Dual-labeled trastuzumab-based imaging agent for the detection of human epidermal growth factor receptor 2 overexpression in breast cancer.

Overexpression of the human epidermal growth factor receptor (HER) family has been implicated in cancer because of its participation in signaling pathways regulating cellular proliferation, differentiation, motility, and survival. In this work, we exploited the extracellular binding property of trastuzumab, a clinically therapeutic monoclonal antibody to the second member of the HER family (HER2), to design a diagnostic imaging agent, ((111)In-DTPA)(n)-trastuzumab-(IRDye 800CW)(m), that is dual labeled with (111)In, a gamma-emitter, and a near-infrared (NIR) fluorescent dye, IRDye 800CW, to detect HER2 overexpression in breast cancer cells. The stoichiometric ratios "n" and "m" refer to the number of diethylenetriaminepentaacetic acid dianhydride (DTPA) and IRDye 800CW molecules bound per trastuzumab molecule, respectively. METHODS: Fluorescence microscopy and confocal microscopy were used to determine the molecular specificity of (DTPA)(n)-trastuzumab-(IRDye800)(m) in vitro in SKBr3 (HER2-positive) and MDA-MB-231 (HER2-negative) breast cancer cells. SKBr3 cells were incubated with (DTPA)(n)-trastuzumab-(IRDye800)(m) or IRDye800CW or pretreated with trastuzumab or human IgG followed by (DTPA)(n)-trastuzumab-(IRDye800)(m) and examined under a fluorescence microscope. For in vivo characterization, athymic nude mice bearing HER2-overexpressing SKBr3-luc subcutaneous xenografts were injected intravenously with ((111)In-DTPA)(n)-trastuzumab-(IRDye800)(m) and imaged with SPECT and NIR fluorescence imaging at 48 h. Tumor-bearing mice were also injected intravenously with trastuzumab 24 h before administration of ((111)In-DTPA)(n)-trastuzumab-(IRDye800)(m). Nonspecific uptake in the SKBr3-luc tumors was analyzed by injecting the mice with IRDye 800CW and ((111)In-DTPA)(p)-IgG-(IRDye800)(q), where "p" and "q" are the stoichiometric ratios of DTPA and IRDye 800CW bound per IgG antibody, respectively. RESULTS: (DTPA)(n)-trastuzumab-(IRDye800)(m) showed significantly greater binding to SKBr3 cells than to MDA-MB-231 cells. Confocal imaging revealed that this binding occurred predominantly around the cell membrane. Competitive binding studies with excess trastuzumab before incubation with (DTPA)(n)-trastuzumab-(IRDye800)(m) abolished this binding affinity, but pretreatment with nonspecific IgG did not alter binding. In vivo nuclear and optical imaging of SKBr3-luc xenografts injected with ((111)In-DTPA)(n)-trastuzumab-(IRDye800)(m) revealed significantly more uptake in the tumor region than in the contralateral muscle region. The tumor-to-muscle ratio decreased in mice pretreated with trastuzumab and in mice injected with IRDye 800CW and ((111)In-DTPA)(p)-IgG-(IRDye800)(q). Ex vivo imaging of dissected organs confirmed these results. Finally, coregistration of histologic hematoxylin-eosin stains with autoradiography signals from tumor and muscle tissue slices indicated that ((111)In-DTPA)(n)-trastuzumab-(IRDye800)(m) bound only in tumor tissue and not to muscle. CONCLUSION: Dual-labeled ((111)In-DTPA)(n)-trastuzumab-(IRDye800)(m) may be an effective diagnostic biomarker capable of tracking HER2 overexpression in breast cancer patients.     

<Superscript>68</Superscript>Ga- and <Superscript>111</Superscript>In-labelled DOTA-RGD peptides for imaging of αvβ3 integrin expression

