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Annals of Nuclear Medicine (v.25, #9)

Usefulness of Tc-99m-GSA scintigraphy for liver surgery by Masaki Kaibori; Sang Kil Ha-Kawa; Minoru Maehara; Morihiko Ishizaki; Kosuke Matsui; Satoshi Sawada; A-Hon Kwon (pp. 593-602).

Postoperative mortality remains high after hepatectomy compared with other types of surgery in patients who have cirrhosis or chronic hepatitis. Although there are several useful perioperative indicators of liver dysfunction, no standard markers are available to predict postoperative liver failure in patients with hepatocellular carcinoma (HCC) undergoing hepatectomy. The best preoperative method for evaluating the hepatic functional reserve of patients with HCC remains unclear, but technetium-99m diethylenetriamine pentaacetic acid galactosyl human serum albumin (^99mTc-GSA) scintigraphy is a candidate. ^99mTc-GSA is a liver scintigraphy agent that binds to the asialoglycoprotein receptor, and can be used to assess the functional hepatocyte mass and thus determine the hepatic functional reserve in various physiological and pathological states. The maximum removal rate of ^99m Tc-GSA (GSA-Rmax) calculated by using a radiopharmacokinetic model is correlated with the severity of liver disease. There is also a significant difference of GSA-Rmax between patients with chronic hepatitis and persons with normal liver function. Regeneration of the remnant liver and recurrence of hepatitis C virus infection in the donor organ after living donor liver transplantation have also been investigated by ^99mTc-GSA scintigraphy. This review discusses the usefulness of ^99mTc-GSA scintigraphy for liver surgery.

Keywords: GSA-Rmax; Hepatocellular carcinoma; Hepatectomy; Living donor liver transplantation; Regeneration; Hepatitis C virus

Pulmonary embolism in pregnancy: a diagnostic dilemma by Nosheen Fatima; Maseeh uz Zaman; Zafar Sajjad; Ibrahim Hashmi (pp. 603-608).

The diagnosis of PE in pregnancy poses a challenge due to pregnancy-related physiological changes. Missing the PE or wrongly treating a pregnant woman for PE has serious clinical consequences. There has been concern over the use of radiation-based imaging modalities due to risk of teratogenicity and oncogenicity. This review is focused on various diagnostic options and risks of radiation to the fetus and mother from radiation-based procedures.

Keywords: Pulmonary embolism; V/Q scans; DVT; Radiation exposure; CT pulmonary angiography; MRA

Double-phase ¹³¹I whole body scan and ¹³¹I SPECT-CT images in patients with differentiated thyroid cancer: their effectiveness for accurate identification by Hiroshi Wakabayashi; Kenichi Nakajima; Makoto Fukuoka; Anri Inaki; Ayane Nakamura; Daiki Kayano; Seigo Kinuya (pp. 609-615).

This study aims to determine whether a ¹³¹I double-phase whole body scan (WBS) and SPECT-CT images have added value over a single-phase WBS image in identifying benign and malignant lesions in patients with well-differentiated thyroid cancer (DTC) at their first radioactive iodine (RAI) treatment.This study included 42 DTC patients who underwent their first radioablation. Post-therapeutic WBS images were acquired after 3 days (early phase) and 7 days (delayed phase). Following early-phase WBS, SPECT-CT images were obtained. The images were reviewed independently of the clinical data by 2 board-certified observers with a 6-point scoring system (benign to malignant −3 to +3).The double-phase WBS and SPECT-CT images showed 115 radioiodine-avid localizations (81 benign and 34 malignant accumulations). Confidence levels of benign accumulations were significantly higher with SPECT-CT (average score −2.40 ± 1.06) compared to those of the early-phase WBS (average score −1.39 ± 1.88) (p < 0.0001) and delayed-phase WBS images (average score −1.49 ± 1.19) (p < 0.0001). When the analysis was restricted to accumulations with a low confidence score in the early-phase WBS image, the confidence level of the delayed-phase WBS was higher compared to that of the early-phase WBS images (p = 0.0012). The confidence levels of malignant accumulations were significantly higher with SPECT-CT images (average score 2.37 ± 0.96) compared to the early-phase WBS (average score 1.44 ± 1.21) (p < 0.0001) and the delayed-phase WBS images (average score 1.50 ± 1.13) (p < 0.0001).Post-therapeutic SPECT-CT image was superior to the early-phase WBS image in enhancing the confidence level and accurately localizing the lesions. The delayed-phase WBS image contributed to the accurate diagnosis of benign lesions with a low confidence level in the early-phase WBS image.

