Guest Editorial - Multirow Detector and Cone-Beam Spiral/Helical CT

S PIRAL/HELICAL multirow detector computed tomog-raphy (MDCT), also referred to as multislice spiral CT (MSCT), has attracted a major interest since its recent introduction [18], [33]. Compared with single-row-detector systems, MDCT scanners allow faster data collection and thinner slices that support more demanding clinical applications and present new research opportunities. This special issue consists of 12 original papers from this rapidly expanding field. Although MDCT generally refers to commercial CT scanners used by radiologists, the work in this issue is also applicable to emission CT as well as nonmedical applications of X-ray CT, including nondestructive testing and microtomography. In this editorial, we provide a summary of the special issue, an overview of the field, and suggestions for future work. The first eight papers represent recent work on X-ray CT image reconstruction in multirow detector or cone-beam geometry. The first two papers by Schaller et al.report an adap-tive axial interpolation theory for a MDCT scanner with experimental verification [13], [29]. Adaptive axial interpolation provides increased flexibility for image reconstruction in clinical practice. By keeping slice thickness and image noise independent of pitch, the MDCT parameter selection is simplified. The paper by Proksa et al. introduces the-PI-method for spiral/helical cone-beam CT (CBCT) [27]. This method assumes a detector array shaped by a helix, permits variable pitch, and is amendable to both exact and approximate reconstruction. The paper by Hsieh addresses the degradation in image quality of spiral/helical MDCT when the gantry is tilted to produce oblique sections [17]. He formulated a model as an analytical basis and developed several compensation schemes. The paper by Bruder et al. describes two different approximate single-slice algorithms for CBCT: multirow Fourier reconstruction (MFR) and advanced single-slice rebinning (ASSR), in the framework of the generalized parallel projection using-filtering [3]. Their studies contain data valuable for the design of spiral/helical CT scanners with medium cone-beam angles. The paper by Kachel-rieß et al. proposes MDCT algorithms for cardiac imaging [19]. Based on ECG signals, the two dedicated cardiac reconstruction algorithms improve image quality compared with the standard reconstruction algorithms. The paper by Kudo et al. [21] deals with the long-object problem; that is, to reconstruct a region of interest (ROI) of a long object from data collected along a helical path that extends only marginally above and below the ROI. Their quasi-exact reconstruction algorithms require no Publisher Item Identifier S 0278-0062(00)09415-5. additional circular scans and are in the filtered …