Geoffrey Storey

Single-photon emission tomography of a computerised model of pulmonary embolism

Abstract. Planar pulmonary scintigraphy is currently the standard investigation for the diagnosis of pulmonary embolism. There are a number of problems with the technique, particularly in patients with an intermediate scan report under the PIOPED criteria. The technique is also under threat from the increasing use of spiral CT angiography. A putative improvement may be gained by use of tomography. The incremental value of tomography over planar studies was therefore evaluated in a virtual model of pulmonary scintigraphy. A model of the segmental anatomy of the lungs was developed from computed tomography, cadaveric human lungs and available anatomical texts. Counts were generated within the phantom by Monte Carlo simulation of photon emission. Eighteen single segmental lesions were interspersed with 47 subsegmental defects and displayed on an Icon reporting station. These were presented in the transaxial, sagittal and coronal planes to four experienced reporters to obtain assessment of defect size. Planar studies of the same defects were displayed to the same observers in the standard eight views with a normal study for comparison. With planar studies, the accuracy of estimation of defect size was 51% compared with 97% using tomographic studies. Defects in the medial basal segment of the right lower lobe were not identified in planar studies but were easily seen by all observers in the tomographic study. It is concluded that there is marked improvement in the accuracy of determination of defect size for tomographic studies over the planar equivalents. This is especially important in the lung bases, the most common reported site of pulmonary emboli. Tomography permits visualisation of defects in the medial basal segment of the right lung, which are not seen in planar studies.

Bone scintigraphy in acetabular labral tears.

Background: Acetabular labral tears are an increasingly recognized cause of hip pain in young adults with hip dysplasia and older patients with degenerative disease of the hips. Methods: The authors analyzed retrospectively bone scintigraphy in 27 patients with acetabular labral tears diagnosed by MRI/arthroscopy. Analysis was also made of scintigraphy in 30 patients without labral tears being investigated for other causes of hip pain for comparison. Results: Patients with labral tears had hyperemia of the superior or superomedial aspect of the acetabulum and increased delayed uptake in either a focal superior pattern or in an “eyebrow” pattern of a superomedial tear. This pattern was not seen in any other sources of hip pathology. Conclusion: Uptake in the superior or superomedial aspect of the acetabular rim is characteristic of a labral tear. Absence of this pattern carries a high negative predictive value for the diagnosis.

Novel imaging strategy for the detection of fat embolism after arthroplasty

Introduction:u2003 Respiratory complications are common after arthroplasty with fat emboli and thromboembolic disease (PTE) being the most serious. As fat embolism from bone marrow should contain reticuloendothelial cells, we hypothesized that these cells take up colloid in the lung. A prospective tomographic study of 99m Tc phytate and perfusion was performed within 24u2003h after arthroplasty.

Ossification of the ligamentum flavum demonstrated by Tc-99m MDP SPECT imaging of the thoracic spine.

A 72-year-old white woman with untreated locally advanced carcinoma of the right breast was examined for bilateral leg weakness and dysasthesia below the waist. Positive findings on physical examination were 4–5 power of hip flexion, reduced sensation to light touch and pinprick below the T11 dermatome level, and absent patellar tendon reflexes. No spinal cord compression was evident on a magnetic resonance scan. A bone scan showed increased tracer uptake bilaterally in the spine at the T9 vertebral level. SPECT images revealed increased uptake localized to the lateral neural arch at T9-T10. A computed tomographic scan of this site showed ossification of the ligamentum flavum with indentation of the thecal sac. In the absence of spinal cord compression, the final diagnosis was paraneoplastic paraparesis.

