Annals of Nuclear Medicine (v.21, #10)
Usefulness of 67Ga SPECT and integrated low-dose CT scanning (SPECT/CT) in the diagnosis of cardiac sarcoidosis by Mitsuhiro Momose; Masumi Kadoya; Megumi Koshikawa; Tsuyoshi Matsushita; Akira Yamada (545-551).
We performed 67Gallium (Ga) single-photon emission computed tomography (SPECT) with integrated low-dose computed tomography (CT) for the interpretation of myocardial outline to investigate the value of co-registered fusion imaging using a hybrid system (SPECT/CT) in patients with cardiac sarcoidosis.SPECT/CT of the region in question was performed with VG Hawkeye. The subjects in this study were 37 patients [mean (±SD) age 61.0 ± 13.0 years; 12 men and 25 women], 13 of whom had a clinical diagnosis of cardiac sarcoidosis and 24 a negative diagnosis. An intravenous injection of Ga (dosage 111 MBq) was performed on patients 48 h or 72 h before obtaining static planar images of the whole-body and the SPECT/CT scan.Abnormal Ga uptake in the myocardium was observed in 10 of the 13 subjects with true sarcoidosis, and in 11 of 24 with negative sarcoidosis without CT fusion. The sensitivity without CT fusion was 77%, the specificity 54%, and the accuracy 62%. Use of SPECT/CT changed the diagnosis only in a patient with true sarcoidosis, and changed the diagnosis in eight patients with negative sarcoidosis. The sensitivity with CT fusion was 69%, the specificity 79%, and the accuracy 76%. The difference in diagnostic accuracy was statistically significant (McNemar's test, P = 0.039).SPECT scanning using Ga and integrated low-dose CT is a very useful diagnostic imaging technique because it improves the diagnostic specificity of Ga SPECT to allow the highly specific diagnosis of cardiac sarcoidosis.
Keywords: Cardiac sarcoidosis; 67Gallium; SPECT; CT; Fusion
Pre-operative estimation of esophageal tumor metabolic length in FDG-PET images with surgical pathology confirmation by Marcelo Mamede; Georges El Fakhri; Paula Abreu-e-Lima; William Gandler; Vânia Nosé; Victor H. Gerbaudo (553-562).
The aim of this study was to evaluate a 3D tumor segmentation method for fluorodeoxyglucose positron emission tomography (FDG-PET) in the context of noninvasive estimation of tumor metabolic length (L m), as it correlates with surgical pathology and phantom results.Thirty-four patients (7 women, 27 men) with esophageal cancer were retrospectively evaluated. All patients underwent FDG-PET-computed tomography (CT) imaging following endoscopic ultrasound (EUS). Seventeen patients had esophagectomy after PET/CT, without prior neoadjuvant therapy. Tumor length was assessed by EUS (L e, n = 31) and histopathology (L p, n = 17). Images were evaluated quantitatively with a 3D threshold-based region-growing program (Medical Image Processing Analysis and Visualization). L m, total metabolic volume (V m), maximum standardized uptake value (SUVmax), and average SUV (SUVa) over the entire tumor were obtained for several threshold values (mean activity in the liver plus 0-, 1-, 2-, 3-, and 4-SD of the activity in the liver). L m showed a good correlation with L p for all thresholds (best correlation for L m(2-SD), r = 0.74, P < 0.001). A positive nonsignificant correlation was observed between L p and L e (r = 0.30, P = 0.29). L m(2-SD) correlated well with L e (r = 0.71, P < 0.001). Good correlations were also observed between L m(2-SD) and V m(2-SD) (r = 0.89, P < 0.001) and SUVa(2-SD) (r = 0.38, P < 0.05). V m(2-SD) also had a significant correlation with L p (r = 0.61, P < 0.05) and L e (r = 0.57, P < 0.001).FDG-PET-derived tumor metabolic length of untreated esophageal carcinomas correlates well with surgical pathology results, and provides preliminary evidence that noninvasive delineation of the superior and inferior extent of viable tumor involvement might be feasible using computer-generated metabolic length measurements.
