Single-Photon Emission Computed Tomography/Computed Tomography in Abdominal Diseases

Imaging of Gastrointestinal Bleeding: An Update

Imaging of gastrointestinal bleeding crucial in the diagnosis of occult gastrointestinal bleeding. Gastrointestinal bleeding scintigraphy is a well-established study to aid localisation of gastrointestinal bleeding site. This article discusses about the use of gastrointestinal bleeding scintigraphy in its current practice with emphasis on radiopharmaceutical, imaging techniques, interpretation and pitfalls. There is also discussion on the use of Single Photon Emission Computed Tomography-Computed Tomography (SPECT-CT) within this method of scintigraphy. Meckel's diverticulum is known to be a frequent source of bleeding, mainly in children. It is also know that nuclear medicine imaging can help with Meckel's diverticulum identification. This article also discusses about the technique, imaging, interpretation and SPECT-CT usage for Meckel's diverticulum imaging.

Subcutaneous Splenosis Presenting 37 years post-traumatic splenectomy; A Case Report

INTRODUCTION

The term splenosis refers to autotransplantation of splenic tissue in ectopic sites. Ectopic splenic tissue may be found in the liver, thorax, pelvis and subcutaneous tissues following traumatic splenectomy. Although clinically insignificant, local symptoms such as abdominal pain may arise. In this paper we report a case of subcutaneous splenosis presenting 37 years post-traumatic splenectomy.

CASE PRESENTATION

A 40-year-old medically free lady presented to our institution with a surgical history of post-traumatic splenectomy at the age of three and two cesarean sections. She complained for nonpainful right upper quadrant soft mass that has been stable in size over the years. Her laboratory results, including peripheral blood smear, were all within normal limits and no asplenic changes were detected. SPECT scan confirmed extraperitoneal splenosis in right upper quadrant.

DISCUSSION

Splenosis is an acquired form of ectopic splenic tissue that is defined as an auto-transplantation of a viable splenic tissue. It commonly occurs after traumatic rupture of the spleen.5 Splenosis has been widely reported around the world with an incidence of 16-67% after traumatic splenic rupture or splenectomy. Subcutaneous splenosis is an extremely rare condition, mostly observed in abdominal surgical scars. It is believed to follow laparotomy for splenectomy where splenic cells auto-implant or spread hematogenously at different locations.

CONCLUSION

Subcutaneous splenosis is a rare consequence of post-traumatic splenectomy that can manifest itself up to three decades after. Although concerning to the patient and alarming to the surgeon as it may resemble more serious entities such as abdominal wall sarcoma, surgical removal of asymptomatic splenosis is subject to the location of mass and patients' wishes.

Imaging findings of a rare pararectal splenosis and literature review

Pararectal splenosis is an extremely rare lesion caused by ectopic auto-transplantation of splenic tissue after splenic trauma or splenectomy. It is often asymptomatic and detected incidentally during radiologic evaluation. We present a 24-year-old male with pararectal splenosis. The patient had a history of splenectomy and presented with complaints of abdominal discomfort and chronic constipation. Contrast-enhanced computed tomography (CT) revealed multiple well-enhanced masses located in the abdominal cavity and one mass in pararectal area. Additionally, the pararectal lesion showed diffusion restriction on diffusion-weighted magnetic resonance imaging (DW-MRI). In this case report, we aim to highlight the significance of taking a detailed medical history; and using DW-MRI for diagnosis of splenosis by presenting a case in a rare location.

Colonic transit in patients after anterior resection: prospective, comparative study using single-photon emission CT/CT scintigraphy

BACKGROUND

Bowel dysfunction after anterior resection is well documented, but its pathophysiology remains poorly understood. No study has assessed whether postoperative variation in colonic transit contributes to symptoms. This study measured colonic transit using planar scintigraphy and single-photon emission CT (SPECT)/CT in patients after anterior resection, stratified according to postoperative bowel function.

METHODS

Symptoms were assessed using the low anterior resection syndrome (LARS) score. Following gallium-67 ingestion, scintigraphy was performed at predefined time points. Nine regions of interest were defined, and geometric centre (GC), percentage isotope retained, GC velocity index and colonic half-clearance time (T_½ ) determined. Transit parameters were compared between subgroups based on LARS score using receiver operating characteristic (ROC) curve analyses.

