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Annals of Nuclear Medicine (v.22, #9)

Maximal safe dose of I-131 after failure of standard fixed dose therapy in patients with differentiated thyroid carcinoma by Jong Jin Lee; June-Key Chung; Sung Eun Kim; Won Jun Kang; Do Joon Park; Dong Soo Lee; Bo Youn Cho; Myung Chul Lee (pp. 727-734).

The maximal safe dose (MSD) on the basis of bone marrow irradiation levels allows the delivery of a large amount of I-131 to thyroid cancer tissue. The efficacy of MSD therapy in differentiated metastatic thyroid cancers that persisted after conventional fixed dose therapy is investigated.Forty-seven differentiated thyroid carcinoma patients with non-responsive residual disease despite repetitive fixed dose I-131 therapy were enrolled in this study. Their postoperative pathologies were 43 papillary carcinomas and 4 follicular carcinomas. The MSD was calculated with the Memorial Sloan-Kettering Cancer Center protocol using serial blood samples. The MSDs were administered at intervals of 6 months. Treatment responses were evaluated using I-131 whole-body scans and serum thyroglobulin measurements.The mean calculated MSD was 12.5 ± 2.1 GBq (339.6 ± 57.5 mCi). Of the 46 patients, 7 (14.9%) showed complete remission, 15 (31.9%) partial remission, 19 (40.4%) stable disease, and 6 (12.8%) disease progression. Of the patients who showed complete or partial remission, 15 (65%) showed response after the first MSD session and 6 (26%) showed response after the second session. Twenty-nine patients (62%) experienced transient cytopenia after therapy, but three did not recover to the baseline level.The maximal safe dose provides an effective means of treatment in patients who failed to respond adequately to conventional fixed dose therapy. I-131 MSD therapy can be considered in patients who fail fixed dose therapy.

Keywords: Thyroid carcinoma; I-131 therapy; Maximal safe dose

Radiosynoviorthesis (RSO): influencing factors and therapy monitoring by Lidiya Zuderman; Knut Liepe; Klaus Zöphel; Michael Andreeff; Joerg Kotzerke; Wolfgang Luboldt (pp. 735-741).

To evaluate the effectiveness of radiosynoviorthesis (RSO) in relation to joint type and underlying disease by both self-assessment of patients and scintigraphic assessment to determine conditions under which RSO might be preferable to the sole intra-articular corticoid injection.Radiosynoviorthesis was performed on 136 patients for 424 joints [242 small, 130 medium-sized, and 52 large joints; 313 with rheumatoid arthritis (RA) and 111 with osteoarthritis (OA)]. The success of RSO was evaluated after 12 months by patients’ estimation, and in 35 patients for 157 joints additionally by two-phase bone scintigraphy. The relative change in the scintigraphic uptake was compared with the patients’ estimation.The subjectively estimated success rates for the small, medium-sized, and large joints were 89% (215/242), 86% (112/130), and 79% (41/52), and for RA and OA 89% (280/313) and 79% (88/111), respectively. The scintigraphically determined response rates for small and medium-sized joints were 81% (86/106) and 69% (35/51), respectively. There was a mismatch between patients’ assessment and scintigraphic assessments in 18% (28/157) with 6 false-negative and 22 false-positive estimations using scintigraphy as the standard of reference.The success of RSO is higher in patients with RA than in patients with OA. For the finger, ankle, and wrist joints in RA, RSO is so promising that we would like to advocate its preference over the sole intraarticular corticoid injection. Perfusion bone scintigraphy can be used for therapy monitoring and earlier switching to RSO by showing that other therapies have failed.

Keywords: Synovitis; Rheumatoid arthritis; Osteoarthritis; Radiosynoviorthesis (RSO); Bone scintigraphy

Frequency and characteristics of extremely low accumulation of ¹²³I-metaiodobenzylguanidine (MIBG) in patients with and without cardiovascular diseases by Kazuyuki Sakata; Kei Iida; Nao Motiduki; Yoshihiro Nakaya (pp. 743-749).

