HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nijsen, J. F. W. Articles by van het Schip, A. D. Search for Related Content PubMed PubMed Citation Articles by Nijsen, J. F. W. Articles by van het Schip, A. D.

Liver Tumors: MR Imaging of Radioactive Holmium Microspheres—Phantom and Rabbit Study¹

¹ From the Department of Nuclear Medicine, University Medical Centre, Heidelberglaan 100, Room E02.222, 3584 CX, Utrecht, the Netherlands (J.F.W.N., T.H., A.D.v.h.S.); and Image Sciences Institute, University Medical Centre, Utrecht, the Netherlands (J.H.S., C.B., C.J.G.B.). Received April 15, 2003; revision requested July 1; revision received August 22; accepted October 8. Address correspondence to J.F.W.N. (e-mail: f.nijsen@azu.nl).

View larger version (55K): [in a new window]   Figure 1. A, Scanning electron micrograph of Ho-PLLA-MS (original magnification, x500). B, Graph shows volume-weight distribution of sieved microspheres, which had a mean diameter of 30 µm. Ninety-six percent of the volume of the particles had a diameter of 20-40 µm.

View larger version (17K): [in a new window]   Figure 2. A, Graph shows R1 values versus Ho-PLLA-MS concentration. B, Graph shows R2 values versus Ho-PLLA-MS concentration. C, Graph shows R2* values versus Ho-PLLA-MS concentration. The solid line is a least squares fit to the data points and represents the theoretical result in the static dephasing regime (equation 11 in reference 23) as calculated from the holmium content of the microspheres.

View larger version (17K): [in a new window]   Figure 3. Graph shows detection of Ho-PLLA-MS passing a scaled model of a human vena cava. Dashed lines denote the baseline values before injection of the boluses. For the small dose (5.5 mg), a rapid injection was given at point A, whereas the large dose was injected from points B to C. Point D is a rapid flushing of the injection catheter with the circulating fluid. The areas between the baseline values and the curves are proportional to the injected doses. a.u. = arbitrary units.

View larger version (137K): [in a new window]   Figure 4. Images show results of dynamic MR imaging of the administration of Ho-PLLA-MS in an ex vivo rabbit liver (without tumor). A, Photograph of the ex vivo liver. B, Diagram of the ex vivo liver. Microsphere administration was mainly selective for the medial lobe and left lateral lobe. C, Dynamic coronal T2*-weighted FFE MR images (12/4.6, 9.2; 25.6 x 19.2-cm field of view; 256 x 192 matrix; 4.0- or 10.0-mm transverse sections; 10° flip angle; temporal resolution of 1 second per image) show administration of the microspheres in the liver. Images 1-3, section thickness of 4 mm; images 4-8, section thickness of 10 mm. Microspheres first collect in the more peripheral regions of the liver; thereafter, larger central arterial vessels are filled.

View larger version (85K): [in a new window]   Figure 5. Coronal MR and scintigraphic images of one of the treated tumor-bearing rabbits. A, Anatomic T1-weighted spin-echo MR image (466/13, 25.6 x 15.3-cm field of view, 205 x 256 matrix, 15 adjacent sections with 5.0-mm thickness, four signals acquired, and 90° flip angle). B, Holmium-sensitive T2*-weighted FFE MR image (30/4.6, 9.2; 25.6 x 15.3-cm field of view; 128 x 128 matrix [reconstruction, 256 x 256]; 15 adjacent sections with 5.0-mm thickness; eight signals acquired; 15° flip angle). A and B were obtained after Ho-PLLA-MS administration (48 mg, 560 MBq) into the hepatic artery, showing the biodistribution of Ho-PLLA-MS in relation to the surrounding areas. Increased accumulations of paramagnetic holmium are seen on the T2*-weighted MR image (B) as signal voids (small arrows) due to the paramagnetic nature of the holmium. The larger arrow indicates the substantial accumulation of microspheres in and around the tumor. C, Schematic shows the organs and tumor in the rabbit. D, Whole-body scintigraphic image of the rabbit obtained 3 days after injection of radioactive Ho-PLLA-MS. Increased accumulation of radioactivity due to Ho-PLLA-MS is indicated by small arrows. Larger arrow shows increased radioactivity in and around the tumor.

View larger version (124K): [in a new window]   Figure 6. A, Schematic shows the rabbit organs, which are seen in the following transverse MR images. B-F, Transverse MR images obtained in a rabbit in prone position. Thick arrows indicate implanted tumor. The gray scale and position of the organs correspond with the small schematics on each MR image. B, Representative anatomic T1-weighted spin-echo MR image obtained before administration of Ho-PLLA-MS (466/13, 25.6 x 15.3-cm field of view, 205 x 256 matrix, 15 adjacent sections with 5.0-mm thickness, four signals acquired, and 90° flip angle). C, T2-weighted spin-echo MR image obtained before administration of Ho-PLLA-MS (1,800/90, 25.6 x 15.3-cm field of view, 128 x 128 matrix [reconstruction, 256 x 256], 15 adjacent sections with 5.0-mm thickness, four signals acquired, turbo factor of 12, and 90° flip angle). D, T2*-weighted FFE MR image obtained before administration of Ho-PLLA-MS (30/4.6, 9.2; 25.6 x 15.3-cm field of view; 128 x 128 matrix [reconstruction, 256 x 256]; 15 adjacent sections with 5.0-mm thickness; eight signals acquired; and 15° flip angle). E, Repeat T1-weighted spin-echo MR image obtained after administration of Ho-PLLA-MS. F, Repeat holmium-sensitive T2*-weighted FFE MR image obtained after administration of Ho-PLLA-MS. Increased holmium accumulation is clearly seen in and around the tumor, as indicated with the thick arrow. Small signal voids (thin arrows) indicate holmium accumulation in liver tissue.

View larger version (139K): [in a new window]   Figure 7. Photomicrograph of large arterial blood vessels (1) filled with Ho-PLLA-MS. Single microspheres are observed in the smaller arterial blood vessels (arrow). Portal veins (2) contain no Ho-PLLA-MS. Tumor (3) and surrounding liver tissue (4) are destroyed by the radioactive Ho-PLLA-MS. Bar = 0.5 mm. (Hematoxylin-eosin stain; original magnification, x40.)