PURPOSE: alphavbeta3 integrins are important cell adhesion receptors involved in angiogenic processes. Recently, we demonstrated using [(18)F]Galacto-RGD that monitoring of alphavbeta3 expression is feasible. Here, we introduce (68)Ga- and (111)In-labelled derivatives and compare them with [(18)F]Galacto-RGD. METHODS: For radiolabelling, cyclo(RGDfK(DOTA)) was synthesised using SPPS. For in vitro characterisation determination of partition coefficients, protein binding, metabolic stability, alphavbeta3 affinity and cell uptake and for in vivo characterization, biodistribution studies and micro positron emission tomography (PET) imaging were carried out. For in vivo and in vitro studies, human melanoma M21 (alphavbeta3 positive) and M21-L (alphavbeta3 negative) cells were used. RESULTS: Both tracers can be synthesised straightforward. The compounds showed hydrophilic properties and high metabolic stability. Up to 23% protein-bound activity for [(68)Ga]DOTA-RGD and only up to 1.4% for [(111)In]DOTA-RGD was found. Cell uptake studies indicate receptor-specific accumulation. This is confirmed by the biodistribution data. One hour p.i. accumulation in alphavbeta3-positive tumours was 2.9 +/- 0.3%ID/g and in alphavbeta3-negative tumours 0.8 +/- 0.1%ID/g for [(68)Ga]DOTA-RGD ([(111)In]DOTA-RGD: 1.9 +/- 0.3%ID/g and 0.5 +/- 0.2%ID/g; [(18)F]Galacto-RGD: 1.6 +/- 0.2%ID/g and 0.4 +/- 0.1%ID/g). Thus, tumour uptake ratios were comparable. Due to approx. 3-fold higher blood pool activities for [(68)Ga]DOTA-RGD, tumour/blood ratios were higher for [(111)In]DOTA-RGD and [(18)F]Galacto-RGD. However, microPET studies demonstrated that visualisation of alphavbeta3-positive tumours using [(68)Ga]DOTA-RGD is possible. CONCLUSIONS: Our data indicate that [(68)Ga]DOTA-RGD allows monitoring of alphavbeta3 expression. Especially, the much easier radiosynthesis compared to [(18)F]Galacto-RGD would make it an attractive alternative. However, due to higher blood pool activity, [(18)F]Galacto-RGD remains superior for imaging alphavbeta3 expression. Introduction of alternative chelator systems may overcome the disadvantages.     

Rapid optical imaging of human breast tumour xenografts using anti-HER2 VHHs site-directly conjugated to IRDye 800CW for image-guided surgery

Purpose

Molecular optical imaging using monoclonal antibodies is slow with low tumour to background ratio. We used anti-HER2 VHHs conjugated to IRDye 800CW to investigate their potential as probes for rapid optical molecular imaging of HER2-positive tumours by the determination of tumour accumulation and tumour to background levels.

Methods

Three anti-HER2 VHHs (11A4, 18C3, 22G12) were selected with phage display and produced in Escherichia coli. Binding affinities of these probes to SKBR3 cells were determined before and after site-specific conjugation to IRDye 800CW. To determine the potential of VHH-IR as imaging probes, serial optical imaging studies were carried out using human SKBR3 and human MDA-MB-231 xenograft breast cancer models. Performance of the anti-HER2 VHH-IR was compared to that of trastuzumab-IR and a non-HER2-specific VHH-IR. Image-guided surgery was performed during which SKBR3 tumour was removed under the guidance of the VHH-IR signal.

Results

Site-specific conjugation of IRDye 800CW to three anti-HER2 VHHs preserved high affinity binding with the following dissociation constants (K_D): 11A4 1.9?±?0.03, 18C3 14.3?±?1.8 and 22G12 3.2?±?0.5 nM. Based upon different criteria such as binding, production yield and tumour accumulation, 11A4 was selected for further studies. Comparison of 11A4-IR with trastuzumab-IR showed ～20 times faster tumour accumulation of the anti-HER2 VHH, with a much higher contrast between tumour and background tissue (11A4-IR 2.5?±?0.3, trastuzumab-IR 1.4?±?0.4, 4 h post-injection). 11A4-IR was demonstrated to be a useful tool in image-guided surgery.

Conclusion

VHH-IR led to a much faster tumour accumulation with high tumour to background ratios as compared to trastuzumab-IR allowing same-day imaging for clinical investigation as well as image-guided surgery.     

Fluorescence reflectance imaging of macrophage-rich atherosclerotic plaques using an alphavbeta3 integrin-targeted fluorochrome