Very low accumulation of ¹²³I-metaiodobenzylguanidine (LoMIBG) in the human heart has been reported. This study assessed the frequency and characteristics of LoMIBG in the human heart.A total of 2212 patients (male/female ratio 1442/770, mean age 64 ± 12 years) who underwent MIBG imaging were included. LoMIBG was defined as an initial heart-to-mediastinum (H/M) ratio of less than 1.4.Of the 114 patients with LoMIBG, 2 patients were excluded because of taking imipramine. Patients with LoMIBG were older than those without LoMIBG (P < 0.0001). The main diagnosis and the number of patients with each disease were as follows: 28 of 410 coronary artery disease patients, 13 of 371 vasospastic angina patients, 3 of 86 various arrhythmias patients, 4 of 23 valvular heart disease patients, 9 of 101 dilated cardiomyopathy patients, 13 of 512 essential hypertension patients, 2 of 20 hypertrophic cardiomyopathy patients, 24 of 511 subjects without any definite disease (control), and 16 of 176 patients with miscellaneous diseases. When compared with patients without LoMIBG in each cardiovascular disease, LoMIBG patients had left ventricular function and frequency similar to critically ill patients. In the control group, the subjects with LoMIBG were significantly older (P < 0.0001) and had significantly higher HF (P < 0.03) and lower LF/HF (P < 0.001) than those without LoMIBG. In addition, the incidence of LoMIBG was significantly elevated in the elderly (P < 0.002).LoMIBG occurred in patients both with various diseases and without obvious diseases. Aging may be one of the mechanisms contributing to LoMIBG, especially in patients without obvious diseases.

Keywords: MIBG imaging; Ageing; MIBG uptake; Heart

Relationship between left ventricular function and wall motion synchrony in heart failure assessed by ECG-gated myocardial perfusion SPECT by Akira Yamamoto; Naoto Takahashi; Masahiro Ishikawa; Kazuya Abe; Yuko Kobayashi; Jin Tamai; Kazuo Munakata (pp. 751-759).

To confirm the relationship between left ventricular (LV) function and wall motion synchrony, and to identify the difference of synchrony between an ischemic heart disease (IHD) patient group and other heart disease (OHD) patient group among classified groups in heart failure, systolic, and diastolic parameters were compared using electrocardiograph-gated single-photon emission computed tomography.Twenty IHD and 30 OHD patient groups, comprised New York Heart Association functional class I–III (IHD1-3 and OHD1-3), and 15 controls were examined. The LV functions (ejection fraction, EF; peak-filling rate, PFR) and synchrony, which was estimated from the time lag between the earliest and latest regional systolic or diastolic temporal parameters (maximum difference of regional time to end-systole, MD-TES, or maximum difference of regional time to peak filling, MD-TPF), were compared. The LV function correlated with its synchrony in IHD and OHD (EF vs. MD-TES: r = −0.86, P = 1.3 × 10⁻⁶ in IHD and r = −0.69, P = 2.8 × 10⁻⁵ in OHD. PFR versus MD-TPF: r = −0.67, P < 0.002 in IHD and r = −0.63, P < 0.0002 in OHD). Dyssynchronous normal EF was observed in three IHD (15%) and six OHD (20%). Dyssynchronous normal PFR was observed in six IHD (30%) and six OHD (20%). MD-TES was significantly smaller in control group (CG) than in IHD3 and OHD3 (P < 0.005), and in IHD1 than in IHD3 and OHD3 (P < 0.05). MD-TPF was significantly smaller in CG than in IHD2, IHD3, and OHD3 (P < 0.05). However, there was no significant difference between LV synchrony in IHD and OHD, or among LV synchrony of the same functional classes between these two groups.This study confirms that LV function is correlated with wall motion synchrony. No statistically significant difference was confirmed in wall motion synchrony between IHD and OHD. However, dyssynchrony appears in the patients without apparent global LV dysfunction. This feature may facilitate identification of synchronous disorder in HF patients with preserved global LV function. It is expected that detection of such a disorder may lead to the initiation of appropriate treatments for early stage HF and prevent its progression.

Keywords: Heart failure; Left ventricular function; Synchrony; Gated myocardial perfusion SPECT

Comparison between manual and automated techniques for assessment of data from dynamic antral scintigraphy by Gustavo P. Misiara; Luiz E. A. Troncon; Eder R. Moraes; Marie Secaf (pp. 761-767).