RESULTS

Fifty patients (37 men; median age 72·6 (range 44·4-87·7) years) underwent planar and SPECT scintigraphy. Overall, 17 patients had major and nine had minor LARS; 24 did not have LARS. There were significant differences in transit profiles between patients with major LARs and those without LARS: GCs were greater (median 5·94 (range 2·35-7·72) versus 4·30 (2·12-6·47) at 32 h; P = 0·015); the percentage retained isotope was lower (median 53·8 (range 6·5-100) versus 89·9 (38·4-100) per cent at 32 h; P = 0·002); GC velocity indices were greater (median 1·70 (range 1·18-1·92) versus 1·45 (0·98-1·80); P = 0·013); and T_½ was shorter (median 38·3 (17·0-65·0) versus 57·0 (32·1-160·0) h; P = 0·003). Percentage tracer retained at 32 h best discriminated major LARS from no LARS (area under curve (AUC) 0·828).

CONCLUSION

Patients with major LARS had accelerated colonic transit compared with those without LARS, which may help explain postoperative bowel dysfunction in this group. The percentage tracer retained at 32 h had the greatest AUC value in discriminating such patients.

A Lower Gastrointestinal Bleeding Due to a Post-Traumatic Splenosis: "Wait and See" Represents a Feasible Attitude: A Case Report

Splenosis represents a benign condition due to an ectopic localization of splenic tissue caused by pathologic or traumatic spleen rupture. Generally, it is asymptomatic and incidentally diagnosed during imaging performed for other reasons. Occult gastrointestinal bleeding due to an extraperitoneal localization is a rare occurrence. Differential diagnosis may be very hard and includes benign and malignant neoplasms.We describe the case of a 68-year-old Caucasian man that was admitted for an increasing lower gastrointestinal bleeding associated to a vague abdominal pain.He was assessed by means of laboratory tests, as well as by endoscopic and radiological examinations, and successfully treated with an exclusive medical approach.The patient was discharged on the ninth day and currently he is doing well.This case shows that wait and see could prove a feasible attitude for the management of clinically stable patients.

Gastrointestinal Bleeding Scintigraphy in the Early 21st Century

Gastrointestinal bleeding scintigraphy performed with (99m)Tc-labeled autologous erythrocytes or historically with (99m)Tc-sulfur colloid has been a clinically useful tool since the 1970s. This article reviews the history of the techniques, the different methods of radiolabeling erythrocytes, the procedure, useful indications, diagnostic accuracy, the use of SPECT/CT and CT angiography to evaluate gastrointestinal bleeding, and Meckel diverticulum imaging. The causes of pediatric bleeding are discussed by age.

Precise Localization of Occult Gastrointestinal Hemorrhage Using Dynamic SPECT/CT

Active but intermittent gastrointestinal (GI) bleeding can be readily detected with dynamic planar scintigraphic imaging. This is a case of a 48-year-old woman who presented from an outside institution with active GI bleeding on 99mTc-labeled RBC (99mTc-RBC) scintigraphy, but the upper and lower GI evaluations failed to subsequently localize the site of persistent bleeding. Repeat 99mTc-RBC planar scintigraphy identified a focus of active extravasation in the right lower quadrant of the abdomen. Dynamic SPECT/CT imaging was immediately performed and further identified the ileocecal valve region as the precise site of active extravasation, which was confirmed at surgery.

Selective Spleen Scintigraphy in the Evaluation of Accessory Spleen/Splenosis in Splenectomized/Nonsplenectomized Patients and the Contribution of SPECT Imaging

OBJECTIVE

We aimed to evaluate the results of selective spleen scintigraphy (SSS) and contribution of SPECT imaging to planar imaging in splenectomized and nonsplenectomized patients.

METHODS

We retrospectively examined 112 SSSs of 96 patients. The patients were divided into two groups as splenectomized group (SP) and non-splenectomized group (NSP). The findings were evaluated by comparing the results of surgery,computerized tomography (CT), ultrasonography (USG) and magnetic resonance imaging (MRI). In addition, whether or not differences existed between the results of SPECT and planar imaging was determined.

RESULTS

Of 66 scintigraphies performed in the NSP group, 3 (5%) had positive, 3 (5%) had suspicious and 60 (90%) had negative results. In the NSP group, 28 patients underwent surgery and 12 accessory spleens were removed. Only 3 of these tissues were detected by scintigraphy. Of 46 patients in the SP group, 26 (57%) had positive findings whereas 20 (43%) had negative scintigraphies. Twelve accessory spleens/splenosis were removed surgically in 10 patients with a positive SSS in the SP group. There were no false positive results in both groups of patients who underwent surgery. There was no significant difference between the results of SSS, USG and CT. Of 39 patients to whom SPECT were performed, 10 had positive results both with planar and SPECT imaging. On the other hand, 26 patients, 3 of whom had suspected findings in SPECT images, demonstrated negative results when evaluated with both imaging methods. Remaining 3 were considered suspicious by only SPECT images for the hilar area.

CONCLUSION

SSS has high specificity in the detection of accessory spleens/splenosis. The sensitivity of SSS is low in the NSP group,but higher in the SP group. There is no contribution of SPECT imaging to planar imaging.

