Nicolas Dumarey

Radionuclide imaging of spinal infections

BackgroundThe diagnosis of spinal infection, with or without implants, has been a challenge for physicians for many years. Spinal infections are now being recognised more frequently, owing to aging of the population and the increasing use of spinal-fusion surgery.Discussion The diagnosis in many cases is delayed, and this may result in permanent neurological damage or even death. Laboratory evidence of infection is variable. Conventional radiography and radionuclide bone imaging lack both sensitivity and specificity. Neither in vitro labelled leucocyte scintigraphy nor 99mTc-anti-granulocyte antibody scintigraphy is especially useful, because of the frequency with which spinal infection presents as a non-specific photopenic area on these tests. Sequential bone/gallium imaging and 67Ga-SPECT are currently the radionuclide procedures of choice for spinal osteomyelitis, but these tests lack specificity, suffer from poor spatial resolution and require several days to complete. [18F]Fluoro-2-deoxy-D-glucose (FDG) PET is a promising technique for diagnosing spinal infection, and has several potential advantages over conventional radionuclide tests.Results The study is sensitive and is completed in a single session, and image quality is superior to that obtained with single-photon emitting tracers. The specificity of FDG-PET may also be superior to that of conventional tracers because degenerative bone disease and fractures usually do not produce intense FDG uptake; moreover, spinal implants do not affect FDG imaging. However, FDG-PET images have to be read with caution in patients with instrumented spinal-fusion surgery since non-specific accumulation of FDG around the fusion material is not uncommon.Conclusion In the future, PET-CT will likely provide more precise localisation of abnormalities. FDG-PET may prove to be useful for monitoring response to treatment in patients with spinal osteomyelitis. Other tracers for diagnosing spinal osteomyelitis are also under investigation, including radiolabelled antibiotics, such as 99mTc-ciprofloxacin, and radiolabelled streptavidin-biotin complex. Antimicrobial peptides display preferential binding to microorganisms over human cells and perhaps new radiopharmaceuticals will be recruited from the array of human antimicrobial peptides/proteins. In experiments with Tc-ubiquicidin-derived peptides, radioactivity at the site of infection correlated well with the number of viable bacteria present. Finally, radiolabelled antifungal tracers could potentially distinguish fungal from bacterial infections.

Future Diagnostic Agents

Timely and specific diagnosis of infectious diseases can be clinically challenging but essential for the patients outcome. Laboratory tests, such as a blood culture or urine specimen, can detect the responsible micro-organism but cannot discriminate between sterile inflammatory disease and truly infectious disease. Imaging tests, like scintigraphic techniques, can pinpoint the infection in the body. There are a number of clinical scintigraphic tests from which to choose, and no single test is optimal for the various presentations of clinical infectious disease. The currently available radiopharmaceuticals often are not capable of distinguishing between sterile inflammation, and bacterial or fungal infections. Neutrophil-mediated processes, characteristic for both inflammatory and infectious processes, can be targeted in situ by radiolabeled leukocytes, antibodies or fragments, or even by cytokines and (18)F-fluorodeoxyglucose. Unfortunately those techniques are not infection-specific markers, and ongoing research is in progress to tackle this problem. The most promising option in this respect is directly targeting bacteria or fungi with radiolabeled antibiotics or antimicrobial peptides. These theoretically highly infection-specific radiopharmaceuticals could be used for monitoring the success of antimicrobial therapy of infectious disease. Although results from preclinical experiments and pilot studies in patients are promising, radiolabeled anti-infective agents are not currently in routine clinical use and studies are continuing to prove their effectiveness for diagnostic imaging of infections in the future.

11C-methionine PET for the diagnosis and management of recurrent pituitary adenomas

PurposeThe detection of recurrent pituitary adenoma by magnetic resonance imaging (MRI) is rendered uncertain by the tissue remodelling that follows surgery or radiotherapy. We aimed to evaluate the contribution of PET with 11C-methionine (MET-PET) in the detection and management of recurrent pituitary adenoma.MethodsThirty-three patients with pituitary adenoma were evaluated postoperatively by MET-PET, either because of biological evidence of active residual tumour or because of MRI demonstration of non-functional adenoma growth. We studied 24 secreting adenomas and nine non-functional adenomas.ResultsIn 30 patients, MET-PET detected abnormally hypermetabolic tissue. In 14 out of these, MRI did not differentiate between residual tumour and scar formation. In nine of these 14 cases, major therapeutic decisions were undertaken (radiosurgery and surgery). In another group of 16 patients, both MET-PET and MRI detected abnormal tissue. In one case, neither MRI nor MET-PET detected adenomatous tissue. Finally, abnormal tissue was detected in two patients on MRI solely. In these two cases, failure of MET-PET to reveal the adenoma was attributable to concomitant inhibitory therapy. The sensitivity of MET-PET and MRI varied as a function of the tumour type: all non-functional adenomas were localised by both modalities, while MET-PET detected all adrenocorticotropic hormone-secreting adenomas whereas MRI depicted only one of these eight lesions. Fifteen out of 17 patients treated by radiosurgery showed clinical improvement after treatment.ConclusionWe suggest that MET-PET is a sensitive technique complementary to MRI for the detection of residual or recurrent pituitary adenomas. It should gain a place in the efficient management of these tumours.

