In the last two decades, advances in nuclear medicine have been driven mainly by the development of positron emission tomography (PET) imaging, whose value in oncology is unsurpassed. The strength of PET derives not only from its use of one of the most powerful radiopharmaceuticals available, i.e., F-18-deoxyglucose (FDG), but also from the fact that it offers superior image quality compared to single-photon emission computerised tomography (SPECT). Furthermore, SPECT is still largely performed as a standalone procedure, whereas PET imaging is now routinely performed in combination with CT (PET/CT). The tremendous progress of PET/CT has, therefore, opened a discussion on the viability and future of singlephoton imaging procedures. Despite this, a statistical survey conducted by the European Association of Nuclear Medicine in 2010 showed that the majority of in vivo nuclear medical procedures performed in Europe in that year were still conventional. Without doubt, the popularity of conventional nuclear medicine lies in its high cost efficiency. Economic considerations continue to be key factors in developed countries, and are of the utmost importance in less economically developed parts of the world. However, SPECT, too, has undergone dramatic improvements over the last two decades, even though they are less spectacular than those of PET. A major breakthrough was the development of the iterative image reconstruction techniques that substituted filtered back projection in the early 1990s [1]. Iterative image reconstruction allows corrections for the variables that confound image quality to be integrated directly into the reconstruction process; iterative image reconstruction has, since its introduction, been at the root of many technical improvements of SPECT. SPECT/CT hybrid imaging was first introduced as early as 1993 [2]. The CT component of the first of these hybrid systems used low-dose x-ray tubes that did not allow CT examinations of diagnostic quality. Nevertheless, thanks to these systems the benefit of SPECT co-registered with CT images was demonstrated and reported in several publications as a proof of principle [3]. The integration of spiral CT scanners into these hybrid devices in 2005 considerably increased the popularity of SPECT/CT hybrid imaging, as shown by a steep rise in pertinent publications from 2005 onwards (Fig. 1). A multitude of articles has compared the diagnostic utility of SPECT/CT to that of stand-alone planar imaging and SPECT for various indications [3]. The results they report show that SPECT/CT increases the diagnostic accuracy of conventional nuclear medical imaging by up to 30 % in the fields of skeletal, tumour, inflammation and sentinel node scintigraphy. This dramatic improvement in diagnostic performance is based on several factors, the first being the possibility of anatomically localising foci of abnormal tracer uptake. This is particularly important when using radiopharmaceuticals that are highly specific for diseased tissue, but show only little or no uptake in normal anatomical structures. Examples include the iodine isotopes that are frequently used to stage thyroid carcinoma. T. Kuwert (&) Clinic of Nuclear Medicine, University Hospital Erlangen, Erlangen, Germany e-mail: orazio.schillaci@uniroma2.it