Macrophages play an important role during the development and progression of atherosclerotic plaques. alphavbeta3 integrins are highly expressed by macrophages; thus, targeting alphavbeta3 may allow targeting of culprit macrophage-loaded atherosclerotic lesions in vivo. METHODS: An alphavbeta3-targeted Arg-Gly-Asp (RGD) peptide was labeled with the cyanine 5.5 (Cy 5.5) dye and applied to image atherosclerotic plaques in apolipoprotein E-deficient mice. RESULTS: The peptide-dye conjugate binds to alphavbeta3 integrin-positive RAW264.7 macrophages with high affinity. Competition experiments confirmed binding specificity of the probe. A significant fluorochrome accumulation in atherosclerotic plaques was demonstrated 24 h after injection by fluorescence reflectance imaging, which was blocked with high efficiency by competition with the unlabeled peptide. Conversely, the nonconjugated dye revealed only a minor fluorescence signal in the plaques. Fluorescence microscopy revealed colocalization of the probe with macrophages in the plaque of a mouse model for accelerated atherosclerosis, which was corroborated in human carotid artery specimens. In addition to macrophage-associated signals, binding of the probe to the neointima or elastica of the arteries was observed. CONCLUSION: RGD-Cy 5.5, combined with near-infrared optical imaging methods, allows the specific imaging of alphavbeta3-integrin expression on macrophages recruited to vascular lesions and may serve to estimate macrophage-bound inflammatory activity of atherosclerotic lesions.     

Gastroesophageal scintigraphy in children: a comparison of posterior and anterior imaging

The purpose of this study was to compare the posterior dynamic imaging with the anterior imaging in the evaluation of children with gastroesophageal reflux (GER). Sixty-eight children (26 female, 42 male; age range 4 months to 7 years, median 21 months) were studied. After 4-hour fasting, all the subjects underwent gastroesophageal scintigraphy. Synchronous dynamic imaging in the anterior and posterior projections was performed with the subject in the supine position with a dual-head gamma camera equipped with low-energy general-purpose collimators at a rate of 30 s/frame for 40 min. The anterior and posterior images were visually evaluated for the presence of gastroesophageal reflux by two nuclear medicine physicians. The anterior and posterior images were correlated by Pearson correlation analysis, and inter-observer variability was evaluated by paired t-test and kappa value. There was a good correlation between the two projections with r-values of 0.906-0.990. The inter-observer agreement for interpretation of the anterior and posterior imaging was excellent (k: 0.83). In conclusion, anterior and posterior dynamic imaging showed excellent correlation in detection of GER in children. Posterior imaging is superior to anterior imaging in that it is more comfortable, and it reduces motion artifacts, especially for infants and anxious children; thus, it may be preferred over anterior imaging.     

Nuclear magnetic resonance and gamma camera tumor imaging using gadolinium-labeled monoclonal antibodies

Chelate-derivatized monoclonal antibody labeled with paramagnetic gadolinium-3+ ion has been evaluated as a tumor-specific contrast-enhancing agent in nuclear magnetic resonance imaging in the Rauscher murine erythroleukemia system. With 10(-7) M concentrations of Gd3+ delivered to the tumor target, a small but reproducible difference in proton relaxation times (T1S) was observed in excised tumors. Nuclear magnetic resonance imaging of animals, however, failed to show significant contrast enhancement of the tumor; by comparison, gamma camera images with 153Gd-labeled specific antibody did permit clear tumor visualization without subtraction. The potential use of monoclonal antibodies in tumor imaging appears to be far greater in gamma camera and positron imaging than in nuclear magnetic resonance imaging.     

Scintigraphic imaging of uveal melanoma with 99Tcm-glutathione

A prospective study with a new tumour-seeking agent, 99Tcm-glutathione (GSH), was performed on 17 patients with choroidal melanoma. Planar and SPECT images using 99Tcm-GSH clearly demonstrated melanotic melanoma but failed to show amelonotic melanomas. Following confirmation of our results by concurrent ultrasonography and magnetic resonance imaging or computed tomography, patients were managed by either 125I plaque brachytherapy, diode laser transpupillary thermotherapy or enucleation depending on the site and location. In combination with other diagnostic tests, 99Tcm-GSH scintigraphy may play a role in the detection of uveal melanoma and its possible distant metastases.     

Development of a macromolecular dual-modality MR-optical imaging for sentinel lymph node mapping

