Optimization of radioimmunotherapy interactions with hyperthermia

The efficacy of radioimmunotherapy (RIT) employing radiolabelled monoclonal antibodies (MAb) is currently limited in most solid tumours. The combination of local hyperthermia (HT) with RIT has the potential to enhance tumour targeting of MAb; moreover, this approach may add an antitumour effect to radioresistant hypoxic and S-phase cells and may inhibit the cells from repairing sublethal damage or potentially lethal damage caused by ionizing radiation. There are distinct types of protocols in this combination. Hyperthermic temperature and timing relative to RIT administration appear to affect the efficacy of the combination therapy. Responses to heating at any particular condition are not always the same among different tumour types. There are many papers describing influence of HT on the biodistribution of radiolabelled MAb, but only limited information is currently available on 'therapeutic' outcomes regarding the dependency of combination protocols. A previous study suggested that the best therapeutic improvement would be achieved when HT was combined immediately after the administration of MAb, which significantly increases the radiation absorbed dose to tumours and produces a uniform intratumoural dose distribution. Further therapeutic investigation should be required to reach the optimal protocol of combining these two modalities.

Hypoxia as a factor for 67Ga accumulation in tumour cells

Recent reports have demonstrated that hypoxia induces the up-regulation of transferrin receptor expression in tumour cells. Tumour cells take up 67Ga in the form of a 67Ga-transferrin complex via transferrin receptors. As a result, we attempted to determine the influence of hypoxic conditions on 67Ga uptake in tumour cells. B16 melanoma cells and LS180 colon cancer cells were incubated in 95% air/5% CO2 or 95% N2/5% CO2 for 1 h at 37 degrees C. Cellular uptake of 67Ga citrate was subsequently determined at 20, 40, 60 and 90 min. Uptake of the 67Ga-transferrin complex pre-chelated in vitro was similarly assessed. The effect of hypoxia on 67Ga binding to serum proteins was also investigated. Both B16 and LS180 cells displayed increased cellular uptake of 67Ga citrate in N2 gas in comparison to that in air (P < 0.0001). Hypoxia more prominently influenced cellular uptake of Ga-transferrin relative to that of 67Ga citrate (P < 0.0001). Hypoxia did not affect the percentages of 67Ga radioactivity bound to protein in medium supplemented with fetal calf serum, indicating that the results were not caused by the alteration of 67Ga-transferrin formation. These findings suggest the role of tissue hypoxia with respect to accumulation of 67Ga in tumours, which is likely mediated by transferrin receptors.

Estimation of fractional liver uptake and blood retention of 99mTc-DTPA-galactosyl human serum albumin: an application of a simple graphical method to dynamic SPECT

The objective of this study was to investigate clinical utility of a graphical method for estimating liver uptake and blood retention of 99mTc-DTPA-galactosyl human serum albumin (99mTc-GSA; DTPA is diethylenetriaminepentaacetic acid) using dynamic single photon emission computed tomography (SPECT) data. When considering the kinetics of 99mTc-GSA, if it is assumed that (1) 99mTc-GSA distributes only between blood and liver, and (2) no metabolism of 99mTc-GSA occurs during the observation period, a plot of liver counts versus cardiac blood pool counts should, theoretically, be a straight line. From the slope and y intercept of a regression line, coefficients for converting count based liver and blood pool data to the per cent injected dose (%ID) can be calculated. The applicability of this method was tested on dynamic SPECT data from 30 patients with liver dysfunction. To validate this method, plasma concentrations (%ID/ml plasma) at 6, 15 and 30 min after the injection were estimated by this method and compared with the measured ones. To investigate the clinical significance of the per cent liver uptake, the value obtained by this method was compared with the results of conventional liver function tests, including serum albumin, the hepaplastin test, prothrombin time and indocyanine green clearance. In every data set, a plot of liver counts to cardiac blood pool counts was fitted well by a straight line (P<0.00001). Estimated plasma concentrations by this method showed good correlation with the measured ones at 6, 15 and 30 min after the injection (r=0.748, 0.838, 0.875, respectively; P<0.0001). The liver uptake determined by this method showed good correlation with the results of conventional hepatic function tests (P<0.002). The graphical method could provide an accurate estimate of %ID of 99mTc-GSA in blood without the need for blood sampling. The liver uptake determined by this method could be a simple but useful quantitative indicator of hepatic function.

Evaluation of left and right ventricular functional parameters with automatic edge detection program of ECG gated blood SPET

An analysis program for ECG gated, blood pool, single photon emission tomography (SPET GBP) is available. This program permits the automatic evaluation of left and right ventricular function, but its reliability has not been thoroughly assessed. The objective of this investigation was to examine the reliability of the parameters derived from SPET GBP. Fifty-three patients who had undergone both SPET GBP and planar, ECG gated, blood pool scintigraphy (planar GBP) were enrolled in the study. Planar GBP was performed with a single-headed gamma camera. From a left anterior oblique projection, data were acquired at 24 frames/cardiac cycle with ECG gating during the equilibrium state. SPET GBP was carried out utilizing a triple-headed gamma camera, with 60 projection views over 360 degrees, with 60 s per view, in 16 frames/cardiac cycle. Left ventricular ejection fraction (LVEF) and right ventricular ejection fraction (RVEF) were calculated by using the analysis program. The reproducibility of these values and the correlation between SPET and planar GBP were assessed. To evaluate the effect of cut-off frequencies of a Butterworth filter, six different cut-off frequencies (order=8, 0.3-1.0 Nyquist) were tested with data obtained from 12 patients. The reproducibility of LVEF by SPET GBP was satisfactory (intra-observer, r=0.95; inter-observer, r=0.96), whereas reproducibility of RVEF by SPET GBP was fair (intra-observer, r=0.83; inter-observer, r=0.83). LVEF with SPET GBP was well correlated (y=1.1x+6.62, r=0.85, P<0.01) with LVEF readings of planar GBP. However, LVEF with SPET GBP was overestimated (mean difference of 12) in comparison with that of planar GBP. The RVEF derived from SPET GBP showed poor correlation (y=0.52x+33, r=0.53, P<0.01) with planar GBP. No significant effect of cut-off frequencies of Butterworth filters was evident in the calculation of LVEF and RVEF (P=0.48 and 0.67) with SPET GBP. It is concluded that SPET GBP with QBS is useful for the evaluation of LVEF. However, measurement of the RVEF showed lower reproducibility compared with measurement of the LVEF.

Differentiation of soft tissue haemangioma by 201Tl scintigraphy

Radiological diagnosis of deep soft tissue is often difficult. In the present study, thallium-201 ( Tl) uptake into haemangiomas and deep malignant soft tissue tumours was investigated in order to assess its clinical utility. Tl scintigraphy was reviewed in four patients presenting with soft tissue haemangiomas. Early and delayed planar images, obtained at 15 min and 3 h following the intravenous injection of Tl (111 MBq), were examined. The Tl uptake ratio was calculated by dividing the count density of the tumour region of interest (ROI) by that of the background ROI. Results were compared with those of five cases of rhabdomyosarcoma and a single instance of angiosarcoma. All haemangioma lesions demonstrated increased Tl uptake in early images. However, Tl uptake in delayed images was markedly decreased. No significant differences were observed in the early uptake ratio between haemangiomas (1.60-2.72) and reference malignant tumours (1.48-2.45); however, the difference was significant in delayed images (range, 1.01-1.26 vs. 1.43-2.03, respectively) ( P<0.02). Deep soft tissue haemangiomas revealed Tl accumulation in early images; however, a rapid washout was observed in delayed images. This distinctive feature may facilitate the use of Tl scintigraphy in the diagnosis of haemangiomas.

Comparison of 99mTc-MIBI uptakes on planar images with those in excised rats organs

The precision with which images reflect tracer uptake in the myocardium has been studied. Additionally, the degree to which Tc methoxyisobutylisonitrile (99mTc-MIBI) in the liver gave the effect to a myocardial image has been examined. After administering Tc-MIBI to normal male rats, we compared the myocardial uptakes obtained using a gamma camera with the actual uptakes in the excised organs. Twenty-nine rats were used. Following imaging, the anterior view at 5, 10, 15, 30, 45, 60, 90 and 120 min after administration of the tracer, uptakes in the heart, lung, liver and blood were estimated with a well-type scintillation counter (WC) and represented as the percentage of the injected dose per gram of tissue (%ID/g). The regions of interest (ROIs) were placed on planar images (PI) and the uptake in each organ was estimated as the percentage of the injected dose per pixel (%ID/pixel). The ratios of PI-to-WC and heart-to-organ were also evaluated. Cardiac uptake with WC was maximum (1.581%+/-1.893%) at 10 min post-injection. On the other hand, that with PI was maximum (1.493%+/-0.598%) at 45 min post-injection, but there were significant differences between both measurements (PI/WC ratio: about 1.0 time). Pulmonary uptake with WC was the maximum at 5 min (0.808%+/-0.015%) post-injection, and decreased gradually. PI measurement showed the maximum value at 45 min (0.760%+/-0.012%). Hepatic uptake with WC was the maximum at 30 min (0.594%+/-0.254%). On the other hand, PI measurement showed the same pattern with WC, but these values were higher value than WC as the whole. PI measurement showed higher uptakes in each organ than WC measurement. It was concluded that uptakes or the heart-to-organ ratio obtained clinically with PI might not represent a value that is always accurate.

