Ranish Deedar Ali Khawaja MD, Presenter: Nothing to Disclose

Rachna Madan MD, Abstract Co-Author: Nothing to Disclose

Amita Sharma MBBS, Abstract Co-Author: Nothing to Disclose

Subba Rao Digumarthy MD, Abstract Co-Author: Nothing to Disclose

Jo-Anne O. Shepard MD, Abstract Co-Author: Consultant, Agfa-Gevaert Group

Mannudeep K. S. Kalra MD, Abstract Co-Author: Nothing to Disclose

Sarabjeet Singh MD, Abstract Co-Author: Research Grant, Siemens AG Research Grant, Toshiba Corporation Research Grant, General Electric Company Research Grant, Koninklijke Philips NV

Atul Padole MD, Abstract Co-Author: Nothing to Disclose

Thomas Koehler PhD, Abstract Co-Author: Employee, Koninklijke Philips NV

To assess the detection of lung nodules (solid and ground-glass ‘GGO LN’) at microSievert (µSv) chest CT examinations reconstructed with iterative reconstruction techniques (iDose & iterative model reconstruction [IMR]), and non-iterative filtered back projection (FBP) technique.

This IRB-approved prospective study included 116 CT image series for 29 patients (51-87 years, BMI 16-32kg/m2) who underwent a routine chest CT on 256 MDCT(iCT,Philips Healthcare). Each patient underwent three µSv-CT exams at 3 dose levels: 500µSv [120kV,12mA], 250µSv [100kV,10mA], 100µSv [80kV,10mA]) immediately after standard-of-care (SD) CT [3mSv, 120kV AEC enabled]. SD-FBP, µSv-FBP, µSv-IMR & µSv-iDose were reconstructed at 2.5 mm thickness. Four radiologists assessed subjective quality independently using a continuous scale. Lesions (true, pseudo & missed) were detected on µSv-images and compared to SD-FBP “reference-standard”. Noise spectral density (NSD) curves to assess noise in frequency domain were obtained. Student’s t-test, intraclass correlation coefficient, & Jackknife free-response receiver operating characteristic method were used for data analysis.

Missed lesions (mostly GGO LN <5mm) included 24/503 (at 250µSv FBP), 3/503 (at 250µSv IMR/iDose), 32/503 (at 100µSv FBP), and 14/503 (at 100µSv IMR/iDose). FBP images were clinically adequate for all lung findings at 250µSv (in patients with BMI ≤25kg/m2) & at 500µSv (≤30kg/m2) dose levels. Iterative images enabled adequate evaluation for solid LN at 100µSv irrespective of patient BMI (P >0.05), and GGO LN at 100µSv (≤25kg/m2; P 0.02). Irrespective of patient BMI and lesion size, both solid and GG LN were evaluated as “clinically adequate” at 250µSv and 500µSv dose levels on iterative images. Conspicuity of emphysematous and low-contrast mediastinal lesions was better with IMR images at 500µSv dose level. Compared to SD-FBP, objective noise was significantly lower in IMR images at all dose levels (P <0.001). NSD showed higher noise reduction in lower frequency for IMR compared to SD-FBP method. 

Iterative reconstruction techniques enable optimal detection and evaluation of lung nodules (both solid- and ground-glass) at 250µSv radiation dose or higher. 

Clinically adequate lung evaluation in CT is achievable at 500µSv [~0.5 mSv] with filtered back projection technique and at 250µSv [~0.25 mSv] using advanced iterative reconstruction algorithms such as iDose and IMR. 

Khawaja, R, Madan, R, Sharma, A, Digumarthy, S, Shepard, J, Kalra, M, Singh, S, Padole, A, Koehler, T, MicroSievert Chest CT: Detection of Lung Findings Using Three Different Reconstruction Algorithms (IMR, iDose, FBP) in a Prospective Clinical Study.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14003246.html