Keywords: PET/CT; FDG; PET; Esophageal cancer; Tumor length; Tumor segmentation
Benefits of quantitative gated SPECT in evaluation of perioperative cardiac risk in noncardiac surgery by Koji Watanabe; Yukio Ohsumi; Hirohiko Abe; Masahito Hattori; Shinya Minatoguchi; Hisayoshi Fujiwara (563-568).
Gated single-photon emission computed tomography (G-SPECT) was used to evaluate cardiac risk associated with noncardiac surgery and determine the benefits and indications of this technique for this type of surgery.Patients scheduled to undergo noncardiac surgery under the supervision of anesthesiologists and subjected to preoperative cardiac evaluation using G-SPECT during the 26-month period between June 2000 and August 2002 were followed for the presence/absence of cardiac events (i.e., cardiac death, myocardial infarction, unstable angina, congestive heart failure, or fatal arrhythmia) during surgery and the postoperative period until discharged. Relationships between the occurrence of cardiac events and preoperative G-SPECT findings were evaluated.A total of 39 patients underwent G-SPECT; 6 of the 39 exhibited abnormal ejection fraction (left ventricular ejection fraction, LVEF ≤ 50%) and end-systolic volume (ESV ≥ 50 ml). Surgery was suspended for three of these six patients and cardiac events developed in the remaining three patients. Both abnormal perfusion images (PI) and abnormal wall thickening (WT) were observed in all six patients. All six patients exhibited abnormal LVEF and/or ESV. Three patients had either abnormal PI or WT, and a cardiac event occurred in one of them. Of the five patients who experienced cardiac events during or after surgery, two exhibited a short run of ventricular tachycardia requiring a continuous administering of antiarrhythmic drugs, whereas the remaining three patients exhibited cardiac failure requiring inotropic support following surgery.The results of this study indicate that the occurrence of perioperative cardiac events can be predicted by considering the severity of expected surgical stress and preoperative G-SPECT findings for LVEF, PI, and WT. We conclude that G-SPECT is quite useful for cardiac risk assessment in patients undergoing noncardiac surgery.
Keywords: ECG gated SPECT; 99mTc-tetrofosmin; Noncardiac surgery; Preoperative cardiac risk
Quantitative FDG-uptake by positron emission tomography in progressive hypertrophy of rat hearts in vivo by Nobuhiro Handa; Yasuhiro Magata; Takahiro Mukai; Takeshi Nishina; Junji Konishi; Masashi Komeda (569-576).
Quantitative myocardial fluorodeoxyglucose positron emission tomography (FDG-PET) for assessing glucose uptake in vivo is reliable in normal rat heart.To assess the applicability of myocardial FDG-PET on multiple occasions in the longitudinal disease process of progressive hypertrophy of rat heart.Six salt-sensitive Dahl rats (Dahl-S) developing progressive hypertrophy with subsequent dilated cardiomyopathy were compared with salt-resistant Dahl rats (controls). FDG-PET was applied twice at early stage (ES: 14–18 weeks) and at late stage (LS: 22–26 weeks) of hypertrophy. Standardized uptake value (SUV) was calculated for comparing between different animal weights and different injection dosages of FDG. For validating the quantitative study, radioactivity of a total of 36 tissue samples was compared with the corresponding PET values.The left ventricular mass in Dahl-S increased by 17% at ES and by 25% at LS. The SUV in Dahl-S was 95% of controls at ES and reduced to 62% at LS (P = 0.023). The heart function started to deteriorate after LS. Linear regression analysis showed a good correlation between the radioactivity of tissue samples and PET values (Y = 1.20X, P < 0.0001, R 2 = 0.979).Small animal PET studies on longitudinal multiple occasions in vivo were feasible and useful for the repeating assessment of glucose uptake. The reduction of glucose uptake in progressive hypertrophy of heart over time may precede its progression to heart failure.
