Ultra-low-dose CBCT: new cornerstone of paranasal sinus imaging

Background: This study evaluates the clinical image quality (IQ) and usability of a sinonasal ultra-low-dose (ULD) cone-beam computed tomography (CBCT) scan. The results are compared to those of a high resolution (HR) CBCT scan to identify the streng-ths and weaknesses of a ULD CBCT protocol.Methodology: Sixty-six anatomical sites in 33 subjects were imaged twice using two imaging modalities: HR CBCT (Scanora 3Dx scanner; Soredex, Tuusula, Finland) and ULD CBCT (Promax 3D Mid scanner; Plandent, Helsinki, Finland). IQ, opacification and obstruction, structural features and operative usability were assessed.Results: The overall IQ in subjects with "no or minor opacification" was excellent: 100% (HR CBCT) and 99% (ULD CBCT) of ratings were evaluated as sufficient for every structure. Increased opacification reduced the quality of both imaging modalities, resulting in sufficient IQ in 97% (HR CBCT) and 92% (ULD CBCT) of evaluations. With greater opacification, the sufficient-insufficient ratio was better (p< 0.05) for HR CBCT regarding the anterior ethmoidal artery, lateral lamella, frontal recess, cribriform plate, superior concha and posterior ethmoidal artery. ULD CBCT's operative applicability was generally good with moderate restraints in fron-toethmoidectomy, frontal sinusotomy, sphenotomy and posterior ethmoidectomy in cases with greater opacification.Conclusions: IQ of paranasal ULD CBCT is sufficient for clinical diagnostics and should be considered for surgical planning. We recommend it as the primary imaging protocol for all patients who meet imaging criteria due to recurrent or chronic nasal symptoms. Additional or conventional imaging might be needed for patients with extensive chronic rhinosinusitis and/or indicati-ons of frontal sinus involvement.