Tracer uptake in the sternum may be variable. A focal area of increased uptake at the angle of Louis is the most common variant on a bone scan. Further, a photon-deficient area above the xiphoid due to sternal foramina and a midline vertical linear area of increased uptake in the sternum are seen in patients who have undergone cardiothoracic surgery with sternotomy (sternal split sign). Occasionally, increased uptake of tracer is seen at the insertion of the iliocostalis thoracis portion of the erector spinae muscles to the ribs (posterior angle of three or more consecutive ribs) known as rib stippling [11] and this should not be confused with sinister malignancy or fractures and caution in interpretation is suggested. In general, multiple foci of tracer uptake throughout the skeleton in a patient with history of cancer are likely to represent widespread skeletal metastases. However, solitary focal uptake is always challenging [12]. The shape of lesions may often help in identifying the etiology, e.g., tracer uptake tracking along the ribs suggests malignant involvement whereas focal increased uptake in multiple ribs in a linear fashion is most likely to be post-traumatic. In general, clinical history of previous trauma or radiotherapy may be useful to may a definitive diagnosis in most cases [1, 2].

Approximately 70% of radiotracer excretion from bone is via the renal system and a focal uptake in a hydrocalyx in the kidney may be confused with uptake in superimposed ribs [1, 2]. Therefore additional oblique image helps in clarifying this potential pitfall. In patients with a renal transplant, ectopic or low lying kidney, one or both kidneys are seen in unusual positions and may be misinterpreted as abnormal uptake in bone [1]. In post-partum females, increased tracer uptake in the pubic symphysis can be seen due to increased stress reaction/pelvic diastases.

The most common site for bone metastases is the spine because of its high vascularisation and presence of red bone marrow [13]. However, this is also a common site for degenerative disease [1]. However, SPECT/CT often provides a unique opportunity combine scintigraphic findings with CT which aids in definitive diagnosis. A common pattern of widespread skeletal metastases in a bone scan is diffuse, generally heterogeneous uptake throughout the skeleton. However, in advanced cases this may present as a “super scan pattern” on a bone scan, which demonstrates markedly increased tracer uptake throughout the whole skeleton with heightened contrast relative to soft tissues and either none or faint tracer activity in the kidneys [1, 2]. A metabolic superscan usually demonstrates more homogeneous distribution of tracer and increased tracer uptake in the skull and long bones unlike a superscan of malignancy.