Integrated diagnostics: proceedings from the 9th biennial symposium of the International Society for Strategic Studies in Radiology.

The International Society for Strategic Studies in Radiology held its 9th biennial meeting in August 2011. The focus of the programme was integrated diagnostics and massive computing. Participants discussed the opportunities, challenges, and consequences for the discipline of radiology that will likely arise from the integration of diagnostic technologies. Diagnostic technologies are increasing in scope, including advanced imaging techniques, new molecular imaging agents, and sophisticated point-of-use devices. Advanced information technology (IT), which is increasingly influencing the practice of medicine, will aid clinical communication and the development of "population images" that represent the phenotype of particular diseases, which will aid the development of diagnostic algorithms. Integrated diagnostics offer increased operational efficiency and benefits to patients through quicker and more accurate diagnoses. As physicians with the most expertise in IT, radiologists are well placed to take the lead in introducing IT solutions and cloud computing to promote integrated diagnostics. To achieve this, radiologists must adapt to include quantitative data on biomarkers in their reports. Radiologists must also increase their role as participating physicians, collaborating with other medical specialties, not only to avoid being sidelined by other specialties but also to better prepare as leaders in the selection and sequence of diagnostic procedures. Key Points • New diagnostic technologies are yielding unprecedented amounts of diagnostic information.• Advanced IT/cloud computing will aid integration and analysis of diagnostic data.• Better diagnostic algorithms will lead to faster diagnosis and more rapid treatment.

The scintigraphic imaging of endocrine organs.

The nuclear medicine approach to the portrayal of endocrine organs is unique; the scintigraphic images provide not only anatomic and localization information, but in many instances allow a quantitative assessment of organ function. The ability to image endocrine glands is based upon the design of radionuclides and radiopharmaceuticals with characteristics to take advantage of many unique and specific biochemical and advantage of many unique and specific biochemical and metabolic functions of these tissues. The recent introduction of new radiopharmaceutical and tracers has provided the consulting endocrinologist with imaging procedures that allow localization and functional characterization not available by other single, noninvasive diagnostic modalities. This review will serve as an update of the available techniques to image and quantitate the function of the endocrine glands using the nuclear medicine approach.

Tumor blood flow and systemic shunting in patients receiving intraarterial chemotherapy for head and neck cancer.

Radionuclide techniques have been used to estimate the systemic shunt and to quantitate blood flow to the tumor and a reference normal tissue in nine patients undergoing intraarterial chemotherapy for head and neck cancer. The systemic shunt was calculated as the percentage of pulmonary trapping of intraarterially injected 99mTc-labeled macroaggregated albumin. The mean systemic shunt in the 12 separate arteries studied was 23 +/- 13% (SE) (range 8-43%). Quantitative blood flow was determined from the slope of the washout curve of intraarterially injected 133Xe. The mean tumor blood flow was 13.6 +/- 6.7 ml/100 g/min, while the mean blood flow to the scalp was 4.2 +/- 2.1 ml/100 g/min providing a mean tumor/normal tissue ratio of 3.9 +/- 2.7. An estimate of blood flow distribution was obtained by calculating the ratio of counts/pixel in the tumor mass versus the remainder of the head as determined by single photon emission computed tomography following an intraarterial injection of 99mTc-labeled macroaggregated albumin. The mean ratio of tumor to normal tissue perfusion by this technique was 5.6 +/- 3.7. These techniques have allowed noninvasive determination of the blood flow parameters associated with intraarterial chemotherapy. At least part of the therapeutic advantage of regional chemotherapy in patients with head and neck cancer is due to a tumor/normal tissue blood flow ratio that favors drug delivery to the tumor contained within the infused volume.

Impact of radionuclide techniques on evaluation of patients with ischemic heart disease.

Radiotracer studies of the heart have become clinically important in the last decade, especially for evaluation of patients with known or suspected ischemic heart disease. Radionuclide ventriculography provides quantitative measures of biventricular function and regional wall motion. Recent technical advances include the development of computer programs for analyzing diastolic function, parametric imaging methods such as "phase" analysis and methods for calculating absolute ventricular volumes. Thallium-201 scans provide maps of regional myocardial perfusion. Recent advances include development of computer programs to quantitate regional thallium-201 uptake and to calculate thallium-201 turnover rates and the development of tomographic imaging systems. Technetium-99m pyrophosphate localizes in irreversibly damaged myocardium and provides a method for diagnosing, localizing and sizing acute myocardial infarcts. Recent applications include tomographic imaging to improve image contrast and development of criteria to identify high risk patients after infarction. Two important trends affecting the application of all the radionuclide studies in clinical cardiologic practice are the increasing use of decision analysis for incorporating results of multiple tests into single diagnostic probability statements, and the use of diagnostic algorithms that include the radionuclide studies to optimize the cost effectiveness of evaluation of patients with ischemic heart disease.