Intense 201 Tl uptake in giant-cell tumour of bone

The aim of this study was to determine the characteristics and clinical usefulness of 201Tl scintigraphy in giant-cell tumour of bone (GCT). Twenty-one patients with histopathologically proven benign GCT (22 lesions; 18 primary and four recurrent) underwent 201Tl scintigraphy. We also studied conventional osteosarcoma (10 lesions), a very common primary malignant bone tumour; and chordoma in the sacrum (four lesions), an entity requiring differential diagnosis from GCT of the sacrum. Early and delayed planar imaging was performed at 15 min (early) and 3 h (delayed) after the intravenous injection of 201Tl chloride (111 MBq). The Tl uptake ratio was calculated by dividing the count density of the tumour region of interest (ROI) by that of the background ROI. All GCT lesions showed increased Tl uptake in both early and delayed images. The mean Tl uptake ratios of primary GCT were 4.7 (range, 2.0-11.1) in the early images and 2.2 (range, 1.4-3.6) in the delayed images, and those of recurrent lesions were 5.8 (range, 2.4-11.5) in the early images and 2.7 (range, 2.0-4.3) in the delayed images. There were no significant differences between the uptake ratios in GCT and osteosarcoma, but the values of GCT tended to be higher than those of osteosarcoma, 3.1 (range, 1.7-4.4) in the early images and 1.8 (range, 1.3-2.3) in the delayed images. Chordoma did not show appreciable Tl uptake: the uptake ratio was 1.19 (range, 0.98-1.5) in the early images and 1.1 (range, 1.0-1.3) in the delayed images. In GCT, a benign lesion, Tl scintigraphy demonstrated marked uptake in both primary and recurrent lesions with no exceptions, precluding the use of Tl scintigraphy for the differential diagnosis of GCT from malignant tumours. However, the Tl scintigraphy can be used for excluding GCT when no lesional Tl uptake is observed, and diagnosing recurrent lesions on post-operative follow-up.

Prevalence of deep venous thrombosis in the lower limbs and the pelvis and pulmonary embolism in patients with positive antiphospholipid antibodies

BACKGROUND

Antiphospholipid antibodies (AA) are immunoglobulins that cross-react with phospholipid on cell membrane, and are therefore associated with a hypercoagulable state manifested by arterial/venous thromboses. We aimed to determine the prevalence of deep venous thrombosis in the lower limbs and the pelvic region (DVT) and pulmonary embolism (PE) in patients with positive AA.

METHODS

Sixty-six patients (48 female, 18 male) with positive lupus anticoagulant (LA) and/or positive anticardiolipin antibody (aCL) underwent radionuclide (RN) venography with 370 MBq of 99mTc-MAA. Pulmonary perfusion scintigraphy was performed in 58 patients. Fifteen patients had positive LA and positive aCL (LA+/aCL+), 33 patients had positive LA only (LA+/ aCL-) and 18 patients had positive aCL only (LA-/aCL+). 43 patients were diagnosed with primary antiphospholipid syndrome (APS) and 19 were diagnosed with APS associated with SLE.

RESULTS

DVT was detected in 21 of 66 patients (32%). Patients with LA+/aCL+ showed higher prevalence of DVT (53%) as compared to LA+/aCL- (27%) and LA-/aCL+ (22%). PE was found in 13 of 58 patients (22%). The prevalence of PE was higher in patients with positive aCL (33% in LA+/aCL+; 36% in LA-/aCL+) than in patients with negative aCL (10%).

CONCLUSION

Because of the high prevalence of DVT and PE in patients with AA, RN scintigraphy must be recommended in screening for these clinical troubles. These results indicate that the prevalence of DVT and PE may vary in subgroups of AA.

[Improvement of 99mTc-pyrophosphate scintigraphy in detection of acute myocardial infarction: combined with 99mTc-tetrofosmin]

BACKGROUND

201Tl and 99mTc-pyrophosphate (PYP) dual scintigraphy is daily used in the detection of acute myocardial infarction (AMI). However, 201Tl is not available on emergent situation. We proposed a new method for detection of AMI combined 99mTc-PYP with 99mTc-tetrofosmin (TF).

METHODS

99mTc-PYP (740 MBq) was administered to 25 patients with AMI, and 3.5 hours later, planar imaging (PYP planar) and SPECT were performed (PYP-SPECT). Immediately after cessation of PYP-SPECT, 99mTc-TF (370-740 MBq) was injected and 5 minutes later SPECT was performed in the same position (TF-SPECT). PYP-SPECT and TF-SPECT were reconstructed in the same geometric status to permit superimpose of PYP-SPECT and TF-SPECT images. Two experts and 2 beginners of nuclear medicine physician interpreted the images in three ways; PYP planar image only, PYP-SPECT, and PYP-SPECT with TF-SPECT.

RESULTS

PYP-SPECT combined with TF-SPECT shows 100% detectability of the AMI lesions, which is significantly higher than other two methods in both experts and beginners.

CONCLUSION

PYP-SPECT combined with TF-SPECT is a powerful method for detection of AMI.

[Quantitative evaluation of esophageal scintigraphy in systemic sclerosis]

BACKGROUND

Esophageal involvement by systemic sclerosis (SSc) is frequent. The purpose of this study was to evaluate esophageal motility disorders quantitatively.

METHODS

We investigate esophageal scintigraphy in 22 patients with SSc. Esophageal scintigraphy was obtained with swallowing physiological saline in supine position, and swallowing soup in supine and sitting positions. Data was acquired with 0.5 sec per frame for 192 frames in the anterior view. We employed a condensed image as a visual evaluation, half-life and retention rate as a quantitative evaluation, which were obtained from time-activity curves generated from regions of interest on the whole esophagus. The half-life and retention rate were compared with classification of Barnett, stages of SSc, and modified Rodnan total skin score (TSS).

RESULTS

No significant differences were seen in classification of Barnett and the stages of SSc. No significant difference was seen between swallowing water and soup in the supine position. The retention rate was significantly prolonged in the supine position than in the sitting position. The retention rate of soup study in the sitting position correlated with TSS (r = 0.61).

CONCLUSION

Esophageal scintigraphy in the sitting position is useful in evaluation of esophageal motility in SSc.

Accuracy of ventricular volume and ejection fraction measured by gated myocardial SPECT: comparison of 4 software programs

Gated myocardial perfusion SPECT has been used to calculate ejection fraction (EF) and end-diastolic volume (EDV) and has correlated well with conventional methods. However, the comparative accuracy of and correlations across various types of gated SPECT software are not well understood.

METHODS

Mathematic phantoms of cylindric-hemispheric hybrid models, ranging in volume from 34 to 266 mL, were generated. The clinical cases consisted of 30 patients who participated in a radionuclide angiography and gated blood-pool (GBP) study in addition to undergoing (99m)Tc-sestamibi gated SPECT. Four kinds of software, Quantitative Gated SPECT (QGS), the Emory Cardiac Toolbox (ECT), 4D-MSPECT, and Perfusion and Functional Analysis for Gated SPECT (pFAST) were used to compute EF and EDV, and the results were analyzed by multiple comparisons tests. Patients were classified into 4 groups (i.e., no defect, small defect, large defect, and small heart) so that factors affecting variation could be analyzed.

RESULTS

In mathematic models > or = 74 mL, volume error was within +/-15%, whereas for a small volume (34 mL), QGS and 4D-MSPECT underestimated the volume and pFAST overestimated it. The respective intra- and interobserver reproducibility of the results was good for QGS (r = 0.99 and 1.00), ECT (r = 0.98 and 0.98), and 4D-MSPECT (r = 0.98 and 0.98) and fair for pFAST (r = 0.88 and 0.85). The correlation coefficient for EF between gated SPECT and the GBP study was 0.82, 0.78, 0.69, and 0.84 for QGS, ECT, 4D-MSPECT, and pFAST, respectively. The correlation coefficient for EDV between gated SPECT and the GBP study was 0.88, 0.89, 0.85, and 0.90, respectively. Although good correlation was observed among the 4 software packages, QGS, ECT, and 4D-MSPECT overestimated EF in patients with small hearts, and pFAST overestimated the true volume in patients with large perfusion defects. Correlation coefficients among the 4 kinds of software were 0.80-0.95 for EF and 0.89-0.98 for EDV.

CONCLUSION

All 4 software programs showed good correlation between EF or EDV and the GBP study. Good correlation was observed also between each pair of quantification methods. However, because each method has unique characteristics that depend on its specific algorithm and thus behaves differently in the various patient subgroups, the methods should not be used interchangeably.

Assessment of left ventricular systolic and diastolic function based on the edge detection method with myocardial ECG-gated SPET

The aim of this study was to determine the feasibility of assessing left ventricular systolic ejection and diastolic filling by the edge detection method with ECG-gated single-photon emission tomography (G-SPET) data. Fifty-two patients who had undergone both G-SPET and gated equilibrium blood pool scintigraphy (GBP) within an interval of 2 weeks were enrolled. For G-SPET, 740 MBq of technetium-99m methoxyisobutylisonitrile (MIBI) was injected at rest, and myocardial SPET was performed 60 min later using 360 degrees acquisition and 12 frames per cardiac cycle. In each frame, left ventricular volume was determined with automatic edge detection using a quantitative gated SPET program, and the time-volume curve was fitted by Fourier transform of the first to fourth harmonics. Ejection fraction (EF, %), peak ejection rate (PER, /s), peak filling rate (PFR, /s) and mean filling rate during the first third of diastolic time (1/3FRm, /s) were calculated from the fitted curve. These parameters were also calculated by means of GBP performed with 24 frames per cardiac cycle. Correlation coefficients in respect of EF, PER, PFR and 1/3FRm between G-SPET and GBP were 0.90 (P<0.001), 0.88 (P<0.001), 0.80 (P<0.001) and 0.82 (P<0.001), respectively. The correlations were good for EF, PER and 1/3FRm. Gated SPET dV/dt parameters were slightly lower compared with GBP values owing to the limited number of frames per cardiac cycle. It is concluded that left ventricular ejection and filling rates can be calculated using G-SPET with edge detection software, and in this study these parameters were significantly correlated with those derived using GBP. Diastolic abnormality on gated SPET study should be recognised as a positive finding, and appropriate gated SPET parameters should be further investigated.

