ROC study and SUV threshold using quantitative multi-modal SPECT for bone imaging.

BACKGROUND: We investigated the clinical performance of a quantitative multi-modal SPECT/CT reconstruction platform for yielding radioactivity concentrations of bone imaging with 99mTc-methylene diphosphonate (MDP) or 99mTc-dicarboxypropane diphosphonate (DPD). The novel reconstruction incorporates CT-derived tissue information while preserving the delineation of tissue boundaries. We assessed image-based reader concordance and confidence, and determined lesion classification and SUV thresholds from ROC analysis. METHODS: Seventy-two cancer patients were scanned at three US and two German clinical sites, each contributing two experienced board-certified nuclear medicine physicians as readers. We compared four variants of the reconstructed data resulting from the Flash3D (F3D) and the xSPECT Bone™ (xB) iterative reconstruction methods and presented images to the readers with and without a fused CT, resulting in four combinations. We used an all-or-none approach for inclusion, compiling results only when a reader completed all reads in a subset. After the final read, we conducted a "surrogate truth" reading, presenting all data to each reader. For any remaining discordant lesions, we conducted a consensus read. We next undertook ROC analysis to determine SUV thresholds for differentiating benign and lesional uptake. RESULTS: On a five-point rating scale of image quality, xB was deemed better by almost two points in resolution and one point better in overall acceptance compared to F3D. The absolute agreement of the rendered decision between the nine readers was significantly higher with CT information either inside the reconstruction (xB, xBCT) or simply through image fusion (F3DCT): 0.70 (xBCT), 0.67 (F3DCT), 0.64 (xB), and 0.46 (F3D). The confidence level to characterize the lesion was significantly higher (3.03x w/o CT, 1.32x w/CT) for xB than for F3D. There was high correlation between xB and F3D scores for lesion detection and classification, but lesion detection confidence was 41% higher w/o CT, and 21% higher w/CT for xB compared to F3D. Without CT, xB had 6.6% higher sensitivity, 7.1% higher specificity, and 6.9% greater AUC compared to F3D, and similarly with CT-fusion. The overall SUV-criterion (SUVc) of xB (12) exceeded that for xSPECT Quant™ (xQ; 9), an approach not using the tissue delineation of xB. SUV critical numbers depended on lesion volume and location. For non-joint lesions > 6 ml, the AUC for xQ and xB was 94%, with SUVc > 9.28 (xQ) or > 9.68 (xB); for non-joint lesions ≤ 6 ml, AUCs were 81% (xQ) and 88% (xB), and SUVc > 8.2 (xQ) or > 9.1 (xB). For joint lesions, the AUC was 80% (xQ) and 83% (xB), with SUVc > 8.61 (xQ) or > 13.4 (xB). CONCLUSION: The incorporation of high-resolution CT-based tissue delineation in SPECT reconstruction (xSPECT Bone) provides better resolution and detects smaller lesions (6 ml), and the CT component facilitates lesion characterization. Our approach increases confidence, concordance, and accuracy for readers with a wide range of experience. The xB method retained high reading accuracy, despite the unfamiliar image presentation, having greatest impact for smaller lesions, and better localization of foci relative to bone anatomy. The quantitative assessment yielded an SUV-threshold for sensitively distinguishing benign and malignant lesions. Ongoing efforts shall establish clinically usable protocols and SUV thresholds for decision-making based on quantitative SPECT.

Technetium-99m-MAG3 renal studies in spinal cord injury patients: normal range, reproducibility, and change as a function of duration and level of injury.