The use of videotape for off-line viewing of computer-assisted radionuclide cardiology studies.

Videotape offers an inexpensive method for off-line viewing of dynamic radionuclide cardiac studies. Two approaches to videotaping have been explored and demonstrated to be feasible. In the first, a video camera in conjunction with a cassette-type recorder is used to record from the computer display scope. Alternatively, for computer systems already linked to video display units, the video signal can be routed directly to the recorder. Acceptance and use of tracer cardiology studies will be enhanced by increased availability of the studies for clinical review. Videotape offers an inexpensive flexible means of achieving this.

The importance of adequate exercise in the detection of coronary heart disease by radionuclide ventriculography.

Rest and exercise radionuclide ventriculograms were obtained on 77 symptomatic patients without prior documented coronary artery disease (CAD). Coronary artery disease was present by angiograms in 48. Radionuclide ventriculography (RNV) was abnormal in 41 patients (overall sensitivity 85%). In 29 patients with normal coronary arteries, RNV was normal in 24 (specificity 83%). To determine if the exercise level affects sensitivity, the studies were graded for adequacy of exercise. It was considered adequate if patients developed (a) chest pain, or (b) ST segment depression of at least 1 mm, or (c) if they achieved a pressure rate produce greater than 250. Among the 48 patients with coronary artery disease, 35 achieved adequate exercise. Thirty-three had an abnormal RNV (sensitivity 94%). In 13 patients who failed to achieve adequate exercise, RNV was abnormal in eight (sensitivity of only 62%). Some patients with coronary artery disease may have a normal ventricular response at inadequate levels of stress.

Cardiac function in patients with prior myocarditis.

Gated cardiac blood-pool imaging under rest and exercise was used to assess left-ventricular functional reserve in six asymptomatic patients with prior myocarditis and six age matched control subjects. Coronary artery disease was excluded in three of the six patients by coronary arteriography. In the remaining three, coronary artery disease was thought unlikely on the basis of history and the presence, during exercise, of a normal ECG and normal Tl-201 myocardial image. Conventional indices of resting left-ventricular function--including cardiothoracic ratio, echocardiographic left-ventricular diameter, and percentage change in minor diameter--were normal in those with prior myocarditis. The mean resting left-ventricular ejection fraction was also normal by gated blood-pool imaging, and not significantly different from that for control patients: 0.58 +/- 0.05 and 0.65 +/- 0.02, respectively. Three patients with prior myocarditis had resting left-ventricular ejection fractions of less than 0.50. On exercise, the patients with prior myocarditis decreased their mean left-ventricular ejection fraction by an average of 8% compared with an increase of 15% in the control group (p less than 0.01). This study suggests that asymptomatic patients with prior myocarditis have left-ventricular dysfunction that may not be clinically apparent, and suggests the need for further long-term follow-up.

99mTc-pyrophosphate scan and radiographic correlation in thyroid acropachy: case report.

A case of thyroid acropachy secondary to Graves' disease is described. Radiographic abnormalities were found to correlate with those in a 99mTc-pyrophosphate bone scan. Abnormal tracer concentrations were observed in the diaphyses of the metacarpals and phalanges of both hands and also in regions of pretibial myxedema. The differential diagnosis of the scan abnormalities is discussed.

Oblique-angle tomography: a restructuring algorithm for transaxial tomographic data.

A set of contiguous transaxial tomographic sections obtained with a rotating-camera tomograph represents the full three-dimensional distribution of activity within a volume of the body. Tomographic sections in planes other than the origianl transverse plane can be produced from these data merely by resorting the data appropriately. The paper presents a simple and efficient algorithm for producing tomograms of the heart oriented either at right angles to the long axis of the left ventricle, or parallel to it. Tomograms in these orientations have specific advantages for imaging the heart and avoid some of the limitations seen in comparable tomograms obtained by the seven-pinhole technique.

Absorbed dose to the human adrenals from lodomethylnorcholesterol (I-131) "NP-59": concise communication.