This work aimed at determining whether data from dynamic antral scintigraphy (DAS) yielded by a simple, manual technique are as accurate as those generated by a conventional automated technique (fast Fourier transform) for assessing gastric contractility.Seventy-one stretches (4 min) of “activity versus time” curves obtained by DAS from 10 healthy volunteers and 11 functional dyspepsia patients, after ingesting a liquid meal (320 ml, 437 kcal) labeled with technetium-99m (^99mTc)-phytate, were independently analyzed by manual and automated techniques.Data obtained by both techniques for the frequency of antral contractions were similar. Contraction amplitude determined by the manual technique was significantly higher than that estimated by the automated method, in both patients and controls. The contraction frequency 30 min post-meal was significantly lower in patients than in controls, which was correctly shown by both techniques.A manual technique using ordinary resources of the gamma camera workstation, despite yielding higher figures for the amplitude of gastric contractions, is as accurate as the conventional automated technique of DAS analysis. These findings may favor a more intensive use of DAS coupled to gastric emptying studies, which would provide a more comprehensive assessment of gastric motor function in disease.

Keywords: Gastric antrum; Scintigraphy; Radio nuclide imaging; Fourier analysis; Dyspepsia

¹²³I-BMIPP delayed scintigraphic imaging in patients with chronic heart failure by Keisuke Kida; Yoshihiro J. Akashi; Kihei Yoneyama; Mitsuhiro Shimokawa; Haruki Musha (pp. 769-775).

The objective of the present study was to clarify the ability of ¹²³I-beta-methyl-iodophenylpentadecanoic acid (¹²³I-BMIPP) to evaluate the heart-to-mediastinum (H/M) ratio and myocardial global washout rate (WR) in patients with chronic heart failure (CHF).The severity of CHF was evaluated on the basis of the New York Heart Association (NYHA) classification. Twenty patients with CHF (13 with idiopathic dilated cardiomyopathy and 7 with ischemic cardiomyopathy) and 11 age-matched controls underwent myocardial radionuclide imaging. Scintigraphic images were obtained from each participant at the early (30 min following radio-isotope injection) and late (4 h) phases using ¹²³I-BMIPP. The H/M ratio and WR were calculated from planar images. Concentrations of plasma brain natriuretic peptide (BNP) were measured prior to the scintigraphic study.The ¹²³I-BMIPP uptake of early H/M and global WR did not significantly differ among groups, but uptake of delayed H/M was significantly lower in patients with NYHA class III than in controls (control 2.47 ± 0.39; class III 1.78 ± 0.28, P < 0.05). The uptake of delayed H/M and global WR correlated with plasma log BNP in all participants (r = −0.38, P < 0.05; 0.43, P < 0.05, respectively).These data suggest that ¹²³I-BMIPP uptake of delayed H/M enhances the image of CHF severity. The myocardial WR of ¹²³I-BMIPP also effectively depicted the severity of CHF.

Keywords: Brain natriuretic peptide; Free fatty acid; Heart-to-mediastinum ratio; Washout; Heart failure

Lymphatic mapping with ^99mTc-Evans Blue dye in sheep by Chris Tsopelas; Max Bellon; Elaine Bevington; James Kollias; Sabah Shibli; Barry E. Chatterton (pp. 777-785).

^99mTc-Evans Blue (EB) is an agent that contains both radioactive and color signals in a single dose. Earlier studies in animal models have suggested that this agent when compared with the dual-injection technique of radiocolloid/blue dye can successfully discriminate the sentinel lymph node. The aim of this study was to investigate the potential of ^99mTc-EB as an agent to map the lymphatic system in an ovine model.Doses of ^99mTc-EB (23 MBq) containing EB dye (4 mg) were administered intradermally to the limbs of four anesthetized sheep, and they were then imaged over 20–30 min using a gamma camera. The study protocol was repeated using ^99mTc-antimony trisulfide colloid (ATC) and Patent Blue V dye. The lymph nodes (popliteal, inguinal, and iliac for hind limbs or prescapular for fore limbs) were identified with a gamma probe during the operative exposure, then dissected and counted in a large volume counter.Simple and complex (dual) drainage patterns were visible on the scans, and the sentinel node was more radioactive than higher tier nodes in a chain, for both radiotracers. For ^99mTc-EB, maximum radioactive uptake was achieved at 3–6 min for popliteal lymph nodes, 12–14 min for iliac nodes, and 13–14 min for prescapular nodes. ^99mTc-ATC resulted in maximum radioactive uptake at 4–6 min for popliteal lymph nodes, 13 min for an inguinal node, 13–20 min for iliac nodes, and 18 min for a prescapular node. Following ^99mTc-EB injection, 15/15 lymph nodes harvested were all radioactive and blue. For ^99mTc-radiocolloid/Patent Blue V injection, 8/14 nodes were radioactive and blue, and 6/14 nodes were radioactive only.The soluble radiotracer ^99mTc-EB appeared to be a useful lymphoscintigraphic agent in sheep, in which radioactive counts from superficial lymphatic channels and lymph nodes were sufficient for planar imaging. In comparison with ^99mTc-antimony trisulfide colloid, both tracers discriminated the sentinel lymph node up to 50 min after administration; however, ^99mTc-EB had the advantage of providing radioactive (gamma probe) and color signals simultaneously during the operative exposure.

