Labeled Leukocyte Scintigraphy Research Articles

Technetium-99m hexamethyl propylene amine oxime-labeled leukocyte scintigraphy at three different times in active ulcerative colitis: comparison with colonoscopy and clinico-biochemical parameters in the assessment of disease extension and severity

In this study, our objective was to define the usefulness of technetium-99m hexamethyl propylene amine oxime (Tc-99m HMPAO)-labeled leukocyte scintigraphy at three different time points in the assessment of disease extension and severity in patients with active ulcerative colitis (UC). Twenty-one consecutive patients (10 women, 11 men; mean age 42.4 +/- 12 years) with active UC were prospectively studied. All patients were diagnosed by colonoscopy and histopathology prior to inclusion. Scintigraphy was performed at 1 h, 2 h, and 4 h after Tc-99m HMPAO-labeled leukocyte injection. Clinic-biochemical activity score, total colonoscopic activity score, and total scintigraphic activity score at 1 h, 2 h, and 4 h were calculated for each patient. Sensitivity, specificity, and accuracy values of Tc-99m HMPAO-labeled leukocyte scintigraphy were calculated as follows, respectively: 1 h imaging 86%, 73%, and 83%; 2 h imaging 89%, 74%, and 86%; 4 h imaging 90%, 58%, and 83% in the detection of active inflammatory segments. Even though no statistically significant difference was found between 1 h, 2 h, and 4 h imaging with respect to the sensitivity, specificity of labeled leukocyte scintigraphy, the largest area under the curve value was found for 2 h imaging. Tc-99m HMPAO-labeled leukocyte scintigraphy has been found to be correlated well with colonoscopy in the assessment of both the extension and severity of UC. We recommend 2 h scintigraphic imaging because it provides the largest area under the curve value and decreases the number of false-positive results.

Usefulness of Technetium-99m Hexamethylpropylene Amine Oxime-Labeled Leukocyte Scintigraphy to Detect Pancreatic Necrosis in Patients with Acute Pancreatitis: Prospective Comparison with Ranson, Glasgow and APACHE-II Scores and Serum C-Reactive Protein

Background: In acute pancreatitis (AP), pancreatic necrosis (PN) is an important local complication that can be identified by means of contrast-enhanced computed tomography (CECT). Pancreatic leukocyte infiltration is a significant pathogenic event in the development of PN that can be detected by labeled leukocyte scintigraphy (LLS). The aim of this study was to evaluate the utility of LLS with technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) to detect the presence of PN in patients with AP. Methods: Prospective cohort study of 84 patients with AP. Patients underwent LLS and the activity of images was scored on a 0–3 scale. CETC was performed to assess PN. Ranson, Glasgow and APACHE-II scores were calculated. Serum C-reactive protein (CRP) was measured. Sensitivity (Sn), specificity (Sp), positive predictive values (PPV), negative predictive values (NPV), areas under receiver operating characteristic (ROC) curves, likelihood ratios, odds ratios, analysis of variances between groups and correlation coefficients between tests were calculated. Results: PN was present in 11 (13%) patients. Pancreatic labeled leukocyte uptake was present in 38 patients (45%). Sn, Sp, PPV and NPV of LLS grade 2–3 for PN diagnosis were the highest (91, 88, 53 and 98%, respectively) of all tests. Patients with LLS grade 2–3 were 71 times more likely to be at risk of PN compared to those with LLS grade 0-1. The area under ROC curve of the LLS was the largest. A significant correlation was obtained between LLS and CRP (p < 0.001). Conclusion: In patients with AP, LLS with 99mTc-HMPAO detects PN with an acceptable level of confidence and therefore could be considered an alternative technique to CECT in detecting PN.

Scintigraphic evaluation of acute pancreatitis patients with 99mTc-HMPAO-labelled leukocytes