During the past 2 years, adrenal uptake percentage values were measured in more than 40 patients, using an external counting technique. They suggest that the absorbed dose to the adrenals is significantly less than 150 rads/mCIi previously estimated using concentration values from animal adrenals. The measured combined uptake percentage for both adrenals ranged from 0.15% to 0.52% in 21 patients without evidence of adrenal disease, with a mean of 0.33% +/- 0.1%; also from 0.22% to 1.5% in 22 patients with Cushing's disease, with a mean uptake of 0.78% +/- 0.35%. The absorbed dose to the adrenals was estimated to be 25 rads/mCi for patients without evidence of adrenal disease, and 57 rads/mCi for patients with Cushing's disease. Both values are calculated for the respective mean uptake percentages by using MIRD formalism.

Body-background defects with 99mTc-DTPA after renal transplantation: case reports.

Photon-deficient areas adjacent to transplanted kidneys were seen in the early phases of several dynamic studies obtained with 99mTc-diethylenetri-aminepentaacetic acid (99mTc-DTPA). The causes included hematoma, urinoma, and lymphocele. These fluid collections do not readily exchange as part of the extracellular space and, if sufficiently large, may be visualized as photon-deficient areas in the normally homogeneous background of 99mTc-DTPA studies.

Evaluation of a thyroid fluorescent scanning system of concentric source-detector design.

A concentric source-detector system for thyroid fluorescent scanning is described, including fundamental parameters of system response and adaptation of a conventional rectilinear scanner for use with it. The basic system consists of twenty 1-Ci sources of 241Am, a 500-mm2 Si(Li) detector, and associated pulse-height electronics. The image-forming equipment of the rectilinear scanner is retained. We have developed a clinical imaging technique that provides a photon density of 600-800 counts/cm2 over the thyroid gland in subjects with normal iodine pools. Comparisons are made between the outrigger design for fluorescent scanning and conventional emission scanning.

Facial bone scanning by emission tomography.

A single-photon emission tomographic system was used to study the normal anatomy of the facial bones and the usefulness of emission computed tomography in evaluating diseases of the bones of the face. The examination was performed following routine bone scintigraphy and took an additional 20-30 min. The anatomy of the facial bones was well defined, with clear separation of deep and superficial structures. Early experience with tumor, infection, bone grafts, and postirradiation osteonecrosis indicates that useful added diagnositc information can be obtained by this method.

Gallium-67 scintigraphy in untreated and treated non-hodgkin lymphomas.

One hundred and seventy-four gallium scans of patients with biopsy-proved non-Hodgkin lymphoma were reviewed. When the lymphomas were subdivided into histologic groups, there was a significant difference in detection rates, with 62% of the histiocytic lymphomas being identified, while only 39% of the poorly differentiated lymphocytic lymphomas were detected. There was a high detection rate for lesions in the mediastinum and in extranodal locations. When analyzed with regard to therapy, the detection rate was higher in all histologic subgroups after therapy than before.

Normal adrenal asymmetry: explanation and interpretation.

Although adrenal imaging with 19-iodocholesterol provided much useful diagnostic information, spatial resolution was less than ideal. With the greater target-to-background ratios afforded by NP-59, differences between the right and left adrenal glands--in terms of position, configuration, and depth-related activity--can now be defined. Analysis of the scintigrams of 21 individuals with no evidence of adrenal disease has allowed us to characterize the normal degree of adrenal asymmetry. Appreciation of this asymmetry is necessary if the potential for greater diagnostic accuracy afforded by NP-59 is to be realized.

Quantitative hepatic arterial perfusion scintigraphy and starch microspheres in cancer chemotherapy.

Hepatic arterial infusion chemotherapy results in a higher concentration of drug delivered to the tumor with less systemic exposure than is possible with intravenous therapy. However, extrahepatic blood flow and/or shunting to the lung can impose a limitation. This study describes a quantitative method for calculating the extrahepatic component and monitoring its changes due to a new adjunctive therapy, degradable starch microspheres (DSM). DSM temporarily occlude the hepatic arterial circulation, thereby increasing the uptake of therapeutic drugs. Twenty patients with metastatic liver cancer underwent hepatic arterial perfusion scintigraphy (HAPS) using Tc-99m MAA to determine blood-flow distribution and to quantitate extrahepatic uptake. The percent shunt index (PSI) was determined at baseline and after each incremental dose of DSM. The baseline PSI ranged from 6-26% (mean 12.3 +/- 5.8 s.d.) and changed progressively after each injection of DSM/Tc-MAA suspension. The patterns of change in shunting are described. Quantitative HAPS provides a means of measuring the extrahepatic component, warns of potential side effects, and helps guide chemotherapeutic decisions.