OBJECTIVE: To evaluate the effectiveness of a dual magnetic resonance-near infrared fluorescence optical imaging agent, poly(l-glutamic acid)-DTPA-Gd-NIR813, for both preoperative and intraoperative visualization and characterization of sentinel lymph nodes (SLN) in mice. MATERIALS AND METHODS: Poly(L-glutamic acid) was conjugated with DTPA-Gd and NIR813 dye to obtain PG-DTPA-Gd-NIR813. To confirm drainage into the SLNs, this agent was injected subcutaneously into the front paw of nude mice followed by isosulfan blue (n = 6). Furthermore, PG-DTPA-Gd-NIR813 was injected subcutaneously at doses of 0.002 mmol Gd/kg (4.8 nmol eq. NIR813) and 0.02 mmol Gd/kg (48 nmol eq. NIR813) (n = 3/dose). To differentiate metastatic from nonmetastatic lymph nodes, nude mice bearing human oral squamous cell carcinoma (DM14) were injected intralingually with 0.02 mmol Gd/kg PG-DTPA-Gd-NIR813 (n = 3). Pre- and postcontrast images were taken using 4.7 T Bruker MRI scanner and Xenogen optical imaging system. The status of lymph nodes resected under the guidance of optical imaging was confirmed by histologic examinations. RESULTS: PG-DTPA-Gd-NIR813 colocalized with isosulfan blue, indicating drainage to the SLN. After subcutaneous injection, axiliary and branchial lymph nodes were clearly visualized with both T1-weighted MR and optical imaging within 3 minutes of contrast injection, even at the lowest dose tested (0.002 mmol Gd/kg). After intralingual injection in tumor-bearing mice, MR imaging identified 4 of the 6 superficial cervical lymph nodes, whereas near-infrared fluorescence (NIRF) optical imaging identified all 6 cervical nodes. The pattern of contrast enhancement of SLN visualized in MR images showed a characteristic ring-shaped appearance with a central filling defect, possibly resulting from nodal infiltration of metastatic lesions. Histopathologic examination of the SLNs resected under NIRF imaging guidance revealed micrometastases in all 6 SLNs identified by NIRF imaging. CONCLUSIONS: The dual modality imaging method demonstrated in this study represents an effective technique for localization and characterization of SLN.     

I-123 MIBG imaging and intraoperative localization of metastatic pheochromocytoma: a case report

The authors describe the diagnostic use of I-123 MIBG scintigraphy in a 61-year-old man who was thought to have a recurrence 25 years after a left adrenalectomy for a pheochromocytoma. Preoperative I-123 MIBG scintigraphy was performed twice along with intraoperative gamma probe localization of the lesions. The preoperative MIBG scintigraphy revealed three pathologic processes in the upper left abdomen, whereas computed tomographic scanning identified only one site of involvement. All three metastatic lesions were removed successfully with the aid of a gamma probe. Preoperative I-123 MIBG scintigraphy, combined with intraoperative gamma probe identification of I-123 MIBG foci, is feasible and a valuable tool to detect malignant masses possibly overlooked by other imaging techniques.     

Diagnostic and therapeutic evaluation of 111In-vinorelbine-liposomes in a human colorectal carcinoma HT-29/luc-bearing animal model

Colorectal carcinoma is a highly prevalent and common cause of cancer in Taiwan. There is still no available cure for this malignant disease. To address this issue, we applied the multimodality of molecular imaging to explore the efficacy of diagnostic and therapeutic nanoradiopharmaceuticals in an animal model of human colorectal adenocarcinoma [colorectal cancer (CRC)] that stably expresses luciferase (luc) as a reporter. In this study, an in vivo therapeutic efficacy evaluation of dual-nanoliposome (100 nm in diameter) encaged vinorelbine (VNB) and (111)In-oxine on HT-29/luc mouse xenografts was carried out. HT-29/luc tumor cells were transplanted subcutaneously into male SCID mice. Multimodality of molecular imaging approaches including bioluminescence imaging (BLI), gamma scintigraphy, whole-body autoradiography (WBAR) and in vivo tumor growth tracing, histopathology and biochemistry/hematology analyses were applied on xenografted SCID mice to study the treatments with 6% polyethylene glycol (PEG) of (111)In-NanoX/VNB-liposomes. In vivo tumor growth tracing and BLI showed that tumor volume could be completely inhibited by the combination therapy with (111)In-VNB-liposomes and by chemotherapy with NanoX/VNB-liposomes (i.e., without Indium-111) (P<.01). The nuclear medicine images of gamma scintigraphy and WBAR also revealed the conspicuous inhibition of tumor growth by the combination therapy with (111)In-VNB-liposomes. Animal body weights, histopathology and biochemistry/hematology analyses were used to confirm the safety and feasibility of radiopharmaceuticals. A synergistic therapeutic effect on CRC xenografted SCID mice was proven by combining an Auger electron-emitting radioisotope (Indium-111) with an anticancer drug (VNB). This study further demonstrates the beneficial potential applications of multimodality molecular imaging as part of the diagnostic and therapeutic approaches available for the evaluation of new drugs and other strategic approaches to disease treatment.     