To demonstrate the localization of leukocytes in the pancreas during acute pancreatitis and to evaluate the potential use of 99mTc-HMPAO-labelled leukocytes in the diagnostic assessment of patients with acute pancreatitis. The study was performed with 20 patients (11 females, nine males; ranging in age from 26 to 86 years, mean 55 years). Labelled leukocyte scintigraphy using planar imaging was performed on all patients, seven of whom were also examined by single photon emission computed tomography (SPECT). According to Ranson criteria, 10 patients had mild pancreatitis (group A), six had severe pancreatitis (group B) and four had necrotic pancreatitis (group C). Twelve patients had biliary pancreatitis and the other eight patients had no obvious cause. All patients of group C, four of group B, two of group A had a positive leukocyte scan. The positive leukocyte scintigraphy value for the detection of a lethal course of acute pancreatitis was 100%; of a severe course, 66.7%; and of a mild course, 20%. These findings are statistically significant (P=0.005 in chi-squared tests result). The results of leukocyte scintigraphy compared with those of CT were also statistically significant (P=0.001 in chi-squared tests). All the patients diagnosed with pancreatic necrosis by CT had a positive leukocyte scan, but only three of 13 patients without pancreatic necrosis that could be detected by computed tomography had a positive leukocyte scan. There was a significant correlation between the severity of the disease and leukocyte infiltration. Considering these results, we believe that leukocyte infiltration in acute pancreatitis can be demonstrated rapidly and accurately and by noninvasive 99mTc-HMPAO labelled leukocyte scintigraphy.

Radionuclide imaging of spinal infections

The 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. 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. 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. 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.

The Role of FDG-PET Imaging in Diagnosing Periprosthetic Infection After Total Hip Arthroplasty

The accurate noninvasive diagnosis of periprosthetic joint infection remains a challenge. In recent years, fluorodeoxyglucose positron emission tomography (FDG-PET) imaging has shown great promise in delineating areas of infection. We aimed to determine the accuracy of FDG-PET in diagnosing periprosthetic infection as compared with conventional studies, such as indium 111–labeled leukocyte scintigraphy.

99mTc-HMPAO labelled leucocyte scintigraphy in the diagnosis of pelvic inflammatory disease

Scintigraphy using leucocytes labelled with 99mTc hexamethylpropyleneamine oxime (99mTc-HMPAO) is widely used for the localization of inflammatory foci and abscesses in cases of acute pelvic inflammatory disease, which is one of the serious health problems of women of child-bearing age. Early diagnosis and effective management of this condition can preserve fertility and prevent serious complications, such as peritonitis and sepsis. To evaluate the importance of scintigraphy using 99mTc-HMPAO labelled leucocytes in the early diagnosis of patients with pelvic inflammatory disease. Fifteen women (mean age 29.2+/-8 years, range 25-46 years) with suspicion of pyogenic pelvic inflammatory disease based on gynaecological examinations, clinical findings and blood tests were included in this study. The patients received 555 MBq 99mTc-HMPAO labelled leucocytes, by injection, and were scanned by scintigraphy 0.5-1, 3 and 24 h later in the anterior abdominal projection. Ten of the patients were then evaluated by abdominal or transvaginal ultrasonography, four by computed tomography and two by both ultrasound and computed tomography. The final diagnosis was made by surgical intervention. Scintigraphy detected pelvic inflammatory disease in five of the patients. In three of them the disease was apparent on the scans taken at 0.5-1 h, and in the other two it was apparent at 3 h. There were no false negative results, and one false positive result. The scan accurately reflected the absence of pelvic inflammatory disease in nine patients showing non-pathological tracer uptake in the lower abdominal region. We showed that scintigraphy with 99mTc-HMPAO labelled leucocytes had a sensitivity of 100%, specificity of 90%, overall accuracy of 93%, positive predictive value of 83%, and negative predictive value of 100%. Therefore, we conclude that 99mTc-HMPAO labelled leucocyte scans provide a rapid and highly accurate method for diagnosing pelvic inflammatory disease in women of child-bearing age. This adds an important contribution to the diagnosis of infection and helps determine further operative or conservative treatment.

Usefulness of Tc99m HMPAO Labeled Leukocyte Scintigraphy in differentiating Splenic Abscess from Infarct

Radionuclide labeled leukocyte studies are routinely performed in the evaluation of patients with fever of unknown origin and occult infections. Cerebral perfusion agent Tc99m hexamethylpropyleneamine oxime (Tc99m — HMPAO) is one of the radiopharmaceuticals widely used for labeling of mixed leukocytes. It is a lipophilic agent which crosses cell membranes readily and preferentially labels granulocytes. This mechanism is used for labeling of leukocytes. Tc99m labeled leukocytes normally accumulate in spleen by sequestration. At sites of acute infection, focal increased radiotracer labeled leukocyte uptake is seen. Hence, focal defects in spleen represent infarcts. We present in this report two cases of splenic infarct diagnosed by Tc99m HMPAO labeled leukocytes.