Phantom studies for estimation of defect size on cardiac (18)F SPECT and PET: implications for myocardial viability assessment

SPECT with (18)F-FDG has emerged as an alternative to dedicated PET for the assessment of myocardial viability. However, whether FDG SPECT can reliably quantify the extent of viable and scarred myocardium is uncertain. The aim of this study was to investigate whether SPECT with an (18)F-labeled agent would provide information on defect size similar to that provided by dedicated PET.

METHODS

Imaging was performed using an elliptic cylinder chest phantom with simulated bone, lung, mediastinum, liver, and heart. (18)F was administered into the myocardium, mediastinum, right and left ventricular cavities, and liver. Plastic inserts (n = 11) ranging in size from 2% to 60% of the myocardium were used to simulate transmural myocardial infarctions. The chest phantom was imaged with a dedicated PET camera and with a double-head SPECT camera equipped with ultra-high-energy collimators. Both SPECT and PET data were analyzed using a semiquantitative polar map approach. Defects were quantified using various cutoff thresholds ranging from 30% to 80% of peak activity and were expressed as a percentage of the left ventricular myocardium. Defect size as measured by SPECT or PET was compared with true defect size.

RESULTS

The measured SPECT defect size was highly variable depending on the cutoff used, whereas PET defect size was relatively constant over the range of cutoffs tested. The mean absolute difference between measured and true defect sizes was minimal at a cutoff of 50% of peak activity for both SPECT (3.3% +/- 3.3%) and PET (2.7% +/- 2.5%). For this threshold, both SPECT and PET measurements showed an excellent correlation with true defect size (r = 0.98 for SPECT and 0.99 for PET). The correlation between SPECT and PET measurements was also excellent (r = 0.99; P < 0.01).

CONCLUSION

If an appropriate threshold is used to define a defect, SPECT with an (18)F-labeled agent can accurately measure defect size similarly to the manner of PET.

(99m)Tc-sestamibi retention characteristics during pharmacologic hyperemia in human myocardium: comparison with coronary flow reserve measured by Doppler flowire

The aim of the study was to investigate the increase in myocardial (99m)Tc-methoxyisobutylisonitrile (sestamibi) retention in humans during pharmacologic vasodilation.

METHODS

For calculation of the increase in (99m)Tc-sestamibi retention during hyperemia, baseline and adenosine triphosphate (ATP)-induced hyperemic stress sestamibi studies were performed using a same-day rest-stress protocol. On the injection of sestamibi, left ventricular dynamic data were obtained for 90 s. The increase in sestamibi retention from baseline to hyperemia was calculated by the formula [abstract: see text] where Cm(h)(t) and Cm(b)(t) are myocardial counts on the tomographic image, and Cb(b)(tau) and Cb(h)(tau) are the left ventricular blood-pool counts during the first transit of sestamibi at baseline and during hyperemia, respectively. Coronary flow increase during intravenous ATP stress was measured using intracoronary Doppler flow guide wire and compared with the scintigraphic results of 28 measurements in 22 patients.

RESULTS

Sestamibi retention increased as coronary flow velocity increased but plateaued at >2.5-3 times baseline flow velocity. The relationship between the increase in sestamibi retention (Y) and the increase in flow (X) is expressed as follows: Y = 0.44 + 0.60X - 0.068X(2) (r = 0.82).

CONCLUSION

In humans, the increase in (99m)Tc-sestamibi myocardial retention underestimates coronary flow reserve, particularly at high flow rates. Knowledge of these tracer retention characteristics will contribute to a more comprehensive understanding of the manner and interpretation of stress sestamibi imaging.

Thymic lesions in patients with myasthenia gravis: characterization with thallium 201 scintigraphy

PURPOSE

To assess thallium 201 ((201)Tl) single photon emission computed tomography (SPECT) for evaluation of thymic lesions associated with myasthenia gravis (MG), including lymphoid follicular hyperplasia (LFH) and thymoma.

MATERIALS AND METHODS

(201)Tl SPECT and computed tomography (CT) were performed preoperatively in 46 patients with MG who had undergone thymectomy. SPECT was conducted 15 (early image) and 180 (delayed image) minutes after (201)Tl injection. Results were visually assessed, and (201)Tl uptake ratios (thymic lesion count density/lung count density) were measured for quantitative analysis. Uptake was analyzed among the normal thymus, LFH, and thymoma patient groups.

RESULTS

Histopathologic results indicated a normal thymus, LFH, and thymoma in 19, 16, and 11 patients, respectively. Mean uptake ratios in the normal thymus, LFH, and thymoma were 0.96 (95% CI: 0.90, 1.03), 1.14 (95% CI: 1.04, 1.25), and 1.87 (95% CI: 1.56, 2.25), respectively, on early images and 1.09 (95% CI: 1.00, 1.18), 1.65 (95% CI: 1.48, 1.85), and 2.03 (95% CI: 1.65, 2.50), respectively, on delayed images. Thymoma showed more intense (201)Tl accumulation than did the normal thymus (P <.001) and LFH (P <.001) on early images. Both thymoma (P <.001) and LFH (P <.001) displayed more intense uptake than did the normal thymus on delayed images.

CONCLUSION

(201)Tl SPECT can enable differentiation between normal thymus, LFH, and thymoma in patients with MG.

Anti-angiogenic therapy and radioimmunotherapy in colon cancer xenografts

Angiogenesis is critical to the growth and metastatic process of malignant tumors. An endogenous estrogen metabolite, 2-methoxyestradiol (2-ME), displays anti-angiogenic and anti-tumorigenic effects. The purpose of this investigation was to determine whether exogenously administered 2-ME would enhance the efficacy of radioimmunotherapy (RIT). Experimental RIT with 4.63 MBq of 131I-A7, an IgG1 anti-colorectal monoclonal antibody, was conducted in mice xenografted with LS 180 human colon cancer cells. 2-ME suspended in 0.5% carboxymethylcellulose was administered daily at a dose of 75 mg/kg per day. 2-ME administration suppressed tumor growth and improved the efficacy of RIT in comparison to RIT alone. Tumor volumes on day 13, expressed as a ratio relative to the initial volume, were 12.7 +/- 2.95 in the nontreated control, 4.73 +/- 0.89 with 2-ME, 3.05 +/- 0.37 with RIT and 0.97 +/- 0.20 with RIT+2-ME. Immunohistochemistry of tumor sections stained with an antibody against factor VIII demonstrated a decrease in microvessel number within tumors treated with 2-ME (7.9 +/- 0.8/200x field) as compared with that in control tumors (29.9 +/- 2.5). Cell proliferation assay at increasing concentrations of 2-ME showed direct cytotoxicity of 2-ME in vitro at 5 microM and greater. In conclusion, 2-ME enhanced the efficacy of RIT with 131I-A7 via inhibition of angiogenesis within the xenografts. The direct cytotoxicity of 2-ME appears to have contributed to this improvement. Anti-angiogenic therapy may prolong the dormancy of microscopic metastases while RIT may exterminate this population of cells. Therefore, the combined treatment may improve the therapeutic outcome of patients with disseminated cancer.

A case of double cancers with myocardial metastasis mimicking acute myocardial infarction both on an electrocardiogram and on Tc-99m-MIBI myocardial SPECT

We report a rare case of double cancers with myocardial metastasis presenting acute myocardial infarction (AMI)-like findings both on an electrocardiogram (ECG) and on Tc-99m-MIBI myocardial SPECT. The ECG showed abnormal Q-waves and ST-segment elevation in leads V1-V4, and Tc-99m-MIBI SPECT showed a photon deficient area in the anteroseptum. These findings were suggestive of AMI, but the patient had been simultaneously suffering from two adenocarcinomas, which were lung cancer and gastric cancer, and consecutive ultrasonic cardiography (UCG) demonstrated a growing mass lesion in the septal aspect of the left ventricle. After a month he died of severe heart failure. The histological diagnosis of a specimen of the cardiac mass lesion was invasive adenocarcinoma infiltrating to the heart, which revealed that the myocardial metastasis had mimicked AMI. This case shows that it is difficult to distinguish between myocardial infarction and myocardial metastasis with myocardial perfusion SPECT. It is necessary to consider the possibility of myocardial metastasis when a patient with malignancy presents AMI-like findings.

Nuclear imaging of bone tumors: thallium-201 scintigraphy

(201)Tl scintigraphy provides important information for the management of patients with bone tumors. Although the role for staging the disease of bone tumors and for differentiation of benign from malignant lesions is limited, (201)Tl scintigraphy reflects the disease activity after treatment and it should be used to determine the treatment response and for early diagnosis of recurrence. Baseline study is essential for future reference to evaluate the response to preoperative chemotherapy and to detect recurrence after surgery. Sequential (201)Tl scintigraphy before and after treatment is useful in assessing the grade of response of the tumor to chemotherapy. The early prediction of chemotherapeutic effect by (201)Tl scintigraphy during treatment will affect the management of patients who do not respond to the therapy. This is of special importance to determine whether the patient needs an amputation or a limb-salvage surgery.

