In a prospective study of 295 male Israeli military recruits a 31% incidence of stress fractures was found. Eighty per cent of the fractures were in the tibial or femoral shaft, while only 8% occurred in the tarsus and metatarsus. Sixty-nine per cent of the femoral stress fractures were asymptomatic, but only 8% of those in the tibia. Even asymptomatic stress fractures do, however, need to be treated. Possible explanations for the unusually high incidence of stress fractures in this study are discussed.

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Scintigraphic diagnosis, based on functional image interpretation, becomes more accurate and meaningful when supported by corresponding anatomical data. In order to produce anatomical images that are inherently registered with images of emission computerised tomography acquired with a gamma camera, an X-ray transmission system was mounted on the slip-ring gantry of a GEMS Millennium VG gamma camera. The X-ray imaging system is composed of an X-ray tube and a set of detectors located on opposite sides of the gantry rotor that moves around the patient along with the nuclear detectors. A cross-sectional anatomical transmission map is acquired as the system rotates around the patient in a manner similar to a third-generation computerised tomography (CT) system. Following transmission, single-photon emission tomography (SPET) or positron emission tomography (PET) coincidence detection images are acquired and the resultant emission images are thus inherently registered to the anatomical maps. Attenuation correction of the emission images is performed with the same anatomical maps to generate transmission maps. Phantom experiments of system performance and examples of first SPET and coincidence detection patient images are presented. Despite limitations of the system when compared with a state of the art CT scanner, the transmission anatomical maps allow for precise anatomical localisation and for attenuation correction of the emission images.

The novel trend toward focused parathyroidectomy requires precise preoperative localization of the parathyroid adenoma in patients with primary hyperparathyroidism (PHPT). The present study evaluated the impact of hybrid single photon emission computed tomography/computed tomography (SPECT/CT), using 99mTc-sestamibi (MIBI), on the surgical management of these patients. In a retrospective study of 36 patients with PHPT, SPECT/CT was undertaken when planar 99mTc-MIBI scintigraphy was negative or when an ill-defined focus in the neck or an ectopic site on planar views was visualized. Imaging data were compared with intraoperative findings, and the incremental value of SPECT/CT to lesion localization and surgical procedure was assessed. Three patients with both negative planar and SPECT/CT studies subsequently underwent bilateral neck exploration, with multiglandular hyperplasia diagnosed in two patients and a parathyroid adenoma in one. Of 33 patients with a positive MIBI study, parathyroid adenoma was confined to the neck in 23 patients and to the lower neck-mediastinum in 10. SPECT/CT facilitated the surgical exploration of all 10 ectopic parathyroid adenomas and 4 of 23 cervical parathyroid adenomas, the latter four either at reexploration or in patients with nonvisualization of the thyroid after thyroidectomy. SPECT/CT contributed to the localization of parathyroid adenomas in patients with PHPT and to planning the surgical exploration in 14 of 36 (39%) patients, predominantly those with ectopic parathyroid adenomas or who had distorted neck anatomy.

Filtered back-projection (FBP) is the most commonly used reconstruction method for PET images, which are usually noisy. The iterative reconstruction segmented attenuation correction (IRSAC) algorithm improves image quality without reducing image resolution. The standardized uptake value (SUV) is the most clinically utilized quantitative parameter of [fluorine-18]fluoro-2-deoxy-D-glucose (FDG) accumulation. The objective of this study was to obtain a table of SUVs for several normal anatomical structures from both routinely used FBP and IRSAC reconstructed images and to compare the data obtained with both methods. Twenty whole-body PET scans performed in consecutive patients with proven or suspected non-small cell lung cancer were retrospectively analyzed. Images were processed using both IRSAC and FBP algorithms. Nonquantitative or gaussian filters were used to smooth the transmission scan when using FBP or IRSAC algorithms, respectively. A phantom study was performed to evaluate the effect of different filters on SUV. Maximum and average SUVs (SUVmax and SUVavg) were calculated in 28 normal anatomical structures and in one pathological site. The phantom study showed that the use of a nonquantitative smoothing filter in the transmission scan results in a less accurate quantification and in a 20% underestimation of the actual measurement. Most anatomical structures were identified in all patients using the IRSAC images. On average, SUVavg and SUVmax measured on IRSAC images using a gaussian filter in the transmission scan were respectively 20% and 8% higher than the SUVs calculated from conventional FBP images. Scatterplots of the data values showed an overall strong relationship between IRSAC and FBP SUVs. Individual scatterplots of each site demonstrated a weaker relationship for lower SUVs and for SUVmax than for higher SUVs and SUVavg. A set of reference values was obtained for SUVmax and SUVavg of normal anatomical structures, calculated with both IRSAC and FBP image reconstruction algorithms. The use of IRSAC and a gaussian filter for the transmission scan seems to give more accurate SUVs than are obtained from conventional FBP images using a nonquantitative filter for the transmission scan.