BackgroundFluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is an important method for detecting tumours, planning radiotherapy treatment, and evaluating treatment responses. However, using the standardized uptake value (SUV) threshold with PET imaging may be suitable not to determine gross tumour volume but to determine biological target volume (BTV). The aim of this study was to extract internal target volume of BTV from PET images.MethodsThree spherical densities of 18F-FDG were employed in a phantom with an air or water background with repetitive motion amplitudes of 0–30 mm. The PET data were reconstructed with attenuation correction (AC) based on CT images obtained by slow CT scanning (SCS) or helical CT scanning (HCS). The errors in measured SUVmax and volumes calculated using SUV threshold values based on SUVmax (THmax) in experiments performed with varying extents of respiratory motion and AC were analysed.ResultsA partial volume effect (PVE) was not observed in spheres with diameters of ≥ 28 mm. When calculating SUVmax and THmax, using SCS for AC yielded smaller variance than using HCS (p < 0.05). For spheres of 37- and 28-mm diameters in the phantom with either an air or water background, significant differences were observed when mean THmax of 30-, 20-, or 10-mm amplitude were compared with the stationary conditions (p < 0.05). The average THmax values for 37-mm and 28-mm spheres with an air background were 0.362 and 0.352 in non-motion, respectively, and the mean THmax values for 37-mm and 28-mm spheres with a water background were 0.404 and 0.387 in non-motion and 0.244 and 0.263 in motion, respectively. When the phantom background was air, regardless of sphere concentration or size, THmax was dependent only on motion amplitude.ConclusionsWe found that there was no PVE for spheres with ≥ 28-mm diameters, and differences between SUVmax and THmax were reduced by using SCS for AC. In the head-and-neck and the abdomen, the standard values of THmax were 0.25 and 0.40 with and without respiratory movement, respectively. In the lungs, the value of THmax became the approximate expression depending on motion amplitude.

An important step in the management of hallux valgus is the objective analysis of foot mechanics in dynamic conditions. However, the manner which hallux valgus affects the foot motion is poorly understood. Moreover, hallux valgus deformity may affect foot intersegmental coordination patterns. The purpose of this study was to investigate the relative motion and intersegmental foot coordination patterns, considering the midfoot, during gait in individuals with hallux valgus. Fifteen females with hallux valgus and 13 females without hallux valgus were recruited in this study. Three-dimensional positional data during gait were collected using a motion capture system and analyzed using a multisegment foot model and an analysis software. Intersegmental foot coordination patterns were assessed using a modified vector-coding technique. In individuals with hallux valgus, the rearfoot was significantly more everted throughout stance, and forefoot motion during late stance was significantly increased. In intersegmental coordination patterns, individuals with hallux valgus exhibited excessive mobility of the rearfoot relative to the midfoot segment during midstance and increased anti-phase motion between rearfoot and midfoot segments during late stance. Excessive rearfoot eversion and altered intersegmental coordination patterns between rearfoot and midfoot may decrease the proper rigidity of the foot and lead to forefoot hypermobility during late stance in individuals with hallux valgus.

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