Clinical approach to renal study incidental to 99mTc-MDP bone scintigraphy

In order to investigate the feasibility of the assessment of renal function with 99mTc-MDP, we compared renographical images, renogram patterns and the glomerular filtration rate (GFR) obtained by means of a modified Gates' method and 200 MBq of 99mTc-MDP with those obtained by means of 99mTc-DTPA. Because 19 of 20 patients had malignant tumors in the genitourinary tract, there was no difference between the two tracers in identifying a parenchymal defect corresponding to renal cancer. Of eight patients with hydronephrosis, four had a defect or decreased uptake with a dilated pelvis, whereas the other four had marked radioisotope retention in the renal pelvis or the whole kidney on serial images. There was also no difference between the two tracers in identifying hydronephrosis. Of 38 paired renograms 35 showed the same renogram patterns with both tracers. Of three patients with different renogram patterns, two had hydronephrosis. In 20 patients including three patients with bone metastasis, total GFR and split GFR obtained with both tracers correlated with a correlation coefficient of r = 0.920 (p < 0.001) and r = 0.944 (p < 0.001), respectively. Excluding bone metastasis from the analysis, a linear-regression analysis showed excellent agreement between the two measurements with a correlation coefficient of r = 0.960 (p < 0.001) and r = 0.963 (p < 0.001), respectively. The linear regression equations were Y = 1.009X - 0.111 and Y = 1.034X - 0.714, respectively. In conclusion, 99mTc-MDP can be used as a supplement to evaluate renal function incidental to the survey of bone metastases in patients with malignant tumor.

Improved response of colon cancer xenografts to radioimmunotherapy with pentoxifylline treatment

A methylxanthine, pentoxifylline (PTX), has the potential to improve tumour microcirculation and oxygenation in vivo. We aimed to determine whether this agent would enhance the response of tumours to experimental radioimmunotherapy (RIT). Balb/c nu/nu mice with xenografts of LS180 human colon cancer were treated with 4.63 MBq of 131I-A7 anti-colorectal monoclonal antibody. A dose of 50 mg/kg of PTX was administered i.p. immediately after the 131I-A7 injection and daily thereafter for 7 days. The effect of PTX administration on 131I-A7 targeting in tumours was assessed with biodistribution and radioluminography on day 2. Intratumoural pO2 was measured with microelectrodes. The administration of PTX alone did not suppress tumour growth, but the efficacy of RIT with 131I-A7 was significantly improved by PTX: tumour volumes on day 15, relative to the initial volume, were 16.8+/-3.60 in the nontreated controls, 13.9+/-2.17 with PTX, 3.43+/-0.44 with RIT, and 1.86+/-0.59 with RIT+PTX (P<0.05). PTX administration did not alter the biodistribution or intratumoural distribution of 131I-A7. However, intratumoural pO2 was significantly improved by PTX administration: 16.9+/-9.75 mmHg in control tumours versus 25.6+/-11.3 mmHg in PTX-treated tumours (P<0.01). These results indicate that PTX-induced radiosensitisation of tumour cells due to better oxygenation is responsible for the better RIT outcomes, because the net radiation absorbed dose to the tumours did not appear to be changed.

Experimental radioimmunotherapy with 186Re-MAG3-A7 anti-colorectal cancer monoclonal antibody: comparison with 131I-counterpart

A murine IgG1 against a Mr 45 kD tumor-associated glycoprotein in human colorectal cancer, A7, was radiolabeled with 186Re by a chelating method with a mercaptoacetyltriglycine (MAG3). Its specific activity was 119 MBq/mg, which would be high enough for a therapeutic purpose, and its immunoreactivity was preserved well as was 131I-A7 labeled by the chloramine-T method. Growth of human colon cancer xenografts, 9.14 +/- 0.44 mm in diameter, in nude mice was significantly suppressed by an intravenous dose of 4.48 MBq of 186Re-A7. The therapeutic outcome with 186Re-A7 was better than that with 4.63 MBq of 131I-A7. Toxicity of treatments assessed by body weight change was similar with both conjugates. These results are likely caused by the tumor size and more favorable physical properties of 186Re than those of 131I.

Esophageal hypomotility in systemic sclerosis: close relationship with pulmonary involvement

PURPOSE

Esophageal motility was assessed in patients with systemic sclerosis (SSc) by scintigraphy and compared with (i) extent of scleroderma, (ii) duration of disease, (iii) index of anti-topoisomerase I antibody (topo I), and (iv) pulmonary involvement.

METHODS

A multiple-swallow test was performed in 47 patients with SSc in the supine position with 99mTc-DTPA. A region of interest on the entire esophagus was defined and the retention ratio (RR) was calculated from a time-activity curve.

RESULTS

Patients with diffuse scleroderma had higher RRs than those with limited scleroderma (48.8% vs. 30.0%; p < 0.05). There was no correlation between the RRs and the duration of disease. Patients with positive topo I had higher RRs than those who were negative (53.8% vs. 29.7%; p < 0.05). Patients with reduced % diffusion capacity for carbon monoxide (%DLCO) had higher RRs than those with normal %DLCO (40.5% vs. 19.6%; p = 0.03). Patients with reduced % vital capacity (%VC) had higher RRs than those with normal %VC (54.6% vs. 25.0%; p < 0.005). Patients with pulmonary fibrosis had higher RRs than those who were negative (58.5% vs. 20.3%; p < 0.00005).

CONCLUSION

Esophageal dysfunction in patients with SSc showed a correlation with the extent of scleroderma, positive topo I, and pulmonary involvement. The RR can be an objective clinical marker for the severity of organ fibrosis.

Methylxanthine sensitization of human colon cancer cells to 186Re-labeled monoclonal antibody

Tumor cells lacking the functional p53 suppressor gene may arrest at the G2 phase of the cell cycle after exposure to ionizing radiation, resulting in increased radioresistance. Methylxanthines (MTXs), such as pentoxifylline (PTX) or caffeine (CAF), can inhibit the G2-phase checkpoint arrest of damaged cells and thus radiosensitize them. However, the effect of MTX in cells irradiated with low-dose-rate beta-emission is not well understood.

METHODS

A clonogenic assay was performed with LS180 human colon cancer cells lacking the functional p53 suppressor gene. Cells were irradiated with increasing concentrations of 186Re-mercaptoacetyltriglycine (186Re-MAG3)-labeled A7 monoclonal antibody against colorectal cancer (0-925 kBq/mL) at 37 degrees C in 5% CO2 for 24 h in the presence or absence of PTX (0-2 mmol/L) or CAF (0-5 mmol/L). The enhancement ratio (ER) with MTX was calculated as a ratio of 50% cell-killing concentration of 186Re-MAG3-A7 in control cells to that in cells treated with PTX or CAF. The cell cycle distribution was analyzed with a flow cytometer.

RESULTS

The concentration of 50% cell kill was 474 kBq/mL 186Re-MAG3-A7. Both PTX and CAF dose dependently enhanced the cytotoxicity of 186Re-MAG3-A7: ERs of 0.5 mmol/L PTX, 2 mmol/L PTX, 1 mmol/L CAF, and 5 mmol/L CAF were 1.50, 2.18, 1.54, and 2.63, respectively. Flow cytometry showed that the percentage nonirradiated cells in the G2/M phase of the cell cycle was 11.3% +/- 1.66%. On the other hand, cells exposed to 186Re-MAG3-A7 accumulated in the G2/M phase of the cell cycle (40.2% +/- 1.46%), which was inhibited by the presence of 1 mmol/L PTX (19.8% +/- 8.12%) or 2 mmol/L CAF (26.9% +/- 6.21%).

CONCLUSION

Cellular modulation of the cell cycle with PTX and CAF radiosensitized LS180 colon cancer cells exposed to 186Re radiation.

The potential of radioiodinated (-)-m-iodovesamicol for diagnosing cholinergic deficit dementia

We investigated changes in the brain distribution of (-)-[(125)I]-m-iodovesamicol [(-)-[(125)I]mIV] in cholinergic denervation rats produced by a unilateral lesion of the nucleus basalis magnocellularis (NBM). Dual-tracer ex vivo autoradiographic analysis using (-)-[(125)I]mIV and [(99m)Tc]HMPAO was conducted to the effect of regional cerebral perfusion on the brain distribution of (-)-[(125)I]mIV in a unilateral NBM-lesioned rat. (-)-[(125)I]mIV binding in the ipsilateral cortex to the lesion significantly reduced by 10.4 %, compared with that in the contralateral cortex, while (-)-[(125)I]mIV binding in the ipsilateral caudate putamen, hippocampus and thalamus did not change. The rate of reduction in the (-)-[(125)I]mIV binding (10.4 %) was significantly higher than that of [(99m)Tc]HMPAO accumulation (4.0%) in the ipsilateral cortex to the lesion (P < 0.01). These results suggested that radioiodinated (-)-mIV may be useful in the study of dementia characterized by degeneration of the cholinergic neurotransmitter system, such as Alzheimer's disease.

Effect of vagal autotransplantation on quantitative [3H]-vesamicol binding image in rats with unilateral lesions of nucleus baslis magnocellularis

It is considered that nodosal ganglion grafting improves learning and memory disorder in nucleus basalis magnocellularis lesioned rats, and that [3H]-vesamicol is one of the mapping agents for presynaptic cholinergic neurons. Quantitative autoradiography was performed using high sensitive imaging plate system to evaluate the effect of neurotransplantation on [3H]-vesamicol binding. The affected-side to unaffected-side ratio of [3H]-vesamicol in the nucleus basalis magnocellularis lesioned group was significantly lower than that in the sham-operated group at 1, 2 and 4weeks (P<0.01). In the transplanted group, the ratio was significantly higher than that in the untreated group at 4weeks (P<0.05). [3H]-vesamicol binding is one of the most sensitive indicators of nucleus basalis magnocellularis lesions and the effect of the nodosal ganglion grafting.

