US and MR imaging findings to detect placental adhesion spectrum (PAS) in patients with placenta previa: a comparative systematic study.

PURPOSE: To compare the performance US and MR in identifying placental adhesion spectrum (PAS) in placenta previa (PP) and to establish a potential method of image interpretation. METHODS: US and MR examinations of 51 patients with PP were selected. The presence of imaging signs commonly used to detect PAS was assessed. Penalized logistic regression was performed considering histology as standard of reference; only signs statistically significant (p < 0.05) were considered for ROC and multivariate analysis. The probability of PAS according to the presence of US and/or MR signs was then assessed. RESULTS: At univariate analysis, loss of retroplacental clear space, myometrial thinning (MT) and placenta lacunar spaces on US, intraplacental dark bands (IDBs), focal interruption of myometrial border (FIMB) and abnormal vascularity (AV) on MR were statistically significant (p < 0.01). Three diagnostic methods for PAS were then developed for both US and MR when at least one (Method 1), two (Method 2) or three (Method 3) imaging signs occurred, respectively. Method 2 for MR showed a significantly (p < 0.05) higher accuracy (91%) compared to the other methods. When MR IDBs and AV as well as IDBs and FIMB were present in combination with US MT the probability of PAS increased from 75 to 90% and from 80 to 91%, respectively. CONCLUSION: MR demonstrated a higher diagnostic accuracy than US to detect PAS. However, since the combination of MR and US signs could improve the probability to detect PAS, a complementary diagnostic role of these techniques could be considered.

Diagnostic accuracy of magnetic resonance imaging in assessing placental adhesion disorder in patients with placenta previa: Correlation with histological findings.

OBJECTIVE: To evaluate MRI accuracy in assessing placental adhesion disorders (PAD) in patients with placenta previa correlating imaging results with histological findings. MATERIALS AND METHODS: Sixty-one patients who underwent abdomino-pelvic magnetic resonance imaging (MRI) for ultrasound suspicion of PAD were prospectively evaluated. T1- and T2-weighted images, with and without fat suppression, were obtained in the three conventional planes using a 1.5 T MRI scanner. MRI accuracy to evaluate the presence of PAD was assessed on the basis of the occurrence of the following abnormal MRI signs: 1) intraplacental dark bands; 2) focal interruption of myometrial border; 3) intraplacental abnormal vascularity; 4) uterine bulging; 5) tenting of the bladder and/or 6) direct visualization of adjacent tissues invasion only in case of percretism. Imaging results were classified as suggestive or not of PAD using histological data as standard of reference; two methods of imaging analysis were used represented by the presence of at least one (Method A) or two (Method B) abnormal MRI signs; the correlation between the presence of each abnormal MRI sign of PAD and the corresponding histological finding was also assessed. RESULTS: The accuracy, as the area under the receiver operating characteristic curve, was significantly (p = 0.001) higher for Method B (0.92, C.I. 95%: 0.82-0.97) compared to Method A (0.764, C.I. 95%: 0.64-0.86). Among the abnormal MRI signs, intraplacental dark bands and focal interruption of myometrial border were those highly correlated with histological proof of PAD (ρ > 0.71, p < 0.001, for both); as result, a modified version of Method B (Method C) was identified considering as criterion for PAD the combined presence of the two abnormal MRI signs highly correlated with histologically proven PAD; however, the accuracy of Method C was significantly (p = 0.005) lower (0.80, C.I. 95%: 0.67-0.89) than Method B and comparable to Method A. CONCLUSIONS: MRI is a useful imaging technique to assess PAD in patients with placenta previa; in particular, the presence of at least two among all the abnormal MRI signs represents the most accurate criterion (Method B) to identify PAD. Although intraplacental dark bands and focal interruption of myometrial border showed the highest correlation with histological proof of PAD as well as this association was the most frequent in PAD, the combination of these latter MRI signs along with other abnormal signs should be considered diagnostic for PAD.

Comparative diagnostic evaluation with MR cholangiopancreatography, ultrasonography and CT in patients with pancreatobiliary disease.

