Zusammenfassung
Ziel: Effekt einer Dosisverringerung auf die computerassistierte Detektion (CAD) von Lungenrundherden in der Mehrschicht-Computertomografie (MSCT): CAD-Analyse an Ultra-Niedrigdosis- (ULD-CT) und Standarddosis-(SD-CT)CT-Daten. Material und Methoden: MSCT-Datensätze von 26 Patienten (13 Frauen, 13 Männer, 31 – 74 Jahre) wurden retrospektiv mittels zweier CAD-Systeme analysiert. Die CT-Daten waren konsekutiv mit 5 mAs (ULD-CT) sowie mit 75 mAs (SD-CT) bei einer Röhrenspannung von 120 kV akquiriert und mit einer Schichtdicke von 1 mm rekonstruiert worden. Indikationen für die computertomografische Untersuchung waren Tumorstaging bzw. -suche. Der Referenzstandard wurde von 3 erfahrenen Radiologen im Konsensus festgelegt. Zwei CAD-Algorithmen (CAD-System [Prototyp], Philips, Niederlande: CAD-1; LungCARE, Siemens, Deutschland: CAD-2) wurden an den 52 Datensätzen angewendet und die Ergebnisse der CAD-Analyse mit dem Referenzstandard verglichen. Ergebnisse: Mittels Konsensusanalyse wurden 253 Rundherde in SD-CT und ULD-CT als Referenzstandard festgelegt. Der Durchmesser der Rundherde betrug 2 bis 41 mm (Mittelwert: 4,8 mm). Die Detektionsraten erreichten 72 % (CAD-1) und 62 % (CAD-2) bei SD-CT sowie 73 % und 56 % bei ULD-CT. Die Anzahl der falsch positiven Befunde lag im Median bei jeweils 6 und 5 (SD-CT; CAD-1 vs. CAD-2) sowie bei 8 und 3 (ULD-CT). Die Detektionsrate für Rundherde mit einem Durchmesser von > 5 mm betrug 83 % und 61 % bei SD-CT sowie 89 % und 67 % bei ULD-CT (CAD-1 vs. CAD-2). Für beide CAD-Systeme gab es keine statistisch signifikanten Unterschiede zwischen der Detektionsrate bei SD-CT und ULD-CT (p > 0,05). Schlussfolgerung: Die Verringerung der Strahlendosis hatte keinen statistisch signifikanten Effekt auf die Detektion von Lungenrundherden der 2 getesteten CAD-Systeme bei vergleichbarer Anzahl der falsch positiven Befunde.
Abstract
Purpose: To evaluate the impact of dose reduction on the performance of computer-aided lung nodule detection systems (CAD) of two manufacturers by comparing respective CAD results on ultra-low-dose computed tomography (ULD-CT) and standard dose CT (SD-CT). Materials and Methods: Multi-slice computed tomography (MSCT) data sets of 26 patients (13 male and 13 female, patients 31 – 74 years old) were retrospectively selected for CAD analysis. Indication for CT examination was staging of a known primary malignancy or suspected pulmonary malignancy. CT images were consecutively acquired at 5 mAs (ULD-CT) and 75 mAs (SD-CT) with 120 kV tube voltage (1 mm slice thickness). The standard of reference was determined by three experienced readers in consensus. CAD reading algorithms (pre-commercial CAD system, Philips, Netherlands: CAD-1; LungCARE, Siemens, Germany: CAD-2) were applied to the CT data sets. Results: Consensus reading identified 253 nodules on SD-CT and ULD-CT. Nodules ranged in diameter between 2 and 41 mm (mean diameter 4.8 mm). Detection rates were recorded with 72 % and 62 % (CAD-1 vs. CAD-2) for SD-CT and with 73 % and 56 % for ULD-CT. Median false positive rates per patient were calculated with 6 and 5 (CAD-1 vs. CAD-2) for SD-CT and with 8 and 3 for ULD-CT. After separate statistical analysis of nodules with diameters of 5 mm and greater, the detection rates increased to 83 % and 61 % for SD-CT and to 89 % and 67 % for ULD-CT (CAD-1 vs. CAD-2). For both CAD systems there were no significant differences between the detection rates for standard and ultra-low-dose data sets (p > 0.05). Conclusion: Dose reduction of the underlying CT scan did not significantly influence nodule detection performance of the tested CAD systems.
Key words
thorax - neoplasms - CT spiral - computer-aided detection - radiation dose
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Dr. Patrick Alexander Hein
Institut für Radiologie, Charité Campus Mitte, Charité-Universitätsmedizin Berlin
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