Keywords: Small animal PET; Glucose metabolism; Fluorodeoxyglucose (FDG); Quantitative analysis; Hypertrophied heart
Semi-quantitation of pulmonary perfusion heterogeneity on respiratory-gated inspiratory and expiratory perfusion SPECT in patients with pulmonary emphysema by Yasuhiko Kawakami; Kazuyoshi Suga; Mohammed Zaki; Hideyuki Iwanaga; Tomio Yamashita; Noriko Hayashi; Naofumi Matsunaga (577-584).
Pulmonary perfusion heterogeneity (PPH) in pulmonary emphysema (PE) was semi-quantified by functional lung volume rate (FLVR) curves obtained from respiratory-gated inspiratory and expiratory single-photon emission computed tomography (SPECT).Gated and ungated SPECT were obtained in 36 PE patients [25 with stage IIA and 11 with stage IIB for global initiative for chronic obstructive lung disease (GOLD) stage classification] and 12 controls, using a triple-head SPECT system and a respiratory tracking device. On gated SPECT, the voxel numbers calculated at the 10% cutoff threshold for the maximum lung radioactivity were assumed to be the functional lung volume of the lung (V). FLVR (%) was calculated as FLV divided by V at every additional 10% thresholds, yielding inspiratory and expiratory FLVR curves. The dissociations between these curves (ΔFLVRinsp − exsp) and the total difference (D index) of these curves from the normal standard curve (averaged inspiratory and expiratory curve in controls) were calculated. D index and the extent of low attenuation area (%LAA) on CT were correlated with the transfer coefficient for carbon monoxide (K CO) in PE patients.Although gated and ungated SPECT showed fairly uniform perfusion in controls, gated SPECT-enhanced PPH compared with ungated SPECT in PE patients, with significantly higher dissociation (ΔFLVRinsp − exsp) than that in controls (24.9% ± 9.5% vs. 4.5% ± 1.3%; P < 0.0001). ΔFLVRinsp − exsp was significantly higher even in stage IIA patients (P < 0.0001). Expiratory D index was significantly higher than the inspiratory one in PE patients (P < 0.01). This index was significantly higher in stage IIB patients than in stage IIA patients (44.1% ± 19.0% vs. 29.4% ± 13.7%; P < 0.05), and was significantly correlated with K CO (R = 0.642, P < 0.0001) in all PE patients, although %LAA was not correlated with K CO.FLVR curve analysis on gated SPECT appears useful for semi-quantitation of respiratory change of PPH in PE. Expiratory D index may better reflect the lung pathophysiology of PE than morphologic CT.
Keywords: Single-photon emission computed tomography (SPECT); Gated image; Lung perfusion; Pulmonary emphysema; Computed tomography (CT)
Nonionic intravenous contrast agent does not cause clinically significant artifacts to 18F-FDG PET/CT in patients with lung cancer by Young-Sil An; Seung S. Sheen; Y. J. Oh; Sung C. Hwang; Joon-Kee Yoon (585-592).
This study was performed to evaluate the effects of intravenous (i.v.) contrast agent on semi-quantitative values and lymph node (LN) staging of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in patients with lung cancer.Thirty-five patients with lung cancer were prospectively included. Whole-body PET and nonenhanced CT images were acquired 60 min following the i.v. injection of 370 MBq 18F-FDG and subsequently, enhanced-CT images were acquired with the i.v. administration of 400 mg iodinated contrast agent without positional change. PET images were reconstructed with both nonenhanced and enhanced CTs, and the maximum and average standardized uptake values (SUVmax and SUVave) calculated from lung masses, LNs, metastatic lesions, and normal structures were compared. To evaluate the effects of the i.v. contrast agent on LN staging, we compared the LN status on the basis of SUVs (cut-offs; SUVmax = 3.5, SUVave = 3.0).The mean differences of SUVmax in normal structures between enhanced and nonenhanced PET/CT were 15.23% ± 13.19% for contralateral lung, 8.53% ± 6.11% for aorta, 5.85% ± 4.99% for liver, 5.47% ± 6.81% for muscle, and 2.81% ± 3.05% for bone marrow, and those of SUVave were 10.17% ± 9.00%, 10.51% ± 7.89%, 4.95% ± 3.89%, 5.66% ± 9.12%, and 2.49% ± 2.50%, respectively. The mean differences of SUVmax between enhanced and nonenhanced PET/CT were 5.89% ± 3.92% for lung lesions (n = 41), 6.27% ± 3.79% for LNs (n = 76), and 3.55% ± 3.38% for metastatic lesions (n = 35), and those of SUVave were 3.22% ± 3.01%, 2.86% ± 1.71%, and 2.33% ± 3.95%, respectively. Although one LN status changed from benign to malignant because of contrast-related artifact, there was no up- or down-staging in any of the patients after contrast enhancement.An i.v. contrast agent may be used in PET/CT without producing any clinically significant artifact.