Keywords: Radioactive blue dye; Lymphoscintigraphy; Sentinel lymph node; Evans Blue

[F-18]-fluorodeoxyglucose PET-CT of the normal prostate gland by Hossein Jadvar; Wei Ye; Susan Groshen; Peter S. Conti (pp. 787-793).

We determined the glucose metabolism and computed tomographic (CT) density of the normal prostate gland in relation to age and prostate size on [F-18] fluorodeoxyglucose positron emission tomography (PET)-CT.We determined the CT density (Hounsfield Units, HU) and glucose metabolism (standardized uptake value, SUV) of the normal prostate in 145 men (age range 22–97 years) on PET-CT scans which were performed for indications unrelated to prostate pathology. Correlations among SUV, HU, prostate size, and age were calculated using Pearson’s correlation coefficients, scatter plots, and linear regression trend lines. The SUV and HU values were also compared among different primary cancer types using the Kruskal-Wallis test.The population average and range of the normal prostate size were 4.3 ± 0.5 cm (mean ± SD) and 2.9–5.5 cm, respectively. The population average of mean and maximum CT densities was 36.0 ± 5.1 HU (range 23-57) and 91.7 ± 20.1 HU (range 62-211), respectively. The population average of mean and maximum SUV was 1.3 ± 0.4 (range 0.1–2.7) and 1.6 ± 0.4 (range 1.1–3.7), respectively. Mean SUV tended to decrease as the prostate size increased (r = −0.16, P = 0.058). Higher mean HU was correlated with higher mean SUV (r = 0.18, P = 0.033). The strongest association was observed between age and prostate size. The prostate gets larger as age increases (r = 0.32, P < 0.001). Prostate mean SUV, max SUV, mean HU, and max HU were not significantly different among different types of primary cancers.Although the normal prostate size increases with age, it does not significantly affect the gland’s metabolism and CT density, and therefore age-correction of these parameters may be unnecessary.

Keywords: Prostate; FDG; PET-CT

¹⁸F-FDG-PET in patients with malignant lymphoma having long-term follow-up: staging and restaging, and evaluation of treatment response and recurrence by Kayako Isohashi; Mitsuaki Tatsumi; Ichiro Higuchi; Atsuo Inoue; Kazuya Nakajo; Jun Ishikawa; Eku Shimosegawa; Yuzuru Kanakura; Hironobu Nakamura; Jun Hatazawa (pp. 795-802).

The aim of this study was to evaluate the diagnostic accuracy of positron emission tomography (PET) with 2-[¹⁸F]fluoro-2-deoxy-d-glucose (¹⁸F-FDG) for staging/restaging, evaluating the treatment response, and screening of recurrence in patients with malignant lymphoma (ML) during long-term follow-up, and to compare that with computer tomography (CT)/magnetic resonance imaging (MRI).The study was conducted in 59 ML patients who underwent whole-body ¹⁸F-FDG-PET examinations three times or more from October 1998 to August 2006. The location of the lesions in the patients with positive findings on ¹⁸F-FDG-PET and/or the corresponding CT/MRI was classified into supradiaphragmatic (n = 10), infradiaphragmatic (n = 7), and extranodal sites (n = 20), and the findings were compared on a site basis according to the gold standard, which consisted of all clinical information available, including follow-up results.A total of 156 ¹⁸F-FDG-PET examinations for which the corresponding CT/MRI images were also available were evaluated, and a total of 305 sites showed positive findings on ¹⁸F-FDG-PET and/or CT/MRI. Concordant positive findings were obtained in 76% for staging/restaging, 34% for evaluation of the treatment response, and 50% for screening of recurrence. The accuracy of ¹⁸F-FDG-PET versus CT/MRI was 92% versus 84% (P = 0.06) for staging/restaging, 84% versus 50% (P < 0.05) for the evaluation of the treatment response, and 83% versus 72% (P = 0.21) for the screening of recurrence. At pathologic sites with discrepant findings between ¹⁸F-FDG-PET and CT/MRI (n = 122), the frequency of accurate diagnosis by ¹⁸F-FDG-PET (76%) was higher than that by CT/MRI (24%), especially for the evaluation of the treatment response. ¹⁸F-FDG-PET is expected to play a significant role in the management of ML patients even after effective treatment is initiated.

