Jean-Claude Liehn

Superimposition of computed tomography and single photon emission tomography immunoscintigraphic images in the pelvis: validation in patients with colorectal or ovarian carcinoma recurrence

A method of superimposing computed tomography (CT) and immunoscintigraphic (IS) single photon emission tomography (SPET) slices is presented and has been applied to 10 patients with suspected cancer recurrence. IS was performed with carcinoembryonic antigen (CEA)-specific indium-111 monoclonal antibodies (MoAbs) in 5 patients with colorectal cancer, and with OC125 111In-MoAbs in 5 patients with ovarian cancer. All patients had an abnormal CT image result in the pelvis, which was interpreted 5 times as recurrence, once as doubtful and four times as scar fibrosis. Recurrence was subsequently proven in all patients. Bone scintigraphy (BS) SPET was recorded at the same time as IS. No special technique was used during BS, IS or CT acquisition. CT images were fed into a computer using a CCD camera. Using the internal anatomical landmarks provided by the pelvic bone structures seen on CT and BS, an operator had to select corresponding fiducial points, which were used by the software to register the images. The final results were CT-BS and CT-IS superimposed images. CT-BS images were used for quality control. In all patients, the inspection of CT-BS and CT-IS showed that the registration process is accurate and assists in the co-interpretation of CT and IS images.

Quantitative comparison of prone and supine myocardial SPECT MIBI images.

The myocardial count distribution and the stress/rest ratio distribution were compared between prone and supine Tc-99m MIBI myocardial SPECT acquisitions. Ninety-nine male patients with a low stress supine inferior wall count underwent stress and rest acquisitions in the supine and prone positions successively. For each study, values depicting the inferior, anterior, septal, and lateral wall counts were extracted from a medioventricular normalized circumferential profile and underwent a statistical analysis (Students paired t-test). On prone imaging, when compared to supine imaging, counts showed a highly significant mean relative increase of 11% ± 1% in the inferior wall and of 7% ± 1% in the septum. Conversely, these counts showed a significant mean relative decrease of 4% ± 1% in the anterior wall and of 3% ± 1% in the lateral wall. Moreover, the inferior wall stress/rest ratio showed a highly significant mean relative increase (6% ± 2%). The prone position is probably preferable for interpreting the inferior wall and septum, where relative counts are enhanced, as with TI-201, and because the inferior stress-rest discrepancies are reduced in that position. But the anterior and lateral wall information is impaired in the prone position. The authors suggest, in case of a low stress supine inferior count, the combination of both positions, which is feasible with Tc-99m MIBI, in order to prevent a misleading interpretation.

ROC analysis in radioimmunoassay: An application to the interpretation of thyroglobulin measurement in the follow-up of thyroid carcinoma

This study is an application of the ROC technique to the determination of threshold values (TV) for the interpretation of serum thyroglobulin (Tg) measurements in the follow-up of differentiated thyroid cancer. Serum Tg was assayed using the Henning kit in 1466 samples from 245 individuals. A local or distant recurrence was assessed by clinical examination, radiological and scintigraphic investigations, and was present in 23 patients. The measurements were divided into four groups: 1) measurements performed less than 6 months after thyroidectomy; 2) measurements performed more than 6 months after thyroidectomy; 3) measurements performed during the suppression of pituitary secretion; 4) measurements performed during withdrawal of the substitutive therapy. An ROC curve was calculated for each group and for each curve three TVs were determined: TV1, TV2, and TV3 corresponding to a high sensitivity, a high specificity and a high sum of sensitivity and specificity respectively. TV1 is 3.12 μg/l in the four groups. TV2 is 44 μg/l, 19 μg/l and 30 μg/l, in the first, second, third and fourth groups respectively. TV3 is 35 μg/l in the first group, 3.12 μg/l in both the second and third groups and 30 μg/l in the fourth group. When the classical method allows the determination of only one threshold value, the ROC technique allows us to determine threshold values adapted to both the patient clinical status and the chosen sensitivity or specificity.

Improvement of parathyroid Tl-Tc scintigraphy by using a new image subtraction method.