A dendrimer-based nanosized contrast agent dual-labeled for magnetic resonance and optical fluorescence imaging to localize the sentinel lymph node in mice

PURPOSE: To preoperatively and intraoperatively localize the sentinel lymph node (SLN), a single hybrid probe for MR and near infrared (NIR) optical imaging was synthesized and tested. MATERIALS AND METHODS: A macromolecular MR/NIR optical contrast agent was synthesized based on a approximately 191 gadolinium-labeled contrast agent using generation-6 polyamidoamine dendrimer (G6), which is also labeled with 2 Cy5.5, an NIR fluorophore. After establishing the optimal dose, the agent was injected into mammary glands of 10 normal mice to examine the lymphatic drainage from the breast using a 3T clinical scanner. Immediately after the MRI scan, NIR optical imaging and image-guided surgery were performed to compare the two imaging modalities. RESULTS: To consistently identify the SLNs, we needed to inject 25 microL of 30 mM [Gd] G6-Cy5.5. All SLNs could be easily identified and resected under NIR optical imaging-guided surgery. Although external NIR optical imaging failed to identify SLNs close to the injection site due to shinethrough, MR lymphography (MRL) consistently identified all SLNs regardless of their location. CONCLUSION: We have successfully synthesized and tested a dual labeled MR/NIR optical hybrid contrast agent, G6-Cy5.5 for reoperative and intraoperative localization of SLNs.     

Bone marrow investigation with technetium-99m microcolloid and magnetic resonance imaging in patients with malignant myelolympho-proliferative diseases

In 63 patients with primary extramedullary malignant lymphoma or plasmacytoma, a study was performed in order to evaluate bone marrow involvement. All patients underwent a 99mTc microcolloid bone marrow whole body imaging (scintigraphy), using a gamma camera interfaced with a computer, followed by nuclear magnetic resonance bone marrow imaging (MRI), (1.5 Tesla). MR images were made of the lumbosacral region, the pelvic region, both femoral and other parts of the skeleton, according to focal lesions in the scintigraphy. A posterior iliac crest bone marrow biopsy was used as a standard reference. In the present study, both scintigraphy and MRI showed a dissiminated or focal involvement or a combination of both. In 53 of the 63 patients (84%) the results were in accordance. Pathological MR signals or pathological findings in scintigraphy did not always correspond to tumorous bone marrow involvement, and were shown to reflect reactive changes in the central part of the skeleton in combination with a periphery radionuclide extention interpreted as a periphery compensatory hematopoietic proliferation. The negative predictive value of scintigraphy and MRI was 92% and 100%, respectively. When combining the results of both examinations, the positive predictive value increased from 49% to 58%, if the bone marrow biopsy is accepted as gold standard. The results indicate that bone marrow investigation performed simultaneously using scintigraphy and MRI is superior both to the use of either of the methods alone and to the traditional iliac crest bone marrow biopsy.     

64Cu-TETA-octreotide as a PET imaging agent for patients with neuroendocrine tumors.

64Cu (half-life, 12.7 h; beta+, 0.653 MeV [17.4%]; beta-, 0.579 MeV [39%]) has shown potential as a radioisotope for PET imaging and radiotherapy. (111)In-diethylenetriaminepentaacetic acid (DTPA)-D-Phe1-octreotide (OC) was developed for imaging somatostatin-receptor-positive tumors using conventional scintigraphy. With the advantages of PET over conventional scintigraphy, an agent for PET imaging of these tumors is desirable. Here, we show that 64Cu-TETA-OC (where TETA is 1,4,8,11-tetraazacyclotetradecane-N,N',N',N'-tetraacetic acid) and PET can be used to detect somatostatin-receptor-positive tumors in humans. METHODS: Eight patients with a history of neuroendocrine tumors (five patients with carcinoid tumors and three patients with islet cell tumors) were imaged by conventional scintigraphy with (111)In-DTPA-OC (204-233 MBq [5.5-6.3 mCi]) and by PET imaging with 64Cu-TETA-OC (111 MBq [3 mCi]). Blood and urine samples were collected for pharmacokinetic analysis. PET images were collected at times ranging from 0 to 36 h after injection, and the absorbed doses to normal organs were determined. RESULTS: In six of the eight patients, cancerous lesions were visible by both (111)In-DTPA-OC SPECT and 64Cu-TETA-OC PET. In one patient, (111)In-DTPA-OC showed mild uptake in a lung lesion that was not detected by 64Cu-TETA-OC PET. In one patient, no tumors were detected by either agent; however, pathologic follow-up indicated that the patient had no tumors. In two patients whose tumors were visualized with (111)In-DTPA-OC and 64Cu-TETA-OC, 64Cu-TETA-OC and PET showed more lesions than (111)In-DTPA-OC. Pharmacokinetic studies showed that 64Cu-TETA-OC was rapidly cleared from the blood and that 59.2% +/- 17.6% of the injected dose was excreted in the urine. Absorbed dose measurements indicated that the bladder wall was the dose-limiting organ. CONCLUSION: The high rate of lesion detection, sensitivity, and favorable dosimetry and pharmacokinetics of 64Cu-TETA-OC indicate that it is a promising radiopharmaceutical for PET imaging of patients with neuroendocrine tumors.     