Keywords: Fluorodeoxyglucose; FDG; PET; Malignant lymphoma; Treatment response

Incidence and characteristics of uterine leiomyomas with FDG uptake by Sadahiko Nishizawa; Masayuki Inubushi; Aki Kido; Masao Miyagawa; Takeshi Inoue; Katsura Shinohara; Makoto Kajihara (pp. 803-810).

Uterine leiomyomas sometimes show focal ¹⁸F-fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET) images that may result in a false-positive diagnosis for malignant lesions. This study was conducted to investigate the incidence and characteristics of uterine leiomyomas that showed FDG uptake.We reviewed FDG-PET and pelvic magnetic resonance (MR) images of 477 pre-menopausal (pre-MP, age 42.1 ± 7.3 years) and 880 post-MP (age 59.9 ± 6.8 years) healthy women who underwent these tests as parts of cancer screening. Of 1357, 323 underwent annual cancer screening four times, 97 did three times, 191 did twice, and the rest were screened once. Focal FDG uptake (maximal standardized uptake value > 3.0) in the pelvis was localized and characterized on co-registered PET/MR images.Uterine leiomyomas were found in 164 pre-MP and 338 post-MP women. FDG uptake was observed in 18 leiomyomas of 17 of the 164 (10.4%) pre-MP women and in 4 leiomyomas of 4 of the 338 (1.2%) post-MP women. The incidence was significantly higher in pre-MP women than in post-MP women (chi-square, P < 0.001). Of the 22, 13 showed signal intensity equal to or higher than that of the myometrium on T2-weighted MR images, which suggested abundant cellularity, whereas the majority of leiomyomas without FDG uptake showed low signal intensity. Of the 13 women, 12 examined more than twice showed substantial changes in the level of FDG uptake in leiomyomas each year with FDG uptake disappearing or newly appearing. These changes were observed frequently in relation with menopause or menstrual phases.Leiomyomas with focal FDG uptake were seen in both pre-and post-MP women with a higher incidence in pre-MP women. Abundant cellularity and hormonal dependency may explain a part of the mechanisms of FDG uptake in leiomyomas. It is important to know that the level of FDG uptake in leiomyomas can change and newly appearing FDG uptake does not necessarily mean malignant transformation.

Keywords: FDG-PET; MRI; Uterine leiomyomas; Genitourinary oncology

Occult myofibroblastic sarcoma detected on FDG-PET performed for cancer screening by Takeshi Morii; Kazuo Mochizuki; Hideto Sano; Takashi Fujino; Arimi Harasawa; Kazuhiko Satomi (pp. 811-815).

We present a rare case of occult low-grade myofibroblastic sarcoma (LGMFS) detected by marked 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) uptake on positron emission tomography (PET). A 46-year-old woman presented with abnormal FDG uptake in her back when FDG-PET was performed for cancer screening. The maximum standard uptake values (SUV_max) were 9.8. Physical examination and laboratory investigations revealed no abnormalities. Magnetic resonance images demonstrated an ill-defined 2 × 3 cm mass in the multifidus muscle. Excisional biopsy led to a pathological diagnosis of LGMFS. Additional wide resection was performed for local control. No local recurrence or distant metastasis was observed 12 months after the initial operation. This is the first report describing FDG-PET findings of LGMFS, suggesting a discrepancy between histological grade and SUV intensity in this low-grade entity.

Keywords: Soft tissue sarcoma; Low-grade myofibroblastic sarcoma; FDG-PET; SUV

^99mTc-HYNIC octreotide in neuroblastoma by Juan P. Gambini; Juan J. López Lerena; Adriana Quagliata; Juan C. Hermida; Carlos Heuguerot; Omar Alonso (pp. 817-819).

