Tensor network methods for extracting conformal field theory data from fixed-point tensors and defect coarse graining

We present a comprehensive study on extracting conformal field theory data using tensor network methods, especially, from the fixed-point tensor of the linearized tensor renormalization group (lTRG) for the classical two-dimensional Ising model near the critical temperature. Utilizing two different methods, we extract operator scaling dimensions and operator product expansion coefficients by introducing defects on the lattice and by employing the fixed-point tensor. We also explore the effects of pointlike defects in the lattice on the coarse-graining process. We find that there is a correspondence between coarse-grained defect tensors and conformal states obtained from the lTRG fixed-point equation. We also analyze the capabilities and limitations of our proposed coarse-graining scheme for tensor networks with pointlike defects, including graph-independent local truncation (GILT) and higher-order tensor renormalization group (HOTRG). Our results provide a better understanding of the capacity and limitations of the tensor renormalization group scheme in coarse-graining defect tensors, and we show that GILT+HOTRG can be used to give accurate two- and four-point functions under specific conditions. We also find that employing the minimal canonical form further improves the stability of the RG flow.

A universal variational quantum eigensolver for non-Hermitian systems

Many quantum algorithms are developed to evaluate eigenvalues for Hermitian matrices. However, few practical approach exists for the eigenanalysis of non-Hermintian ones, such as arising from modern power systems. The main difficulty lies in the fact that, as the eigenvector matrix of a general matrix can be non-unitary, solving a general eigenvalue problem is inherently incompatible with existing unitary-gate-based quantum methods. To fill this gap, this paper introduces a Variational Quantum Universal Eigensolver (VQUE), which is deployable on noisy intermediate scale quantum computers. Our new contributions include: (1) The first universal variational quantum algorithm capable of evaluating the eigenvalues of non-Hermitian matrices-Inspired by Schur's triangularization theory, VQUE unitarizes the eigenvalue problem to a procedure of searching unitary transformation matrices via quantum devices; (2) A Quantum Process Snapshot technique is devised to make VQUE maintain the potential quantum advantage inherited from the original variational quantum eigensolver-With additional [Formula: see text] quantum gates, this method efficiently identifies whether a unitary operator is triangular with respect to a given basis; (3) Successful deployment and validation of VQUE on a real noisy quantum computer, which demonstrates the algorithm's feasibility. We also undertake a comprehensive parametric study to validate VQUE's scalability, generality, and performance in realistic applications.

Demonstrating the Affleck-Kennedy-Lieb-Tasaki Spectral Gap on 2D Degree-3 Lattices

We report results on solving a long outstanding problem-whether the two-dimensional spin-3/2 antiferromagnetic valence-bond model of Affleck, Kennedy, Lieb, and Tasaki (AKLT) possesses a nonzero gap above its ground state. We exploit a relation between the anticommutator and sum of two projectors and apply it to ground-space projectors on regions of the honeycomb lattice. After analytically reducing the complexity of the resultant problem, we are able to use a standard Lanczos method to establish the existence of a nonzero gap. This approach is also successfully applied to spin-3/2 AKLT models on other degree-3 semiregular tilings, namely, the square-octagon, star, and cross lattices, where the complexity is low enough that exact diagonalization can be used instead. In addition, we close the previously open cases of hybrid AKLT models on the singly decorated honeycomb and singly decorated square lattices.

Machine learning of phase transitions in the percolation and XY models

In this paper, we apply machine learning methods to study phase transitions in certain statistical mechanical models on the two-dimensional lattices, whose transitions involve nonlocal or topological properties, including site and bond percolations, the XY model, and the generalized XY model. We find that using just one hidden layer in a fully connected neural network, the percolation transition can be learned and the data collapse by using the average output layer gives correct estimate of the critical exponent ν. We also study the Berezinskii-Kosterlitz-Thouless transition, which involves binding and unbinding of topological defects, vortices and antivortices, in the classical XY model. The generalized XY model contains richer phases, such as the nematic phase, the paramagnetic and the quasi-long-range ferromagnetic phases, and we also apply machine learning method to it. We obtain a consistent phase diagram from the network trained with only data along the temperature axis at two particular parameter Δ values, where Δ is the relative weight of pure XY coupling. Aside from using the spin configurations (either angles or spin components) as the input information in a convolutional neural network, we devise a feature engineering approach using the histograms of the spin orientations in order to train the network to learn the three phases in the generalized XY model and demonstrate that it indeed works. The trained network by using system size L×L can be used to the phase diagram for other sizes (L^{'}×L^{'}, where L^{'}≠L) without any further training.

Computational Power of Symmetry-Protected Topological Phases

We consider ground states of quantum spin chains with symmetry-protected topological (SPT) order as resources for measurement-based quantum computation (MBQC). We show that, for a wide range of SPT phases, the computational power of ground states is uniform throughout each phase. This computational power, defined as the Lie group of executable gates in MBQC, is determined by the same algebraic information that labels the SPT phase itself. We prove that these Lie groups always contain a full set of single-qubit gates, thereby affirming the long-standing conjecture that general SPT phases can serve as computationally useful phases of matter.

Superdense teleportation using hyperentangled photons

Transmitting quantum information between two remote parties is a requirement for many quantum applications; however, direct transmission of states is often impossible because of noise and loss in the communication channel. Entanglement-enhanced state communication can be used to avoid this issue, but current techniques require extensive experimental resources to transmit large quantum states deterministically. To reduce these resource requirements, we use photon pairs hyperentangled in polarization and orbital angular momentum to implement superdense teleportation, which can communicate a specific class of single-photon ququarts. We achieve an average fidelity of 87.0(1)%, almost twice the classical limit of 44% with reduced experimental resources than traditional techniques. We conclude by discussing the information content of this constrained set of states and demonstrate that this set has an exponentially larger state space volume than the lower-dimensional general states with the same number of state parameters.

Implementations of known quantum teleportation techniques suffer from a number of technical limitations, most notably the scaling of the required classical resources. Here, the authors implement a new protocol, superdense teleportation, which requires fewer resources than the conventional approaches.