Technetium-99m-tetrofosmin would be a substrate for multidrug resistance-associated protein (MRP): comparison between a leukemia cell line with high MRP gene expression and its parental cell line

The kinetics of cellular accumulation and retention of technetium-99m-tetrofosmin (99mTc-TF) were investigated in wild type HL60/WT cell line and in its doxorubicin-resistant HL60/DOX cell line with multidrug resistance-associated protein (MRP), but without P-gp overexpression, to determine whether 99mTc-TF is a substrate for MRP.

METHODS

The accumulation and washout of 99mTc-TF were observed in both cell lines at 37 degrees C. The effect of verapamil on the kinetics was also assessed.

RESULTS

99mTc-TF net accumulation was significantly lower in HL60/DOX (1.35 +/- 0.23%) than in HL60/WT (12.79 +/- 0.47%) at 60 min (P < 0.001). Three minutes after exchanging the incubation solution to the tracer-free medium, only 18.20 +/- 0.34% of 99mTc-TF remained in HL60/DOX, whereas 84.74 +/- 0.65% did in HL60/WT (P < 0.001). In the presence of 10 microM verapamil, 99mTc-TF net accumulation in HL60/DOX was 302% of the control and the washout was significantly delayed.

CONCLUSION

99mTc-TF would be a substrate for MRP and 99mTc-TF may be used as a functional imaging agent of MRP in vivo.

Comparison of99mTc-tetrofosmin uptakes on planar images with those in excised rats organs with those in excised rats organs

The radioactivity in the organs adjacent to the heart causes interference with the quantitative assessment of myocardial uptake of tracer on scintigraphy. In order to investigate how much the functions of these organs affect myocardial uptake seen in imaging, we compared the myocardial uptake measured by means of a gamma camera with the actual activity in the excised organs.

METHODS

Thirty-three rats were imaged at 5, 10, 15, 30, 45, 60, 90 and 120 min after the administration of 99mTc-tetrofosmin, and % injected dose per pixel (%ID/pixel) for each organ was assessed on planar images (PI measurement). Percent injected dose per gram of tissue (%ID/g) in the heart as well as lungs, liver, gastrointestines and blood was measured by means of a well scintillation counter (WC measurement). Comparison between PI and WC measurements was performed with % uptake, the PI-to-WC ratio and heart-to-organ ratios.

RESULTS

Our WC measurement showed an increase in cardiac uptake until 30 min (1.67 +/- 0.31%) postinjection and subsequent gradual decrease, whereas PI measurement showed maximum activity of 1.81 +/- 0.52% at 15 min postinjection. There was a prominent difference between the two measurements, particularly at 10 min, with a PI/WC ratio of about 1.6 times. Our WC measurement showed maximum pulmonary uptake at 15 min (0.87 +/- 0.31%) and a gradual decrease over 15 min, whereas PI measurement showed maximum uptake at 10 min (1.14 +/- 0.38%). There was hardly any variation in activity observed later than at 10 min. Our WC measurement showed hardly any variance in hepatic activity from 5 min (0.77 +/- 0.19%) to 30 min (0.69 +/- 0.27%) with a subsequent gradual decrease. The percent uptake in PI measurement was generally greater than that in WC measurement, and high values were found at 10 min and 15 min with PI/WC ratios of about 3.3 times and 2.3 times, respectively.

CONCLUSION

Percent uptakes in PI measurement were greater than those in WC measurement. The difference between the two measurements was prominent in the early phases. The cardiac uptake in PI measurement was significantly greater than that in WC measurement at 10 min. It was considered that this discrepancy between the two measurements was caused by the Compton scatter from the organs adjacent to the heart.

Diastolic dysfunction in patients with systemic sclerosis detected by gated myocardial perfusion SPECT: an early sign of cardiac involvement

Diagnosis of cardiac involvement is important for the management of patients with systemic sclerosis (SSc). This study was undertaken to determine the significance of gated myocardial perfusion SPECT in patients with SSc and whether diastolic function measured by gated SPECT is an early sign of cardiac complications.

METHODS

Thirty-four patients with SSc and 16 control patients were studied using exercise nongated and resting gated myocardial perfusion SPECT. The SSc was classified by the modified Rodnan total skin score (TSS) into high-TSS (score > or = 10; n = 18) and low-TSS (score < 10; n = 16) groups. Gated SPECT was performed using 99mTc-methoxyisobutylisonitrile with 16 frames per cardiac cycle and quantitatively analyzed by QGS software and Fourier filtering of the volume curve. The parameters of ejection fraction (EF), peak filling rate (PFR), one-third mean filling rate, and time to PFR (TPFR) were calculated.

RESULTS

A slight perfusion abnormality was observed in four and five patients in the low-TSS and high-TSS groups, respectively (not statistically significant). A decreased resting EF less than 55% was found in no and two patients in the low-TSS and high-TSS groups, respectively. TPFR was 166 +/- 22, 168 +/- 38, and 216 +/- 82 ms (P = 0.05, high-TSS group versus low-TSS group; P = 0.04, control group versus high-TSS group) and TPFR/R-R interval was 0.18 +/- 0.02, 0.19 +/- 0.04, and 0.26 +/- 0.09 (P = 0.01, high-TSS group versus low-TSS group; P = 0.005, control group versus high-TSS group) for the control, low-TSS, and high-TSS groups, respectively.

CONCLUSION

Diastolic function can be evaluated by gated myocardial perfusion SPECT. Significant diastolic abnormalities were shown even in patients with normal perfusion and systolic function and were related to the severity of SSc.

Detecting meningeal carcinomatosis from breast cancer with thallium-201 SPECT

Thallium-201 (201Tl) scintigraphy is one of the imaging methods used in the detection of various tumors including brain metastasis. We evaluated a patient with meningeal carcinomatosis from breast cancer by using 201Tl single-photon emission computed tomography (SPECT). Meningeal spread of a tumor was noted on enhanced CT. SPECT revealed tumor localization in meningeal carcinomatosis. These results suggest that SPECT with 201Tl may be useful in detecting meningeal carcinomatosis from breast cancer.

Gliosarcoma with thallium-201 SPECT

Thallium-201 (201Tl) chloride scintigraphy is the imaging method use for the detection of various tumors including glioblastoma, but only limited information on 201Tl uptake in gliosarcoma is available. We investigated a patient with gliosarcoma by means of 201Tl single-photon emission computed tomography (SPECT) and MRI. SPECT imaging revealed high 201Tl uptake in the tumor, which was closely correlated with contrast-enhancement on MRI. These results suggest that SPECT with 201Tl may be useful for detecting gliosarcoma and provide physiological information on this tumor.

Reduction of vesicular acetylcholine transporter in beta-amyloid protein-infused rats with memory impairment

The aim of this study was to investigate spatial memory and quantitative acetylcholine transporter autoradiography using a high-sensitivity imaging plate system in rats treated with beta-amyloid protein, a model of Alzheimer's disease. An eight-arm radial maze was used to evaluate spatial memory. The performance of the eight-arm radial maze task was impaired in beta-amyloid protein-treated rats. In the parietal cortex, [3H]-vesamicol binding to the vesicular acetylcholine transporter was significantly lower in beta-amyloid protein-treated rats than in vehicle-treated rats, and was significantly correlated with the mean number of correct selections in the maze task of the first 5 days in the post-operative state. These results indicate that the reduction in [3H]-vesamicol binding to vesicular acetylcholine transporter is related to memory impairment induced by beta-amyloid protein. Beta-amyloid protein-infused rats with spatial memory impairment may be useful for the development of new radiolabelled vesamicol analogues for the objective evaluation of Alzheimer's disease.

Gated SPET quantification of small hearts: mathematical simulation and clinical application

Quantification of gated single-photon emission tomography (SPET) in small hearts has been considered to be inaccurate. To evaluate the validity of gated SPET in a small chamber volume, mathematical simulation and clinical application to paediatric patients were performed. Myocardium with various chamber sizes from 14 ml to 326 ml was generated assuming an arbitrary resolution (6.9-15.7 mm in full-width at half-maximum), noise and zooming factors. The cut-off frequency of the Butterworth filter for preprocessing was varied from 0.16 to 0.63 cycles/cm. The chamber volume was calculated by quantitative gated SPET software (QGS). The patients, aged 2 months to 19 years (n=27), were studied by gated technetium-99m methoxyisobutylisonitrile or tetrofosmin SPET. Image magnification as large as possible was performed during data acquisition to include the whole chest using 1.25-2.0 zooming. Based on the simulation study, an underestimation of the chamber volume occurred below a volume of 100 ml. The degree of underestimation for a 37-ml volume was 49% without zooming, but it improved to 3% with 2x zooming. Filters with a higher cut-off frequency, better system resolution and hardware zooming during acquisition improved quantitative accuracy in small hearts. For the subjects under 7 years old (n=7), quantification of volume and ejection fraction (EF) was possible in 72% of the patients. In those over 7 years old, gated SPET quantification was feasible in all cases. The correlation between gated SPET end-diastolic volume (SPET EDV) and both echocardiographic end-diastolic dimension (EDD) and echocardiographic EDV was good (r=0.84 between SPET EDV and echo EDD, r=0.85 between SPET EDV and echo EDV, P<0.0001 for both). The correlation between gated SPET EF and both echocardiographic fractional shortening (FS) and echocardiographic EF was fair (r=0.69 between SPET EF and echo FS, r=0.72 between SPET EF and echo EF, P<0.0001 for both). In conclusion, quantification of gated SPET of small hearts can be improved by means of a SPET filter with a high cut-off frequency, high system resolution and appropriate zooming. Gated SPET should be attempted not only in patients with small hearts but also in paediatric patients.