Nuclear medicine tests for acute gastrointestinal conditions

Acute cholecystitis (AC) and lower-gastrointestinal (GI) bleeding are 2 emergencies commonly encountered in nuclear medicine. Evidence of AC on hepatobiliary scintigraphy (HBS) allows for confident diagnosis and provides support for definitive surgical treatment. Proper patient preparation is essential for HBS including fasting and the use of pharmacologic adjuncts is sometimes required. Pharmacologic adjuncts may also be administered during HBS to shorten the length of the examination and increase its specificity. In the interpretation of HBS, there are several sources of false-positive results to be aware of, most commonly chronic cholecystitis. False-negative results on HBS are usually the result of mistaking another structure, such as a dilated cystic duct, for the gallbladder. Abdominal ultrasound is the appropriate initial test in patients with suspected AC, but HBS is an excellent second tier test for the diagnosis of AC in the work-up of indeterminate cases by sonography. GI bleeding scintigraphy plays an important role in the evaluation and management of patients with acute lower-GI bleeding. Scintigraphy serves to localize sites of active GI bleeding and stratify those patients who would benefit from aggressive treatment (surgery or arteriography) vs those who can be managed medically. Pretest involvement of respective services is critical for successful bleeding site confirmation and therapy by interventional radiology or surgery or both. Single photon emission computed tomography/computed tomography erythrocyte scintigraphy has demonstrated superior accuracy and precision over planar scintigraphy in the diagnosis of acute GI bleeding. Additionally, single photon emission computed tomography/computed tomography scintigraphy of GI bleeding provides useful supplemental anatomical information that benefits patient management.

Diffuse abdominal splenosis mimicking peritoneal metastases in a 35-year-old man with a resectable carcinoma of the ampulla of vater

A 35-year-old man with a history of blunt abdominal trauma and splenic rupture was diagnosed with an ampullary adenocarcinoma. At workup, a CT scan showed multiple intra-abdominal lesions similar to peritoneal carcinosis, and the patient was referred for palliative chemotherapy. On clinical suspicion, however, a biopsy was performed on an intra-abdominal lesion, establishing the diagnosis of abdominal splenosis. A radical pancreaticoduodenectomy ad modum Whipple was performed, followed by adjuvant chemotherapy with gemcitabine. At the 18-month follow-up, the patient was free from recurrent disease. We conclude that splenosis should be considered as a differential diagnosis of peritoneal metastases in cancer patients with a history of abdominal trauma and/or splenectomy. Other reports on splenosis in cancer patients and diagnostic workup are discussed.

[Gastrointestinal bleeding: the role of radiology]

Gastrointestinal bleeding represents a diagnostic challenge both in its acute presentation, which requires the point of bleeding to be located quickly, and in its chronic presentation, which requires repeated examinations to determine its etiology. Although the diagnosis and treatment of gastrointestinal bleeding is based on endoscopic examinations, radiological studies like computed tomography (CT) angiography for acute bleeding or CT enterography for chronic bleeding are becoming more and more common in clinical practice, even though they have not yet been included in the clinical guidelines for gastrointestinal bleeding. CT can replace angiography as the diagnostic test of choice in acute massive gastrointestinal bleeding, and CT can complement the endoscopic capsule and scintigraphy in chronic or recurrent bleeding suspected to originate in the small bowel. Angiography is currently used to complement endoscopy for the treatment of gastrointestinal bleeding.

Optimizing analysis, visualization, and navigation of large image data sets: one 5000-section CT scan can ruin your whole day

The technology revolution in image acquisition, instrumentation, and methods has resulted in vast data sets that far outstrip the human observers' ability to view, digest, and interpret modern medical images by using traditional methods. This may require a paradigm shift in the radiologic interpretation process. As human observers, radiologists must search for, detect, and interpret targets. Potential interventions should be based on an understanding of human perceptual and attentional abilities and limitations. New technologies and tools already in use in other fields can be adapted to the health care environment to improve medical image analysis, visualization, and navigation through large data sets. This historical psychophysical and technical review touches on a broad range of disciplines but focuses mainly on the analysis, visualization, and navigation of image data performed during the interpretive process. Advanced postprocessing, including three-dimensional image display, multimodality image fusion, quantitative measures, and incorporation of innovative human-machine interfaces, will likely be the future. Successful new paradigms will integrate image and nonimage data, incorporate workflow considerations, and be informed by evidence-based practices. This overview is meant to heighten the awareness of the complexities and limitations of how radiologists interact with images, particularly the large image sets generated today. Also addressed is how human-machine interface and informatics technologies could combine to transform the interpretation process in the future to achieve safer and better quality care for patients and a more efficient and effective work environment for radiologists.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11091276/-/DC1.