Topological transitions from multipartite entanglement with tensor networks: a procedure for sharper and faster characterization

Topological order in two-dimensional (2D) quantum matter can be determined by the topological contribution to the entanglement Rényi entropies. However, when close to a quantum phase transition, its calculation becomes cumbersome. Here, we show how topological phase transitions in 2D systems can be much better assessed by multipartite entanglement, as measured by the topological geometric entanglement of blocks. Specifically, we present an efficient tensor network algorithm based on projected entangled pair states to compute this quantity for a torus partitioned into cylinders and then use this method to find sharp evidence of topological phase transitions in 2D systems with a string-tension perturbation. When compared to tensor network methods for Rényi entropies, our approach produces almost perfect accuracies close to criticality and, additionally, is orders of magnitude faster. The method can be adapted to deal with any topological state of the system, including minimally entangled ground states. It also allows us to extract the critical exponent of the correlation length and shows that there is no continuous entanglement loss along renormalization group flows in topological phases.

Thermal states as universal resources for quantum computation with always-on interactions

Measurement-based quantum computation utilizes an initial entangled resource state and proceeds with subsequent single-qubit measurements. It is implicitly assumed that the interactions between qubits can be switched off so that the dynamics of the measured qubits do not affect the computation. By proposing a model spin Hamiltonian, we demonstrate that measurement-based quantum computation can be achieved on a thermal state with always-on interactions. Moreover, computational errors induced by thermal fluctuations can be corrected and thus the computation can be executed fault tolerantly if the temperature is below a threshold value.

Experimental quantum simulation of entanglement in many-body systems

We employ a nuclear magnetic resonance (NMR) quantum information processor to simulate the ground state of an XXZ spin chain and measure its NMR analog of entanglement, or pseudoentanglement. The observed pseudoentanglement for a small-size system already displays a singularity, a signature which is qualitatively similar to that in the thermodynamical limit across quantum phase transitions, including an infinite-order critical point. The experimental results illustrate a successful approach to investigate quantum correlations in many-body systems using quantum simulators.

Affleck-Kennedy-Lieb-Tasaki state on a honeycomb lattice is a universal quantum computational resource

Universal quantum computation can be achieved by simply performing single-qubit measurements on a highly entangled resource state, such as cluster states. The family of Affleck-Kennedy-Lieb-Tasaki states has recently been intensively explored and shown to provide restricted computation. Here, we show that the two-dimensional Affleck-Kennedy-Lieb-Tasaki state on a honeycomb lattice is a universal resource for measurement-based quantum computation.

Remote preparation of single-photon "hybrid" entangled and vector-polarization States

Quantum teleportation faces increasingly demanding requirements for transmitting large or even entangled systems. However, knowledge of the state to be transmitted eases its reconstruction, resulting in a protocol known as remote state preparation. A number of experimental demonstrations to date have been restricted to single-qubit systems. We report the remote preparation of two-qubit "hybrid" entangled states, including a family of vector-polarization beams. Our single-photon states are encoded in the photon spin and orbital angular momentum. We reconstruct the states by spin-orbit state tomography and transverse polarization tomography. The high fidelities achieved for the vector-polarization states opens the door to optimal coupling of down-converted photons to other physical systems, such as an atom, as required for scalable quantum networks, or plasmons in photonic nanostructures.

Tunable Luttinger liquid physics in biased bilayer graphene

Electronically gated bilayer graphene behaves as a tunable gap semiconductor under a uniform interlayer bias V(g). Imposing a spatially varying bias, which changes polarity from -V(g) to +V(g), leads to one dimensional (1D) chiral modes localized along the domain wall of the bias. Because of the broad transverse spread of their low-energy wave functions, we find that the dominant interaction between these 1D electrons is the forward scattering part of the Coulomb repulsion. Incorporating these interactions and the gate voltage dependence of the dispersion and wave functions, we find that these 1D modes behave as a strongly interacting Tomonaga-Luttinger liquid with three distinct mode velocities and a bias dependent Luttinger parameter, and discuss its experimental signatures.

Interacting boson problems can be QMA hard

Computing the ground-state energy of interacting electron problems has recently been shown to be hard for quantum Merlin Arthur (QMA), a quantum analogue of the complexity class NP. Fermionic problems are usually hard, a phenomenon widely attributed to the so-called sign problem. The corresponding bosonic problems are, according to conventional wisdom, tractable. Here, we demonstrate that the complexity of interacting boson problems is also QMA hard. Moreover, the bosonic version of N-representability problem is QMA complete. Consequently, these problems are unlikely to have efficient quantum algorithms.

Remote state preparation: arbitrary remote control of photon polarization

We experimentally demonstrate the first remote state preparation of arbitrary single-qubit states, encoded in the polarization of photons generated by spontaneous parametric down-conversion. Utilizing degenerate and nondegenerate wavelength entangled sources, we remotely prepare arbitrary states at two wavelengths. Further, we derive theoretical bounds on the states that may be remotely prepared for given two-qubit resources.

h/e Magnetic Flux Modulation of the Energy Gap in Nanotube Quantum Dots

We report experiments on quantum dot single-electron-tunneling (SET) transistors made from short multiwall nanotubes and threaded by magnetic flux. Such systems allow us to probe the electronic energy spectrum of the nanotube and its dependence on the magnetic field. Evidence is provided for the interconversion between gapped (semiconducting) and ungapped (metallic) states. Our tubes exhibit h/e-period magnetic flux dependence, in agreement with simple tight-binding calculations.

Maximally entangled mixed states: creation and concentration

Using correlated photons from parametric down-conversion, we extend the boundaries of experimentally accessible two-qubit Hilbert space. Specifically, we have created and characterized maximally entangled mixed states that lie above the Werner boundary in the linear entropy-tangle plane. In addition, we demonstrate that such states can be efficiently concentrated, simultaneously increasing both the purity and the degree of entanglement. We investigate a previously unsuspected sensitivity imbalance in common state measures, i.e., the tangle, linear entropy, and fidelity.

Ancilla-assisted quantum process tomography

Complete and precise characterization of a quantum dynamical process can be achieved via the method of quantum process tomography. Using a source of correlated photons, we have implemented several methods, each investigating a wide range of processes, e.g., unitary, decohering, and polarizing. One of these methods, ancilla-assisted process tomography (AAPT), makes use of an additional "ancilla system," and we have theoretically determined the conditions when AAPT is possible. Surprisingly, entanglement is not required. We present data obtained using both separable and entangled input states. The use of entanglement yields superior results, however.

Thalamic activation during an attention-to-prepulse startle modification paradigm: a functional MRI study

BACKGROUND

Prepulse inhibition (PPI) of the startle reflex reflects early stages of information processing and is modulated by selective attention. Animal models indicate medial frontal-thalamic circuitry is important in PPI modulation. We report data from the first functional magnetic resonance imaging (fMRI) study examining whether attending to or ignoring a prepulse differentially activates brain areas within this circuitry.