PURPOSE: The aim of this study was to directly compare the results of magnetic resonance cholangiopancreatography (MRCP) with those of ultrasonography (US) and multislice computed tomography (MSCT) in the diagnosis of pancreaticobiliary diseases. MATERIALS AND METHODS: A total of 70 patients (41 men, 29 women) aged 22-89 years were studied either before (n=59) or after cholecystectomy (n=11) for biliary lithiasis. Clinical signs and symptoms were jaundice (n=15), abdominal pain (n=37) and proven biliary lithiasis (n=18). MRCP was performed in all patients, whereas abdominal US was performed in 55 (group 1) and MSCT in 37 (group 2) patients. A regional evaluation of the main structures of the pancreaticobiliary system was performed: gallbladder and cystic duct, intra- and extrahepatic bile ducts and main pancreatic duct. Histology (n=27), biopsy (n=5), endoscopic retrograde cholangiopancreatography (ERCP) (n=28) and/or clinical-imaging follow-up (n=10) were considered standards of reference. In particular, patients were classified as showing benign (n=47) or malignant (n=12) lesions or normal biliary anatomy (n=11). RESULTS: In group 1, the results of MRCP and US were concordant in the majority (92%) of cases; however, statistically significant discordance (p<0.01) was found in the evaluation of the extrahepatic ducts, with nine cases (16%) of middle-distal common bile duct stones being detected on MRCP only. In group 2, the results of MRCP and MSCT were also concordant in most cases (87%). However, findings were significantly discordant when the intra- and extrahepatic ducts were analysed, with seven (19%) and six (16%) cases, respectively, of lithiasis being detected on MRCP only (p<0.01 for both). CONCLUSIONS: The results of our study confirm the diagnostic potential of MRCP in the study of the pancreaticobiliary duct system. In particular, the comparison between MRCP and US and MSCT indicates the superiority of MRCP in evaluating bile ducts and detecting stones in the common bile duct.

Measurement of the intrarenal arterial resistance index for the identification and prediction of diabetic nephropathy.

BACKGROUND AND AIMS: High intrarenal resistance index (RI) predicts renal function in several conditions; its use in the prediction of diabetic nephropathy (DN) is little explored. We aimed (1) to compare RI in diabetic and non diabetic hypertensive patients, and (2) to evaluate whether high RI is associated with clinical signs of DN and its progression over time. DESIGN: observational, prospective. PARTICIPANTS: 92 type 2 diabetic patients and 37 non-diabetic controls aged 40-70, with hypertension and normal renal function. We measured ultrasound RI and, among others, creatinine, estimated glomerular filtration rate and urinary albumin excretion rate (AER) at baseline and after 4.5 years follow-up. Progression of albuminuric state (i.e., transition from baseline normo-microalbuminuria to follow-up micro-macroalbuminuria) was evaluated. RI was significantly higher in diabetic than non-diabetic participants (0.69+/-0.05 vs 0.59+/-0.05, p<0.001). Diabetic patients with RI>or=0.73, i.e., above the 80th percentile of the RI distribution, had significantly higher baseline AER and a more frequent progression of the albuminuric state compared to patients with RI<0.73 (27.7microg/mg [12.1-235.4] vs 15.1microg/mg [8.6-33.4]; 52.9% vs 9.5%, respectively). AER increased significantly from baseline to follow-up in patients with RI>or=0.73 (from 27.7microg/mg [12.1-235.4] to 265.0microg/mg [23.8-1018.1], p<0.01), but not in those with RI<0.73 (from 15.1microg/mg [8.6-33.4] to 16.1microg/mg [10.7-67.2], ns). OR for progression of albuminuric state, adjusted for established predictors of DN, including baseline AER, was 5.01 (1.4-17.7, 95% CI) for patients with RI>or=0.73 vs <0.73. Findings were confirmed in patients with normoalbuminuria at baseline. CONCLUSIONS: In diabetic patients, high RI (>or=0.73) is associated with features of DN and its progression over time, independent of albuminuria.

Triphasic helical CT in Budd-Chiari syndrome: patterns of enhancement in acute, subacute and chronic disease.

AIM: To retrospectively evaluate helical computed tomography (CT) findings in a series of consecutive patients with Budd-Chiari syndrome. METHODS: Patterns of enhancement observed at contrast-enhanced helical CT in 10 consecutive patients (six women, four men; aged 27-51 years) with either acute, subacute or chronic Budd-Chiari syndrome were retrospectively evaluated along with the status of the hepatic veins. All patients underwent triphasic helical CT (10 mm beam collimation, 7 mm rec. intervals, 120 kV, 200-250 mA, pitch = 1.0) performed at 20-25, 70-75 and 300 s after i.v. bolus (3 ml/s) injection of 150 ml iodinated non-ionic contrast media. RESULTS: Abnormal patterns of enhancement were identified in eight patients. In all patients with acute Budd-Chiari disease (3/3) abnormal arterial enhancement of the caudate lobe, the so-called "fan-shaped pattern" was observed, whereas visible venous thrombosis was only depicted in two. Conversely, a "patchy pattern" of enhancement was observed in five out of seven patients with either sub-acute (2) or chronic Budd-Chiari disease (5) along with a strip-like appearance or lack of visualization of hepatic veins. CONCLUSIONS: The "fan-shaped" pattern of enhancement represent a characteristic finding of acute Budd-Chiari disease, and it may help to suggest the correct diagnosis even in absence of visible venous thrombosis.

