Single photon emission computed tomography (SPECT), planar scintigraphy, and transmission computed tomography: a comparison of accuracy in diagnosing focal hepatic disease

Scintigraphic Evaluation of Traumatic Splenic Lesions in Children

Ninety-eight children with recent blunt abdominal trauma which initially evoked clinical suspicion of splenic injury were examined with colloid scintigraphy of the spleen and the liver using multiple imaging views and with abdominal survey. Nineteen children were, in addition, examined with tomographic scintigraphy. The clinical findings and the course of the disorder were reanalysed. Scintigraphy indicated splenic injury in 56 children and hepatic injury in another 5 children. The left lateral and the left oblique were the optimum imaging views for detecting splenic ruptures. Tomographic scintigraphy did not improve the diagnostic yield. Abdominal survey failed to indicate almost every second case of splenic rupture and provided no additional information of significance. The clinical review agreed with the scintigraphic diagnosis of splenic lesions but, in addition, it suggested possible splenic lesions in another 10 children with normal scintigraphy. This discrepancy cannot be explained as surgery was not employed; the occurrence of splenic lesions too small to become detectable at scintigraphy or to provoke clinically evident symptoms may be supposed.

Nodular regenerative hyperplasia of the liver

Nodular regenerative hyperplasia (NRH), characterized by diffuse hepatic micronodular transformation in groups without fibrous septa between the nodules, is a rare benign liver lesion that has many synonyms in previous literature. Pathologic evaluation is the mainstay of accurate diagnosis. Treatment is focused on its underlying conditions and complications of portal hypertension. A 39-year-old man visited our hospital due to right upper quadrant pain and a palpable liver mass. Magnetic resonance examination revealed a slightly hyperintense tumor on T2-weighted images, and focal nodular hyperplasia was diagnosed by the radiologists. Atypical radiologic findings could not yield an accurate diagnosis. Surgical intervention was therefore performed. Pathologic examination of the resected liver tumor confirmed the diagnosis of NRH. We conclude that NRH should be included in the differential diagnosis of benign liver tumor.

Single photon emission computed tomography and positron emission tomography in cancer imaging

Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are now being used to improve the information available from radioisotopic imaging of patients with cancer. These nuclear medicine techniques offer the potential for studying regional function and biochemistry by using radiolabeled substrates. The chemical changes of malignancy precede anatomic changes, and PET and/or SPECT may detect these changes before anatomic changes have occurred. The superiority of SPECT compared with planar imaging has been demonstrated for cardiac and brain imaging. Radiopharmaceuticals containing technetium 99 m (99mTc) are best suited for SPECT imaging because large amounts of radioactivity are administered and the collimator-camera systems are optimized for the 140 keV photons of 99mTc. The current interest in imaging cancer with SPECT relates to the use of gallium 67 citrate and monoclonal antibodies labeled with iodine 123 or indium 111. SPECT can image these radioisotopes, but the advantages compared with planar imaging have not been clearly defined. Furthermore, the ability to quantitate the distribution of single photon emitters other than 99mTc has not been demonstrated. New SPECT systems with three heads or rings of detectors offer promise for improved, quantitative imaging. PET has the capability of imaging tracers with the biologically important elements C-11, N-13, O-15, and F-18 used for positron labeling. These radioisotopes have short half-lives and require a cyclotron close to the PET facility. The most prominently used radiopharmaceutical for PET is F-18 fluorodeoxyglucose (FDG). PET studies with FDG in patients with primary brain tumors have demonstrated the ability to determine the degree of malignancy, to differentiate necrosis from recurrent tumor after radiation therapy or chemotherapy, and to predict prognosis. Other metabolic functions of cancer have been studied, including amino acid accumulation, thymidine uptake, oxygen utilization, intermediary metabolism, and receptor status. PET has the potential to make a major impact on the characterization of a malignancy and the effect of therapy.

Diagnosis of hepatic hemangioma with 99mTc-labeled red cells: single photon emission computed tomography (SPECT) versus planar imaging

This paper reports the results of a prospective study carried out to demonstrate the most important advantages of 99mTc-blood pool single emission computed tomography (SPECT) versus the established method of planar scintigraphy (PS) in the non-invasive diagnosis of liver hemangiomas. The study group comprised 40 patients in whom positive evidence of 56 hemangiomas, detected incidentally in the course of screening examinations, was established via SPECT and PS. The sensitivity of SPECT was 51/56 (91%), of PS 22/56 (39.3%); for lesions smaller than 30 mm in diameter, the sensitivity of SPECT was 31/38 (81.6%), of PS 6/38 (15.8%). All lesions with diameters of more than 30 mm were detected by both PS and SPECT. However, the SPECT method proved to be clearly superior in the identification of lesions which were smaller than 30 mm and located in unfavourable topographical sites (dorsal or subphrenic). The study proves that SPECT with 99mTc-labeled erythrocytes is the ideal complement to ultrasonography in the detection of liver hemangionas; its major advantage over TCT (transmission computed tomography) is its safe application in cases with contrast agent intolerance and hyperthyroid patients. Moreover, liver biopsies are dangerous and ill-suited for the verification of diagnosis.

Malignant liver tumors

In this monograph we have presented the most important liver tumors in children and adults with pathological correlation. We believe that this information may be useful for understanding the varying radiological findings in malignant liver tumors since it includes pathological findings responsible for the radiographic images. It is clear that there are no characteristic signs that could establish a specific radiological diagnosis in malignant liver tumors. However, careful analysis of the radiographic images provided by different modalities and correlations with the clinical data may, in many cases, suggest a correct preoperative diagnosis.

Abdominal SPECT imaging

Over the past several years, abdominal single photon emission computed tomography (SPECT) imaging has evolved from a research tool to an important clinical imaging modality that is helpful in the diagnostic assessment of a wide variety of disorders involving the abdominal viscera. Although liver-spleen imaging is the most popular of the abdominal SPECT procedures, blood pool imaging is becoming much more widely utilized for the evaluation of cavernous hemangiomas of the liver as well as other vascular abnormalities in the abdomen. Adjunctive indium leukocyte and gallium SPECT studies are also proving to be of value in the assessment of a variety of infectious and neoplastic diseases. As more experience is acquired in this area, SPECT should become the primary imaging modality for both gallium and indium white blood cells in many institutions. Renal SPECT, on the other hand, has only recently been used as a clinical imaging modality for the assessment of such parameters as renal depth and volume. The exact role of renal SPECT as a clinical tool is, therefore, yet to be determined.

Specific considerations in the interpretation of single-photon-emission computed tomography of the normal liver

In our hospital, single-photon-emission computed tomography (SPECT) has been routinely used instead of conventional scintigraphy in the examination of the liver and spleen in more than 3,000 patients. This technique is preferred because it provides more detailed information and better contrast resolution than planar views. However, using the SPECT technique, normal variations in liver anatomy are more apparent, and certain cases--in particular those with a wide main lobar fissure combined with a prominent gall bladder fossa as well as cases with a large hilus--may erroneously be interpreted as having a focal lesion. In order to facilitate the interpretation of SPECT examinations of the liver, the most common difficulties and pitfalls arising from normal variations in hepatic anatomy, indentations caused by surrounding organs and partial-volume effects are described and compared with the findings of corresponding transmission computed tomograms.