METHODS

Ten healthy subjects received structural and functional MRI. During fMRI acquisition, subjects heard intermixed attended and ignored tones serving as prepulses to the startle stimulus. Regions of interest were traced on structural MRI and coregistered to fMRI images.

RESULTS

Greater amplitude fMRI blood-oxygen-level-dependent response to attended than ignored PPI conditions occurred in the right thalamus, and bilaterally in the anterior and mediodorsal thalamic nuclei, whereas the startle-alone condition showed deactivation. In transitional medial cortex (Brodmann Area 32), which is involved in affective processing of noxious stimuli, the startle-alone condition elicited the greatest response, the attended-PPI condition showed the smallest response, and the ignored-PPI condition was intermediate.

CONCLUSIONS

These findings extend animal models to humans by indicating thalamic involvement in the modulation of PPI. Further fMRI investigations may elucidate other key structures in the circuitry underlying normal and disordered modulation of PPI.

Differential amygdala activation during emotional decision and recognition memory tasks using unpleasant words: an fMRI study

This study used fMRI to examine the response of the amygdala in the evaluation and short-term recognition memory of unpleasant vs. neutral words in nine right-handed healthy adult women. To establish specificity of the amygdala response, we examined the fMRI BOLD signal in one control region (visual cortex). Alternating blocks of unpleasant and neutral trials were presented. During the emotional decision task, subjects viewed sets of three unpleasant or three neutral words while selecting the most unpleasant or neutral word, respectively. During the memory task, subjects identified words that were presented during the emotional decision task (0.50 probability). Images were detrended, filtered, and coregistered to standard brain coordinates. The Talairach coordinates for the center of the amygdala were chosen before analysis. The BOLD signal at this location in the right hemisphere revealed a greater amplitude signal for the unpleasant relative to the neutral words during the emotional decision but not the memory task, confirmed by Time Course x Word Condition ANOVAs. These results are consistent with the memory modulatory view of amygdala function, which suggests that the amygdala facilitates long-term, but not short-term, memory consolidation of emotionally significant material. The control area showed only an effect for Time Course for both the emotional decision and memory tasks, indicating the specificity of the amygdala response to the evaluation of unpleasant words. Moreover, the right-sided amygdala activation during the unpleasant word condition was strongly correlated with the BOLD response in the occipital cortex. These findings corroborate those by other researchers that the amygdala can modulate early processing of visual information in the occipital cortex. Finally, an increase in subject's state anxiety (evaluated by questionnaire) while in the scanner correlated with amygdala activation under some conditions.

Effect of fluoxetine on regional cerebral metabolism in autistic spectrum disorders: a pilot study

The regional metabolic effects of fluoxetine were examined in patients with autism spectrum disorders. Six adult patients with DSM-IV and Autism Diagnostic Interview (ADI) diagnoses of autism (n = 5) and Asperger's syndrome (n = 1), entered a 16-wk placebo-controlled cross-over trial of fluoxetine. The patients received (18)F-deoxyglucose positron emission tomography with co-registered magnetic resonance imaging at baseline and at the end of the period of fluoxetine administration. After treatment, the patients showed significant improvement on the scores of the Yale--Brown Obsessive--Compulsive Scale -- Obsessions subscale and the Hamilton Anxiety Scale; Clinical Global Impressions -- Autism scores showed 3 of the patients much improved and 3 unchanged. Relative metabolic rates were significantly higher in the right frontal lobe following fluoxetine, especially in the anterior cingulate gyrus and the orbitofrontal cortex. Patients with higher metabolic rates in the medial frontal region and anterior cingulate when unmedicated were more likely to respond favourably to fluoxetine. These results are consistent with those in depression indicating that higher cingulate gyrus metabolic rates at baseline predict SRI response.

Patterns of cortical activity and memory performance in Alzheimer's disease

BACKGROUND

Declarative memory changes are the hallmark of Alzheimer's disease, although their functional neuroanatomy is not restricted to a single structure. Factor analysis provides statistical methods for evaluating patterns of cerebral changes in regional glucose uptake.

METHODS

Thirty-three Alzheimer's patients and 33 age- and gender-matched control subjects were studied with magnetic resonance imaging and positron emission tomography with [(18)F] deoxyglucose. During the tracer-uptake period, subjects performed a serial verbal learning task. Cortical activity was measured in 32 regions of interest, four in each lobe on both hemispheres.

RESULTS

Factor analysis with varimax rotation identified seven factors explaining 80% of the variance ("parietal cortex," "occipital cortex," "right temporo-prefrontal areas," "frontal cortex," "motor strip," "left temporal cortex," and "posterior temporal cortex"). Relative to control subjects, Alzheimer's patients showed significantly reduced values on the factors occipital cortex, right temporo-prefrontal areas, frontal cortex, and left temporal cortex. The factor temporo-prefrontal areas showed large differences between patients with good and poor performance, but little difference when control subjects were similarly divided.

CONCLUSIONS

Findings suggest that Alzheimer's disease is characterized by altered patterns of cortical activity, rather than deficits in a single location, and emphasize the importance of right temporo-prefrontal circuitry for understanding memory deficits.

Regional and global changes in cerebral diffusion with normal aging

BACKGROUND AND PURPOSE

We used quantitative diffusion MR imaging to investigate the microstructural changes that occur in white matter during normal aging in order to identify regional changes in anisotropy and to quantify global microstructural changes by use of whole-brain diffusion histograms.

METHODS

Full diffusion tensor MR imaging was performed in 20 healthy volunteers, 20 to 91 years old. Thirteen subjects also underwent high-resolution T1-weighted imaging, so that diffusion images could be coregistered and standardized to normal coordinates for statistical probability mapping. Relative anisotropy (RA) was calculated, as was linear regression of RA with age for each pixel; pixels with a significant correlation coefficient were displayed. For histographic analysis, the average apparent diffusion coefficient (ADC) histograms were calculated on a pixel-by-pixel basis. Subjects were divided into two equal groups by the median age (55 years) of the population and plotted for statistical comparison.

RESULTS

Regional analysis showed statistically significant decreases in RA with increasing age in the periventricular white matter, frontal white matter, and genu and splenium of the corpus callosum, despite the absence of signal abnormalities on visual inspection of conventional images. Significant increases in RA were found in the internal capsules bilaterally. ADC histograms showed higher mean ADC and reduced peak height and skew in the older age group on group comparisons.