Keywords: Lung cancer; 18F-FDG PET/CT; Intravenous contrast; Contrast-related artifact; Nodal stage
FDG-PET/CT findings of autoimmune pancreatitis associated with idiopathic retroperitoneal fibrosis by Hideki Otsuka; Naomi Morita; Kyo Yamashita; Hiromu Nishitani (593-596).
We report the fluorodeoxyglucose positron emission tomography (FDG-PET)/computed tomography (CT) findings of autoimmune pancreatitis (AIP) associated with idiopathic retroperitoneal fibrosis. A 69-year-old male patient was admitted to our hospital with obstructive jaundice. Six months prior to this admission, he was treated with steroid therapy for retroperitoneal fibrosis. Laboratory data showed that elevated T-bil, C-reactive protein, amylase and immunoglobulin 4, and antinuclear antibodies were positive. Clinical history, laboratory data, CT image, and magnetic resonance imaging led to a diagnosis of autoimmune pancreatitis. To investigate the inflammatory activity, FDG-PET/CT was undertaken. FDG-PET/CT demonstrated diffuse intense FDG uptake in the enlarged pancreas and diffuse mild uptake in the region of the abdominal aorta-bilateral iliac arteries. A dilated right renal pelvis and upper ureter, corresponding to hydronephrosis probably caused by retroperitoneal fibrosis, were shown. An FDG-PET/CT was useful to evaluate inflammatory activity and morphological imaging, and supported our diagnosis of AIP and retroperitoneal fibrosis.
Keywords: Autoimmune pancreatitis; Retroperitoneal fibrosis; FDG-PET/CT
Evaluation of portosystemic shunt caused by patent ductus venosus through sequential whole-body scanning using per-sigmoid colon 123I-IMP scintigraphy by Tomohiro Kaneta; Motoshi Wada; Kentaro Takanami; Tomohiro Ishii; Setsu Matsumoto; Ken Okada; Hiroshi Fukuda; Shogo Yamada; Shoki Takahashi (597-601).
The correct estimation of the portosystemic shunt (PSS) ratio prior to surgery for patent ductus venosus is important. Until now, formulas using the lung and liver uptake for per-rectal portal scintigraphy using 123I-iodoamphetamine (IMP) have been mainly used for calculating the PSS ratio. However, these methods did not take radioactivity in the brain or changes in organ radioactivity over time into consideration. Here, we performed sequential whole-body scanning by per-sigmoid colon 123I-IMP scintigraphy, and evaluated the changes in radioactivity in the liver, lungs, and brain over time.The patient was 7-year-old boy with a patent ductus venosus. A 10 Fr. catheter was inserted into the sigmoid colon under fluoroscopic guidance, through which about 55.5 MBq of 123I-IMP was administered. Following the administration, the patient was placed in the supine position and sequential whole-body scanning (from head to thigh) was performed for up to about 80 min. Four regions of interest (ROIs) were placed on the whole brain, lungs, liver, and mediastinum. The PSS ratios were calculated using both the traditional formula (PSS index: brain uptake is not considered) and our original formula (new index: brain uptake is considered).Prior to surgery, the radioactivity could be seen clearly in the brain and lungs just following the injection. The liver uptake was faint on the first and second scans (15 min/scan), and increased gradually over time. In contrast, almost no radioactivity was detected in the brain or lungs following surgery. The liver uptake could be seen clearly just following the injection. The new index was significantly higher than the PSS index. Both the new index and the PSS index showed changes over time especially prior to surgery.Distinct brain radioactivity was observed early following administration in a patient with PSS. The calculation of the PSS fraction should be performed taking the brain radioactivity into consideration. The timing of the scan should be fixed, but 30 min following administration may be too early to begin scanning.