Keywords: Thyroid cancer; ¹³¹I; Whole body scan; SPECT-CT

Impact of chronic kidney disease and stress myocardial perfusion imaging as a predictor of cardiovascular events by Tatsuhiko Furuhashi; Masao Moroi; Nobuhiko Joki; Hiroki Hase; Hirofumi Masai; Taeko Kunimasa; Ryo Nakazato; Hiroshi Fukuda; Kaoru Sugi (pp. 616-624).

Stress myocardial perfusion imaging (MPI) is an established means of predicting cardiovascular events and is suitable in chronic kidney disease (CKD) patients. We aimed to evaluate the prognostic value of CKD parameters and an abnormal stress MPI for cardiovascular events.A total of 495 patients with suspected coronary artery disease (CAD) or history of CAD including 130 CKD patients not undergoing hemodialysis, underwent stress MPI (313 males, mean age 70 years) and were followed up for 14 months (mean period). CKD was defined as an estimated GFR of <60 ml/min/1.73 m² and/or persistent proteinuria. Cardiovascular events were defined as sudden cardiac death, acute coronary syndrome and congestive heart failure requiring hospitalization.Cardiovascular events occurred in 41 (8.3%) patients. Multivariate Cox regression analysis indicated that CKD [hazard ratio (HR) = 3.76, p < 0.001] and a stress MPI summed difference score (SDS) of ≥2 (HR = 3.78, p < 0.001) were independent predictors of cardiovascular events; CKD plus abnormal stress MPI was also a strong predictor of cardiovascular events (non-CKD and SDS <2 vs. CKD and SDS ≥2, HR = 15.9, p < 0.001).Both CKD and myocardial ischemia detected by stress MPI are independent predictors for cardiovascular events. Coexistence of CKD and myocardial ischemia detected by stress MPI is more useful for short-term risk stratification of cardiovascular events.

Keywords: Thallium-201; Myocardial perfusion imaging; SPECT; Coronary artery disease

18F-fluoromisonidazole positron emission tomography before treatment is a predictor of radiotherapy outcome and survival prognosis in patients with head and neck squamous cell carcinoma by Masahiro Kikuchi; Tomohiko Yamane; Shogo Shinohara; Keizo Fujiwara; Shin-ya Hori; Yosuke Tona; Hiroshi Yamazaki; Yasushi Naito; Michio Senda (pp. 625-633).

To evaluate the usefulness of [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO)-positron emission tomography (PET) prior to the treatment of head and neck squamous cell carcinoma.Seventeen patients with untreated HNSCC underwent pretreatment [¹⁸F]FMISO PET. Six of them underwent definitive surgery and the remaining 11 definitive (chemo-)radiotherapy. We evaluated 30 lesions from the 17 patients. SUVmax and tumor-to-muscle ratios (TMR) were measured as hypoxia indicators. Tumors equal to or above the median value were defined as tumor with high uptake of [¹⁸F]FMISO and those below as tumor with low uptake of [¹⁸F]FMISO in both indicators. Local control rates with radiotherapy, event-free survival and disease-specific survival (DSS) rates with radiotherapy or operation were compared.[¹⁸F]FMISO-PET imaging of 30 lesions resulted in a SUVmax median value of 2.3 and a TMR median value of 1.3. Local control rates with radiotherapy (20-month median follow-up duration) were significantly lower in the tumor group with high uptake of [¹⁸F]FMISO compared to the tumor group with low uptake of [¹⁸F]FMISO using either SUVmax or TMR as the hypoxic indicator (P = 0.02 and 0.04, respectively). DSS rate with radiotherapy or operation (21-month median follow-up duration) was significantly lower in the patient group with high uptake of [¹⁸F]FMISO compared to the patient group with low uptake of [¹⁸F]FMISO defined by SUVmax (P = 0.04), but was not by TMR (P = 0.57).Radiotherapy outcome and survival prognosis (radiotherapy or operation) in HNSCC may be predicted by carrying out [¹⁸F]FMISO PET before treatment.

Keywords: [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO); Positron emission tomography (PET); Hypoxia; Head and neck cancer; Prediction of prognosis

Correlation of chronic kidney disease, diabetes and peripheral artery disease with cardiovascular events in patients using stress myocardial perfusion imaging by Tatsuhiko Furuhashi; Masao Moroi; Hirofumi Masai; Taeko Kunimasa; Ryo Nakazato; Hiroshi Fukuda; Kaoru Sugi (pp. 634-642).