CONCLUSION

Quantitative diffusion histograms correlate with normal aging and may provide a global assessment of normal age-related changes and serve as a standard for comparison with neurodegenerative diseases.

Limbic circuitry in patients with autism spectrum disorders studied with positron emission tomography and magnetic resonance imaging

OBJECTIVE

Cytoarchitectonic changes in the anterior cingulate cortex, hippocampus, subiculum, entorhinal cortex, amygdala, mammillary bodies, and septum were reported in a postmortem study of autism. Previously, the authors found smaller cingulate volume and decreased metabolism of the cingulate in seven autistic patients. In this study, they measured the volume and glucose metabolism of the amygdala, hippocampus, and cingulate gyrus in an expanded group of 17 patients with autism spectrum disorders (autism [N=10] or Asperger's disorder [N=7]) and 17 age- and sex-matched healthy volunteers.

METHOD

Subjects performed a serial verbal learning test during (18)F-deoxyglucose uptake. The amygdala, hippocampus, and cingulate gyrus were outlined on magnetic resonance imaging scans, volumes of the structures were applied to matching coregistered positron emission tomography scans, and three-dimensional significance probability mapping was performed.

RESULTS

Significant metabolic reductions in both the anterior and posterior cingulate gyri were visualized in the patients with autism spectrum disorders. Both Asperger's and autism patients had relative glucose hypometabolism in the anterior and posterior cingulate as confirmed by analysis of variance; regional differences were also found with three-dimensional significance probability mapping. No group differences were found in either the metabolism or the volume of the amygdala or the hippocampus. However, patients with autism spectrum disorders showed reduced volume of the right anterior cingulate gyrus, specifically in Brodmann's area 24'.

CONCLUSIONS

Compared with age- and sex-matched healthy volunteers, patients with autism spectrum disorders showed significantly decreased metabolism in both the anterior and posterior cingulate gyri.

Three-dimensional analysis with MRI and PET of the size, shape, and function of the thalamus in the schizophrenia spectrum

OBJECTIVE

In an exploration of the schizophrenia spectrum, the authors compared thalamic size, shape, and metabolic activity in unmedicated patients with schizophrenia and schizotypal personality disorder to findings in age- and sex-matched healthy control subjects.

METHOD

Coregistered magnetic resonance imaging (MRI) and positron emission tomography scans were obtained in 27 schizophrenic patients, 13 patients with schizotypal personality disorder, and 32 control subjects who performed a serial verbal learning test during tracer uptake. After thalamus edges were outlined on 1.2-mm MRI scans, a radial warping program yielded significance probability mapping in three dimensions.

RESULTS

Significance probability mapping (with resampling) identified an area in the region of the mediodorsal nucleus bilaterally with significantly lower relative metabolism in the schizophrenia group than in either the control or schizotypal personality disorder groups, which did not differ from each other. The three groups did not differ significantly in total thalamic volume in square millimeters or thalamic volume relative to brain volume. Shape analyses revealed that schizophrenic patients had significantly fewer pixels in the left anterior region, whereas patients with schizotypal personality disorder had significantly fewer pixels in the region of the right mediodorsal nucleus than did control subjects.

CONCLUSIONS

Schizophrenic patients showed significant metabolism and shape differences from control subjects in selective subregions of the thalamus, whereas patients with schizotypal personality disorder showed only a difference in shape. Because the mediodorsal and anterior nuclei have different connections with limbic and prefrontal structures, the anterior thalamic shrinkage and mediodorsal metabolic and shape changes might relate to the different clinical pictures in schizotypal personality disorder and schizophrenia.

Visualizing fronto-striatal circuitry and neuroleptic effects in schizophrenia

Disturbances in fronto-striatal circuitry have been postulated to be important in schizophrenia. Positron emission tomography typically shows decreased metabolic rates in these areas relative to other brain areas in schizophrenia. After treatment with typical neuroleptics, striatal metabolic rates are increased, but other brain areas tend not to show significant changes. Atypical neuroleptics less markedly affect striatal metabolic rates, but show wider cortical effects. In order to examine fronto-striatal circuitry, a technique for visualizing the correlations between metabolic rates in all brain areas was applied in 33 controls and 27 unmedicated schizophrenic patients. Correlation images revealed strong fronto-striatal connections in controls, but weak fronto-striatal links in schizophrenic patients. Changes in striatal circuits, also reflected in recent anatomical studies, may be important for understanding antipsychotic effects.

A method of basal forebrain anatomical standardization for functional image analysis

Functional as well as structural assessment of the basal forebrain has mostly focused on the dorsal caudate and putamen in axial slices where they are easily outlined or their centers located with stereotaxic methods. The more ventral extent of the basal forebrain, where the irregular form and indistinct boundaries of the nucleus accumbens and substantia innominata are difficult to trace and where the brain's ventral surface may contribute partial volume artifacts to measurement, has been less studied. We present a method based on coronal sections, landmarks placed on clearly visible anchor points, and the computational technique of thin-plate spline warping which allows the alignment of groups of individuals to common coordinates for pixel-by-pixel statistical mapping. The reliability of the landmarks across independent raters yields a median absolute difference of 1.3-1.6 mm. The validity of the method is confirmed by variance maps which reveal significant decreases in variance over spindle and bounding box alignment.

Age-related shift in brain region activity during successful memory performance

Coregistered positron emission tomography (PET)/magnetic resonance imaging (MRI) was used to characterize brain function in 70 volunteers, aged 20-87 years, during a verbal memory task. Frontal activity showed an age-related decline that remained significant after statistical control for sulcal atrophy. Analyses of young and old subgroups matched for memory scores revealed that young good performers activated frontal regions, whereas old good performers relied on occipital regions. Although activating different cortical regions, good performers of all ages used the same cognitive strategy semantic clustering. Age-related functional change may reflect dynamic re-allocation in a network of brain areas, not merely anatomically fixed neuronal loss or diminished capacity to perform.

