99m Tc-MDP bone scintigraphy of the hand: comparing the use of novel cadmium zinc telluride (CZT) and routine NaI(Tl) detectors

Novel gamma cameras with CZT detectors have been recently introduced in the routine
of nuclear medicine, and currently, there are systems dedicated to molecular breast
imaging (MBI) and cardiac perfusion imaging. The novel geometric design and new detector
material combined with new reconstruction algorithms have been shown in the literature
to improve the diagnostic performance of gamma cameras in cardiac perfusion studies
and scintimammography with superior image quality, shorter acquisition times, and
reduced radiation exposure 1]–14].

Bone scintigraphy is the most common procedure in nuclear medicine departments that
plays an important role in the diagnosis of various skeletal disorders, including
trauma, joint disease, infection, inflammation, and neoplastic conditions. The role
of CZT detectors for bone scintigraphy has not been fully appreciated. As the CZT
camera available in our facility is that composed of a 20?×?20 cm
²
detection area tailored from breast imaging, we chose a small organ of interest, the
hands, to explore the potential benefit of CZT detectors in bone scintigraphy. Bone
scintigraphy is a common procedure for assessment of bone and joint pathology in the
hand allowing the detection of posttraumatic changes, infection, inflammatory or degenerative
changes, avascular necrosis, reflex sympathetic dystrophy, and neoplastic processes.
Bone scintigraphy of the peripheral skeleton mainly of the small bones and joints
of the hands burdens a potential suboptimal spatial resolution and poor anatomical
definition often requiring a longer acquisition time, zoomed acquisition, and even
change of collimators. Image quality may be even more deteriorated in patients with
poor blood perfusion secondary to cardiovascular disease or peripheral vascular disease,
who are overweight, or with renal and metabolic diseases resulting in a decreased
tracer dose in the extremities. In children, the bones and joints composing the hands
are of particular small size and there should be an ongoing effort to reduce administered
dose and radiation exposure.

Evaluation of arthritis is an ongoing imaging challenge. Scintigraphy using
^99m
Tc-MDP, labeled immunoglobulin G (IgG) gamma imaging, and
¹⁸
F-FDG PET are used for joint imaging 15]–20]. Improved image quality and visualization of the hand joints was achieved by using
a positron emission mammography (PEM) scanner (arthro-PEM) 21]. The detection of active inflammation using non-specific tracers is primarily based
on non-specific mechanisms such as hyperemia and increased vascular permeability.
Recently, specific radiolabeled mAb including anti-CD20 and anti-TNF-? have been introduced
for imaging of chronic inflammatory autoimmune joint diseases such as rheumatoid arthritis.
In addition to evaluation of disease extent and severity, findings of immunoscintigraphy
may assist in selection of patients that could benefit from immunotherapy and for
monitoring response to therapy, maintaining the approach of personalized medicine
22]–26]. The results of our study indicate that image quality reflected by visualization
of joints is significantly improved with the CZT detectors compared to imaging using
the routine NaI(Tl)-based camera, occasionally allowing to define whether the scintigraphic
abnormality is one sided or present on both sides of the articulation. These results
raise a potential improved performance of immunoscintigraphy of the joints using a
CZT-based device. However, at present, the commercially available CZT systems are
organ specific and/or small while imaging of joint diseases warrants imaging of larger
joints and a whole-body approach.

In the current study, we did not find a significant difference neither in lesion detection
nor in image quality between full-dose data and data that simulated reduced acquisition
time or reduced injected dose. This is a major potential benefit of CZT detectors
in the clinical practice of nuclear medicine.

There are several limitations to the study. First is the inherent lack of a gold standard
for the final diagnosis of the abnormal scintigraphic findings. The other is the variable
indications of bone scan of the hands and therefore the heterogeneous study cohort.
This is however a pilot study, and its results encourage further evaluation of the
role of CZT technology in specific indications of bone scan as well as scintigraphy
using other tracers.