Endovascular vs. open surgery of abdominal aortic aneurysm in high-risk patients: a single center experience.

BACKGROUND: We compared two groups of high-risk patients with abdominal aortic aneurysm to assess the safety and efficacy of endovascular repair vs. open surgery. METHODS: From January 1998 to July 2003, sixty-two high-risk patients were divided into two groups: group A consisted of 28 (46 %) open surgery patients and group B consisted of 34 (54 %) patients who underwent endovascular repair. RESULTS: Four patients (14.3 %) in the open surgery group died, while no deaths occurred in the endovascular group ( p < 0.05). There were 14 complications in 8 patients of the open surgery group versus 2 complications in 2 patients of the endovascular group ( p = 0.01). At follow-up there were 4 (16.6 %) deaths in group A and 3 (8.8 %) in the endovascular group ( p = n. s.). CONCLUSIONS: While the use of endovascular repair in patients who are physiologically fit for open surgical repair remains controversial, we believe that patients with multiple or advanced comorbidities, i.e. high-risk patients, can benefit from the endografting procedure.

Splenic hypoperfusion as a sign of systemic amyloidosis.

BACKGROUND: The spleen is frequently involved in systemic amyloidosis; however, the computed tomographic (CT) or magnetic resonance (MR) pattern of splenic amyloidosis is not sufficiently described in the literature. This study evaluated the contrast-enhanced CT and MR findings of the spleen in patients with systemic amyloidosis. METHODS: Data were extracted by reviewing pathology and radiology department records of the teaching hospital of Naples over 10 years, from 1 January 1993 to 31 December 2002. Thirty-three patients with amyloidosis were identified, 10 of whom had a CT scan and two of whom had an MR study. The population-based study was composed of 12 patients with histologically proved amyloidosis who underwent contrast-enhanced CT or MR scan of the abdomen. The spleen and liver were evaluated for organ size and perfusion. RESULTS: The spleen was hypoperfused in nine of 12 patients. Mild splenomegaly was present in only one case. Hepatomegaly was associated with markedly acute left lobe margin in nine patients and with rounded anterior profile of segments 3 and 4 in four patients. Moreover, a large area of low attenuation with indefinite geographic margins involving the right hepatic lobe was observed in three patients. CONCLUSION: The finding of splenic hypoperfusion may be a marker of systemic amyloidosis, which represents a useful clue when clinical findings fail to suggest the proper diagnosis.

Added value of CT colonography after a positive conventional colonoscopy: impact on treatment strategy.

BACKGROUND: Conventional colonoscopy (CC) requires an experienced operator to avoid technical or interpretative errors, and an endoscopic error rate of 14% for tumor localization has been reported. We evaluated the impact of computed tomographic colonography (CTC) on surgical treatment strategy in patients with CC reported as having colorectal neoplasm. METHODS: Fifty-three patients testing positive for colorectal neoplasm on CC underwent CTC: 32 patients had CC in our hospital (group A) and 21 had CC in area hospitals (group B). All CTC procedures were performed with a multidetector CT system. The results of CTC and CC were compared with that of surgery. The preoperative surgical planning evaluated on the basis of CC and CTC was compared with the actual surgical approach, and the percentage of patients in whom CTC modified the treatment strategy suggested by CC was calculated. RESULTS: CTC changed the treatment strategy in four of 53 patients (7.5%) in whom CC showed technical or interpretative errors. Group analysis showed that CTC did not influence the surgical management in any patient in group A but did affect treatment strategy in four of 21 patients (19%) in group B. The effect of CTC on treatment strategy between groups was statistically significant (p < 0.05). CTC identified five adenomas and three adenocarcinomas localized proximally to an impassable stenosis. CONCLUSION: CTC can be used to reevaluate the findings of a positive CC and can indicate a more correct therapeutic approach in patients with colorectal neoplasms who are candidates for surgery.

Small bowel Crohn's disease: comparison of enteroclysis, bowel sonography and Tc-99m-HMPAO leukocyte scintigraphy.