Detection of hepatic neoplasms by computed tomographic arterial portography in cirrhotic patients

Computed tomography (CT) during arterial portography (CTAP) is useful in detecting hepatic tumors but cirrhotic change may interfere with portal flow and the prediction of resectability. We evaluated the usefulness of CTAP in detecting hepatic tumors, especially hepatocellular carcinoma (HCC), in patients with or without cirrhotic change. Ninety-six patients with pathologically proven hepatic tumors were assessed, of whom 90 had hepatocellular carcinoma. The tumors had been previously detected by abdominal ultrasound and CT scans, after which the patients were referred for angiography and CTAP. The CTAP findings were compared with ultrasonographic, conventional CT, angiographic, and subsequent surgical and pathologic findings regarding size, number, and location of the hepatic lesions. CTAP detected 134 of 143 pathologically proven lesions. The overall sensitivity of CTAP in the 96 patients was 94%, with a false-positive rate of 22%. The detection rate of CTAP for tumors less than 2 cm in diameter was high (92%). The sensitivity and false-positive rate for CTAP in 60 cirrhotic patients were 94% and 23%, respectively, CTAP is a sensitive imaging modality for detection of hepatic neoplasms even in patients with cirrhosis, but its false-positive rate is high.

Prevalence of human papilloma virus 16 or 18 in cervical cancer in Hualien, eastern Taiwan

In order to determine the association of human papilloma virus (HPV) with cervical cancer of patients in the Hualien area, we analyzed 40 cervical cancer specimens using polymerase chain reaction (PCR) to detect the presence of HPV type 16 (HPV-16) and type 18 (HPV-18) genomes. The results showed that at least 70% (28/40) of the specimens had HPV DNA. Of the 37 squamous cell carcinomas of the cervix, HPV-16 was present in 25 cases (68%) and HPV-18 in 2 (5.4%). HPV-16 DNA was detected in one of 2 adenocarcinomas and HPV-18 in a case of small cell carcinoma. Seven (87.5%) of 8 specimens from aborigines were HPV-positive. These findings support a role for HPV in the development of cervical cancer in the Hualien population.

Comparison of intravenous granisetron with metoclopramide plus dexamethasone in the prevention of nausea and vomiting associated with emetogenic cytotoxic chemotherapy

Fifty-one patients who received their first course of chemotherapy were studied to compare the respective efficacy and safety of granisetron and metoclopramide plus dexamethasone in the prevention of nausea and vomiting induced by emetogenic cytotoxic drugs. The results showed the response rate of antiemesis in the first 24 hours was higher in the metoclopramide plus dexamethasone group than in the granisetron group: 95% vs 84%. For the next six days of the study period, the response rate of the granisetron group was shown to be more effective than that of metoclopramide plus dexamethasone group: 77% vs 60%. Furthermore, the granisetron seemed to display enhanced tolerability with less drug-related side effects and no extrapyramidal effects which appeared in 2 cases of the metoclopramide plus dexamethasone group. In conclusion, a single dose of granisetron can be as effective as the gold standard of metoclopramide plus dexamethasone regimen in preventing and treating acute nausea and vomiting. For preventing delayed nausea and vomiting, granisetron is shown to be more effective than metoclopramide plus dexamethasone.

Surgical treatment of peptic ulcer disease: changing patterns in the past 40 years

During the past 40 years (1951-1990), 7,663 patients with peptic ulcer disease underwent surgical treatment at the National Taiwan University Hospital. A great change in patient characteristics and operative procedures was noted between the last 10 years and the previous three decades. There were 7,105 patients (92.7%) between 1951 and 1980, an average of 237 patients per year. However, only 558 patients received surgery in the last 10 years, an average of 56 patients per year. The proportion of female patients increased from 9.5% in the earlier period to 20.4% in the last 10 years; the average age of patients also increased. In the earlier period, the indications for surgery were hemorrhage (38.4%), perforation (36.1%), intractable pain (16.4%) and stenosis (9.1%). Perforation (89.2%) was the most common indication for surgical treatment in the last 10 years. Hemorrhage (4.9%), pain (4.1%) and stenosis (1.8%) were less common. There was no significant difference in surgical morbidity between the two periods. Primary subtotal gastrectomy (SG) accounted for 75.4% of operations in the earlier period, but vagotomy became the main treatment in the last 10 years, including highly selective vagotomy (HSV) (31.9%), and truncal vagotomy with drainage procedure (TV + D) (31.0%). The surgical mortality in the earlier period was 1.3% for SG, 1.8% for TV + D and 16.1% for simple closure. There was no significant change in ulcer location between the two periods. The overall mortality rate was higher in the last 10 years (5.2%) than in the earlier 30 years (2.7%) (p < 0.001). In follow-up studies, the satisfactory rate after operation was similar among patients receiving SG (89.8%), HSV (90.3%) and TV + D (91.1%) between 1977 and 1990.

Experiences in surgical management of cavernous hemangioma of the liver

BACKGROUND/AIMS

Observation is usually recommended for managing patients with cavernous hemangioma of the liver. To assess the indications for surgical management, we make a retrospective analysis.

PATIENTS AND METHODS

There were 14 patients with cavernous hemangioma of the liver who were surgically treated in National Taiwan University Hospital from 1984 to 1993.

RESULTS

The surgical indications included uncertain diagnosis in 10 patients, progressive tumor enlargement in two, symptomatic tumor in one and subcapsular bleeding in one. The tumors were 2-15 cm in diameter and the median was 6 cm. The operation procedures included atypical hepatectomy in 6 patients, lateral segmentectomy in 4, right lobectomy in one, extended right lobectomy in one and open biopsy in two. There was no mortality. Wound infection occurred in one patient. The average blood transfusion was 0.79 unit (range: 0-3 units)(1 unit=500 ml). The postoperative hospital stay was 13.2 days (range: 10-18 days).

CONCLUSION

Surgical management of cavernous hemangioma of the liver is safe.

Clinicopathologic characteristics of Helicobacter pyloric seropositive gastric adenocarcinomas

To compare and characterize retrospectively the clinicopathologic features of gastric cancers with and without previous Helicobacter pylori infection, we determined the preoperative seropositivity of H. pylori in 151 patients who had undergone gastric resection for primary gastric adenocarcinoma between 1988 and 1993. The overall seroprevalence of H. pylori was 60.9%. H. pylori-positive gastric cancers were frequently associated (p<0.05) with macroscopic localized types (Borrmann I and II) in which negative cancer associated with infiltrative types (Borrmann III and IV) and cancer invasion of the duodenum. Multivariate analysis showed that H. pylori seropositivity was not an independent prognostic factor. Pathologic tumor-node-metastases (TNM) stage remained the only prognostic indicator. Our study suggests that H. pylori has a significant impact on the clinically relevant tumor biology of gastric cancer. Investigation along this line is warranted.