Optimal timing of administration of hyperthermia in combined radioimmunotherapy

Local hyperthermia (HT) may enhance the efficacy of radioimmunotherapy (RIT). However, the optimal timing of HT relative to administration of antibody is unknown. Human colon cancer xenografts (290 +/- 26 mm3) were treated with 4.63 MBq 131I-A7 monoclonal antibody (MAb) anti-Mr 45,000 glycoprotein antigen on colorectal cancer, and HT at 43 degrees C for 1 h was administered at: (A), 2 days after the 131I-A7 injection at the maximum 131I-A7 tumor accumulation (radiation); (B), soon after the 131I-A7 injection aiming to increase the tumor accumulation of 131I-A7 due to HT vascular effects; or (C), 2 days before the 131I-A7 injection in an attempt at injecting 131I-A7 when increased antigen expression could be expected. Specific growth delay (SGD) of tumors was calculated as (Tqtreat-Tqcontrol)/Tqcontrol where Tq was tumor quadrupling time. The biodistribution and intratumoral distribution of 131I-A7 were investigated to explore the mechanism of tumor response among the different HT regimens. HT alone produced some antitumor effect (SGD 1.90 +/- 0.26), which was less effective than RIT (3.11 +/- 0.50). HT soon after 131I-A7 RIT (B) significantly enhanced RIT efficacy (6.57 +/- 0.51, p < 0.0001) whereas neither HT at 2 days after RIT (A) nor at 2 days before RIT (C) did so. Biodistribution study revealed that HT soon after RIT (B) increased the tumor radiation absorbed dose by a factor of 2.4, while HT after RIT (A) did not increase radiation dose and HT before RIT (C) decreased it. Radioluminograms of tumor sections indicated that HT soon after RIT (B) improved the uniformity of 131I-A7 distribution whereas HT after RIT (A) did not and HT before RIT (C) diminished the uniformity of A7 distribution. In conclusion, the best therapeutic efficacy was obtained when HT was combined soon after the initiation of RIT with 131I-A7. The increased tumor radiation absorbed dose and the uniform intratumoral distribution of 131I-A7 were important factors underlying this improvement, and the additive cytotoxicity of HT is suspected to some extent. HT-induced radiosensitization of tumor was not apparent in this model when HT was given 2 days after 131I-A7 MAb.

Pharmacologic intervention with angiotensin II and kininase inhibitor enhanced efficacy of radioimmunotherapy in human colon cancer xenografts

Induced hypertension and kininase inhibition can enhance tumor targeting of radiolabeled monoclonal antibody (MAb) by altering tumor circulation. This study investigated the effect of this manipulation on the antitumor efficacy of radioimmunotherapy (RIT).

METHODS

Mice bearing human colon cancer xenografts were administered 2.0 microg/kg/min of angiotensin II (AT-II) for 1 h and 30 microg of a kininase inhibitor, enalapril maleate, before the administration of 3.7 MBq (131)I-A7, an IgG1 against 45-kDa glycoprotein on colorectal cancer, and tumor growth was observed thereafter. The mechanism of the manipulation effect was investigated by estimation of the tissue absorbed dose and radioluminography of tumors.

RESULTS

The pharmacologic manipulation with AT-II and enalapril improved the tumor quadrupling time (Tq) of 3.7 MBq RIT from 24.3 +/- 2.75 d to 33.1 +/- 2.83 d (P < 0.05). Addition of this manipulation made 3.7 MBq RIT as effective as 9.25 MBq RIT alone (Tq, 37.2 +/- 2.97 d). Dose estimation showed that the manipulation increased the tumor absorbed dose 1.55-fold without affecting the doses to normal tissues. Uniform intratumoral distribution in the manipulated tumors was shown by radioluminography.

CONCLUSION

Larger and more uniform tumor radiation produced by this pharmacologic manipulation can benefit RIT with (131)I-MAb.

Enhanced efficacy of radioimmunotherapy combined with systemic chemotherapy and local hyperthermia in xenograft model

We previously found that the efficacy of radioimmunotherapy (RIT) with (131)I-A7, an IgG(1) against M(r) 45000 glycoprotein on colon cancer, was enhanced by local hyperthermia (HT) or chemotherapy with 5-fluorouracil (5-FU). In this study, we aimed to further enhance its efficacy by combining these three modalities. Human colon cancer xenografts (146 x 12 mm(3)) in Balb / c nu / nu female mice were treated with 9.25 MBq (131)I-A7 i.v. combined with HT (43 degrees C for 1 h) and 5-FU (30 mg / kg / day i.p. for 5 days). Tumor growth delay, (Tq(treated) - Tq(control) )/ Tq(control) where Tq is tumor quadrupling time, in mice treated with RIT + HT + 5-FU was improved to 12.7 from 5.90, 7.55 and 10.1 with RIT alone, RIT + 5-FU and RIT + HT, respectively. Complete response was observed in 4 out of 8 tumors with RIT + HT + 5-FU and 3 out of 10 with RIT + HT. No tumor showed complete response with RIT + 5-FU or RIT alone. 5-FU slightly increased myelotoxicity of RIT, but HT did not affect it. Body weight loss was not enhanced by the combination. These results indicate that the combination of three modalities is a feasible approach to enhance the antitumor efficacy of RIT without serious increase of toxicity.

Peripheral sympathetic dysfunction in patients with Parkinson's disease without autonomic failure is heart selective and disease specific. taki@med.kanazawa-u.ac.jp

The study was undertaken to investigate by means of iodine-123-labelled metaiodobenzylguanidine (MIBG) scintigraphy the peripheral sympathetic function in patients with Parkinson's disease (PD) without autonomic failure and in patients with related neurodegenerative diseases with parkinsonism. Seventy patients (33 men and 37 women, mean age 63+/-9.7 years) with parkinsonism and ten control subjects underwent MIBG scintigraphy. Of these 70 patients, 41 were diagnosed as having idiopathic PD, 9 multiple system atrophy (MSA), 6 progressive supranuclear palsy (PSP) and 2 corticobasal degeneration (CBD); the remaining 12 were diagnosed as having neurodegenerative disease with parkinsonism (P-nism) that did not meet the diagnostic criteria of any specific disease. Cardiac planar and tomographic imaging studies and subsequent whole-body imaging were performed 20 min and 3 h after the injection of 111 MBq MIBG. The early MIBG heart to mediastinum (H/M) ratio in PD (1.61+/-0.29) was significantly lower than that in the control group (2.24+/-0.14, P<0.01), P-nism (2.15+/-0.31, P<0.01), MSA (2.08+/-0.31, P<0.05) and PSP (2.30+/-0.24, P<0.01). The delayed H/M ratio in PD (1.47+/-0.34) was also significantly lower than that in the control group (2.37+/-0.14, P<0.01), P-nism (2.13+/-0.38, P<0.01), PSP (2.36+/-0.36, P<0.01) and MSA (2.17+/-0.36, P<0.01). In patients with PD, early and delayed H/M ratios were significantly decreased in disease stages I, II and III (established using the Hoehn and Yahr criteria) as compared with control subjects, and there were no significant differences among the stages. Only PD showed a significantly higher washout rate (WR) than that in the control subjects (27%+/-8.0% vs. 11%+/-4.2%, P<0.01). Early and delayed uptake ratios of the lung, parotid gland, thyroid gland, liver and femoral muscles in each of the patient groups were not significantly different from those in control subjects. Only the early and delayed uptake ratios of the lower leg muscles in MSA were significantly lower than those in the control group (P<0.05).

IN CONCLUSION

In patients with PD without autonomic failure, only cardiac MIBG uptake was severely reduced in the earliest phase of the disease (stage I). Parkinsonian syndromes other than PD did not demonstrate significant reduction in MIBG uptake in any organs except for the lower legs in MSA. In patients with PD without autonomic failure, reduction in MIBG uptake occurs selectively in the heart; this is considered to be a specific finding for PD and useful for the differential diagnosis of the parkinsonian syndromes.

Thallium-201 SPECT with triple-headed gamma camera for differential diagnosis of small pulmonary nodular lesion 20 mm in diameter or smaller

AIM

Although thallium-201 (201Tl) has been used for the diagnosis of lung cancer, its detectability of small pulmonary nodules is not known. The aim of this study was to evaluate the ability of 201Tl SPECT for the differential diagnosis for the pulmonary nodules 20 mm in diameter or smaller.

METHODS

201Tl SPECT was performed in 31 patients suspected of having primary lung cancer. The final diagnosis was established by histology, and tumor size was 10 to 20 mm in diameter. Twenty of 31 patients had malignant tumors, including squamous cell lung cancer (n = 5), adenocarcinoma (n = 14) and small cell lung cancer (n = 1), but in none of them was there mediastinal lymphnode involvement.

RESULTS

Ten of 20 malignant tumors and 1 of 11 benign lesions demonstrated significant 201Tl uptake, so that the positive predictive value, negative predictive value, sensitivity and specificity for the diagnosis of lung cancer were 90.9% (10/11), 50.0% (10/20), 50.0% (10/20) and 90.9% (10/11), respectively.