BACKGROUND: Crohn's disease (CD) frequently involves the small bowel. Actually, the diagnosis of CD is made by ileocolonoscopy (IC) and small bowel enteroclysis (SBE), while trans-abdominal bowel sonography (BS) and Tc-99m-HMPAO leukocyte scintigraphy (LS) are only partially used in spite of their minimal invasiveness. AIM: to compare the diagnostic accuracy of these procedures for the diagnosis of small bowel CD. PATIENTS AND METHODS: in about two years a series of consecutive subjects underwent IC, SBE, BS and LS for either suspected or known small bowel CD. RESULTS: Sensitivity, specificity, positive and negative predictive value for CD diagnosis of the studied procedures were respectively: 98%, 97%, 98% and 97% for SBE; 92%, 97%, 98%, and 88% for BS; 90%, 93%, 96% and 85% for LS. In addition, the parallel combined use of BS and LS led to overall sensitivity, specificity, positive and negative predictive value of 100%, 93%, 96%, 100%, respectively. CONCLUSION: SBE, BS and LS are accurate procedures for the diagnosis of small bowel Crohn's disease. The use of BS and LS, particularly in combination, can be proposed as early diagnostic approach to subjects with a suspicion of disease.

Hepatic and splenic amyloidosis: dual-phase spiral CT findings.

Although the liver and spleen are frequently involved in primary systemic amyloidosis, the clinical manifestations of hepatic and splenic involvement are usually mild and a dominant symptomatic hepatic presentation is uncommon. We report a case of a 51-year-old woman with giant hepatomegaly, hypertransaminasemia, increase in alkaline phosphatase, and ascites, in whom the findings of dual-phase spiral computed tomography suggested liver and splenic amyloidosis.

Rare diffuse peritoneal malignant neoplasms: CT findings in two cases.

In the peritoneal cavity, diffuse serosal replacement by tumor is demonstrated usually by extensive carcinomatous involvement from gastric, colonic, or pancreatic tumors or less frequently by mesothelioma. Primary tumors other than mesothelioma are extremely rare in the peritoneum. The computed tomographic appearances of two cases of rare peritoneal tumors, epithelioid hemangioendothelioma and desmoplastic small round cell tumor, are described.

[Morphological imaging of gastroenteropancreatic neuroendocrine tumours]. / Imaging morfologico dei tumori neuroendocrini gastroenteropancreatici.

Biologically active neuroendocrine tumours produce early symptoms and are often difficult to diagnose owing to their small dimensions (<1 cm), whereas biologically inactive forms are often coarse and sometimes found by chance. As well as identifying the lesion, locoregional staging is also particularly important for therapeutic planning. Morphological imaging plays an important role in the identification of gastroenteropancreatic neuroendocrine tumours, providing an anatomic substrate for receptorial imaging which usually precede it in the diagnostic work-up, whereas it plays a primary role in the locoregional staging of these neoplasms for which surgery is the first and essential therapeutic approach. In the case of endocrine tumours of the pancreas alone, the most accurate method of diagnosis is currently echo-endoscopy using high-frequency probes. Two-phase spiral CT and dynamic MR have proved equally effective means of identifying endocrine tumours of the pancreas with slightly higher sensitivity for MR, both playing a role in the locoregional staging of biologically active and inactive tumours. Traditional radiology also plays a role in the identification of intestinal carcinoids.

Synchronous primary adenocarcinoma and adenosquamous carcinoma of the esophagus.

Multiple malignant esophageal tumors of the same cell type are described. In the esophageal mucosa, widespread carcinomatous transformation may be observed and multicentric invasive squamous cell carcinomas may develop. The concomitance of two independent esophageal malignant neoplasms of different epithelial histogenesis is uncommon. Synchronous adenocarcinoma and squamous cell carcinoma of the esophagus is reported. Adenosquamous carcinoma of the esophagus is a rare tumor. Adenocarcinoma of the esophagus represents 10% of esophageal cancer. We report a case of a synchronous primary invasive adenosquamous carcinoma and adenocarcinoma of the esophagus. Both tumors were demonstrated radiographically. The peculiarity of this neoplastic association and the importance of complete radiographic esophageal evaluation in patients with one obvious obstructing tumor of the esophagus are emphasized.

[Computerized tomography-guided drainage of postoperative abdominal fluid collections]. / Drenaggio guidato con tomografia computerizzata delle raccolte addominali post-operatorie.