Survival after resection of gastric cancer and prognostic relevance of systematic lymph node dissection: twenty years experience in Taiwan

A retrospective study of 954 resectable gastric cancers in a single institute of Taiwan from 1971 to 1990 was performed to evaluate improvements in gastric cancer surgery. The patients were divided into four time periods representing an overall experience of progressive implementation of aggressive resection and increased extent of systematic lymph node dissection. The clinicopathologic data and survival rates were statistically compared and the significance of the extent of resection on survival analyzed. A significant increase in the proportion of upper one-third tumors (from 14.8% to 20.4%) and a decrease in the incidence of intestinal type (73.6% to 41.5%) was found within the overall period. The proportion of patients with early gastric cancer increased from 11.5% to 19.4%. Patients who underwent total gastrectomy and combined visceral resection increased from 13.7% to 27.4% and 19.8% to 41.1%, respectively. An increase of both total dissected lymph node number and the incidence of detected lymph node metastases in early gastric cancer were associated with more extensive lymphadenectomy. An improved 5-year survival rate following aggressive resection was found for all stages except stage IV and T4 lesions, and the surgical mortality decreased from 5.5% to 2.0%. Patients with earlier stage lesions benefited more from radical resection, especially those with stage II and T2 lesions. Systematic lymph node dissection increased the 5-year survival of patients by about 10% for stage III or T3 lesions but not for patients with stage IV or T4 lesions. Multivariate analysis confirmed the significance of the improved technique of lymphadenectomy on the prognosis of gastric cancer following resection in Taiwan.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma of the gastric cardia: prognostic significance of pathologic and treatment factors

The records of 146 patients who had surgery for adenocarcinoma of the gastric cardia between 1977 and 1992 at National Taiwan University Hospital were retrospectively analyzed. The prognostic significance of pathologic and surgical treatment factors was examined by log rank test and stepwise regression procedures. The overall 2-year and 5-year survival rates were 40.2% and 23.7%, respectively. The pathologic factors analyzed included: age, sex, tumor diameter, esophageal invasion, pathologic grading, vascular invasion, perineural invasion, depth of invasion, node-status, distant metastasis and number of positive lymph nodes. The surgical treatment factors analyzed included:surgical procedure, region of lymphadenectomy, resection margin and resection status. Resection status was classified into three categories: absolute curative, relative curative and palliative. Univariate analyses showed that esophageal invasion, vascular invasion, depth of invasion, node status, node number, resection margin and resection status were significant prognostic factors. The selected stepwise regression model identified three significant independent factors: node status, resection status and esophageal invasion. Aggressive surgical management, including combined resection and extended lymphadenectomy, may be helpful for patients with adenocarcinoma of the gastric cardia.

Gonadoblastoma and chroiocarcinoma in dysgenic gonads: report of a case

Dysgenetic gonads are well known to be associated with gonadoblastoma and various germ cell tumors, but very rarely with choriocarcinoma. We describe a 16-year-old, phenotypic female patient with a 46XY karyotype who developed gonadoblastoma on the right gonad and choriocarcinoma on the left. There was no co-existence of the two tumor cell types in the same gonad. This case emphasizes the importance of bilateral gonadectomy for "46XY female" patients, as soon as the cytogenetic evidence is known.

Comparison between resectable gastric adenocarcinomas seropositive and seronegative for Helicobacter pylori

The preoperative seropositivity of Helicobacter pylori was determined in 128 patients who had undergone gastrectomy for primary gastric adenocarcinoma during the past 5 years. The overall seroprevalence of H. pylori was 64 per cent. Gastric cancers positive for H. pylori were associated with tumours located in the lower third of the stomach which were of localized type (Borrmann I and II) (P < 0.05), but not with age, sex, blood type, tumour size, invasion depth, lymph node metastases, histological type, DNA ploidy or type of surgery. The cumulative 5-year survival curves after surgical resection were significantly better in patients who were positive for H. pylori. Multivariate analysis revealed that seropositivity for H. pylori was not an independent prognostic factor. Pathological tumour node metastasis staging was the only prognostic indicator. Better prognosis for those with H. pylori-seropositive gastric cancer may be attributed to the more advanced stage of H. pylori-seronegative gastric cancers. The potential role of H. pylori in gastric cancer carcinogenesis and its biological significance warrant further investigation.

Surgical treatment of gastric adenocarcinoma: the role of lymph node dissection

In this retrospective study, 652 patients who had curative resections for gastric cancer from 1977 to 1991 were reviewed to evaluate improvements in gastric cancer surgery and the influence of the extent of lymphadenectomy on survival. The patients were grouped into three time periods: 1977 to 1981, 1982 to 1986 and 1987 to 1991. The percentage of patients with early gastric cancer increased from 17.7% during 1977 to 1981, to 24.3% during 1987 to 1991. The average number of dissected lymph nodes was 7.5 +/- 8.1 during 1977 to 1981 and 16.4 +/- 10.3 during 1987 to 1991, when more radical lymphadenectomy was adopted. Total gastrectomies increased from 10.9% to 25.9% in the same time periods while combined visceral resections increased from 26.7% to 38.1%. Operative mortality decreased from 5.0% to 1.7%. The overall 5-year survival rate increased from 34.8% to 59.4%. In subgroup analysis, significant improvement of the 5-year survival rate was noted in the following groups: patients with stage I, II and III tumors but not stage IV; both proximal and distally located tumors; tumors with or without lymph node metastases; T1 and T2 but not in T3 and T4 (cancer invasion beyond the serosa). The decreased surgical mortality in recent years suggests that curative resection with extensive lymph node dissection can now be safely performed. Radical gastrectomy with extended lymphadenectomy may be adopted in gastric cancer resection for better control of regional disease.

Lymph node metastases in gastric cancer: significance of positive number

To investigate the significance of the number of node metastases in gastric cancer and its relationship to traditional anatomical classification, 305 patients who underwent a radical gastrectomy and extended lymphadenectomy (R3/4) with curative intent were reviewed. Lymph node metastases was found in 191 (62.6%) patients. The incidence of lymph node metastases was closely related to the depth of cancer invasion as well as the extent of lymph node group involvement. The frequency of metastases in different lymph node locations was related to the location of the primary tumor. The 3-year survival rates for patients with node involvement and without were 42.1 and 92.3%, respectively. In node number analysis, the distribution of the N1 group and the N4 group involvement was rather characteristic and could be predicted from a node number < 4 or > 12. The predictability of N2 and N3 involvement from node numbers 4-8 and 9-12 was less satisfactory. On the whole, patients with a metastatic node number < 4 could be considered to be N1 and had a relative good prognosis. Patients with node number 4-10 could be considered as N2 and > 10 as an incurable disease with distant metastases. Both had a poor prognosis. The data suggest that lymph node number represents the biologic behavior of cancer instead of the anatomic consideration of conventional N stage. The number of metastatic lymph node number is a good prognostic indicator with similar predicting power as the conventional node stage.

