February 2007         

PET Scan Demonstrating Infectious Disease

Radiology Report:

LL is a 38 y/o white woman recently diagnosed with IgG Lambda Multiple Myeloma after chief complaints of back pain. MRI showed multiple lesions and compression fractures in the thoracic and lumbosacral spine.

This visit is subsequent to LL’s second treatment with high dose chemotherapy and autologous stem cell support. Post treatment LL experienced fever of 102.9, chills, shortness of breath, and respiratory distress. Prior to admission, LL had already been scheduled for a PET scan for the same day. The PET study was performed…
 

Click here to view avi file of PET scan

PET SCAN

INDICATION:  Multiple myeloma evaluating for restaging/infection.  Patient has had fever of unknown origin for one week and is hypoxemic.

RADIOPHARMACEUTICAL: 15.4 mCi, F-18 FDG, IV, via right wrist vein.

PROCEDURE: Following injection of radioisotope, imaging was performed from top of head to hips 90 minutes following injection of the radioisotope. Emission and transmission imaging was performed with attenuation correction. Correction was also performed for random events. Iterative reconstructions were performed with axial, coronal, and sagittal reconstructions, as well as with 3D volume rendering. Emission imaging of the lower extremities was performed from hips to toes, also with axial, coronal, and sagittal reconstructions with 3D imaging.

REVIEW OF PREVIOUS STUDIES: Patient had portable chest x-ray same day as PET scan with no acute finding identified.

Magnetic resonance imaging examination of brain, calvaria, vertebral column, and pelvis demonstrated resolution of skull base lesion and decrease in size of the single diploic lesion.

The vertebral column demonstrated iso- to hypointense homogenous marrow on STIR weighting, hyperintense and homogenous on T1 weighting. Multiple focal lesions of the vertebral column and pelvis were stable or improved.

Specifically, a 2 cm focal lesion at C2 was stable, as well as a 1 cm focal lesion at C3, with the previously noted C5 focal lesion resolved.

In the dorsal spine, the focal lesion involving T5 was stable at 2.5 cm, as were subcentimeter focal lesions at T4, T10, T11, and T8 posterior elements. There were stable compression fractures at T4, T5, T7, T9, and T11.

There were multiple focal lesions, all 1 cm or less in size, in the lumbar spine, which were unchanged. These were present at all levels. No new focal lesions were seen.

In the pelvis, there was resolution of the previously noted iliac focal lesion. A 2 cm right ischial lesion was stable. The right sacral lesion had decreased in size to under 1 cm. No new lesions were seen.

High-resolution computed tomography chest without contrast demonstrated stable peribronchial infiltrate in the superior segment of the right lower lobe with no new changes seen.

Previous PET scan demonstrated moderate heterogenous uptake in the vertebral column, particularly in the lumbar region, with average SUV value on previous study of 4.1. This pattern was also seen in the pelvis and femurs. No focal lesions were seen on the previous PET scan.

PET SCAN FINDINGS:
Current PET scan demonstrates intense uptake in the upper lobes of the lungs bilaterally, with maximum SUV value being 12.3 on the left and 7.5 on the right with normal SUV values for lungs being 0.8 or less.

In the lower and middle lobe regions, the SUV value is 2.8 on the right and in the left lower lobe, the SUV value is 3.0.

No focal lesions are seen. No extramedullary disease is seen felt to represent myeloma.

There is mild homogenous uptake in the vertebral column, pelvis, and femurs as noted on previous study, with SUV value decreasing to 2.0.

IMPRESSION:
1. PROBABLE BILATERAL INFECTIOUS PROCESS INVOLVING THE LUNGS, PERHAPS OPPORTUNISTIC.
2. DECREASE IN DIFFUSE PATTERN OF DISEASE OF THE LUMBAR SPINE, PELVIS AND FEMURS WITH SOME INVOLVEMENT OF THE REMAINDER OF THE VERTEBRAL COLUMN FROM A PREVIOUS DIFFUSE UPTAKE VALUE OF 4.1 TO CURRENT SUV READING OF 2.0 WITH NO FOCAL LESIONS IDENTIFIED.


A/P:
1. PET and CXR confirmed bilateral pneumonia – started on Primaxin, Tequin, Ambisome, and Methylprednisolone IV; vancomycin was already being given.
2. MM: Current PET imaging for LL show good response to treatment with no focal lesions or extramedullary disease seen. Mild uptake is still being seen in the lumbar spine, but this is stable, with a current SUV of 1.5.

Journal Articles References about PET for Infectious Imaging

·                     Stumpe KD,

·                     Dazzi H,

·                     Schaffner A,

·                     von Schulthess GK.

Department of Medical Radiology: Nuclear Medicine, University Hospital Zurich, Switzerland.

