction in single-source dual-energy CT angiography: feasibility of low and ultra-low volume contrast medium protocols

“…In addition, patients such as those with cancer undergoing chemotherapy may be in poor peripheral venous status and require the use of smallbore cannulas for CT scans. 42 The proposed ultra-low-CM protocol can thus be applied to patients with poor renal (30 # eGFR , 45 ml min 21 /1.73 m 2 ) and peripheral venous conditions to minimize the side effects of CM while keeping the image quality. For patients of relatively good renal function and peripheral venous status, the protocol of low CM volume and injection rate can be utilized to obtain improved image quality.…”