Focused image recovery from two defocused images recorded with different camera settings

Two new methods are presented for recovering the focused image of an object from only two blurred images recorded with different camera parameter settings. The camera parameters include lens position, focal length, and aperture diameter. First a blur parameter sigma is estimated using one of our proposed depth-from-defocus methods. Then one of the two blurred images is deconvolved to recover the focused image. The first method is based on a spatial domain convolution/deconvolution transform. This method requires only the knowledge of sigma of the camera's point spread function (PSF). It does not require information about the actual form of the camera's PSF. The second method, in contrast to the first, requires full knowledge of the form of the PSF. As part of the second method, we present a calibration procedure for estimating the camera's PSF for different values of the blur parameter sigma. In the second method, the focused image is obtained through deconvolution in the Fourier domain using a Wiener filter. For both methods, the results of experiments on actual defocused images recorded by a CCD camera are given. The first method requires much less computation than the second method. The first method gives satisfactory results for up to medium levels of blur and the second method gives good results for up to relatively high levels of blur.

An uncommon cause of biliary obstruction (Mirizzi syndrome): report of five cases

Mirizzi syndrome is a rare form of common hepatic duct obstruction resulting from an inflammatory response secondary to a gallstone impacted in the cystic duct or neck of the gallbladder. Herein, we report five patients with this syndrome. Clinically, all patients had prominent jaundice. Ultrasound examination showed a large stone in the neck of the gallbladder. Endoscopic retrograde cholangiopancreaticography demonstrated a filling defect in the biliary tract the cystic duct level. Four patients possessed cholecystobiliary fistulas. Two patients also had common bile duct stones. Operations included simple cholecystectomy in one patient, and partial cholecystectomy with choledochoplasty with the use of gallbladder flap and T-tube insertion in the other four patients. All patients were uneventfully discharged. If a patient has clinical obstructive jaundice, a huge stone encased in the neck of the gallbladder and a filling defect of the biliary tract at the cystic duct level shown on a cholangiogram, Mirizzi syndrome must be considered. A cholecystobiliary fistula will probably be present if the cholangiogram further reveals an excavated filling defect or a block of the common duct; in this case, partial cholecystectomy and choledochoplasty with a gallbladder flap is the treatment of choice. Mirizzi syndrome is a contraindication for laparoscopic cholecystectomy which can easily result in common duct injury.

Can cecal diverticulitis be differentiated from acute appendicitis?

Cecal diverticulitis is a rare disease entity, the diagnosis of which remains a difficult problem. The clinical picture of cecal diverticulitis is almost indistinguishable from acute appendicitis. We reviewed 11 cases of pathologically documented cecal diverticulitis who underwent treatment from May 1981 to April 1992. They were diagnosed incorrectly as acute appendicitis, ruptured appendicitis or appendiceal abscess prior to operative intervention. Thirty patients diagnosed correctly with acute appendicitis from March 1992 to April 1992 were included for a comparative study. We found that cecal diverticulitis presented with a longer duration of symptoms, initial pain over the right lower quadrant of the abdomen, older age, less migration of pain, nausea, vomiting, fever and leukocytosis, and an incidence of Alvarado's score > or = 7 than acute appendicitis.

Therapeutic effect of liver resection in patients with metastatic liver tumors

Thirty-five hepatectomies for metastatic liver malignancy were performed from January 1986 to July 1992 at the National Taiwan University Hospital. Twenty-six of them were of colorectal origin and nine were of other origins. We analyzed the risk factors for recurrence and survival rate after hepatectomy of colorectal origin under curative intention with both univariate and multivariate analysis. The calculated median disease free interval after hepatectomy was 11 months (recurrence rate 65% in one year and 85% in two years). The median survival rate was 24 months (calculated one-year survival 86%, two-year survival 41%). In univariate analysis, the number of metastatic lesions and operation procedures significantly affect the recurrence rate (p = 0.033 and p = 0.042, respectively). In survival univariate analysis, only a safety margin > 1 cm and age > 50 years had significant benefit (p = 0.0014 and p = 0.045, respectively). By multivariate analysis, only solitary metastasis was beneficial to the recurrence rate (p = 0.013), an age > 50 years had a borderline beneficial effect to the recurrence rate (p = 0.052), while earlier liver stage, older age, larger safety margin and minor operative procedures positively affected the survival rate (p = 0.039, 0.018, 0.034 and 0.017, respectively). As the sample number was small, it was hard to draw any conclusions for metastatic liver tumors of other origins. The complication rate (5/35) and mortality rate (1/35) of hepatectomy were low. We concluded that for selected cases of metastatic hepatic malignancy, especially from colorectal cancer, hepatectomy is a promising treatment of choice.

Is previous abdominal surgery a contraindication to laparoscopic cholecystectomy?

Previous abdominal surgery has been reported as a relative contraindication to laparoscopic cholecystectomy. An analysis of 193 laparoscopic cholecystectomies was undertaken to determine whether this relative contraindication led to increased morbidity, an increased rate of conversion to open cholecystectomy, or longer operating time. The results of 55 patients who had previous abdominal surgery were compared with those of 138 patients without previous abdominal surgery. Morbidity, conversion rate, and operating time were not increased in patients with previous abdominal surgery. We found both previous upper and previous lower abdominal surgery to be risk for laparoscopic cholecystectomy. Laparoscopic cholecystectomy can be performed safely in patients with previous abdominal surgery if we (1) use the cutdown technique initially, (2) dissect the adhesion before the upper midline port is inserted, (3) retrogradely dissect the gallbladder from the liver bed, and (4) divide the cystic artery and duct last.