Keywords: Portosystemic shunt; Ductus venosus; IMP; Scintigraphy
Simple provocative maneuvers in renal transplant scintigraphy for detecting urine leak by Fuat Dede; Tunc Ones; Billur Caliskan; Huseyin Civen; Tanju Y. Erdil; Sabahat Inanir; Zubeyde S. Tuglular; Cumhur Yegen; Emel Akoglu; Halil T. Turoglu (603-606).
Urine leak in the early postoperative period following renal transplantation is a serious complication requiring early identification and aggressive intervention, which significantly reduces the morbidity and mortality. Renal transplant scintigraphy is a noninvasive method to evaluate the perfusion and function of a transplanted kidney and urinary drainage including urine leak. Here, we reported two cases in which the standard transplant renogram failed to demonstrate urine leak. The cases were referred for a diethylenetriaminepentaacetic acid renogram following the transplantation to evaluate the cause of symptoms or elevated serum creatinine level. In both the cases, urine leak was successfully detected following simple maneuvers such as diuretic administration or Foley catheter irrigation. Renal transplant scintigraphy is an effective and safe technique and the use of these simple maneuvers can enhance the diagnostic sensitivity of the transplant renogram in the detection of urine leak.
Keywords: Urine leak; Tc-99 m DTPA; Renal scintigraphy; Transplanted kidney; Diuretic; Catheter irrigation
SUV correction for injection errors in FDG-PET examination by Kouichi Miyashita; Nobukazu Takahashi; Takashi Oka; Shinobu Asakawa; Jin Lee; Kazuya Shizukuishi; Tomio Inoue (607-613).
Many studies have documented the clinical usefulness of standardized uptake values (SUV) for diagnosis. However, in the event of injection error, accurate measurements cannot be obtained if the radioactivity of fluorodeoxyglucose (FDG) leakage is not subtracted from the administered dosage. Here, a correction formula for radioactivity estimation that takes into account the radioactivity of FDG leakage was derived on the basis of a phantom experiment. Furthermore, to determine whether SUV could be accurately calculated by the correction formula, we performed a volunteer study.Images were displayed by altering the conversion constant from 1.0, 0.1 to 0.01, and the range of correctable counts was verified on the basis of image inversion. To estimate the radioactivity of FDG leakage by imaging, the count of the leakage was measured, converted into a radioactivity concentration using a cross-calibration factor (CCF), and multiplied by volume, as measured by imaging. Three factors that markedly affect count, i.e., count rate performance, partial volume effect and crosstalk, were assessed in phantom studies in order to derive a correction formula. In addition, to clarify the accuracy of the correction formula, we attached to the right elbow.With a conversion constant of 0.1, there was no image inversion at ≤1.565 MBq/ml. At concentrations below this, the average detection rate was 90%. This suggests that count rate performance can be corrected at ≤1.0 MBq/ml. Crosstalk investigations clarified that the effects of adjacent radioactivity concentrations on FDG leakage were not marked. On the basis of investigations on partial volume effect and count rate performance, the following formulas were derived:For leakages of ≥28 mmLeakage radioactivity (MBq) = positron emission tomography (PET) radioactivity (MBq) × 0.9.For leakages of ≥15 mm but <28 mmLeakage radioactivity (MBq) = PET radioactivity (MBq) × 0.9 × (0.0517 × leakage size (mm) − 0.4029).In a volunteer study with 10 MBq leakage, SUV recalculated using the formula achieved 99.97% correction, whereas with 100 MBq leakage, SUV achieved 67.5% resulting in poor correction.The present correction technique can accurately calculate SUV and could be useful for the clinical diagnosis of malignant tumors.
Keywords: FDG; PET; SUV correction; Injection errors; Phantom studies