Intra-abdominal splenosis mimicking metastatic cancer

Splenosis, the heterotopic autotransplantion of splenic tissue, is a common benign condition among patients with a history of splenic trauma. Most cases of splenosis are intra-abdominal due to direct seeding of surrounding structures, although these ectopic rests may occur almost anywhere in the body, and its diffuse nature may raise the suspicion of metastatic cancer. Confirmation of splenic tissue can be made by technetium-99m (Tc-99m) sulfur colloid scintigraphy or with Tc-99m heat-damaged red blood cells; however, in some cases, biopsy may be required for definitive diagnosis. Here, the authors present a patient with a remote history of posttraumatic splenectomy who was discovered to have multiple intra-abdominal nodules by CT scan. A diagnosis of diffuse metastatic disease was initially considered before a diagnosis of intraabdominal splenosis was ultimately made with the aid of Tc-99m sulfur colloid single-positron emission computed tomography (SPECT) and computed tomography imaging.

Hybrid imaging (SPECT/CT and PET/CT): improving therapeutic decisions

The incremental diagnostic value of integrated positron emission tomography-computed tomography (PET/CT) or single-photon emission computed tomography (SPECT)/CT images compared with PET or SPECT alone, or PET or SPECT correlated with a CT obtained at a different time includes the following: (1) improvement in lesion detection on both CT and PET or SPECT images, (2) improvement in the localization of foci of uptake resulting in better differentiation of physiological from pathologic uptake, (3) precise localization of the malignant foci, for example, in the skeleton vs soft tissue or liver vs adjacent bowel or node (4) characterization of serendipitous lesions, and (5) confirmation of small, subtle, or unusual lesions. The use of these techniques can occur at the time of initial diagnosis, in assessing the early response of disease to treatment, at the conclusion of treatment, and in continuing follow-up of patients. PET/CT and SPECT/CT fusion images affect the clinical management in a significant proportion of patients with a wide range of diseases by (1) guiding further procedures, (2) excluding the need of further procedures, (3) changing both inter- and intramodality therapy, including soon after treatment has been initiated, and (4) by providing prognostic information. PET/CT fusion images have the potential to provide important information to guide the biopsy of a mass to active regions of the tumor and to provide better maps than CT alone to modulate field and dose of radiation therapy. It is expected that the role of PET/CT and SPECT/CT in changing management will continue to evolve in the future and that these tools will be fundamental components of the truly "personalized medicine" we are striving to deliver.

The role of single-photon emission computed tomography/computed tomography for precise localization of metastases in patients with differentiated thyroid cancer

PURPOSE

It is very important in the management of patients with differentiated thyroid cancer (DTC) to precisely localize the foci of I-131 uptake, but it is difficult because of a lack of anatomic landmarks. The purpose of this study was to investigate the added value of I-131 single-photon emission computed tomography (SPECT)/computed tomography (CT) fusion imaging using a hybrid system in patients with DTC.

METHODS

Ninety-four patients with DTC underwent I-131 SPECT/CT using a hybrid tomography consisting of a dual-head variable-angle gamma camera and a low-dose X-ray tube. Results were compared with I-131 whole-body scan (WBS). SPECT/CT was performed 5-7 days after administration of a therapeutic dose of I-131. Fusion images were constructed by combining the digital CT and SPECT images on a computer workstation.

RESULTS

Compared with I-131 WBS, SPECT/CT imaging had improved the precise localization in 21% (20/94) of patients. In addition, SPECT/CT provided additional clinical data in 12 of the patients examined (12/94) and also caused physicians to reconsider the (131)I therapeutic approach in 22 patients.

CONCLUSION

The results of the current study indicate that the addition of I-131 SPECT/CT to WBS can improve the localization of metastases in patients with DTC. It may also detect metastases missed by WBS and adjust the therapy plan.

SPECT/CT imaging: clinical utility of an emerging technology

Single-photon emission computed tomography (SPECT) has been a mainstay of nuclear medicine practice for several decades. More recently, combining the functional imaging available with SPECT and the anatomic imaging of computed tomography (CT) has gained more acceptance and proved useful in many clinical situations. Most vendors now offer integrated SPECT/CT systems that can perform both functions on one gantry and provide fused functional and anatomic data in a single imaging session. In addition to allowing anatomic localization of nuclear imaging findings, SPECT/CT also enables accurate and rapid attenuation correction of SPECT studies. These attributes have proved useful in many cardiac, general nuclear medicine, oncologic, and neurologic applications in which the SPECT results alone were inconclusive. Optimal clinical use of this rapidly emerging imaging modality requires an understanding of the fundamental principles of SPECT/CT, including quality control issues as well as potential pitfalls and limitations. The long-term clinical and economic effects of this technology have yet to be established.