INTRODUCTION: We report our personal technique and the results of CT-guided percutaneous drainage of postoperative abdominal fluid collections. MATERIAL AND METHODS: January 1990 to March 1998, eighty-three patients were treated for postoperative abdominal fluid collections. Forty-eight patients had undergone bowel resection, 11 laparoscopic cholecystectomy, 3 cholecystectomy, 5 splenectomy, 3 cephalopancreasectomy, 6 hepaticojejunal anastomosis, 4 hepatic resection, 2 laparocele, 1 hysterectomy. The complications had developed few days to about one year postoperatively. The suspicion of abdominal fluid collection was supported by clinical and laboratory findings. All patients were submitted to a preliminary CT scan to locate the fluid collection, assess its morphology and relationships with surrounding structures, and plan the safest access route. After local anesthesia, a trial fine needle (Chiba 20-22 G) aspiration was performed and then the draining tube was inserted into the collection under CT guidance; the tube caliber depended on the fluid amount and viscosity. After drainage, the tube was removed if CT showed complete resolution of the fluid collection; otherwise it was left in place for subsequent washing of the cavity. Based on clinical, laboratory and CT findings, another CT-guided percutaneous drainage was judged necessary in 30 patients, 2-9 days after the first one. Drainage was considered successful when sepsis resolved and no further percutaneous/surgical drainages were needed. RESULTS: CT-guided percutaneous drainage was successful in 61 of 83 patients (73.5%); the fluid collection resolved after one drainage in 26/61 patients, in 2-9 days in 18/61, and after a second CT-guided drainage in 17/61. Drainage was not resolutive in 22 of 83 patients, because major postoperative complications required laparotomic surgery; these complications were fistulas (anastomotic in 12 cases; pancreatic in 5 and biliary in 3) and segmentary bowel necrosis in 2 cases. Intracavitary bleeding as a catheter-related complication occurred only in one patient with an anterior abdominal wall abscess. CONCLUSIONS: CT-guided percutaneous drainage offers many advantages over surgery: it is less invasive, can be repeated and requires no anesthesia; there are no surgery-related risks and lower morbidity and mortality rates. Moreover, subsequent hospitalization is shorter and costs are consequently reduced. We conclude that CT-guided percutaneous drainage is the method of choice in the treatment of postoperative abdominal fluid collections.

Cerebral blood flow in spinocerebellar degenerations: a single photon emission tomography study in 28 patients.

We used single photon emission tomography to study regional cerebral perfusion in patients with different forms of spinocerebellar degeneration: 6 patients with Friedreich's ataxia (FA), 6 with early-onset cerebellar ataxia with retained tendon reflexes (EOCA), 5 with autosomal dominant cerebellar ataxia type 1 (ADCA I) and 11 with idiopathic late-onset cerebellar ataxia (ILOCA). The results were related to clinical and magnetic resonance imaging (MRI) findings. Cerebellar hypoperfusion was constant in ADCA I and frequent in patients with other spinocerebellar degenerations. Brain stem hypoperfusion was constant in ADCA I, frequent in ILOCA patients with pontocerebellar atrophy and absent in FA and EOCA. FA and EOCA often showed a reduction in the parietotemporal cortex blood flow, which was not related to cortical atrophy. ILOCA patients had an asymmetric pattern in the temporal areas with decreased blood flow in the right side only. Caudate hypoperfusion was found in ADCA I patients. Cerebral atrophy did not account for changes in regional blood flow, which probably indicate early involvement of cerebral structures.

Technetium-99m-tetrofosmin uptake in brain tumors by SPECT: comparison with thallium-201 imaging.

UNLABELLED: Thallium-201 is clinically used for the assessment of primary and recurrent brain tumors. The biologic properties of 201Tl that allow it to accumulate within the tumor cells render 201Tl useful in evaluating tumor malignancy, but its physical characteristics and nonroutine availability limits its use in some institutions, as compared to 99mTc-labeled compounds. The aim of this study was to assess the feasibility of using 99mTc-tetrofosmin for imaging brain tumors and to compare its uptake with that of 201Tl. METHODS: Twenty-six patients with 27 intracranial masses were studied with SPECT. In the first group of seven patients (Group A), the timing for optimal acquisition of the 99mTc-tetrofosmin scan was assessed. In the second group of 19 patients (Group B), two sequential 201Tl (74-148 MBq intravenous) and 99mTc-tetrofosmin (740-925 MBq intravenous) studies were performed 20 min after tracer injection and compared. RESULTS: In Group A, no significant difference in the tumor-to-background (T/B) ratio among the 20-, 40- and 120-min postinjection studies was observed. In Group B, the quality of reconstructed images with 99mTc-tetrofosmin, judged visually, was superior to that of 201Tl in 47% of all studies and was comparable in the remaining 53%. A significant relationship between 201Tl and 99mTc-tetrofosmin T/B ratio (r = 0.75, p < 0.01) was found. The T/B ratio of 99mTc-tetrofosmin was significantly higher than that of 201Tl (23.3 +/- 21.5 compared to 6.1 +/- 2.9, p < 0.005). CONCLUSION: Technetium-99m-tetrofosmin is a suitable radiotracer for the imaging of intracranial lesions with SPECT. Moreover, a better definition of tumor margins and a higher contrast between neoplastic and normal brain tissue can be achieved.