UNLABELLED: The normal range, reproducibility, and change as a function of duration and level of injury for Tc-99m-MAG3 renal studies were quantitated in spinal cord injury (SCI) patients. METHODS: Five SCI patients without evidence of renal disease in each of four groups: less than 2 months, 2-12 months, 1-2 years, and greater than 2 years from time of injury, were each studied twice. There were at least two patients with paraplegia and two with tetraplegia in each group. Renal clearance (camera based method), percent function in each kidney, time of peak renal parenchymal activity, and half time of parenchymal activity following the peak were evaluated. The peak and half times were determined with regions of interest (ROIs) over the entire kidney and over just the cortex. All results were compared to normal ranges previously established in normal subjects of the same age range using the same methodology. RESULTS: Renal clearance in the less than 2 month SCI patients was not significantly different from normal subjects in either paraplegic or in tetraplegic individuals. However, clearance in tetraplegics was increased by 28.5% at 2-12 month, increased by 50.6% at 1-2 years, and decreased by 25.9% at greater than 2 years compared to normal subjects (all P < 0.02). Clearance in those with paraplegia showed a similar, but less marked, trend (P = NS). The time of peak parenchymal activity when measured with cortical ROIs did not vary among patient groups or level of injury, but was increased compared to normal subjects (P < 0.05). The percent function in each kidney and half time following the peak were symmetrical, did not differ among patient groups or with level of injury, and did not differ from normal subjects. The parenchymal peak time was significantly shorter with cortical rather than renal ROIs in all patient groups (P < 0.05). In serial studies in the same patient the percent standard deviation in total renal clearance was less than between single studies in different patients, but the decrease was significant for only the right kidney (P < 0.03), and the decrease was not as great as in normal subjects. In addition, the percent standard deviation for percent function in each kidney was significantly less than the percent standard deviations in single studies (P < 0.02). There were no significant differences between intra- and interpatient studies for any other parameter. CONCLUSION: We conclude that: (1) renal clearance measured with Tc-99m-MAG3 in tetraplegic patients increases significantly during the first 2 years following injury and decreases significantly thereafter; there is a similar, but much less marked, trend in paraplegics, (2) parenchymal peak times with cortical ROIs occur later for SCI patients than for normal subjects, and (3) there is more intrapatient variation in total renal clearance and percent renal clearance on a side in SCI patients than in normal subjects suggesting that it may be harder to study SCI patients reproducibly. These findings should be taken into account when performing and interpreting Tc-99m-MAG3 renal studies in SCI patients.

Ventilation-perfusion scintigraphy in the PIOPED study. Part I. Data collection and tabulation.

The Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study of more than 700 patients is the largest existing study of the accuracy of lung scintigraphy in the diagnosis of acute pulmonary embolism. Perfusion scans were obtained in all patients and ventilation scans in almost all, using standardized techniques. Chest radiographs were obtained in all patients within 12 hr of the lung scan. Most patients underwent pulmonary arteriography. The images were interpreted according to a set of interpretive criteria which remained constant throughout the trial. A standardized, detailed description of each image set was derived by consensus of teams of two readers blinded to clinical and arteriographic findings. This communication reports the methods used to describe and categorize the ventilation-perfusion scintigrams obtained in patients who were enrolled in the PIOPED study. Scintigraphic technique is reviewed briefly, probability assessment is described and the scan description is reviewed in detail. The form used to describe the findings on ventilation-perfusion scans is reproduced. Use of this standardized description permits retrospective evaluation of the PIOPED interpretive criteria. In addition, it represents a rigorous approach to scan analysis which could facilitate application of formal interpretive schemes and enhance the reproducibility of lung scan interpretations in the clinical setting.

Ventilation-perfusion scintigraphy in the PIOPED study. Part II. Evaluation of the scintigraphic criteria and interpretations.

This article presents an evaluation of the criteria used for categorical interpretation of the ventilation-perfusion (V/Q) scans performed in the PIOPED study. In addition, the correlation of percent probability estimates with the actual frequency of pulmonary embolism (PE) is presented. Cases which met the PIOPED criteria for various diagnostic categories were selected by computerized search of the detailed scan descriptions that had been done as part of the study. The process by which the scans were described was detailed in Part I of this report. Most of the criteria appropriately categorized V/Q scans which satisfied them. However, we recommend that three criteria should be reconsidered: 1. A single moderate perfusion defect is appropriately categorized as intermediate, rather than as low probability. 2. Extensive matched V/Q abnormalities are appropriate for low probability, provided that the chest radiograph is clear. On the other hand, single-matched defects may be better categorized as intermediate probability. Although due to the small number of cases with this finding, no definite, statistically founded recommendation can be made. 3. Two segmental mismatches may not be the optimum threshold for high probability, and in some cases should be considered for intermediate probability. However, due to the small number of cases with this finding, no definite, statistically founded recommendation can be made. We suggest that the revised criteria resulting from these adjustments should now be used for the interpretation of V/Q scans.

