18F-FDG PET/CT as a potential valuable adjunct to MRI in characterising the Brodie's abscess
1 Damai Service Hospital, Jalan Ipoh, Kuala Lumpur , Malaysia
2 Faculty of Medicine and Health Sciences,
Universiti Putra Malaysia, Selangor, Malaysia
Chronic osteomyelitis (Brodie's abscess) is essentially a
problem of diagnosis, and there may be considerable difficulty in
distinguishing it from other benign and malignant bone lesions. Early diagnosis
of Brodie's abscess is deemed important as the disease has a good curative
potential following an appropriate antibiotic treatment. Of late, PET/CT using 18F-FDG
is taking a centre stage in the imaging of bone infection though documentation
on its role in characterising the feature of Brodie's abscess is exceedingly
scarce. On the other hand, it is well known that MRI imaging plays a very
important role in distinguishing abscess loculation from malignancy. The authors
present the case of a 13-year-old boy with pain in the right heel for few
months. Radiograph of the right foot revealed a lucent focus with sclerotic margin
in the right calcaneum. MRI T1-weighted images were inconclusive of penumbra
sign to characterise abscess cavity due to the small volume lesion. Whole-body 18F-FDG
PET/CT scan showed multiple small avid lesions at the margin of the sclerotic
rim in the right calcaneum. Final diagnosis of Brodie's abscess with Klebsiella
culture was confirmed via bone debridement. � 2010 Biomedical Imaging and
Intervention Journal. All rights reserved.
Keywords: 18F-FDG PET/CT; Brodie's abscess,
Brodie's abscess is a rare lesion manifesting as a chronic
form of intraosseous osteomyelitis surrounded by dense fibrous tissue and
sclerotic bone . It is predominantly reported in young male with unfused
epiphyseal plate typically presenting during the second decade of life. The
pathogenesis is due to an insidious bacteremia with septic emboli to normal or
minimally traumatised bone as a result of an inadequately treated
osteomyelitis. Radiography of Brodie's abscess often defines a localised area
of radiolucency with surrounding sclerosis but most of the lesions are
imperceptible in the early stage. Pathologically, the wall of the abscess
contains large amounts of granulation tissue, accounting for pronounced rim
enhancement on contrast-enhanced T1-weighted MRI image with outer layer of
hypointensity of which configurations are largely referred as penumbra sign.
The central portions are mainly constituted of necrotic
fluid and pathologic organisms . Grey et al. stated that penumbra sign has
an accuracy of 99% in diagnosing chronic osteomyelitis and differentiating it
from malignancy . The advancement in PET/CT technology using 18F-FDG
tracer as glucose analog provide a considerably good complementary functional
biomarker in defining the chronic osteomyelitis and is a highly sensitive and
specific method for the evaluation of chronic infection in the axial and
appendicular skeleton in patients with trauma . Furthermore, in certain
circumstances, PET/CT is exceptionally effective in delineating inflammatory
process in the bone where MRI image-characterisation is degraded by bone
implants or due to small volume lesion . The authors highlight the
importance of 18F-FDG PET/CT utility as a potential adjunct to MRI
in characterising Brodie's abscess in a 13-year-old boy in whom diagnosis was
proven by isolation of Klebsiella organism culture via bone debridement.
A 13-year-old boy presented with a history of right heel
pain for a few months. His right foot was swollen and tender. He recalled an
accidental step on a rusty nail two years back following which he had pain and
swelling. The symptoms subsided following courses of antibiotic treatment. The
recent radiography of the right ankle revealed a focus of intraosseous lucency
within the right calcaneum (Figure 1). MRI study was inconclusive of the
penumbra sign as seen on T1-weighted sequences to characterise abscess cavity
given the small volume of the lesions (Figure: 2a-c). Co-registered PET/CT
images of the right calcaneum displayed multiple foci of 18F-FDG avidity
at the margin of the sclerotic margin consistence with granulation tissue
formation (Figure: 3a-c). Bone debridement yielded the culture of Klebsiella
organism and the final diagnosis of Brodie's abscess was made.