Effects of myocardial revascularization on regional thallium-201 uptake and systolic function in regions with reverse redistribution on tomographic thallium-201 imaging at rest in patients with chronic coronary artery disease.

OBJECTIVES: There is growing evidence that myocardial segments with reverse redistribution are viable in patients with chronic coronary artery disease. The aim of this study was to assess the effects of myocardial revascularization on systolic function and thallium-201 uptake in such segments. METHODS: Rest-redistribution thallium-201 tomography before and after myocardial revascularization was performed in 47 patients with chronic coronary artery disease. Regional function was evaluated by two-dimensional echocardiography before and after revascularization according to a 3-point scale (1 = normal, 2 = hypokinetic, 3 = a/dyskinetic). Improvement of dysfunctional segments was defined when systolic function score decreased > or =1 after revascularization. Reverse redistribution was defined as >8% decrease in relative thallium-201 uptake between rest and redistribution images. RESULTS: Reverse redistribution was found in 27 (57%) of 47 patients, corresponding to 60 (11%) of 564 myocardial segments. Of such segments, 24 (40%) had normal systolic function, 19 (32%) were hypokinetic, and 17 (28%) were a/dyskinetic. Thirty-six segments underwent myocardial revascularization, and reverse redistribution was no longer present in 86% of them subsequent to the procedure. Of 26 dyssynergic segments with reverse redistribution subjected to revascularization, 18 (69%) improved at follow-up. CONCLUSIONS: The findings of the present study indicate that reverse redistribution is a reversible phenomenon and is often associated with improvement of systolic function following revascularization in patients with chronic coronary artery disease.

Primary systemic amyloidosis with giant hepatomegaly and a swiftly progressive course.

Although the involvement of the liver is common in systemic amyloidosis (AL), clinical features of hepatic dysfunction and liver chemistry abnormalities are often mild or absent. A mild increase in the serum alkaline phosphatase value is the most common finding. Hypertransaminasemia, hyperbilirubinemia, and portal hypertension with ascites and gastroesophageal varices occur late in the course of the disease and predict a short survival. We describe the case of a 58-year-old woman with AL, whose dramatic and unusual clinical picture, consisting of giant hepatomegaly, hypertransaminasemia, increase in alkaline phosphatase, esophageal varices, and ascites, was rapidly complicated by severe obstructive cholestasis.

Reduced cortical distribution volume of iodine-123 iomazenil in Alzheimer's disease as a measure of loss of synapses.

Iodine-123 labelled iomazenil (IMZ) is a specific tracer for the GABAA receptor, the dominant inhibitory synapse of the brain. The cerebral distribution volume (Vd) of IMZ may be taken as a quantitative measure of these synapses in Alzheimer's disease (AD), where synaptic loss tends indiscriminately to affect all cortical neurons, albeit more so in some areas than in others. In this pilot study we measured Vd in six patients with probable AD and in five age-matched controls using a brain-dedicated single-photon emission tomography scanner allowing all cortical levels to be sampled simultaneously. Reduced values were found in all regions except in the occipital (visual) cortex. In particular, temporal and parietal cortex Vd was significantly (P<0.02) reduced: temporal Vd averaged 69 ml/ml in normals and 51 ml/ml in AD, and parietal Vd averaged 71 ml/ml in normals and 48 ml/ml in AD. These results accord well with emission tomographic studies of blood flow or labelled glucose. This supports the idea that while only measuring a subpopulation of synapses, the IMZ method reflects synaptic loss and hence functional loss in AD. The method constitutes an in vivo version of synaptic quantitation that in histopathological studies has been shown to correlate closely with the mental deterioration in AD.