Eigenimage filtering in MR imaging: an application in the abnormal chest wall.

A postprocessing linear filter was applied to spin-echo images on 10 patients with known or suspected chest wall invasion due to bronchogenic carcinoma. This technique known as eigenimage filtering allows selective feature extraction of suspected abnormalities from conventional MR images. The final result is an image with marked increased contrast range through enhancement of a desired process (tumor) with suppression of an interfering process (e.g., normal surrounding tissue). This preliminary work demonstrates the ease with which the technique may be implemented, the contrast enhancement obtained between the desired and the interfering feature in the final eigenimage, and its ability to correct for partial volume averaging effects. Also demonstrated are artifacts that can interfere with the interpretation of the eigenimage and a method for minimizing these artifacts in the final eigenimage.

Primary tumors of the foot: MR imaging.

The findings at magnetic resonance (MR) imaging of eight patients with primary tumors of the foot were compared with those at gross pathologic examination. In all cases, there was excellent correlation between the two studies. When compared with computed tomography (CT), MR imaging was superior in defining the presence and extent of local disease. While the appearances of various foot neoplasms are nonspecific, the ease of multiplanar imaging, the superior contrast resolution, and the sensitivity to marrow abnormalities are major advantages of MR imaging over CT in staging foot neoplasms. These advantages are crucial when foot-sparing curative resection of a malignancy is contemplated. The combination of plain radiography and MR imaging may be all that is necessary for optimal preoperative detection and local staging of tumors of the foot.

The role of indium-111 white blood cells in inflammatory bowel disease.

Inflammatory bowel disease in patients may be difficult to diagnose because of the complex problems associated with this disease. Radionuclides are able to provide a rapid and effective method of imaging the bowel in patients with active inflammatory bowel disease. In the past, clinical work-ups have included barium x-ray studies and endoscopy. Scarring and fistula formation have made it difficult to determine between the active disease and abscesses that may occur. Gallium-67 (67Ga) has been very useful in imaging patients with inflammatory bowel disease, but the multiple-day imaging procedure has been a limitation for the clinicians when achieving a diagnosis. Recent results with Indium-111 (111In)--labeled WBCs have provided excellent correlation between clinical symptoms and colonoscopy findings in patients with inflammatory bowel disease. This technique has also allowed the differentiation between reoccurring inflammatory bowel disease and abscesses that accompany the disease within a 24-hour time period. The use of intravenous (IV) glucagon has increased the clarity of the images in the small bowel. Technetium 99m (99mTc) diethylenetriaminepentaacetic acid (DTPA) has been used in patients with inflammatory bowel disease demonstrating promising results. Investigators feel labelling 99mTc with WBCs will be improved, therefore yielding a greater efficiency, which will have a major impact on imaging patients with inflammatory bowel disease. Imaging patients with inflammatory bowel disease using radionuclides has yielded promising results. This is a significant advancement over barium radiography and endoscopy exams.

Redistribution of visceral blood volume in upright exercise in healthy volunteers.

Exercise induced changes in the blood volume of visceral organs (cardiopulmonary and liver, spleen, and kidneys) were determined by scintillation camera imaging of the distribution of technetium-99m-labeled red blood cells in the thorax and abdomen of ten healthy adult volunteers. Graded upright bicycle exercise was performed to the point of exhaustion with the volunteer positioned with his/her back to the scintillation camera and data recording was synchronized to the pedal cycle to minimize patient motion artifacts within the data. The first image from each level of exercise was analyzed by placing regions of interest over the spleen, liver, kidneys, and right lung. The counts in each organ were expressed as a percent of activity at zero workload. Analysis of data using Hotelling's t-squared analysis to see if overall differences existed between the last four measurements (up to the time of exhaustion) regarding percent change from baseline for spleen, kidney, liver, and right lung were made. The splanchnic bed had a significant decrease in blood volume. The spleen decreased 39%, while the liver decreased 14%. For the kidney and liver, no significant differences were achieved (p greater than 0.24, p less than 0.15, respectively). The lung increased its blood volume to 128% of control, significant with p less than 0.02. This data demonstrates that in healthy volunteers there is normal redistribution of blood volume during maximal exercise with a significant reduction in blood volume of the spleen as well as a significant rise in blood volume within the lungs.