Role of Delayed Tc-99m HMPAO Labeled Leukocyte Scintigraphy In the Diagnosis of Coronary Mycotic Aneurysm

Coronary mycotic aneurysms are rare with a poor prognosis. Atherosclerosis often predisposes to aneurysmal dilatation. In children, Kawasaki disease and in adults trauma, vasculitis, syphilis, dissection, and postcoronary angioplasty contribute to coronary mycotic aneurysms. Radiolabeled leukocytes have been used in the diagnosis of prosthetic valve endocarditis and vascular graft infections. Abnormal accumulation of radiolabeled leukocytes have also been reported in infra renal aortic aneurysms. We present a case of a coronary mycotic aneurysm where delayed Tc-99m HMPAO labeled leukocyte imaging played an important role leading to the diagnosis.

Occult Bony Metastatic Disease Demonstrated on Labeled Leukocyte Scintigraphy

Labeled leukocyte scintigraphy is well established in confirming the presence of infection and/or inflammation. There are various methods of labeling leukocytes with either indium-111 or technetium-99m. Although the procedure is sensitive, it is not specific. As a result of the low specificity of the test, abnormal findings may reveal pathology other than infection and/or inflammation. A 69-year-old woman underwent a labeled leukocyte scan to assess for a possible renal abscess after an episode of pyelonephritis not responding to antibiotic therapy. Areas of absent bone marrow activity were incidentally noted, which demonstrated increased osteoblastic activity on a subsequent bone scan and lytic lesions on a computed tomography scan consistent with osseous metastases. Renal biopsy confirmed the diagnosis of transitional cell carcinoma.

Vascular Graft Thromboses: 99mTc-HMPAO Leukocyte Scintigraphy False Positive Result in Diagnosis of Infection

We describe a case of a 76-year-old male admitted with fever and pain in his left leg. He had an axillobifemoral bypass, 1 year previously physical examination revealed weak peripheral pulses in both legs and a fluid collection in the left groin. A technetium scan showed intense leukocyte uptake in pelvic graft and in the left groin. This was considered diagnostic for infection. On removal of the graft it was found to be thrombosed. Culture of the graft was negative. Thrombosis of vascular prosthetic grafts can give a false positive result with labelled leukocytes. In case of positive uptake in 99mTc-HMPAO labelled leukocyte scintigraphy, thrombosis must be ruled out by means of complementary techniques.

Vascular Graft Thromboses: 99mTc-HMPAO Leukocyte Scintigraphy False Positive Result in Diagnosis of Infection

We describe a case of a 76-year-old male admitted with fever and pain in his left leg. He had an axillobifemoral bypass, 1 year previously physical examination revealed weak peripheral pulses in both legs and a fluid collection in the left groin. A technetium scan showed intense leukocyte uptake in pelvic graft and in the left groin. This was considered diagnostic for infection. On removal of the graft it was found to be thrombosed. Culture of the graft was negative. Thrombosis of vascular prosthetic grafts can give a false positive result with labelled leukocytes. In case of positive uptake in 99mTc-HMPAO labelled leukocyte scintigraphy, thrombosis must be ruled out by means of complementary techniques.

99mTc-Hexamethylpropylene Amineoxime Leukocyte Scintigraphy in Acute Pancreatitis: An Alternative to Contrast-Enhanced Computed Tomography?

Contrast-enhanced computed tomography (CECT) is the most efficient imaging technique for the diagnosis and staging of acute pancreatitis (AP); its use, however, may be unfeasible in some patients as a consequence of the drawbacks of intravenous (IV) contrast material. The aim of this study was to test the utility of labeled leukocyte scintigraphy (LLS) as an alternative imaging technique to CECT for the staging of AP. Sixty-six patients with AP were prospectively studied. All patients underwent CECT and pancreatic LLS using (99m)Tc-hexamethylpropylene amineoxime as leukocyte label within a time interval of 2 days, in the early phase of AP. In addition, all patients had their serum C-reactive protein (CRP) concentration measured within 48-72 h after admission. CECT images were analyzed for Balthazar's grade of pancreatitis and for the presence or absence of pancreatic necrosis. Scintigraphic activity of 3-4 h planar images was scored on a 0-2 scale in relation to physiological liver uptake. LLS score was significantly related (p < 0.001) to both components of CECT (grade of pancreatitis and pancreatic necrosis). LLS and serum CRP showed similar results for detecting the most severe pancreatic damage as showed by their respective receiver operating characteristic (ROC) curves. Sensitivities and specificities of LLS score of 2 were, respectively, 62% and 96% for the detection of grade D-E pancreatitis and 90% and 89% for the detection of pancreatic necrosis. Scintigraphic score of 2 increased the likelihood of grade D-E pancreatitis from 32% (pretest probability) to 87% (posttest probability) (likelihood ratio: 13.9) and that of pancreatic necrosis from 16% to 60% (likelihood ratio: 8.4). Our results show that leukocytes are related to the severity of local pancreatic damage in AP. Thus, LLS is a potential alternative technique to CECT for staging AP.