CONCLUSION

These data suggest that sensitivity for detecting lung cancer 20 mm or less in diameter may be insufficient, but even in patients with small pulmonary nodules, a positive 201Tl result is highly predictive of lung cancer.

Increased uptake of 99mTc-HL91 in tumor cells exposed to X-ray radiation

99mTc-HL91, a hypoxic marker, may be a predictor of tumor response to radiotherapy and an indicator of tumor oxygenation in the course of treatment. In this study, serial changes in 99mTc-HL91 uptake were observed in the normoxic condition in a human bladder cancer cell line exposed to a single dose or a fractionated dose of 10 Gy with an x-ray beam. The uptake per cell increased during cell growth retardation induced by the irradiation. This finding indicates that 99mTc-HL91 uptake is affected by injury to cells due to radiation; it may therefore be difficult to correctly assess the tissue oxygenation status during radiotherapy with 99mTc-HL91.

Regional cerebral blood flow in male schizophrenic patients performing an auditory discrimination task

Regional cerebral blood flow (rCBF) was measured in 11 schizophrenic patients amid 10 normal controls, both at rest and while performing an auditory discrimination task. Single photon emission computed tomography with technetium-99m hexamethylpropylene amine oxime was used for quantitative evaluation of rCBF. The schizophrenic patients showed greater rCBF in the temporal and parietal regions at rest than the controls, but no abnormalities were found in frontal perfusion. During task performance. on the other hand, the patients showed a reduced frontal rCBF. whereas there was no group difference in rCBF in the temporal and parietal regions. In addition, the left> right hemisphere asymmetries of rCBF observed in the controls during task performance were not present in the patients. although there was no group difference in hemisphere laterality in rCBF at rest. These findings suggest that the employment of a cognitive task for neuroimaging studies is useful for detecting abnormalities of brain activation. such as hypofrontality and altered hemisphere laterality. in patients with schizophrenia.

Production of 105Rh-EDTMP and its bone accumulation

105Rh has favorable physical characteristics as a radiotherapeutic nuclide. Carrier-free 105Rh can be produced by the neutron activation of 104Ru followed by beta decay of 105Ru. It was clarified that carrier-free 105Rh can be produced in quantities and the purity necessary for chemical and clinical investigations of its use as a nuclide for radiotherapy. 105Rh-EDTMP was simply obtained from 105Rh3+ and EDTMP by heating for 30 min in boiling water, giving a radiochemical yield of > 99%. Dissociation of radioactivity assessed by paperchromatography was negligible for up to 5 days after its preparation. In animals, 105Rh-EDTMP showed rapid blood clearance and selective uptake in the bone. Hence, 105Rh-EDTMP is thought to be a promising therapeutic agent for the treatment of pain due to bone metastases.

Dye- and gamma probe-guided sentinel lymph node biopsy in breast cancer patients: using patent blue dye and technetium-99m-labeled human serum albumin

BACKGROUND

Sentinel lymph node (SLN) biopsy is a promising method for the diagnosis of the axillary nodal status. We examined the availability of the SLN biopsy using two mapping procedures: the dye- and gamma probe-guided method, and preoperative lymphoscintigraphy by gamma camera imaging.

METHODS

We enrolled 48 patients with breast cancer. Technetium-99m-labeled human serum albumin was injected into the subdermal tissue above the primary tumor or biopsy cavity, and preoperative gamma camera imaging was performed. After induction of general anesthesia, patent blue dye was injected into the peritumoral area prior to the surgical procedure. A handheld gamma-detection probe was used to assist in SLN detection. Careful dissection was performed to identify blue-stained afferent lymphatic vessels and nodes. An SLN was defined as any blue and/or radioactive node, and was excised. After SLN biopsy, axillary lymph node dissection of level I, II, and III was completed, in order to confirm the diagnostic ability of the SLN biopsy.

RESULTS

Intraoperative SLN identification of axillary lesions was successful in 43 of 48 patients (90%). The dye- and gamma probe-guided method was successful in 25 patients (52%), the dye-guided method alone succeeded in 11 patients (23%), and the gamma probe-guided method alone succeeded in 7 patients (15%). Preoperative lymphoscintigraphy revealed axillary focal accumulations in 29 of 48 patients (60%). All patients who underwent successful preoperative SLN identification by lymphoscintigraphy had successful intraoperative SLN identification. A diagnostic accuracy of 95%, a sensitivity of 89%, and a specificity of 100% were achieved in the diagnosis of axillary metastasis. Internal mammary SLNs were identified in four patients intraoperatively, but we could not detect cancer metastasis in the internal mammary SLNs.

CONCLUSIONS

The dye-guided and gamma probe-guided methods were complementary. Preoperative lymphoscintigraphy was useful to predict intraoperative SLN identification. Further study is necessary to assess the role of SLN biopsy of the internal mammary lymph nodes.

[Measurement of myocardial blood flow increase rate at exercise with 99mTc-tetrofosmin radionuclide angiography]

We developed new method to calculate myocardial blood flow increase rate at exercise (MBF-IR) with 99mTc-tetrofosmin (TF) radionuclide (RN) angiography and myocardial perfusion SPECT and assessed its feasibility using clinical data.

METHOD

Fifteen patients who were suspected to have coronary artery disease underwent TF RN angiography and SPECT at exercise and at rest. Seven patients had coronary stenosis and eight patients had no significant coronary stenosis in coronary angiography. MBF-IRs were calculated by the following equation: [formula: see text] where Cr = regional myocardial count at rest, Ce = regional myocardial count at exercise [formula: see text] = the area under ventricular time activity curve at rest and [formula: see text] = the area under ventricular time activity curve at exercise.

RESULT

Rate pressure product (RPP) was similar in patients with and without coronary stenosis (24,509 +/- 6701.9 vs. 27,196 +/- 4862.4, p = 0.39). MBF-IR was 1.88 +/- 0.73 in the area covered by stenosed coronary artery, 2.53 +/- 0.75 in unstenosed coronary artery in patients who have significant coronary stenosis and 2.97 +/- 0.77 in normal coronary patients. MBF-IRs in the area covered by stenosed coronary arteries were significantly smaller than that of normal coronary artery patient (p = 0.037). Interobserver and intraobserber reproducibility were good (r = 0.96, 0.95 respectively). There was strong positive correlation between MBF-IR and RPP in normal patients (r = 0.69, p = 0.0018), suggesting MBF increase depends on the cardiac workload.

CONCLUSION

MBF-IR can be estimated by the combination of TF RN angiography and SPECT at exercise and at rest.

[Nuclear medicine imaging for cardiomyopathy]

Nuclear medicine techniques have been applied to cardiomyopathy as well as in ischemic heart diseases. Various types of radiopharmaceutical including 201Tl and 99mTc-labeled perfusion tracers, 123I-labeled fatty acid(BMIPP), sympathetic function (MIBG) and tracers for myocardial injuries have been used. Perfusion imaging identifies stress-induced ischemia associated with myocardial damage. Recent application of gated SPECT enables simultaneous assessment of ventricular function. 123I-BMIPP and MIBG can detect metabolic abnormality, which has diagnostic and prognostic value for hypertrophic cardiomyopathy. The MIBG uptake index, heart-to-mediastinum ratio, is known to show good prognostic value for estimating dilated cardiomyopathy. Nuclear medicine plays unique roles for evaluating functional and metabolic derangement in cardiomyopathy.

[Assessment of regional quantitative analysis by ECG-gated myocardial SPECT after coronary artery bypass surgery]

PURPOSE

ECG-gated myocardial SPECT (G-SPECT) was performed before and after coronary artery bypass surgery (CABG) to investigate how this operation would affect the assessment of regional quantitative analyses.

METHODS

Nineteen patients with coronary artery disease underwent G-SPECT before and 1 month after uncomplicated CABG. 99mTc-MIBI 740 MBq was injected at rest, then G-SPECT was performed 60 min later. Regional ejection fraction (rEF), wall motion (WM), systolic wall thickening (WT) and % tracer uptake were evaluated by quantitative gated SPECT program (QGS). Parameters were obtained quantitatively in 16 segments based on the functional bull's eye map.

RESULTS

Percent tracer uptake increased in septum from 75 +/- 11% to 78 +/- 11% (p < 0.001), while WT did not change (40 +/- 19% to 41 +/- 20%) after CABG. However, in septum rEF decreased from 17 +/- 13% to 6 +/- 9% (p < 0.001) and WM decreased in septum from 1.6 +/- 1.1 mm to 0.6 +/- 0.9 mm (p < 0.001).

CONCLUSION

Significant reduction of rEF and WM despite of no deterioration of WT and % tracer uptake suggested that rEF and WM were affected by pseudoparadoxical asynergy after uncomplicated CABG. For the evaluation of regional function after CABG by G-SPECT, WT might be the preferred parameter.

Forward cardiac output measurement with first-pass technique using 99mTc-labeled myocardial perfusion imaging agents

The aim of this study was to develop and validate a new first-pass method for the measurement of forward cardiac output (CO) using 99mTc-labeled myocardial perfusion imaging agents.