Normal stress myocardial perfusion imaging (MPI) studies generally suggest an excellent prognosis for cardiovascular events. Chronic kidney disease (CKD), diabetes and peripheral artery disease (PAD) have been established as the risk factors for cardiovascular events. However, whether these risk factors significantly predict cardiovascular events in patients with normal stress MPI is unclear. The purpose of this study was to evaluate the prognostic value of these risk factors in patients with normal stress MPI.Patients with normal stress MPI (n = 372, male = 215 and female = 157, age = 69 years, CKD without hemodialysis = 95, diabetes = 99, PAD = 19, previous coronary artery disease = 116) were followed up for 14 months. Normal stress MPI was defined as a summed stress score of <4 and a summed difference score of <2. CKD was defined by an estimated glomerular filtration rate of <60 ml/min/1.73 m² and/or persistent proteinuria. Cardiovascular events included cardiac death, non-fatal myocardial infarction and congestive heart failure requiring hospitalization.Cardiovascular events occurred in 20 of 372 patients (5.4%). In univariate Cox regression analysis, PAD, diabetes, diabetic retinopathy, insulin use, anemia, hypoalbuminemia, CKD, left ventricular ejection fraction and pharmacological stress tests were significant predictors of cardiovascular events. In multivariate Cox regression analysis, PAD, diabetes and CKD were independent and significant predictors for cardiovascular events, and their number was the strongest predictor for cardiovascular events (hazard ratio = 21.7, P < 0.001).PAD, diabetes and CKD are coexisting, independent and significant risk factors for cardiovascular events, CKD being the strongest predictor. The number of coexisting risk factors is important in predicting cardiovascular events in patients with normal stress MPI.

Keywords: Thallium-201; Myocardial perfusion imaging; SPECT; Coronary artery disease

Comparative evaluation of scatter correction in 3D PET using different scatter-level approximations by Irene Polycarpou; Kris Thielemans; Ravindra Manjeshwar; Pablo Aguiar; Paul K. Marsden; Charalampos Tsoumpas (pp. 643-649).

In 3D PET, scatter of the gamma photons is one of the most significant physical factors which degrades not only image quality but also quantification. The currently most used scatter estimation method is the analytic single scatter simulation (SSS) which usually accommodates for multiple scattering by scaling the single scatter estimation. However, it has not been clear yet how accurate this approximation is for cases where multiple scatter is significant, raising the question: “How important is correction for multiple scattered photons, and how accurately do we need to simulate all scattered events by appropriate scaling?” This study answers these questions and evaluates the accuracy of SSS implementation in the open-source library STIR.Different scatter orders approximations are evaluated including different levels of scattering and different scaling approaches using Monte Carlo (i.e. SimSET) data. SimSET simulations of a large anthropomorphic phantom were reconstructed with iterative reconstruction algorithms. Images reconstructed with 3D filtered back-projection reprojection algorithm have been compared quantitatively in order to clarify the errors due to different scatter order approximations.Quantification in regions has improved by scatter correction. For example, in the heart the ideal value was 3, whereas before scatter correction the standard uptake value (SUV) was 4.0, after single scatter correction was 3.3 and after single and double scatter correction was 3.0. After correction by scaling single scatter with tail-fit, the SUV was 3.1, whereas with total-fit it was 3.0. Similarly, for the SSS correction methodology implemented in STIR using tail-fit the heart SUV was 3.1 whereas using total-fit it was 3.0.The results demonstrate that correction for double scatter improves image contrast and therefore it is required for the accurate estimation of activity distribution in PET imaging. However, it has been also shown that scaling the single scatter distribution is a reasonable approximation to compensate for total scatter. Finally, scatter correction with STIR has shown excellent agreement with Monte Carlo simulations.

Keywords: Scatter; Quantification; Monte Carlo; STIR

The relationship between stress-induced myocardial ischemia and coronary artery atherosclerosis measured by hybrid SPECT/CT camera by Shinro Matsuo; Kenichi Nakajima; Koichi Okuda; Seigo Kinuya (pp. 650-656).

The coronary artery calcium (CAC) score and myocardial perfusion imaging can now be detected simultaneously using a hybrid SPECT/CT camera. However, there has been little evaluation on the relationship between stress-induced ischemia and coronary artery calcification in a Japanese population. The aim of this study was to investigate the relationship between these parameters and to elucidate the diagnostic value of the CAC score as an adjunct to myocardial perfusion imaging (MPI) for the assessment of coronary artery disease (CAD) in an intermediate-risk population.We retrospectively analyzed 105 patients (63% men, mean age 71 years) with CAD or suspected CAD who underwent MPI using SPECT/CT. CAC scanning was performed using a SPECT/CT camera.There was a significant difference in the CAC score between patients with ischemia (n = 42) and those without ischemia (n = 63) (1353 ± 1524 vs. 332 ± 554, p < 0.01). The frequency of ischemic MPI determined by summed difference score tended to be higher in patients with high CAC (CAC = 0; 0.8 ± 1.3 vs. CAC > 1000; 3.0 ± 2.0). Higher age is related roughly with higher CAC score with no statistical significance (r ² = 0.1) (<60 years old; 200 ± 692, vs. >80 years old; 1258 ± 1546, ns). The location of calcification was not related to the ischemic area. In a population with a predominately intermediate likelihood of CAD, a calcium score of zero has a possibility of excluding inducible ischemia on MPI. In part, ischemic MPI is associated with a high likelihood of subclinical atherosclerosis as detected by CAC.Hybrid SPECT/CT might be useful for diagnostic assessment and coronary artery with known or suspected CAD.