Use of 99mtechnetium hexamethylpropyleneamine oxime labelled leucocyte scintigraphy in equine medical investigations: 8 cases

Equine Veterinary EducationVolume 16, Issue 3 p. 122-127 Use of 99mtechnetium hexamethylpropyleneamine oxime labelled leucocyte scintigraphy in equine medical investigations: 8 cases P. H. L. Ramzan, Corresponding Author P. H. L. Ramzan Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UK*Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UKSearch for more papers by this authorR. J. Malton, R. J. Malton Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UKSearch for more papers by this authorA. J. McGladdery, A. J. McGladdery Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UKSearch for more papers by this author P. H. L. Ramzan, Corresponding Author P. H. L. Ramzan Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UK*Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UKSearch for more papers by this authorR. J. Malton, R. J. Malton Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UKSearch for more papers by this authorA. J. McGladdery, A. J. McGladdery Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UKSearch for more papers by this author First published: 05 January 2010 https://doi.org/10.1111/j.2042-3292.2004.tb00280.xCitations: 2AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume16, Issue3June 2004Pages 122-127 RelatedInformation

Pulmonary activity on labeled leukocyte images: physiologic, pathologic, and imaging correlation.

Accurate interpretation of labeled leukocyte images requires knowledge of pulmonary labeled leukocyte uptake: its prevalence and patterns and its correlation with technical, physiologic, and pathologic conditions as well as with other imaging findings. Images obtained shortly after injection of labeled cells are characterized by diffuse pulmonary activity, which decreases over time, until about 4 hours after injection when it becomes indistinguishable from background activity, remaining constant thereafter. Focal pulmonary uptake that is segmental or lobar in appearance is most often associated with bacterial pneumonia. Focal pulmonary uptake that is not segmental or lobar results from technical problems during labeling or reinfusion and is not usually associated with infection. Diffuse pulmonary uptake on images obtained more than 4 hours after reinjection of labeled cells is associated with a variety of pathologic conditions, some of the more common being opportunistic infection, radiation pneumonitis, pulmonary drug toxicity, adult respiratory distress syndrome, and sepsis. However, this pattern is almost never seen in bacterial pneumonia. When pulmonary uptake patterns are analyzed and correlated with the clinical situation, labeled leukocyte scintigraphy can provide useful information about pulmonary disease.

111Indium labelled leukocyte scintigraphy in the detection of acute prostatitis

Although prostatitis is a common problem the diagnosis is still controversial despite the availability of a wide variety of diagnostic tools. In fact, there is still no accurate method of localizing the infected tissue. The aims of the present study were to assess whether 111In labelled leukocytes (ILLs) accumulated in the infected tissue of acute prostatitis and if such uptake responded to treatment. We prospectively studied 10 adult male patients who had community acquired prostatitis and compared them with six male patients who had urinary tract infections but without prostatitis. An initial urinary culture and two blood cultures were carried out for each patient. All patients were followed up for 8 weeks after therapy was completed. Pre- and post-treatment scintigraphies were performed. Before treatment, all patients with prostatitis showed uptake of ILLs in the prostate area. After the patients had completed treatment with antibiotics, the scintigraphy results showed no uptake in the prostate area in 9/10 patients. The remaining patient showed a marked decrease in the uptake of ILLs. None of the six patients with urinary tract infection showed ILL uptake in the prostate region. It is suggested that ILLs could be useful for detecting acute prostatitis, especially in clinically ambiguous patients with urological infections. Furthermore, scintigraphy with 111In labelled leukocytes could help to determine the most appropriate course of therapy.

Abdominal scintigraphy using technetium Tc 99m hexylmethylpropylene amine oxime–labeled leukocytes in patients with seronegative spondyloarthropathies