METHODS

In protocol 1, to test the new method for measuring CO, the conventional method and the new method for CO measurement were performed in 1 d in 57 patients (32 men, 25 women; age 68 +/- 11 y). In the conventional method, radionuclide angiography (1 frame/s) with in vivo 99mTc labeling (110 MBq) of red blood cells was performed for 2 min in the left anterior oblique projection. Five minutes later, a 1-min equilibrium image was obtained, and a blood sample was taken for calculation of the distribution volume. To obtain data for the new method, further radionuclide angiography (1 frame/sec) with 99mTc labeling (600-740 MBq) of red blood cells was then performed in the anterior projection. CO was calculated using the following equation: CO = Cmax x V(LV)/integral of f(t)dt, where Cmax is the background-corrected peak count of the whole thorax during angiography, integral of f(t)dt is the area under the gamma variate-fitted left ventricular (LV) time-activity curve after background correction and V(LV) is the LV volume obtained by the area length method applied to the radionuclide angiography and myocardial tomography. In protocol 2, to evaluate the new method, 24 patients (16 men, 8 women; age 71 +/- 9.2 y) underwent radionuclide angiography with 99mTc-tetrofosmin (600-740 MBq), and the measured CO was compared with the CO obtained by the conventional method with 99mTc-labeled red blood cells.

RESULTS

In protocol 1, good correlation was observed between the CO by the new method (Y) and the CO by the conventional method (X): Y = 1.0X + 57 mL/min and r = 0.95. There was good agreement between the two methods (mean difference -56 +/- 381 mL/min). Inter- and intraobserver correlation coefficients were 0.96 and 0.98, respectively. In protocol 2, the CO by the new method using 99mTc-tetrofosmin (Y) showed a good correlation with the CO by the conventional method (X): Y = 0.90X + 453 mL/min and r = 0.93. Good agreement between the two methods was observed (mean difference 73 +/- 390 mL/min). Inter- and intraobserver correlation coefficients were 0.95 and 0.98, respectively.

CONCLUSION

This new method permits accurate forward CO measurement using the first-pass data with 99mTc-terofosmin, which is applicable to other 99mTc-labeled myocardial perfusion imaging agents.

Efficacy, toxicity and mode of interaction of combination radioimmunotherapy with 5-fluorouracil in colon cancer xenografts

PURPOSE

The feasibility of radioimmunotherapy (RAIT) combined with 5-fluorouracil (5-FU) was examined in colon cancer xenografts. The mode of interaction of the two treatments was also investigated.

METHODS

Mice bearing human colon cancer were treated with a combination of 4.63 MBq (L-RAIT) or 9.25 MBq (H-RAIT) (131)I-A7, an IgG1 against 45-kDa glycoprotein, and 5-FU at a dose of 30 mg kg(-1)day(-1) for 5 days. Myelotoxicity was monitored by blood cell counts and intestinal toxicity was assessed by the dosimetry. The results were compared with those of a single-modality therapy.

RESULTS

The combination of 5-FU with H-RAIT enhanced the antitumor effect, improving the tumor quadrupling time from 25.3 +/- 9.59 days to 31.3 +/- 8.32 days (P < 0.05) and inducing tumor regression in 7 out of 10 mice, compared to 3 out of 9 mice treated with H-RAIT alone. The efficacy of L-RAIT was also improved by the combination. Analysis of the dose/response relationship showed an additive interaction of the two modalities. The combination of 5-FU with RAIT induced slightly more severe myelotoxicity than a single-modality treatment, but blood cell counts recovered similarly. Dose estimation suggested that RAIT does not increase the intestinal toxicity of 5-FU.

CONCLUSION

The combination of two modalities would be feasible for the treatment of colon cancer, increasing antitumor effect with minor effect on toxicity.

Age-related changes in the cerebral distribution of 99mTc-ECD from infancy to adulthood

Although cerebral blood flow in infants differs from that in older individuals, the distribution of 99mTc-ethyl cysteinate dimer (ECD) in infants has not been well studied. This study compared 99mTc-ECD distribution in infants and children with that in young adults.

METHODS

99mTc-ECD SPECT was performed on 37 patients suspected of having epilepsy, ranging in age from 3 mo to 26 y. The patients were divided into two age-matched groups, a drug-free group (n = 19) and a drug-taking group (n = 18), according to their anticonvulsant medication status at the time of examination. 99mTc-ECD (100-740 MBq) was injected interictally, and SPECT data were acquired using a triple-head gamma camera. Mean whole-brain counts were obtained from 10 sequential SPECT images. Regions of interest were set bilaterally on five areas of the cerebral cortex and on the basal ganglia, thalamus and cerebellum. The brain perfusion index (BPI) was obtained as a ratio of the mean counts in each region of interest to the mean whole-brain counts. The relationship between BPI and age in each region in the drug-free and drug-taking groups was analyzed separately and together using linear regression. The relationship between five patient age groups (<1 y, n = 4; 1-4 y, n = 9; 5-9 y, n = 8; 10-15 y, n = 7; >15 y, n = 9) and BPI in each region was also examined using multiple comparison analyses.

RESULTS

Significant positive correlations between BPI and age in the frontal cortex and cerebellum were confirmed in the drug-free group. Anticonvulsant drugs did not affect the regression lines of BPI in the frontal cortex and cerebellum. Significant differences in BPI between age groups were seen in the parietal cortex, frontal cortex, occipital cortex, basal ganglia, thalamus and cerebellum in all patients.

CONCLUSION

Age-related changes in cerebral 99mTc-ECD distribution were confirmed and found to be unaffected by the administration of anticonvulsant drugs. 99mTc-ECD uptake in children and infants is different from cerebral blood flow glucose metabolism as previously reported, especially in the cerebellum.

Preoperative assessment of residual hepatic functional reserve using 99mTc-DTPA-galactosyl-human serum albumin dynamic SPECT

Preoperative assessment of residual hepatic functional reserve offers important strategic information for hepatic resection. To predict the postoperative residual liver function, we assessed the value of hepatic 99mTc-diethylenetriamine pentaacetic acid-galactosyl-human serum albumin (99mTc-GSA) clearance estimated by dynamic SPECT analysis.

METHODS

We investigated 114 consecutive patients with liver disease, including 55 hepatectomy cases. One minute after injection of 185 MBq 99mTc-GSA, 15 serial dynamic SPECT images were obtained every minute. The initial five sets of SPECT images were analyzed by Patlak plot to estimate the sequential initial hepatic 99mTc-GSA clearance (mL/min) as an index of hepatic function. The sum of hepatic 99mTc-GSA clearance of the segments immune from resection was categorized as predicted residual 99mTC-GSA clearance. In the hepatectomy cases, scintigraphy was performed before and 37 +/- 10 d after the operation.

RESULTS

Good correlation was observed between the total hepatic 99mTc-GSA clearance and conventional hepatic function tests: plasma retention rate of iodocyanine green (ICG) at 15 min (ICG R15), r = -0.600, P < 0.0001, n = 94; plasma disappearance rate of ICG (K ICG), r = 0.670, P < 0.0001, n = 83; cholinesterase, r = 0.539, P < 0.0001, n = 121; serum albumin, r = 0.421, P = 0.0001, n = 123; and hepaplastin test, r = 0.456, P < 0.0001, n = 120. There was good correlation between the predicted residual 99mTc-GSA clearance and the postoperative total hepatic 99mTc-GSA clearance in patients who underwent segmentectomy or lobectomy (r = 0.84, P < 0.0001, n = 28) and between the pre- and postoperative total hepatic 99mTc-GSA clearance in patients who underwent subsegmentectomy (r = 0.91, P < 0.0001, n = 25). Five patients who had postoperative complications due to hepatic insufficiency (2 patients died of postoperative hepatic failure within 2 mo after operation) showed significantly lower predicted residual 99mTc-GSA clearance compared with the patients without complications (90.3 +/- 37.2 versus 320.9 +/- 158.8 mL/min; P < 0.005).

CONCLUSION

The total hepatic 99mTC-GSA clearance reflected hepatic function. In addition, preoperative predicted residual hepatic 99mTc-GSA clearance was a good indicator of postoperative hepatic function and early prognosis. 99mTc-GSA dynamic SPECT is assumed to be a useful method for determining the surgical strategy in patients with hepatic tumor and especially in patients with hepatic dysfunction.

Reversible cerebral hypoperfusion observed with Tc-99m HMPAO SPECT in reversible dementia caused by hypothyroidism

A 69-year-old man had hypothyroid dementia as a result of I-131 therapy and an overdose of methimazole. Tc-99m HMPAO SPECT revealed diffuse cerebral hypoperfusion. The findings of brain SPECT normalized with the disappearance of symptoms and a return to the euthyroid state. There was a 25% or 26% reduction of the mean cerebral blood flow during dementia. This may be the first report in which SPECT brain imaging revealed reversible hypoperfusion associated with reversible hypothyroid dementia.

Differential uptake of TI-201 by small-cell lung cancer in a patient with pneumoconiosis-related pulmonary nodules

A 68-year-old man with pneumoconiosis was thought to have small-cell lung cancer based on the results of a biopsy of a bone tumor. Three pulmonary nodules were observed on a chest radiograph. Compared with a chest radiograph taken 4 months earlier, one of the nodules had grown. It was difficult to differentiate this nodule from pneumoconiosis-related benign pulmonary nodules from the appearance on the chest radiograph and CT. Ga-67 scintigraphy and TI-201 lung SPECT were performed to characterize these nodules. TI-201 SPECT showed differential high uptake in the enlarged nodule, whereas Ga-67 scintigraphy showed equally intense uptake in all these nodules. Transbronchial biopsy of the nodule that showed high TI-201 uptake revealed cancer cell nests against a background of interstitial fibrosis. The pathologic diagnosis was small-cell lung cancer that had developed in lung scar tissue. This case suggests the utility of TI-201 in scintigraphic assessments of pneumoconiosis-related pulmonary nodules when lung cancer is suspected.