Secular changes in the clinical manifestation and pathologic pattern of early gastric cancer in Taiwan

To investigate whether there has been a time trend change in the percentage of early gastric cancer to gastric cancer and the clinicopathologic features of early gastric cancer in Taiwan, we reviewed 208 patients diagnosed between 1964 and 1992. Patients were divided into group I from 1964-1980 (n = 106) and group II from 1981-1992 (n = 102). The percentage of early gastric cancer among total gastric resections in group II (14.7%) did not differ from group I (12.7%; p = 0.19). Epigastralgia (58.2%) was the most common complaint; 11.8% (12/102) of cancers in group II were incidentally detected by endoscopy. Endoscopy provided a better diagnostic aid than did radiology. Tumors were frequently located in the antrum (50.9%) with a mean diameter of 2.8 cm. Small cancers of less than 1 cm in diameter were more prevalent in group II (37.3%) than group I (10.4%; p < 0.001). Cancers of the elevated type (17.8%) were uncommon in contrast to depressed ones (82.2%; p < 0.001). The frequency of mucosal carcinoma (51.0%) was similar to submucosal carcinoma (49.0%). Mucosal carcinoma had less lymph node metastases (3.1%) than submucosal carcinoma (12.2%; p < 0.05) with an overall frequency of metastases of 7.5% (14/186). The five-year survival rate of group I (91.7%) was not statistically different from group II (94.6%). We concluded that, except for the symptomatology and the ability to diagnose, the clinicopathologic features of early gastric cancer were similar between these two time periods. Repeated investigation of suspicious lesions and endoscopic screening on asymptomatic subjects may increase the rate of detection and thus guarantee a favorable outcome.

Somatostatin-containing carcinoid tumor of the duodenum in neurofibromatosis: report of a case

We report a case of von-Recklinghausen's disease presenting with obstructive jaundice and found to have a somatostatin-containing carcinoid tumor in the papilla of Vater and a small neurofibroma in the duodenum. A 42-year-old woman with von-Recklinghausen's disease presented with intermittent jaundice, pruritus, and mild steatorrhea of a two-year duration. Abdominal ultrasonography and computed tomography showed dilated intrahepatic ducts, common bile duct and pancreatic ducts. Duodenoscopy showed a tumor at the papilla of Vater, but a preoperative biopsy failed to provide a definite diagnosis. Laparotomy revealed a yellowish tumor at the papilla of Vater and another nodule on the mesenteric side of the second section of the duodenum. Microscopically, the tumor at the papilla of Vater was found to be a somatostatin-containing carcinoid tumor. The small nodule on the mesenteric side was a neurofibroma. The jaundice, pruritus and steatorrhea disappeared after surgery.

[Computed tomography of gastric carcinoma using water as a contrast agent]

To overcome the problem of poor mixing of gastrointestinal tract contents with a diluted iodinated contrast agent in abdominal computed tomography, pure water was adopted as an oral contrast agent. In 25 cases of clinically suspected gastric carcinoma, a subsequent pathological examination revealed six cases of early gastric cancer and 19 cases of advanced gastric cancer. We performed CT of the stomach using the following revised procedure: patients were given 600-1000 mL of water by mouth after an intramuscular dose of Buscopan to distend and immobilize the stomach. Gastric mucosal enhancement and the poorer enhanced submucosal layer were demonstrated by a bolus intravenous injection of iodine-containing contrast medium using an automatic injector synchronized with the CT machine. Based on abnormal gastric wall thickening and the abnormal mural enhancement patterns, an accuracy of 96% was attained in differentiating early gastric cancer from advanced gastric cancer, but the detection rates for extragastric invasion, gastric ulcers and lymphadenopathy were 67%, 43% and 63%, respectively. CT staging of gastric cancer was 72%, and was especially accurate for stages I and IV. Water as oral contrast agent for CT of the GI tract was readily accepted by patients and caused no side effects. Using water as an oral contrast for gastric CT is of great help in staging gastric cancer.

Distributional pattern of diverticular disease of the colon in Taiwan

From May 1981 to October 1991, 66 patients with diverticular disease of the colon were analyzed retrospectively. Data were obtained from medical records. There were 29 men and 37 women, ranging in age from 32 to 85 years, with a mean age of 58.7 years. Forty-nine patients had a singular site of distribution in the diverticulum, and 17 patients had more than two sites of distribution in the diverticula. The locations of the diverticular disease were sigmoid colon (45.4%), ascending colon (36.4%), cecum (33.3%), descending colon (18.2%), transverse colon (12.1%) and rectum (1.5%). The left-sided lesions (46.9%) were approximately equal to the right-sided lesions (43.9%).

Carcinoma of the ampulla of Vater: long-term survival after surgical treatment

Ninety-one patients were identified as having carcinoma arising from the ampulla of Vater. Radical pancreaticoduodenectomy, using either a standard or pylorus-preserving method, was performed in 69 consecutive patients over a 30-year period. Frequent clinical findings included jaundice (84%), a weight loss of more than 10% of the body weight (75%), abdominal pain (59%), chills and fever (52%), pruritus (48%) and a palpable gallbladder (38%). Acute pancreatitis was present in 10%. Postoperative mortality was 11.6%. Surgical mortality was 23.1% from 1962 to 1971 and 12.5% from 1972 to 1981, but was reduced to 6.3% from 1982 to 1991. Surgical mortality was primarily due to pancreaticojejunostomy leaks. The five-year survival rate was 52% and the 10-year rate was 50%. Radical pancreaticoduodenectomy for ampullary carcinoma has a low mortality and should remain the procedure of choice for ampullary carcinoma.

Liver resection for hepatic metastasis from colorectal carcinoma

One hundred and eighteen patients who suffered from metastatic liver tumors from colorectal carcinoma during the period from January 1980 to June 1991 at the National Taiwan University Hospital were retrospectively reviewed. The modes of treatment included hepatic resection (n = 18), transarterial embolization (TAE, n = 17), chemotherapy only (C/T, n = 36), and no treatment (n = 47). In the 18 patients who underwent hepatic resection during the last 10 years, the types of surgery included: wedge resection (n = 8), segmentectomy (n = 2), right hepatic lobectomy (n = 5), left hepatic lobectomy (n = 2) and extended right hepatic lobectomy (n = 1). There were no operative mortalities in this series. The overall three-year actuarial survival rate of the resection group was 57.5%. It was better than that of the TAG group (17%, p < 0.05). For a solitary tumor, the three-year actuarial survival rate rose to 64% in the resection group. There were no three-year survivors in the nonsurgical solitary tumor group. This experience defends aggressive surgical treatment of resectable hepatic metastatic liver cancer from colorectal carcinoma as a safe procedure which is able to prolong a patient's life.