Meniscal abnormalities of the knee: 3DFT fast-scan GRASS MR imaging.

The ability to use fast-scan techniques to obtain MR images without sacrificing diagnostic accuracy is a desirable goal in MR imaging. We describe a series of patients in whom fast-scan MR imaging was found to be equal to conventional spin-echo imaging in the detection and characterization of meniscal abnormalities. Thirty-five patients with suspected meniscal tears were studied with fast-scan imaging (3DFT-GRASS), and the results were compared with those of conventional spin-echo imaging. Three-millimeter contiguous sections through the entire knee were obtained in 5 min by using the 3DFT-GRASS technique. 3DFT-GRASS and spin-echo images agreed in all cases regarding the presence or absence of an abnormality and its degree of severity. We conclude that fast-scan 3DFT-GRASS MR imaging is useful when screening the knee for the presence of meniscal abnormalities.

MR imaging strategies in primary and metastatic malignancy.

This article gives the rationale of the indications for the use of MRI in the evaluation of primary and metastatic malignancies of the neck, chest, abdomen, male and female pelvis, and musculoskeletal system. The imaging protocols for each of these areas is also included.

Treatment of massive acute pulmonary embolism. The use of low doses of intrapulmonary arterial streptokinase combined with full doses of systemic heparin.

The efficacy of low-dose, locally administered streptokinase (SK) combined with full therapeutic systemic doses of heparin was investigated. Seven patients with angiographically proven massive acute pulmonary embolism were treated. Streptokinase, 10,000-20,000 units/hour, was administered directly into the left or right pulmonary artery for 9 to 24 hours. Heparin was administered concurrently. The number of unperfused segments of the infused lung shown on the lung scan decreased from 5 +/- 2 to 2 +/- 1 after 12-24 hours (p less than .01). No change was shown in the contralateral lung. The angiographic index of severity score in the infused lung decreased from 16 +/- 1 to 9 +/- 4 (p less than .01). The partial pressure of oxygen in arterial blood improved within four hours. In spite of the low doses of streptokinase, however, two major bleeding episodes occurred that required blood transfusion. In conclusion, low dose intrapulmonary streptokinase, combined with intravenous heparin, may provide a therapeutic option in patients with life-threatening massive acute pulmonary embolism in whom full dose lytic therapy may be hazardous, although even low dose lytic therapy was associated with risk.

The appended curve technique for deconvolutional analysis--method and validation.

Deconvolutional analysis (DCA) is useful in correction of organ time activity curves (response function) for variations in blood activity (input function). Despite enthusiastic reports of applications of DCA in renal and cardiac scintigraphy, routine use has awaited an easily implemented algorithm which is insensitive to statistical noise. The matrix method suffers from the propagation of errors in early data points through the entire curve. Curve fitting or constraint methods require prior knowledge of the expected form of the results. DCA by Fourier transforms (FT) is less influenced by single data points but often suffers from high frequency artifacts which result from the abrupt termination of data acquisition at a nonzero value. To reduce this artifact, we extend the input (i) and response curves to three to five times the initial period of data acquisition (P) by appending a smooth low frequency curve with a gradual taper to zero. Satisfactory results have been obtained using a half cosine curve of length 2-3P. The FTs of the input and response I and R, are computed and R/I determined. The inverse FT is performed and the curve segment corresponding to the initial period of acquisition (P) is retained. We have validated this technique in a dog model by comparing the mean renal transit times of 131I-iodohippuran by direct renal artery injection to that calculated by deconvolution of an intravenous injection. The correlation was excellent (r = 0.97, P less than 0.005). The extension of the data curves by appending a low frequency "tail" before DCA reduces the data termination artifact. This method is rapid, simple, and easily implemented on a microcomputer.(ABSTRACT TRUNCATED AT 250 WORDS)

Eigenimage filtering in MR imaging.