99mTc-EDDA/HYNIC-TOC: a new 99mTc-labelled radiopharmaceutical for imaging somatostatin receptor-positive tumours; first clinical results and intra-patient comparison with 111In-labelled octreotide derivatives

[111In-diethylene triamine penta-acetic acid-D-Phe1]-octreotide (DTPA-octreotide) scintigraphy has gained widespread acceptance as a diagnostic clinical procedure in oncology for imaging somatostatin receptor-positive tumours. However, indium-111 as a radiolabel has several drawbacks, including limited availability, suboptimal gamma energy and high radiation burden to the patient. We have recently reported on the preclinical development of 99mTc-EDDA/HYNIC-TOC, a new octreotide derivative which showed promising results both in vitro and in vivo. We now report our initial clinical experiences with this new radiopharmaceutical in ten oncological patients. The clinical diagnoses were: carcinoid syndrome (n=5), thyroid cancer (n=3), pancreatic cancer (n=1) and pituitary tumour (n=1). The biodistribution and kinetics of 99mTc-EDDA/HYNIC-TOC were compared with those of 111In-DTPA-octreotide in six cases, and with those of 111In-DOTA-TOC in five cases. With the new tracer tumours were imaged within 15 min after injection and showed the highest target/non-target ratios 4 h after injection. Tumour uptake persisted up to 20 h p.i. The rate of blood clearance was similar to that of 111In-DTPA-octreotide but faster than that of 111In-DOTA-TOC, while urinary excretion was lower compared with the 111In derivatives. Semi-quantitative region of interest analysis showed that 99mTc-EDDA/HYNIC-TOC produced higher tumour/organ (target/non-target) ratios than the 111In derivatives, especially in relation to heart and muscle. Significantly more lesions could be detected in 99mTc images. We conclude that 99mTcEDDA/HYNIC-TOC shows better imaging properties for the identification of somatostatin receptor-positive tumour sites than currently available 111In-labelled octreotide derivatives.     

Correlative imaging in abdominal infection: An algorithmic approach using nuclear medicine, ultrasound, and computed tomography

A wide variety of focal and diffuse infectious processes involve the abdomen. At one extreme are diseases such as pyelonephritis, cystitis, and pelvic inflammatory disease, conditions usually diagnosed without imaging studies and treated without complications. At the other extreme are abdominal abscesses, which may defy clinical diagnosis, are associated with significant morbidity and mortality, and may remain undetected or insufficiently characterized in spite of multiple imaging studies. The limited diagnostic value of clinical evaluation and plain film radiography in abscess detection has lead to widespread use of sophisticated imaging techniques including Gallium-67 (67Ga) scintigraphy, Indium-111 WBC (111In-WBC) scintigraphy, computed tomography (CT), and ultrasonography (US). Abdominal abscesses occur in a wide variety of anatomic sites, may involve any abdominal organ system, and have a number of different causes. The heterogeneity of the disease process and the varying capabilities of the different imaging techniques (with respect to site and organ system) make reliance on a single technique undesirable. An algorithmic approach using 67Ga or 111In-WBC scintigraphy, CT, and US provides a logical and clinically practical approach to complicated abdominal infection. By recognizing differences in clinical presentation and by appreciating the diagnostic strengths and weaknesses of nuclear medicine, CT, and US, the algorithm provides a reliable and direct route to accurate diagnosis while minimizing unnecessary examinations.     

