99mTc MDP SPECT/CT imaging in the evaluation of mandibular osteomyelitis severity

99mTc MDP SPECT/CT imaging
in the evaluation of mandibular osteomyelitis severity

By Partha Ghosh, MD, Siemens Healthineers, Hoffman Estates, IL, USA
Data and images courtesy of Chiba Aoba Municipal Hospital, Chiba, Japan
|2021-03-04
A 67-year-old female reported chronic pain and limited movement in her right temporo-mandibular joint along with difficulty opening her jaw.

Clinical examination showed ankylosis of the right-mandibular joint with extremely restricted movement, suggesting that surgical replacement of the affected mandible with a prosthesis may be difficult.

A 99mTc MDP bone scintigraphy with whole-body planar and SPECT/CT of the head-and-neck region was performed to delineate the extent of mandibular pathology.

As indicated in Figures 1-3, the initial SPECT/CT study showed severe sclerosis and hypermetabolism in the right mandibular condylar process with ankylosis of the right mandibular joint along with involvement of the entire ramus and body of the right and the left mandible. Both the sclerosis and hypermetabolism were particularly high and of similar intensity in the right condylar process and left ramus, suggesting two foci of particular intensity in these areas with a lower level of involvement in the rest of the mandibular body. The sparing of the left mandibular condylar process and the left temporo-mandibular joint of any pathology is clearly defined in the MIP and the fused images.

The SPECT/CT findings show typical CT changes of osteosclerosis, periosteal, and cortical bone thickening, as well as an intense and variegated hypermetabolism in the mandible with particularly intense foci in the right mandibular condylar process; in addition, the ankylosis of the right mandibular joint along with an intense hypermetabolism and sclerosis in the left mandibular ramus, suggest the possibility of severe and diffuse mandibular osteomyelitis. This may be due to a gingival infective foci or osteomyelitis secondary to a mandibular osteonecrosis, which could be related to diphosphonate use. In review of the age and gender of the patient (67-year-old female), the possibility of mandibular osteonecrosis secondary to diphosphonate use is deemed a distinct possibility and needs to be ruled out by conducting a thorough assessment of her medication history. The patient was treated conservatively with antibiotics but continued to display symptoms of pain and extremely restricted jaw movement. A 67Ga scintigraphy conducted two years prior showed limited active osteomyelitis (right mandibular joint; left mandibular superior branch), ruling out multiple myeloma.

Two years following the initial 67Ga scintigraphy, the patient underwent a 99mTc MDP SPECT/CT study on a
Symbia Intevo scanner equipped with xSPECT BoneTM and xSPECT QuantTM to assess the morphological and metabolic change to the mandibular osteomyelitic process. The study was performed 3 hours following an intravenous IV injection of 23.7 mCi (878.7 MBq). A whole-body planar study was performed followed by a SPECT/CT. Additionally, xSPECT Bone and xSPECT Quant reconstructions were performed and fused with CT for evaluation.

Although the visual impression of the sequential SPECT suggests a resolution of the intensity of uptake in the left ramus—including the continuation of similar hypermetabolism levels in the right mandibular condylar process—the xSPECT Quant quantitative evaluation confirms the significant increase in hypermetabolism in the right mandibular condyle in addition to and the decrease in left ramus uptake. Likewise, the follow-up SPECT suggests a resolution of the intensity of uptake in the left ramus—including the continuation of similar hypermetabolism levels in the right mandibular condylar process. However, the xSPECT Quant quantitative evaluation confirms the significant increase in hypermetabolism in the right mandibular condyle. The decrease in the left ramus reflects a variegated response to antibiotic therapy with complicating processes of ankylosis in the right mandibular joint, which may further increase the osteosclerotic and osteolytic processes, leading to higher metabolism.
Mandibular osteomyelitis may be caused by bacterial infections of the teeth and gums and may occur secondary to medication-related osteonecrosis of the mandible and maxillofacial region.1 Medication-related osteonecrosis of the jaw is often related to bisphosphonate therapy for osteoporosis in the elderly.

In this patient, the severity of osteomyelitis was advanced in the right mandibular condylar process with gross sclerosis and fibrosis with ankylosis of the right temporo-mandibular joint. However, the osteomyelitis process also spread to the right mandibular ramus and body and also to the left body and ramus, thereby involving nearly the entire mandible and sparing only the left mandibular condyle and left temporo-mandibular joint.

The CT changes of sclerosis, focal osteolysis, cortical and periosteal thickening, and cortical perforations are typical of mandibular osteomyelitis, although it is not possible to differentiate between bacterial infection-related mandibular osteomyelitis and osteomyelitis secondary to medication-related osteonecrosis of the jaw.2 Furthermore, the CT changes are not reflective of a response of the osteomyelitic process following antibiotic therapy, since the established sclerosis is not altered with therapy.

In this context, quantitative SPECT/CT may be helpful in assessing response and progression of disease process, as evident from the SUV evaluation using sequential xSPECT Quant, which clearly shows resolution in the left ramus with progression in the right mandibular condylar process. Ogura et al performed a quantitative SPECT/CT in 9 patients with medication-related jaw osteonecrosis and 4 patients with chronic mandibular osteomyelitis. The SUVmax was consistently higher in chronic osteomyelitis (mean SUVmax 10.16) compared to that in medication-related osteonecrosis (mean SUVmax 5.50).3 The estimation of total bone uptake—attained by multiplying the SUVmean with the metabolic bone volume measured by the volume of interest (VOI) around the lesion—was also significantly higher in chronic osteomyelitis.

Although the current study is focused on SUVmax within lesions, the estimations of metabolic bone volume from the VOI may be easily obtained for calculation of total bone uptake from the xSPECT Quant data using syngo®.via software. This could further improve evaluation of extensive disease processes, which in this case, involves nearly the entire mandible. The severity of SUVmax increase in the right mandibular joint may have multi-factorial causes, including progression of the chronic osteomyelitic process and progressive ankylosis, limitation of movement, and further alteration of bone metabolism. The left ramus lesion appears to have responded to therapy, as reflected in the decrease in SUVmax.

xSPECT Quant helps provide a reproducible and automated quantitative solution for the sequential evaluation of complicated disease processes. In combination with CT changes evaluated using diagnostic CT as part of the SPECT/CT process, this offers a comprehensive assessment of mandibular osteomyelitis.

Scanner: Symbia Intevo 6

SPECT

 

CT

Injected dose

23.7 mCi (878.7 MBq) 99mTc MDP

Tube voltage

130 kV

Post-injection delay

3 hours

Tube current

13 eff mAs

Acquisition

30 stops/detector, 20 seconds/stop

Slice collimation

6 x 2 mm
Slice thickness

5 mm

Reconstruction kernel

B70s

1

2

3