Definition of hepatic tumor microcirculation by single photon emission computerized tomography (SPECT).

Single photon emission computerized tomography coupled with Tc-99m MAA hepatic-arterial perfusion scintigraphy has been used to examine the density of the functional microcirculation of hepatic tumors relative to normal liver in 24 patients. In both colorectal and carcinoid tumors we have demonstrated an average three-fold greater arteriolar-capillary density in areas of tumor proliferation. The depth of the evoked tumor hypervascularity was found to extend about 4 cm. Tumors greater than 8-9 cm in diameter were uniformly found to have a central hypovascular core. These observations are of importance in the design of selective strategies utilizing therapeutic microspheres directed against the hypervascular proliferating regions of human tumors.

Coded-aperture imaging of the heart.

Coded-aperture imaging of the heart combines the advantages of tomography with good sensitivity, high resolution, and accurate size scaling. Since the images are multiplexed, the method may be adapted to small, portable cameras for bed-side use without sacrificing image resolution. A new coded aperture designed especially for cardiac imaging has been constructed and tested. This aperture incorporates significant improvements over previous designs. Longitudinal tomograms are calculated at 1-cm intervals using a modified ART algorithm. Experimental lateral resulution at 140 keV with a portable scintillation camera is 3.8 mm FWHM at 4 cm, and 7.8 mm FWHM at 12 cm. Dpth resolution determined from a sloping line source is 1.1 cm FWHM at 4 cm, and 2.9 cm at 12 cm. The calculated point-source sensitivities in air at 4 cm and 12 cm, respectively, are 20 and 8 cps/microCi. Images of good diagnostic quality have been obtained in phantoms and in a dog model of acute myocardial infarction, using thallium-201, technetium-99m pyrophosphate, and gated ventricular blood-pool imaging with Tc-labeled red blood cells. Preliminary studies in humans confirm the good results in animals.

Efficacy of hepatobiliary imaging of acute abdominal pain: concise communication.

To assess prospectively the usefullness of hepatobiliary imaging in acute abdominal pain (72 hr or less), 36 patients were scintigraphed after intravenous injection of 5 mCi of Tc-99m p-isopropyl-iminodiacetic acid (PIPIDA). Before the procedure, the referring physician completed Part I of a questionnaire indicating his differential diagnosis, diagnostic confidence (expressed as a percentage), and therapeutic plan. Immediately after the test, the same physician, with knowledge of the results, completed Part II of the questionnaire indicating again his differential diagnosis, diagnostic confidence, and therapeutic plan. The impact of the imaging on the physician's diagnositic confidence was expressed as a log-likelihood-ratio (LLR). The mean LLR for this series was 1.48 +/- 0.93, with 33 of 36 (92%) patients demonstrating a LLR greater than 0.0. In 26 of 33 patients, a LLR greater than 1.0 was achieved; and in 11 of 36 patients, a change in the physician's therapeutic plan occurred, reflecting the considerable impact of hepatobiliary imaging on the decision-making process.

Segmental wall-motion analysis in the right anterior oblique projection: comparison of exercise equilibrium radionuclide ventriculography and exercise contrast ventriculography.

Thirty-nine patients with known or suspected coronary artery disease were studied at rest and during supine bicycle exercise with radionuclide and contrast left ventriculography. Analysis of regional wall motion was made by visual evaluation of the five standard 30 degrees right anterior oblique (RAO) wall segments in the contrast images and the corresponding 10 degrees RAO radionuclide segments. The radionuclide studies were evaluated independently by three observers using a five-point grading system. The interobserver wall-motion grading agreed completely in more than 80% of segments at rest and exercise, and agreed within one wall-motion grade in more than 95% of segments. The comparison of wall-motion grades between radionuclide and contrast ventriculograms showed complete agreement in 86% of segments at rest and in 78% during exercise, and agreement within one wall-motion grade in 97% of rest and 96% of exercise segments. Visual evaluation of 10 degrees RAO rest and exercise radionuclide ventriculograms compares favorably with rest and exercise 30 degrees RAO contrast ventriculograms and demonstrates satisfactory interobserver agreement.