This young boy presented with a history of right heel pain
for a few months without preceding inciting trauma or symptoms. The past
history of trauma to the right heel raises the index of suspicion of an
inadequately treated infective bone inoculation which manifested at the present
time. Initial radiography of the right ankle was indeed nonspecific as a lucent
focus in the right calcaneum may resemble other pathological entity i.e.
eosinophilic granuloma or metastatic deposit but these alternate diagnoses can
be excluded by the extensive soft tissue inflammation clinically . MRI of
the right calcaneum was inconclusive in defining the characteristic penumbra
sign of abscess cavity formation on T1-weighted sequences. On 18F-FDG
PET/CT, foci of tiny rim of avid metabolic activity at the margin of the
sclerotic rims points to the formation of granulation tissue . The sclerotic
margin invariably represents the sclerosis or involucrum. In this particular
case, PET/CT image has successfully defined the disease extent as evident by
involvement of the calcaneal cortex. Stumpe et al. concluded that PET using 18F-FDG
appears to be a highly sensitive method in detecting infective foci in the bone
. Histologically, the 18F-FDG avidity defines the area of fibroblast
proliferation and neovascularisation with mononuclear cell infiltration at the
granulation tissue formation whereby these cells utilise most of their energy
from the trapped 18F-FDG for cells metabolism [1,3]. The reliability
of 18F-FDG as a biomarker in chronic osteomyelitis is further
substantiated by a revelation of an experiment of which findings stated that
the maximum uptake of 18F-FDG was observed in chronic inflammation far more pronounced than in acute
phase . In this regard, it is noteworthy to document that the hybrid
PET/CT using 18F-FDG is exceedingly a sensitive tool in the imaging
of chronic infection given its ability in allowing precise anatomical
localisation and optimal characterisation of the abscess formation and its
extent by its biological 18F-FDG affinity to the chronic
The 18F-FDG PET/CT as a form of molecular
imaging procedure should be viewed as an important adjunct to an
already powerful armamentarium of clinical imaging tools, specifically the
MRI imaging. This report underlies the promising method of 18F-FDG PET/CT
and its further roles as a potential primary workhorse in chronic osteomyelitis
in instances where MRI fails to characterise the differentiating feature of
abscess formation from malignancy.
Figure 1 Lateral view of the right ankle shows a small lucent lesion within the calcaneum (arrow). [Image courtesy of Prince Court Medical Centre, Kuala Lumpur, Malaysia ].
Figure 2 (a) T1SE weighted coronal image of the right ankle displays focus of intermediate intensity intraosseous lesion surrounded by rim of low intensity (arrow); (b) T1SE Fat SAT shows high-intensity focus with the outer layer of low attenuation signal (arrow); (c) T1SE Fat SAT post Gadolinium sagittal image shows no significant rim of enhancement (arrow). Image courtesy of Prince Court Medical Centre, Kuala Lumpur, Malaysia.
Figure 3 (a) Coronal PET image showing foci of avid 18F-FDG intensity signal lesions within the right calcaneum; (b) Coronal low-dose CT image showing foci of low attenuation lesions with rim of sclerosis; (c) A combined PET/CT image displays foci of avid 18F-FDG uptake at the sclerotic rims of the right calcaneum extending to the adjacent inferior cortex (arrow).
Figure 4 An intraoperative image revealed the site of the abscess loculation within the calcaneum (arrow). Image courtesy of Prince Court Medical Centre, Kuala Lumpur, Malaysia and Salam Specialist Medical Centre, Shah Alam, Malaysia.
Grey AC, Davies AM, Mangham DC, et al. The 'penumbra sign' on T1-weighted MR imaging in subacute osteomyelitis: frequency, cause and significance. Clin Radiol. 1998;53(8):587-92.
Guhlmann A, Brecht-Krauss D, Suger G, et al. Chronic osteomyelitis: detection with FDG PET and correlation with histopathologic findings. Radiology. 1998;206(3):749-54.
Jadvar H, Parker JA. Clinical PET and PET/CT: Springer; 2005.
Stumpe KD, Dazzi H, Schaffner A, et al. Infection imaging using whole-body FDG-PET. Eur J Nucl Med. 2000;27(7):822-32.
Yamada S, Kubota K, Kubota R, et al. High accumulation of fluorine-18-fluorodeoxyglucose in turpentine-induced inflammatory tissue. J Nucl Med. 1995;36(7):1301-6.
|Received 5 September 2009; received in revised form 14 February 2010, accepted 18 March 2010
Correspondence: Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Selangor, Malaysia. E-mail: email@example.com (Abdul Jalil Nordin).
Please cite as: Fathinul F, Nordin AJ,
18F-FDG PET/CT as a potential valuable adjunct to MRI in characterising the Brodie's abscess, Biomed Imaging Interv J 2010; 6(3):e26