Objective: To assess the potential benefits of technetium Tc 99m hexylmethylpropylene amine oxime (Tc 99m HMPAO)–labeled leukocyte scintigraphy in a group of patients with spondyloarthropathies (SpAs), overt gastrointestinal symptoms, and negative extensive endoscopic/radiologic test results. Patients and Methods: Ten patients with SpAs and overt gastrointestinal symptoms were included in this study. All patients underwent colonoscopy and small bowel barium studies, and results were negative. Abdominal scintigraphy with Tc 99m HMPAO–labeled leukocytes was performed in all the patients. Clinical and laboratory data and response to treatment was recorded. Results: The Tc 99m HMPAO–labeled leukocyte scintigraphy was positive in 5 of 10 patients, demonstrating uptake at the terminal ileum which is very suggestive of Crohn disease. The 5 scintigraphically positive patients were treated with sulfasalazine (SSZ). Four patients responded to SSZ with significant improvement of both gastrointestinal and joint symptoms. Conclusions: In 5 of 10 patients with SpA and suspected inflammatory bowel disease on clinical grounds, evidence of inflammatory bowel disease was shown by scintigraphic studies in which conventional invasive procedures failed. Tc 99m HMPAO–labeled leukocyte scintigraphy should be considered in the evaluation of patients with SpA. Semin Arthritis Rheum 31:406-412. Copyright 2002, Elsevier Science (USA). All rights reserved.

16. Diagnosis of renal allograft rejection by 99mTc labelled leukocyte scintigraphy

16. Diagnosis of renal allograft rejection by 99mTc labelled leukocyte scintigraphy

The diabetic foot.

Foot complications in diabetics often lead to amputation. Ulceration is the most common complication in the diabetic forefoot and underlies more than 90% of cases of pedal osteomyelitis. The diagnosis of osteomyelitis is, nevertheless, difficult, and imaging is an important part of the work-up. Plain radiographs, although useful for anatomical information, are neither sensitive nor specific. Three-phase bone scintigraphy is sensitive but not specific. Labelled leucocyte scintigraphy and MRI are both useful and are complementary to one another. Labelled leucocyte scintigraphy is valuable for diagnosis as well as follow-up of pedal osteomyelitis. MRI offers exquisite anatomical detail, which is invaluable for guiding surgical management. The principal complication in the mid and hind foot is the neuropathic or Charcot joint. Although infection of the neuropathic joint is infrequent, its diagnosis is difficult. The extensive bony changes that accompany this disorder severely diminish the value of radiography and bone scintigraphy. It is not always possible to distinguish the marrow oedema of neuropathy from that of osteomyelitis and the role of MRI in the evaluation of this entity is still uncertain. Uptake of labelled leucocytes in the absence of infection may occur and is owing, at least in part, to haematopoietically active marrow. Combined leucocyte/marrow scintigraphy holds considerable promise for identifying the infected Charcot joint.

Technetium-99m hexamethylpropylene amine oxime leucocyte scintigraphy in the differential diagnosis of cerebral abscesses.

The diagnosis of brain abscess is often difficult, as the clinical symptoms are not specific. Computed tomography (CT) and magnetic resonance imaging (MRI) are highly sensitive, but different cerebral lesions, especially neoplasms, can have the same ring-like contrast enhancement. Brain abscess is a severe illness requiring rapid diagnosis to choose the most appropriate therapy. Technetium-99m hexamethylpropylene amine oxime (HMPAO)-labelled leucocyte scintigraphy is commonly used to detect an inflammatory process. The aim of this study was to present the results obtained with leucocyte scintigraphy in 65 patients with intracranial mass lesions and clinical findings compatible to or suggestive of brain abscess. The final diagnosis, based on surgery, clinical findings and stereotatic puncture, was brain abscess in 17 patients, primary brain neoplasm in 22, brain metastasis in 16, lymphoma in 2, cysticercosis in 2, hematoma in 2 and cerebral infarction in 4. 99mTc-HMPAO leucocyte scintigraphy was positive in all abscess cases. The scan was negative in the rest of the patients examined, with the exception of one lesion, which was finally diagnosed as a tumour (1 false-positive). All patients who did not have false-negative scans were treated with steroids. The sensitivity, specificity and diagnostic accuracy of leucocyte scintigraphy was 100%, 97.8% and 98.4%, respectively. In conclusion, in our experience, leucocyte scintigraphy is a valuable aid in the differential diagnosis between abscess and neoplasm.

Tubo-ovarian Abscess

Tc-99m hexamethylpropylene amineoxime (HMPAO) leukocytes are used widely to localize inflammatory foci and abscesses. However, the use of radiolabeled leukocytes to detect a tubo-ovarian abscess has not been reported. The authors describe two cases of tubo-ovarian abscess successfully imaged using this technique in obese women with a clinical history of prolonged fever and abdominal pain. Labeled leukocyte scintigraphy with Tc-99m HMPAO is a noninvasive, physiologic procedure with excellent imaging quality that is complementary but not competitive with anatomic imaging techniques such as US and CT. This scan is recommended as one of the steps for rapid accurate diagnosis of gynecologic pyogenic infection.