131I and 111In-labelled monoclonal antibody imaging of primary lung carcinoma

Preliminary clinical studies have been carried out to determine whether the monoclonal antibody 791T/36 would localize in primary lung cancer to an extent sufficient for external detection by gamma scintigraphy. Radiolabelling of the antibody with 131I permitted visualization of three out of eight (38%) tumours using planar imaging with 99Tcm-labelled blood pool subtraction. Radiolabelling of the same antibody with 111In permitted visualization of tumour uptake in nine out of 13 (69%) tumours, without the need for image subtraction. Single photon emission computed tomography (SPECT) studies of seven patients demonstrated concentration of 111In-labelled antibody at the tumour site in each case, four of which were visualized on the planar images. The present study demonstrates localization of the 791T/36 antibody in primary lung carcinoma and confirms the superiority of 111In over 131I as a radiolabel for antibody imaging, especially when emission tomography is performed. These data indicate that further work will be required to determine whether this antibody will be a suitable carrier for cytotoxic agents in the therapy of lung cancer.     

99mTc- and 111In-labeled alpha-melanocyte-stimulating hormone peptides as imaging probes for primary and pulmonary metastatic melanoma detection.

It is highly desired to develop new imaging probes for early detection of melanoma as early diagnosis and prompt surgical removal are a patient's best hope for a cure. The purpose of this study was to determine whether (99m)Tc- and (111)In-labeled alpha-melanocyte-stimulating hormone (alpha-MSH) peptides could be used as imaging probes for primary and metastatic melanoma using dual-modality micro-SPECT/CT detection. METHODS: [Cys(3,4,10),d-Phe(7),Arg(11)]alpha-MSH(3-13) [(Arg(11))CCMSH] and [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]Re(Arg(11))CCMSH [DOTA-Re(Arg(11))CCMSH] were labeled with (99m)Tc and (111)In. The pharmacokinetics of (99m)Tc-(Arg(11))CCMSH were examined in B16/F1 flank and B16/F10 pulmonary metastatic murine melanoma-bearing C57 mice. The biodistribution of (111)In-DOTA-Re(Arg(11))CCMSH was performed in B16/F10 pulmonary metastatic murine melanoma-bearing C57 mice. SPECT/CT of (99m)Tc-(Arg(11))CCMSH and (111)In-DOTA-Re(Arg(11))CCMSH was determined in B16/F1 flank and B16/F10 pulmonary metastatic murine melanoma-bearing C57 mice. RESULTS: (99m)Tc-(Arg(11))CCMSH and (111)In-DOTA-Re(Arg(11))CCMSH exhibited high tumor uptakes (14.03 +/- 2.58 percentage injected dose/gram [%ID/g] at 1 h after injection and 17.29 +/- 2.49 %ID/g at 2 h after injection) in B16/F1 melanoma-bearing mice, and the flank melanoma tumors were clearly imaged by micro-SPECT/CT. Nontarget organ uptakes were considerably lower except for the kidneys. B16/F10 pulmonary melanoma metastases were also clearly visualized by micro-SPECT/CT using (99m)Tc-(Arg(11))CCMSH or (111)In-DOTA-Re(Arg(11))CCMSH as the imaging probe. (99m)Tc-(Arg(11))CCMSH exhibited images with greater resolution of metastatic melanoma lesions compared with (111)In-DOTA-Re(Arg(11))CCMSH. CONCLUSION: The favorable tumor imaging properties of (99m)Tc-(Arg(11))CCMSH and (111)In-DOTA-Re(Arg(11))CCMSH highlighted their potential as novel probes for primary and metastatic melanoma detection.     

Nuclear imaging of solid hepatic masses

This review has focused on the unique role of radionuclide scintigraphy in characterization of hepatic mass lesions. Radionuclide scintigraphy, unlike most other imaging modalities, is based on specific physiological and biochemical properties of each pathological entity that affects the liver. Hepatic scintigraphy, with its widespread availability, noninvasive nature, and relatively low cost is a powerful adjunct to other imaging techniques in the investigation of hepatic mass lesions. We have reviewed clinical presentation and characteristic findings of most hepatic lesions and have described reported findings with all available imaging modalities with particular emphasis on hepatic scintigraphy (Table 1) as well as a suggested algorithm for workup of solid hepatic masses (Fig 6). Additionally, the role of newer, more specialized techniques including PET scanning, ¹²³I-labeled VIP, and ¹¹¹In-labeled DTPA-D-Pheoctreotide scanning are reviewed. Hepatic nuclear scintigraphy continues to play an important role in the management of patients with solid hepatic masses.     