The purpose of this study was to evaluate fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) for the detection of soft tissue and bone infections. Forty-five PET examinations in 39 patients (26 male, 13 female, age range 27-86 years) with suspected infectious foci were examined with whole- or partial-body PET scans using FDG. Twenty-seven scans were done in patients with soft tissue and 18 in patients with bone infections. Corrected and uncorrected transaxial PET images were acquired. Seven hundred and twelve body regions in these 45 PET scans were evaluated. Pathological findings were graded using a confidence scale from A to E (A, definitive infection; E, no infection). Disease status was defined in all patients by culture, biopsy or surgery and clinical follow-up. In 45 PET scans there were 40 true-positive, four false-positive and one false-negative findings. Twelve foci suspected to be infectious in nature on the basis of other imaging examinations were identified as negative by PET, thus representing true-negative findings. Sensitivities for the patients with soft tissue (STI) and bone infections (BI) and for the pooled data were 96%, 100% and 98%, respectively. As the calculation of specificity is not straightforward, it was calculated on a per lesion as well as on a per body region basis to permit estimation of an upper and a lower limit. On a per lesion basis, specificities were 70% (STI), 83% (BI) and 75% for the pooled data and on a per body region basis (dividing the body into 22 regions) they were 99% (STI), 99% (BI) and 99% for the pooled data. One false-negative result was found in a patient with cholangitis. It is concluded that PET appears to be a highly sensitive method to detect infectious foci. Specificity is more difficult to estimate, but is probably in the range from 70% to above 90%.

PMID: 10952494 [PubMed - indexed for MEDLINE

Imaging Infection with ¹⁸F-FDG–Labeled Leukocyte PET/CT: Initial Experience in 21 Patients

Nicolas Dumarey, MD¹, Dominique Egrise, PhD¹, Didier Blocklet, MD¹, Bernard Stallenberg, MD², Myriam Remmelink, MD, PhD³, Véronique del Marmol, MD, PhD⁴, Gaëtan Van Simaeys, PhD¹, Frédérique Jacobs, MD⁵ and Serge Goldman, MD, PhD¹

¹ Department of Nuclear Medicine and PET/Biomedical Cyclotron Unit, CUB-Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium; ² Department of Medical Imaging, CUB-Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium; ³ Department of Pathology, CUB-Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium; ⁴ Department of Dermatology, CUB-Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium; and ⁵ Department of Infectious Diseases, CUB-Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium

Correspondence: For correspondence or reprints contact: Nicolas Dumarey, MD, Department of Nuclear Medicine, Université Libre de Bruxelles Hôpital Erasme, 808 route de Lennik, B-1070 Brussels, Belgium. E-mail: ndumarey@ulb.ac.be

The aim of this study was to assess the feasibility and the potential role of PET/CT with ¹⁸F-FDG–labeled autologous leukocytes in the diagnosis and localization of infectious lesions. Methods: Twenty-one consecutive patients with suspected or documented infection were prospectively evaluated with whole-body PET/CT 3 h after injection of autologous ¹⁸F-FDG–labeled leukocytes. Two experienced nuclear medicine physicians who were unaware of the clinical end-diagnosis reviewed all PET/CT studies. A visual score (0–3)—according to uptake intensity—was used to assess studies. The results of PET/CT with ¹⁸F-FDG–labeled white blood cell (¹⁸F-FDG–WBC) assessment were compared with histologic or biologic diagnosis in 15 patients and with clinical end-diagnosis after complete clinical work-up in 6 patients. Results: Nine patients had fever of unknown etiology, 6 patients had documented infection but with unknown extension of the infectious disease, 4 patients had a documented infection with unfavorable evolution, and 2 patients had a documented infection with known extension. The best trade-off between sensitivity and specificity was obtained when a visual score of 2 was chosen to identify increased tracer uptake as infection. With this threshold, sensitivity, specificity, and accuracy were each 86% on a patient-per-patient basis and 91%, 85%, and 90% on a lesion-per-lesion basis. In this small group of patients, the absence of areas with increased WBC uptake on WBC PET/CT had a 100% negative predictive value. Conclusion: Hybrid ¹⁸F-FDG–WBC PET/CT was found to have a high sensitivity and specificity for the diagnosis of infection. It located infectious lesions with a high precision. In this small series, absence of areas with increased uptake virtually ruled out the presence of infection. ¹⁸F-FDG–WBC PET/CT for infection detection deserves further investigation in a larger prospective series.

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© 2007 Nuclear Education Online

Case submitted by Jason Luper, PharmD candidate, UAMS College of Pharmacy

 Images courtesy of University of Arkansas for Medical Sciences Dept of Nuclear Medicine.