Keywords: SPECT/CT; Coronary calcification; Ischemia; Normal perfusion; Diagnostic work-up

Radiation exposure and risk–benefit analysis in cancer screening using FDG-PET: results of a Japanese nationwide survey by Takeshi Murano; Ryogo Minamimoto; Michio Senda; Kimiichi Uno; Seishi Jinnouchi; Hiroshi Fukuda; Takeshi Iinuma; Eriko Tsukamoto; Takashi Terauchi; Tsuyoshi Yoshida; Shinya Oku; Sadahiko Nishizawa; Kengo Ito; Kazuhiro Oguchi; Masami Kawamoto; Rumi Nakashima; Hiroshi Iwata; Tomio Inoue (pp. 657-666).

The aim of this study was to estimate radiation exposure and evaluate the risks and benefits of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in cancer screening.A nationwide survey of FDG-PET cancer screening was conducted in 2006, and the results were analyzed with a common index, “extension/shortening of the average life expectancy.”The average estimated effective dose was 4.4 mSv (male 4.7 mSv; female 4.0 mSv) for dedicated PET and 13.5 mSv (male 14.2 mSv; female 12.8 mSv) for PET/computed tomography (CT). The risk–benefit break-even age from the viewpoint of radiation exposure was in the 40s for men and 30s for women for dedicated PET and in the 50s for men and 50s (variable injection dose) or 60s (constant injection dose) for women for PET/CT.FDG-PET cancer screening is beneficial for examinees above the break-even ages. The risks and benefits should be explained to examinees because of the larger radiation used in cancer FDG-PET screening compared with other X-ray tests.

Keywords: Cancer screening; Positron emission tomography; Radiation exposure; Risk; Benefit

Cancer screening by FDG-PET: benefit or risk? by Jun Hatazawa (pp. 667-668).

Imaging discordance between hepatic angiography versus Tc-99m-MAA SPECT/CT: a case series, technical discussion and clinical implications by Yung Hsiang Kao; Eik Hock Tan; Terence Kiat Beng Teo; Chee Eng Ng; Soon Whatt Goh (pp. 669-676).

During pre-therapy evaluation for yttrium-90 (Y-90) radioembolization, it is uncommon to find severe imaging discordance between hepatic angiography versus technetium-99m-macroaggregated albumin (Tc-99m-MAA) single photon emission computed tomography with integrated low-dose CT (SPECT/CT). The reasons for severe imaging discordance are unclear, and literature is scarce. We describe 3 patients with severe imaging discordance, whereby tumor angiographic contrast hypervascularity was markedly mismatched to the corresponding Tc-99m-MAA SPECT/CT, and its clinical impact. The incidence of severe imaging discordance at our institution was 4% (3 of 74 cases). We postulate that imaging discordance could be due to a combination of 3 factors: (1) different injection rates between soluble contrast molecules versus Tc-99m-MAA; (2) different arterial flow hemodynamics between soluble contrast molecules versus Tc-99m-MAA; (3) eccentric release position of Tc-99m-MAA due to microcatheter tip location, inadvertently selecting non-target microparticle trajectories. Tc-99m-MAA SPECT/CT more accurately represents hepatic microparticle biodistribution than soluble contrast hepatic angiography and should be a key criterion in patient selection for Y-90 radioembolization. Tc-99m-MAA SPECT/CT provides more information than planar scintigraphy to guide radiation planning and clinical decision making. Severe imaging discordance at pre-therapy evaluation is ominous and should be followed up by changes to the final vascular approach during Y-90 radioembolization.

Keywords: Yttrium-90 radioembolization; Catheter-directed CT hepatic angiography; Tc-99m-MAA SPECT/CT; Imaging discordance; Microparticle trajectory selection; Yttrium-90 time-of-flight PET/CT

Molybdenum-99/technetium-99m management: race against time by Mushtaq Ahmad (pp. 677-679).

Molybdenum-99 is a parent of diagnostic nuclear medicine. It decays to technetium-99m, which used in over 30 million investigations per year around the world. Supplies of Tc-99m remained fragile in the last few years, which may occur again in the short and long term. Few suggestions have been registered in this letter to cope inadequate supply of the most wanted radionuclide for patient care.

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Annals of Nuclear Medicine (v.25, #9)