Bone marrow investigation with technetium-99m microcolloid and magnetic resonance imaging in patients with malignant myelolympho-proliferative diseases

In 63 patients with primary extramedullary malignant lymphoma or plasmacytoma, a study was performed in order to evaluate bone marrow involvement. All patients underwent a ^99mTc microcolloid bone marrow whole body imaging (scintigraphy), using a gamma camera interfaced with a computer, followed by nuclear magnetic resonance bone marrow imaging (MRI), (1.5 Tesla). MR images were made of the lumbosacral region, the pelvic region, both femoral and other parts of the skeleton, according to focal lesions in the scintigraphy. A posterior iliac crest bone marrow biopsy was used as a standard reference. In the present study, both scintigraphy and MRI showed a dissiminated or focal involvement or a combination of both. In 53 of the 63 patients (84%) the results were in accordance. Pathological MR signals or pathological findings in scintigraphy did not always correspond to tumorous bone marrow involvement, and were shown to reflect reactive changes in the central part of the skeleton in combination with a periphery radionuclide extention interpreted as a periphery compensatory hematopoetic proliferation. The negative predictive value of scintigraphy and MRI was 92% and 100%, respectively. When combining the results of both examinations, the positive predictive value increased from 49% to 58%, if the bone marrow biopsy is accepted as gold standard. The results indicate that bone marrow investigation performed simultaneously using scintigraphy and MRI is superior both to the use of either of the methods alone and to the traditional iliac crest bone marrow biopsy.     

A gallium-labeled DOTA-alpha-melanocyte- stimulating hormone analog for PET imaging of melanoma metastases.

Although (18)F-FDG PET is widely used for metastatic melanoma diagnosis, it is less accurate than desirable, particularly for small foci. Since both melanotic and amelanotic melanomas overexpress receptors for alpha-melanocyte-stimulating hormone (alpha-MSH; receptor name, melanocortin type 1 receptor [MC1R]), radiolabeled alpha-MSH analogs are potential candidates for melanoma diagnosis. The aim of this study was to develop a positron emitter-labeled alpha-MSH analog suitable for PET imaging of melanoma metastases. METHODS: A short linear alpha-MSH analog, [Nle(4),Asp(5),D-Phe(7)]-alpha-MSH(4-11) (NAPamide), was newly designed and conjugated to the metal chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) to enable radiometal incorporation. Compared with our previously reported DOTA-alpha-MSH analog, DOTA-MSH(oct) ([DOTA-betaAla(3),Nle(4),Asp(5),D-Phe(7),Lys(10)]-alpha-MSH(3-10)), the major modification lies in the conjugation of DOTA to the C-terminal end of the peptide via the epsilon-amino group of Lys(11), as opposed to the N-terminal alpha-amino group. After labeling with (111)In, (67)Ga, and the short-lived positron emitter (68)Ga, DOTA-NAPamide was characterized in vitro and in vivo using the mouse melanoma B16F1cell line. RESULTS: DOTA-NAPamide exhibited an almost 7-fold higher MC1R binding potency as compared with DOTA-MSH(oct). In B16F1 melanoma-bearing mice, both (111)In-DOTA-NAPamide and (67)Ga-DOTA-NAPamide behaved more favorably than (111)In-DOTA-MSH(oct). Both radiopeptides exhibited higher tumor and lower kidney uptake leading to tumor-to-kidney ratios of the 4- to 48-h area under the curve that were 4.6 times ((111)In) and 7.5 times ((67)Ga) greater than that obtained with (111)In-DOTA-MSH(oct). In addition, the 4-h kidney uptake of (67)Ga-DOTA-NAPamide could be reduced by 64% by coinjection of 15 mg L-lysine, without affecting tumor uptake. Skin primary melanoma as well as lung and liver melanoma metastases could be easily visualized on tissue section autoradiographs after systemic injection of (67)Ga-DOTA-NAPamide. The melanoma selectivity of DOTA-NAPamide was confirmed by PET imaging studies using (68)Ga-DOTA-NAPamide. Tumor uptake was found to be highest when the smallest amount of peptide was administered. CONCLUSION: DOTA-NAPamide labeled with either (111)In or (67)Ga/(68)Ga is in every way superior to (111)In-DOTA-MSH(oct) in murine models of primary and metastatic melanoma, which makes it a promising agent for melanoma targeting. High-contrast images obtained in PET studies with an experimental tumor model 1 h after injection augurs well for its clinical potential as an imaging tool.