Forty five thallium-technetium parathyroid scans were performed preoperatively in patients with a high suspicion of parathyroid adenoma or hyperplasia. The patients were imaged after sequential IV injection of 201Tl-thallous chloride (74 MBq) and 99mTc-pertechnetate (222 MBq) using a gamma camera with a pinhole collimator. According to surgical findings, the prevalence of parathyroid abnormalities was 42/45: single (34 patients) and double (1 patient) adenomas, hyperplasia (7 patients, 16 hyperplastic glands). Three methods of analysis of scintigraphic images were compared. Method one was the visual comparison of the thallium and the technetium images. Method two used the subtraction image obtained after normalisation. Method three used a new image comparison method which performs the geometric and gray level registrations of the two images and generates the image of the significant differences. Three observers were involved in the evaluation procedures. Surgery and histological examinations were taken as the gold standard. Results show that the sensitivity is increased by applying method three. The interobserver reproducibility of the results is also higher for method three. We conclude that an adequate image subtraction technique significantly increases the diagnostic value of parathyroid scintigraphy.

Correlative imaging study in the diagnosis of ovarian cancer recurrences

A correlative imaging study was carried out in 61 female patients previously treated for ovarian carcinoma. Upon suspicion of recurrence, abdominopelvic immunoscintigraphy (IS) using F(ab′)2 fragments of indium-111-labelled OC 125 monoclonal antibody was performed in all patients, Ultrasonography (US) and computed tomography (CT) were performed 53 and 37 times, respectively. The diagnostic accuracy of the different imaging techniques was studied per site (abdomen and pelvis) and per patient. The diagnostic accuracy of planar scintigraphy (PS) was slightly lower than that of emission computed tomography (ECT): 66% vs 73% for abdomen, 65% vs 72% for pelvis, and 78% vs 84% in analysis per patient. The accuracy of IS (PS and ECT combined) was markedly better than that of US and CT for abdomen (IS=73%; US=30%; CT=47%), pelvis (IS=73%; US=37%; CT=52%) and analysis per patient (IS=85%; US=43%; CT =59%). The results of IS and morphological imaging techniques (MIT: US and/or CT) were correlatively analysed with the frequency of recurrence. When IS and MIT were both negative, the frequency of non-recurrence was 14/23 for abdomen, 7/12 for pelvis and 8/13 in analysis per patient. On the other hand, when both IS and MIT were positive, the frequency of recurrence was high (9/9 for abdomen, 17/21 for pelvis and 24/26 for analysis per patient). It was also found that a positive IS associated with a negative MIT was still highly suggestive of recurrence (17/21 for abdomen, 16/22 for pelvis and 17/19 for analysis per patient). The results of this study strongly suggest that 111in-labelled OC 125 IS is accurate for the diagnosis of recurrence of ovarian cancer and provides complementary data to those obtained by MIT.

Volume rendering and bicolour scale in double isotope studies: application to immunoscintigraphy and bone landmarking

Combining the volume rendering and bicolour visualization tehniques is proposed as an aid in interpreting single photon emission tomography (SPET) immunoscintigraphy (IS) recorded simultaneously with SPET bone landmarking (BL). The combination helps in localizing abnormal monoclonal uptake and in differentiating it from a physiological radioactivity distribution. The so-called rendered images (RIs) are obtained in both IS and BL studies according to a depth- weighted maximum activity projection algorithm. Fused BL and IS RIs are constructed by a simple, pixel by pixel addition. They are displayed using a bicolour grey-red scale, which makes it possible to visualize both studies by a transparency effect. This method was applied to patients suspected of suffering colorectal or ovarian cancer recurrences, in whom monoclonal antibodies against carci-noembryonic antigen, B72-3 or OC125 labelled with indium-111 were used.

A Case of Extraosseous Uptake with Bone Scintigraphy of Angiolipoma Masses

The case of a 32-year-old man with large masses in both thighs is reported. Tc-99m HMDP scintigraphy showed increased radionuclide activity in these soft tissue lesions. The bone uptake was normal. After surgical resection, the histological diagnosis was two benign angiolipomas of five kilograms each

Unusual site of extraosseous uptake of Tc 99m-HMDP due to subcutaneous heparin injections

The soft tissue uptake of 99mTc-hydroxymethylene diphosphonate (99mTc-HMDP) due to subcutaneous injections of heparin calcium is reported in two patients with osteosarcoma. This uptake occurs in an unusual site, i.e. the shoulders and the anterior and posterior compartments of the upper arms.

Automatic superimposition of computed tomography and single photon emission tomography immunoscintigraphic images in the pelvis

A method of superimposing computed tomography (CT) and immunoscintigraphic (IS) single photon emission tomography (SPET) pelvic images is applied to patients with suspected cancer recurrence. Bone scintigraphy SPET recorded at the same time as IS allows a fully automatic geometric registration using bone structures. Resulting fused CT-BS and CT-IS images are displayed in a bicolor color-gray scale.