¹⁸F-FDG PET/CT and MRI in the follow-up of head and neck squamous cell carcinoma.

We evaluated the diagnostic performance of (18)F-FDG PET/CT and MRI for the assessment of head and neck squamous cell carcinoma (HNSCC) relapse. Since early treatment might prevent inoperable relapse, we also evaluated THE performance of early unenhanced (18)F-FDG PET/CT in residual tumor detection. The study was prospectively performed on 32 patients who underwent (18)F-FDG PET/CT and MRI before treatment and at 4 and 12 months after treatment. (18)F-FDG PET/CT was also performed 2 weeks after the end of radiotherapy. Histopathology or a minimum of 18 months follow-up were used as gold standard. Before treatment (18)F-FDG PET/CT and MRI detected all primary tumors except for two limited vocal fold lesions (sensitivity 94%). MRI was more sensitive than (18)F-FDG PET/CT for the detection of local extension sites (sensitivity 75 vs 58%), but at the cost of a higher rate of false positive results (positive predictive value 74 vs 86%). For relapse detection at 4 months, sensitivity was significantly higher for (18)F-FDG PET/CT (92%) than for MRI (70%), but the diagnostic performances were not significantly different at 12 months. For the detection of residual malignant tissue 2 weeks post-radiotherapy, sensitivity and specificity of (18)F-FDG PET/CT were respectively 86 and 85% (SUV cut-off value 5.8). (18)F-FDG PET/CT is effective in the differentiation between residual tumor and radiation-induced changes, as early as 2 weeks after treatment of a primary HNSCC. For follow-up, performance of (18)F-FDG PET/CT and MRI are similar except for a higher sensitivity of (18)F-FDG PET/CT at 4 months.

Renal abscess: filling in with Tc-99m ciprofloxacin of defects seen on Tc-99m DMSA SPECT.

Tc-99m DMSA SPECT and Tc-99m ciprofloxacin SPECT images were sequentially acquired (time span, 3 days) in a 21-year-old woman with clinical signs of an upper urinary tract infection, an inflammatory syndrome, and urine cultures positive for Escherichia coil. The patient had an undocumented history of pyelonephritis a few years earlier. A wedge-shaped defect seen in the lateral cortex of the left kidney on Tc-99m DMSA SPECT was filled in on the Tc-99m ciprofloxacin scan. These findings were in favor of an acute inflammatory process and not of a new episode of pyelonephritis or a structural abnormality. Contrast-enhanced computed tomography (CT) revealed the presence of an abscess at this site. To our knowledge, no such case of cold-hot kidney lesions on sequential Tc-99m DMSA and ciprofloxacin SPECT studies has been reported.

AN ATYPICAL CASE OF WHIPPLE’S DISEASE: CASE REPORT AND REVIEW OF THE LITERATURE

Abstract We report the case of a 57-year-old man, presenting with bilateral panuveitis, bilateral sacroiliitis, intermittent pyrexia and a pulmonary nodule. The patient had been under immunosuppressive treatment for 2 years for Behçet’s disease. However, he did not fulfill the diagnostic criteria of Behçet’s disease. Blood analysis showed a very high C reactive protein (CRP at 34 mg/dl). In view of severe intra-ocular inflammation, the anterior chamber was punctured. Polymerase chain reaction (PCR) on the aqueous humour and on the blood revealed the presence of Tropheryma whippelii DNA, an agent responsible for Whipple’s disease. The patient was treated with ceftriaxone followed by trimethoprim-sulfamethoxazol for 1 year with good clinical and biological evolution. This case illustrates the difficulty to diagnose an atypical Whipple’s disease. In cases of uveitis with atypical signs and/or not responding to the treatment, the internist must consider to perform an analysis of the ocular fluids.

Relapse of a renal inflammatory pseudotumour associated with Wegener's granulomatosis.

Abstract We report the case of a 32-year-old patient with Wegener’s granulomatosis (WG) associated with a (biopsy – proven) renal inflammatory pseudotumour (IPT) of the left kidney treated by a partial nephrectomy, glucocorticoids and immunosuppressive drugs, in whom a relapse of renal IPT was found 6 years after the diagnosis of the first IPT. The originality of this observation lies in the fact that a relapse of IPT has never been described and also in the fact that complete regression of the IPT relapse was obtained with immunosuppressive treatment, while renal IPTs are currently treated by total or partial resection of the kidney. Finally, we discuss the potential benefits of an integrated 18fluorodeoxyglucose PET/CT for the follow-up of WG, since this imaging technique contributed to the management of the present case.

From Polyuria to Renal Mass: An Unexpected Link

From Polyuria to Renal Mass: An Unexpected Link Frédéric Vandergheynst, MD, Paraskevi Kazakou, MD, PhD, Bruno Couturier, MD, Nicolas Dumarey, MD, Rose Ghanooni, MD, Agnieszka Pozdzik, MD, PhD, Sandrine Rorive, MD, PhD, Daniel Van Gansbeke, MD, Agnès Burniat, MD, PhD Department of Internal Medicine, Department of Endocrinology, Department of Nuclear Medicine, Department of Otorhinolaryngology, Department of Nephrology, Department of Pathology, and Department of Radiology, Erasme Hospital, Université Libre de Bruxelles, Belgium.