SPET of a computerised model of diffuse lung disease

Emphysema is a common and debilitating disease that is the commonest cause of end-stage respiratory failure. Treatment is either by lung transplantation or by lung volume reduction surgery (LVRS) that improves the biomechanics of respiration. Patient selection for LVRS hinges on the demonstration of heterogeneous disease, predominantly involving the upper lobes, as a good surgical outcome is most likely in these patients. We used a virtual model of lung scintigraphy to compare planar with tomographic scintigraphy for the detection of diffuse lung disease. Lesions of the magnitude of the lung acinus, as well as larger and smaller lesions, were distributed throughout the lungs in volumes from 2% to 50%. Single-photon emission tomography does not add incremental value to planar images for the detection of diffuse lung disease.

Sunburst periosteal reaction in a bony metastasis.

A 92-year-old man with a painful right hip reported a history of transitional cell carcinoma of the kidney that had been surgically excised 6 years previously. Plain radiographs revealed a region of mixed cortical lysis and sclerosis with a widened transition zone and the periosteal sunburst reaction. Bone scintigraphy showed intense uptake in the right femur, extending into the soft tissues. Other sites of uptake compatible with metastases were also present. Biopsy of the femoral lesion confirmed metastatic transitional cell carcinoma.

Tc-99m labeled white blood cell imaging in chronic pancreatitis with pseudocyst

A 36-year-old woman with a history of thyroid carcinoma, peptic ulcer disease, and alcoholism with chronic pancreatitis had a 4-week history of abdominal pain, anorexia, and weight loss. She demonstrated signs of sepsis with fever, tachycardia, and neutrophil leukocytosis. A tender central abdominal mass was noted. Intravenous ampicillin, metronidazole, and gentamicin therapy was commenced. Abdominal CT scan demonstrated several fluid-density collections, only one of which showed Tc-99m labeled leukocyte accumulation on scintigraphy. One of these large collections was subsequently drained. Analysis of the fluid revealed a high amylase collection, but no white cells. Aerobic and anaerobic bacteria cultures were negative.

Sequestered collection in association with infected arthroplasty.

An 82-year-old man had bilateral total knee replacements for severe osteoarthritis. The early postoperative course was complicated by infection of the left knee prosthesis, which was treated with intravenous antibiotics. Infection persisted for 6 months after operation, necessitating removal of the prosthesis and insertion of gentamicin-impregnated spacers. After an additional course of antibiotics, the infection appeared quiescent. The patient was referred for a leukocyte scan to assess the extent and the location of any residual infection. The leukocyte scan revealed a sinus tract extending into the anterior thigh. One week later, a draining sinus developed at the site identified in the study. A sinogram confirmed no communication between the collection and the left knee.

Pain in the anterior pelvis and postoperative prostatectomy findings.

A 68-year-old man came to our institution for a bone scan to evaluate pain of recent onset in the anterior aspect of the pelvis. The results of plain radiographs of the pelvis were reported as normal. His medical history included surgical resection of a carcinoma of the sigmoid colon and transurethral resection of the prostate for urinary obstructive symptoms. Metastatic disease of the pelvic bones was suspected. Extensive evaluations failed to reveal any metastatic disease or specific cause of the pelvic pain.

Tc-99m stannous colloid-labeled leukocyte scintigraphic localization of an ileoperineal fistula complicating Crohn's disease.

A 40-year-old man with a 14-year history of unremitting Crohns disease was seen for lower limb cellulitis and a discharging perineal fistula. Proctocolectomy and multiple small bowel resections had been performed previously. The remnant small bowel drained through an enterocutaneous fistula to the right abdominal wall and through an end-ileostomy located in the left abdominal wall. A Tc-99m stannous colloid-labeled leukocyte study was performed to assess the extent of disease activity. This demonstrated leukocyte accumulation in both stomal collection bags in addition to focal accumulation in the right iliac fossa with inferior extension in a linear pattem consistent with a fistulous tract into the pelvis. An ileostogram confirmed a large fistula extending from the ileum into the presacral region. No mucosal ulceration was demonstrated. Ileoscopy subsequently showed ulceration of the small bowel between the ileostomy and the abdominal wall fistula. Histology confirmed inflammatory changes with crypt abscess formation, consistent with active Crohns disease.