Repeated imaging observations have been made of NGC 3982 with the Hubble Space T elescope between 2000 March and May, over an interval of 53 days. Images were obtained on 12 epochs in the F555W band and on Ðve epochs in the F814W band. The galaxy hosted the Type Ia supernova (SN Ia) SN 1998aq. A total of 26 Cepheid candidates were identiÐed, with periods ranging from 10 to 45 days, using photometry with the DoPHOT program. The dereddened distance to NGC 3982 is estimated from these data using various criteria to maximize signal-to-noise ratio and reliability : the values lie between 31.71 and 31.82, with uncertainties in the mean of typically^0.14 mag for each case. A parallel analysis using photometry with HSTphot discovered 13 variables, yielding a distance modulus of 31.85^0.16. The Ðnal adopted modulus is (22^1. Mpc). Photometry of SN 1998aq that is (M[m)0 \ 31.72^0.14 available in the literature is used in combination with the derived distance to NGC 3982 to obtain the peak absolute magnitude of this supernova. The lower limit (no extinction within the host galaxy) for is [19.47^0.15 mag. Corrections for decline rate and intrinsic color to carry these to the reduced M V system of Parodi and collaborators have been performed. The derived luminosities at hand are fully consistent with the mean of the eight normal SNe Ia previously calibrated with Cepheids. Together they yield km s~1 Mpc~1 based on an assumed LMC distance modulus of 18.50. We H 0 B 60^2(internal) point out that correcting some of the systematic errors and including uncertainty estimates due to them leads to km s~1 Mpc~1. H 0 \ 58. 7^6.3(internal)

Repeated imaging observations have been made of NGC 4527 with the Hubble Space Telescope between April and June 1999, over an interval of 69 days. Images were obtained on 12 epochs in the F 555W band and on five epochs in the F 814W band. The galaxy hosted the type Ia supernova SN1991T, which showed relatively unusual behavior by having both an abnormal spectrum near light maximum, and a slower declining light curve than the proto-typical Branch normal SNe Ia.A total of 86 variables that are putative Cepheids have been found, with periods ranging from 7.4 days to over 70 days. From photometry with the DoPHOT program, the de-reddened distance modulus is determined to be (m − M ) 0 = 30.67 ± 0.12 (internal uncertainty) using a subset of the Cepheid data whose reddening and -2error parameters are secure. A parallel analysis of the Cepheids using photometry with ROMAFOT yields (m − M ) 0 = 30.82 ± 0.11. The final adopted modulus is (m − M ) 0 = 30.74 ± 0.12 ± 0.12 (d = 14.1 ± 0.8 ± 0.8 Mpc).The photometric data for SN1991T are used in combination with the Cepheid distance to NGC 4527 to obtain the absolute magnitude for this supernova of M 0 V (max) = −19.85 ± 0.29. The relatively large uncertainty is a result of the range in estimates of the reddening to the supernova. Thus SN1991T is seen to be only moderately brighter (by ∼ 0.3 mag) than the mean for spectroscopically normal supernovae, although magnitude differences of up to 0.6 mag cannot be ruled out.

Objectives: The aim of this study was to assess artefacts and their impact on cone beam CT (CBCT) image quality (IQ) after head motion simulated by a robot skull. Methods: A fully dentate human skull incorporated into a robot simulated pre-determined patient movements. Ten head motion patterns were selected based on the movement of the C-arm of the CBCT units (no motion as reference). Three CBCT units were used [a threedimensional eXam (K) (KaVo Dental GmbH, Biberach, Germany), a Promax 3D MAX (P) (Planmeca Oy, Helsinki, Finland) and a Scanora ® 3D (S) (Soredex Oy, Tuusula, Finland)]. Axial images were qualitatively assessed at three levels: mental foramen (MF), infraorbital foramen and supraorbital foramen, and artefacts characterized as stripe-like, double contours, unsharpness or ring-like. A 100 mm visual analogue scale (VAS) was used to quantitatively assess IQ. Cross-sectional images of the lower third molar and MF bilaterally were also evaluated by VAS. Four blinded examiners assessed the images. Results: For all units and motion patterns, stripe-like artefacts were the most common. The four observers agreed on the presence of at least one artefact type in 90% of the images. Axial images showed lower overall IQ after motion (VAS 5 72.4 ± 24.0 mm) than reference images (VAS 5 97.3 ± 2.6 mm). The most severe artefacts were seen at the MF level. For cross-sectional images, IQ was lowest after tremor. The mean IQ range was 74-89 and 57-90 for isolated (tilting, rotation and nodding) and combined (nodding 1 tilting and rotation 1 tilting) movements, respectively. IQ for MF was lower than for third molar for any movement except tremor. Conclusions: Head motion of any type resulted in artefacts in CBCT images. The impact on IQ depended on the region and level in the skull.

Objectives: To assess the influence of cone beam CT (CBCT) on treatment plan before surgical intervention of mandibular third molars and to identify radiographic factors with an impact on deciding on coronectomy. Methods: 186 mandibular third molars with an indication for surgical intervention underwent a radiographic examination with two methods: (1) panoramic imaging in combination with stereo-scanography and (2) CBCT. After the radiographic examination a treatment plan (TP) was established: either surgical removal (Sr) or coronectomy (Co). The first TP was based on the panoramic image and stereo-scanogram, while the second TP was established after CBCT was available. Logistic regression analyses were used to identify factors predisposing for Co after CBCT. Results: Treatment was performed according to the second TP. Agreement between the first and second TP was seen in 164 cases (88%), while the TP changed for 22 teeth (12%) after CBCT. Direct contact between the third molar and the mandibular canal had the highest impact on deciding on Co [odds ratio (OR)5101.8, p , 0.001]. Direct contact was not a sufficient factor, however; thus, lumen narrowing of the canal (OR538.9-147.2, p , 0.001) and canal positioned in a bending or a groove in the root complex (OR532.8, p50.016) were additional canal-related factors for deciding on Co. Conclusion: CBCT influenced the treatment plan for 12%. Direct contact in combination with narrowing of the canal lumen and canal positioned in a bending or a groove in the root complex observed in CBCT images were significant factors for deciding on coronectomy. Dentomaxillofacial Radiology (