Disease status assessment of neuroblastoma patients requires computed tomography (or magnetic resonance imaging), bone scan, metaiodobenzylguanidine (MIBG) scan, bone marrow tests, and urine catecholamine measurements. There is no clinical experience concerning the evaluation of these patients by means of technetium-99m (^99mTc)-somatostatin analog scintigraphy. Furthermore, these radiopharmaceuticals are promising imaging agents owing to their lower cost, availability, dosimetry, and ease of preparation. An 8-year-old boy already diagnosed with stage-IV neuroblastoma received chemotherapy. In the follow-up, after obtaining the parents’ informed consent, iodin 131 (¹³¹I)-MIBG and ^99mTc-6-hydrazinopyridine-3-carboxylic acid (HYNIC)-octreotide scans were done on separate days to evaluate tumor extension. Even as the ¹³¹I-IBG scan showed mild diffuse uptake in the projection of both lung hili, the ^99mTc-HYNIC-octreotide scan showed multiple axial and appendicular bone uptakes and paravertebral, abdominal, mediastinal, and supraclavicular ganglionar uptakes. The ^99mTc-HYNIC-octreotide showed much more lesion extension than the ¹³¹I-MIBG. Therefore, ^99mTc-HYNIC-octreotide may be a promising radiopharmaceutical for the evaluation of neuroblastoma patients. This finding justifies the pre liminary evaluation of this tracer in the context of a clinical trial.

Keywords: ¹³¹I-MIBG; ^99mTc-HYNIC-octreotide; Neuroblastom

Adrenocortical oncocytoma displaying intense activity on ¹⁸F-FDG-PET: a case report and a literature review by Dae Jung Kim; Jae-Joon Chung; Young Hoon Ryu; Soon Won Hong; Jeong-Sik Yu; Joo Hee Kim (pp. 821-824).

We report on the ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) findings in a case of adrenocortical oncocytoma, a rare tumor of the adrenal gland with the literature review of other imaging findings including ultrasonography, computed tomography, and magnetic resonance imaging. To our knowledge, there have been no reports published in the English literature about ¹⁸F-FDG-PET findings in adrenocortical oncocytoma.

Keywords: Positron emission tomography; ¹⁸F-fluorodeoxyglucose; Tomography; Adrenal gland neoplasms; Adenoma, oxyphilic

Behaviors of cost functions in image registration between ²⁰¹Tl brain tumor single-photon emission computed tomography and magnetic resonance images by Tsutomu Soma; Akihiro Takaki; Satomi Teraoka; Yasushi Ishikawa; Kenya Murase; Kiyoshi Koizumi (pp. 825-832).

We studied the behaviors of cost functions in the registration of thallium-201 (²⁰¹Tl) brain tumor single-photon emission computed tomography (SPECT) and magnetic resonance (MR) images, as the similarity index of image positioning.A marker for image registration [technetium-99m (^99mTc) point source] was attached at three sites on the heads of 13 patients with brain tumor, from whom 42 sets of ^99mTc-²⁰¹Tl SPECT (the dual-isotope acquisition) and MR images were obtained. The ²⁰¹Tl SPECT and MR images were manually registered according to the markers. From the positions where the two images were registered, the position of the ²⁰¹Tl SPECT was moved to examine the behaviors of the three cost functions, i.e., ratio image uniformity (RIU), mutual information (MI), and normalized MI (NMI).The cost functions MI and NMI reached the maximum at positions adjacent to those where the SPECT and MR images were manually registered. As for the accuracy of image registration in terms of the cost functions MI and NMI, on average, the images were accurately registered within 3° of rotation around the X-, Y-, and Z-axes, and within 1.5 mm (within 2 pixels), 3 mm (within 3 pixels), and 4 mm (within 1 slice) of translation to the X-, Y-, and Z-axes, respectively. In terms of rotation around the Z-axis, the cost function RIU reached the minimum at positions where the manual registration of the two images was substantially inadequate.The MI and NMI were suitable cost functions in the registration of ²⁰¹Tl SPECT and MR images. The behavior of the RIU, in contrast, was unstable, being unsuitable as an index of image registration.

Keywords: Cost function; Registration; Brain tumor; Tl-201 SPECT; Magnetic resonance imaging

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Annals of Nuclear Medicine (v.22, #9)