This article presents the technical aspects of a linear filter, referred to as eigenimage filtering, and its applications in magnetic resonance (MR) imaging. The technique is used to obtain a single composite image depicting a particular feature of interest while suppressing one or more interfering features. The appropriate weighting components to be used in the linear filter are determined on the criterion that the desired feature is enhanced while the interfering features are suppressed. The criterion is expressed mathematically as a ratio. By applying Rayleigh's principle, the ratio is maximized by finding the eigenvector associated with the maximum eigenvalue of the corresponding generalized eigenvalue problem. The appropriate weighting factors for the linear filter are the elements of the eigenvector which maximize the ratio. The utilization of the technique is demonstrated in its application to a simulated MR image sequence as well as to acquired MR image sequences of a normal and an abnormal brain.

Magnetic Resonance Imaging for Meniscal Tears of the Knee.

In brief: Magnetic resonance imaging (MRI). has become a standard diagnostic technique in many medical facilities for evaluating the menisci of the knee. MRI provides superior soft-tissue contrast with high resolution and takes little time (typically less than 30 minutes). It does not require intra-articular contrast media and is not limited to surface abnormalities, as are arthrography and arthroscopy. Unlike MRI, both arthrography and arthroscopy cause disturbances to the external capsule of the knee, with associated patient discomfort and limited physical activity for some time following the procedure. The author discusses the advantages of MRI and presents a case report in which it was used to make the diagnosis and determine the appropriate treatment modality.

Chest-wall invasion by carcinoma of the lung: detection by MR imaging.

Nineteen patients with bronchogenic carcinoma were studied by MR imaging to determine the presence of chest-wall invasion. All studies were carried out at 1.5 T, and the results were correlated with chest radiographs or CT scans. All MR studies were interpreted before surgery (13 cases) and without knowledge of the results of other radiologic studies. MR findings indicative of chest-wall invasion included a high-signal focus within the chest wall and/or chest-wall thickening with increased signal on spin-echo (SE) images having a repetition time of 2500 msec and an echo time of 50-100 msec (SE 2500/50-100). In one case, noncontour-deforming high-signal intensity within chest-wall musculature (but no other abnormality) was demonstrated on SE 2500/50-100 images. Coronal or sagittal imaging facilitated identification of tumor contiguity with extrathoracic structures in apical lesions. Contrast differences between normal and invaded chest wall on T2-weighted images were the most helpful in assessing chest-wall involvement. These preliminary observations indicate that MR imaging is useful in the evaluation of chest-wall invasion by carcinoma of the lung.

Hemodynamic, pharmacokinetic and clinical response to CI-930 in congestive heart failure due to ischemic or dilated cardiomyopathy.

CI-930, a new type III phosphodiesterase inhibitor, was evaluated for treatment of refractory congestive heart failure. The hemodynamic, pharmacokinetic and clinical response to the drug was determined in 10 patients. At the peak plasma concentration after intravenous CI-930, cardiac index increased from 2.0 to 2.7 liters/min/m2 (p less than 0.002), pulmonary artery wedge pressure decreased from 26 to 17 mm Hg (p less than 0.001) and systemic vascular resistance decreased from 1,999 to 1,471 dynes cm-5 (p less than 0.05). Heart rate and blood pressure did not change significantly. Similar changes were observed with oral CI-930. Peak CI-930 plasma concentration occurred 1.2 +/- 0.8 hours after oral administration. Beneficial hemodynamic effects were sustained 12 to 18 hours after the oral dose. The sustained hemodynamic effects observed after oral administration appear to be related to an active metabolite of CI-930 that has prolonged duration of action and slow washout. The drug was well tolerated and has potential for treatment of congestive heart failure.