Chasing "shadows": discovering the subtleties of sestamibi scans to facilitate minimally invasive parathyroidectomy.

BACKGROUND: With the advent of sestamibi scans, high-resolution ultrasonography (US), and intraoperative intact parathyroid hormone (PTH) measurements, minimally invasive parathyroidectomy (MIP) is considered the standard of care for patients with primary hyperparathyroidism (PHPT). Preoperative imaging, however, can be negative more than 20% of the time. METHODS: We chose to examine one surgeon's experience with patients who presented with PHPT and negative or indeterminate preoperative imaging from July 1993 to September 2009. A retrospective review of a parathyroid surgery database and patient records was conducted to collect the following information: patient age and sex; calcium and PTH levels; sestamibi and US results; and operative reports. Each sestamibi scan had been re-reviewed preoperatively by the surgeon with a nuclear medicine physician. The study cohort included patients with negative or indeterminate sestamibi results and a negative or no US report in which the surgeon was able to identify a "shadow" or subtlety on sestamibi and plan an MIP. RESULTS: A total of 126 patients had a negative or indeterminate sestamibi scan and a negative or no US report. "Shadows" or subtleties were found in 18 of 44 (41%) of the cases with a negative sestamibi and in 62 of 82 (76%) of cases with an indeterminate sestamibi scan. For these 80 cases a MIP was planned. In all, 7 of 80 (9%) were converted to a bilateral exploration. The remaining 46 patients underwent a planned bilateral exploration. Cure rates were comparable: 99% in the study group compared to 97% in the group who underwent a planned or converted bilateral exploration. CONCLUSIONS: With careful preoperative re-review of a negative or indeterminate sestamibi scan and the identification of subtleties in patients with a negative preoperative US scan, a successful MIP can be performed 91% of the time with a 98% cure rate.

Dirofilariasis in a 22-year-old airman deployed to the Mediterranean.

A 22-year-old male U.S. Navy airman with new nontender subcutaneous, 4-cm mass inferior to the right anterior costal margin was sent for routine biopsy. Sudden appearance of axillary lymph nodes prompted immediate excisional biopsy of the primary mass. Pathological evaluation was initially read as Onchocerca volvulus, the filarial nematode classically responsible for river blindness. Subsequent evaluation by Armed Forces Institute of Pathology resulted in a change of diagnosis to Dirofilaria species, not pathogenic in humans. The author discusses the literature of Dirofilaria infestations in humans, and how they may affect U.S. servicemen and women traveling to endemic areas.

Recent updates on onchocerciasis: diagnosis and treatment.

Recent progress in onchocerciasis research has led to improved understanding of the immunopathology of Onchocerca volvulus, as well as improvements in diagnosis and treatment of this morbid disease. This article reviews the recent literature, highlighting breakthroughs in sensitive means of antigen testing and an unusual new approach to therapy that targets an endosymbiotic bacterium required for filarial worm fecundity.

Characterization of a perirectal artifact in 18F-FDG PET/CT.

UNLABELLED: Assessing tumor involvement in the rectal region can sometimes be complicated by what appears to be an artifact on (18)F-FDG PET/CT images. This artifact manifests as a high-intensity region on the PET image, extending posterior to the bladder in the area around the rectum. The aim of this study was to describe this artifact, which-as far as we are aware-has not been previously reported, and to investigate its cause. METHODS: One hundred (18)F-FDG PET/CT studies (ordered-subsets expectation maximization reconstruction, CT attenuation correction) of patients with no known malignancy in the pelvis were retrospectively reviewed. Localized regions of apparently high uptake posterior to the bladder were considered an artifact when there was a discrepancy between attenuation-corrected (asymmetric appearance) and non-attenuation-corrected images (symmetric appearance). In addition, an experiment was performed using a body phantom containing 2 cylindric inserts simulating the bladder and a region of low-attenuation rectal gas. Attenuation-corrected images were reconstructed with different amounts of spatial misregistration intentionally introduced between the CT and PET images. RESULTS: The artifact was observed in 15 of 100 patient studies and had a mean maximum standardized uptake value of 4.8 ± 2.7. When fused with sequentially acquired CT images, the artifact always appeared to be in the perirectal region near the bladder and an area of rectal gas. The phantom study indicated this artifact was consistent with an attenuation-correction problem caused by misregistration between CT and PET. Movement of gas within the rectum can cause an air pocket to be present during the PET acquisition at a location where CT indicated soft tissue. The resulting localized overcorrection for attenuation at the margin of the rectum and the extremely high activity concentration in the nearby bladder contributed to the artifact. CONCLUSION: Movement of gas within the rectum between acquisition of CT and PET images can lead to an artifact in attenuation-corrected PET images in the perirectal region. An awareness of this artifact and reference to non-attenuation-corrected images will aid in the interpretation of (18)F-FDG pelvis studies.